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The removal of heavy metals from municipal wastewaters by lime-magnesium coagulation MacLean, Byard H. 1977

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THE REMOVAL OF HEAVY METALS FROM MUNICIPAL WASTEWATERS BY LIME-MAGNESIUM COAGULATION by BYARD H. MACLEAN B . A . S c , U n i v e r s i t y o f B r i t i s h C o l u m b i a , 1971 A T h e s i s S u b m i t t e d i n P a r t i a l F u l f i l l m e n t o f The R e q u i r e m e n t s f o r t h e Deg ree o f M a s t e r o f A p p l i e d S c i e n c e i n The F a c u l t y o f G r a d u a t e S t u d i e s Depa r tment o f C i v i l E n g i n e e r i n g We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRIT ISH COLUMBIA •' J u n e . 1977 @ B y a r d H. MacLean , 1977 In presenting this thesis in partial fulfilment of the requirements f o r an advanced degree at the University of Brit ish Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying o f t h i s t h e s i s for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or p u b l i c a t i o n o f this thesis for financial gain shall not be allowed without my written permission. The University of Brit ish Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i ABSTRACT The e v i d e n c e o f heavy m e t a l b u i l d up i n t h e a q u a t i c e n v i r o n m e n t n e a r sewage t r e a t m e n t p l a n t o u t f a l l s a r ound V a n c o u v e r , c o u p l e d w i t h t h e g e n e r a l l y h e l d t h e o r y t h a t s e c o n d a r y t r e a t m e n t i s no t r e q u i r e d i n t h i s a r e a , l e a d s t o t h e c o n c l u s i o n t h a t a t r e a t m e n t method i s r e q u i r e d t h a t i s p r i m a r i l y a imed a t heavy m e t a l r e m o v a l . I n t h i s s t u d y , j a r t e s t s were p e r f o r m e d t o e v a l u a t e t h e heavy m e t a l r e m o v a l e f f i c i e n c y o f t h e l ime -magne s i um c o a g u l a t i o n p r o c e s s . 3"j_ 2*4* 2"f" 2H~ 21 F i v e heavy m e t a l s (C r , Cu , Pb , N i and Zn ) were a l l t e s t e d a t i n i t i a l c o n c e n t r a t i o n s o f . 5 , 2.5 and 5.0 mg/1 i n d i v i d u a l l y and i n c o m b i n a t i o n . The e x p e r i m e n t s were p e r f o r m e d on p r e c h l o r i n a t e d p r i m a r y e f f l u e n t and raw sewage a t t h e n a t u r a l a l k a l i n i t y l e v e l s (120 -130 mg/1 as CaCO-), and some work was done a t e l e v a t e d a l k a l i n i t y (190 -200 mg/1) . The need f o r f i l t r a t i o n i n t h e p r o c e s s was a l s o r e s e a r c h e d . R e s u l t s o f t h e s t u d y i n d i c a t e d t h a t t he heavy m e t a l r e m o v a l 2+ e f f i c i e n c y was enhanced by t he p r e s e n c e o f Mg a t a g i v e n l i m e dosage f o r a l l o f t h e heavy m e t a l s e x c e p t n i c k e l . A c o m p a r i s o n i n d i c a t e d t h a t 2+ i n t e r m e d i a t e l i m e t r e a t m e n t (220 mg/1) c o u p l e d w i t h 33 mg/1 Mg m i g h t be a more a t t r a c t i v e p r o c e s s t h a n j u s t s t r a i g h t h i g h l i m e t r e a t m e n t (400 mg/1) . i i TABLE OF CONTENTS Page 1. INTRODUCTION 1 2 . HISTORY OF THE HEAVY METAL PROBLEM 4 2.1 T o x i c i t y 4 2.2 Heavy M e t a l C o n c e n t r a t i o n s i n t h e Urban E n v i r o n m e n t 6 2.3 Heavy M e t a l Remova l P r o c e s s e s 8 2 .3 .1 B i o l o g i c a l 8 2 . 3 . 2 Ca rbon A d s o r p t i o n 10 2 . 3 . 3 L ime C o a g u l a t i o n 12 3 . MAGNESIUM SOLUBILITY 16 4. RESEARCH RATIONALE 21 4.1 H i s t o r y o f t h e L ime-Magnes ium P r o c e s s f o r Wa te r R e n o v a t i o n 21 4.2 A p p l i c a t i o n o f t h e L ime-Magnes i um P r o c e s s t o V a n c o u v e r Wa tewa te r s 21 5. EXPERIMENTAL METHODS AND MATERIALS 23 5.1 S e l e c t i o n o f E f f l u e n t 23 5.2 S a m p l i n g P r o c e d u r e 23 5.3 Sample S t o r a g e 23 5.4 C h e m i c a l P r e p a r a t i o n s 24 5 .4 .1 Heavy M e t a l S p i k e S o l u t i o n s 24 5 .4 .2 A .A . S t a n d a r d s 24 5 . 4 .3 L ime 24 5 .4 .4 Magnes ium I o n - 25 5 .4 .5 Sod ium B i c a r b o n a t e 25 i i i 5.5 A n a l y t i c a l Techniques 25 5.5.1 A l k a l i n i t y 25 5.5.2 Heavy Metal Analysis 25 5.5.3 pH 26 5.6 Lime-Magnesium Coagulation Test Procedure 26 6. RESULTS AND DISCUSSION 6.1 The Removal Ef f ic iency of Ind iv idua l Heavy Metals from Prechlorinated Primary Effluent (PPE) - Unf i l te red Results 28 6.1.1 Chromium 28 6.1.2 Copper 32 6.1.3 Lead 36 6.1.4 N icke l 36 6.1.5 Zinc 36 6.1.6 Summary 43 6.2 The Removal Ef f ic iency of Indiv idual Heavy Metals from PPE - F i l t e r e d vs Unf i l te red Results 48 6.3 The Removal Ef f ic iency of Mixed Metals from PPE -F i l t e r e d vs Unf i l te red Results 48 6.4 The Removal Ef f ic iency of Mixed Metals from Raw Sewage - F i l t e r e d vs Unf i l te red Results 56 6.5 The Effect of A l k a l i n i t y on Heavy Metal Removal 56 7. CONCLUSIONS 65 2+ 7.1 The Effectiveness of Mg at various pH's 65 7.1.1 General 65 7.1.2 Indiv idual Metals i n PPE 65 7.1.3 Mixed Metals i n PPE 65 7.1.4 Mixed Metals i n Raw Sewage 65 i v 7.2 R e s i d u a l M e t a l s i n t h e S e t t l e d S u p e r n a t a n t 65 7.3 The E f f e c t o f A l k a l i n i t y on Heavy M e t a l Remova l 66 2+ 7.4 The P o t e n t i a l o f Mg f o r F u l l S c a l e T r ea tmen t 66 BIBLIOGRAPHY 67 APPENDIX A - T e s t P r o c e d u r e Deve lopment 69 APPENDIX B - Compa r i s on o f H i g h L ime T r e a t m e n t (H . L . ) 81 2+ 2+ v s I n t e r m e d i a t e Lime/Mg T r ea tmen t ( I . L . /Mg ) . 1. CHAPTER 1 INTRODUCTION T h e r e has been an i n c r e a s i n g c o n c e r n i n r e c e n t y e a r s o v e r t h e p r ob l ems a s s o c i a t e d w i t h heavy m e t a l b u i l d - u p f r o m c u l t u r a l s o u r c e s i n t h e a q u a t i c e n v i r o n m e n t . The r e a l i z a t i o n o f t h e s e p r ob l ems has moved many governments t o b r i n g i n s t r i c t e r p o l l u t i o n c o n t r o l s t a n d a r d s . A s t u d y o f t h e l o w e r F r a s e r R i v e r s y s t e m c o n d u c t e d by B e n e d i c t e t a l . (5) f ound BOD v a l u e s o f _< 1 mg/1 and 2-4 mg/1 and d i s s o l v e d oxygen l e v e l s o f > 90% and > 80% o f s a t u r a t i o n f o r t he M a i n Arm and N o r t h Arm/ M i d d l e Arm r e s p e c t i v e l y . T h i s i n f o r m a t i o n , c o u p l e d w i t h r i v e r f l o w d a t a , has l e d most r e s e a r c h e r s t o c o n c l u d e t h a t s e c o n d a r y t r e a t m e n t o f V a n c o u v e r m u n i c i p a l w a s t e w a t e r s i s n o t h i g h l y c o s t - e f f e c t i v e . The p r e c i p i t a t i o n o f heavy m e t a l s by l i m e c o a g u l a t i o n i s a w e l l documented p r o c e s s ( 1 1 ) . A s l i g h t m o d i f i c a t i o n , t h e l ime -magne s i um p r o c e s s , i n v o l v e s t he p r e c i p i t a t i o n o f magnes ium i o n i n s i t u d u r i n g l i m e c o a g u l a t i o n . T h i s p r o c e s s has been shown to be e f f e c t i v e f o r t h e r e m o v a l o f cadmium as w e l l as COD, SS and c o l o u r ( 8 ) . The m a i n o b j e c t i v e o f t h e r e s e a r c h r e p o r t e d h e r e i n i s t o e s t a b l i s h t h e heavy m e t a l r e m o v a l e f f i c i e n c y o f t h i s p r o c e s s f o r V a n c o u v e r m u n i c i p a l sewage. The s p e c i f i c o b j e c t i v e s a r e a s f o l l o w s : 1) To d e v e l o p a method t o e v a l u a t e heavy m e t a l r e m o v a l by t he l ime -magne s i um p r o c e s s ( A p p e n d i x A ) . 2) To e v a l u a t e t he r e m o v a l e f f i c i e n c y o f i n d i v i d u a l heavy m e t a l s ( i . e . 3+ 2+ 2+ 2+ 2+ C r , Cu , N i , Pb and Zn ) a t v a r i o u s i n i t i a l c o n c e n t r a t i o n s i n p r e c h l o r i n a t e d p r i m a r y e f f l u e n t (PPE) ( S e c t i o n 7 . 1 ) . 3) To e v a l u a t e t he need f o r f i l t r a t i o n i n t he p r o c e s s ( S e c t i o n 7 . 2 ) . 4) To e v a l u a t e t h e r e m o v a l e f f i c i e n c y o f m i x e d m e t a l s i n PPE and compare t h e s e r e m o v a l s w i t h t h e i n d i v i d u a l m e t a l d a t a ( S e c t i o n 7 . 3 ) . 5) To compare t h e r e m o v a l e f f i c i e n c y f r o m PPE t o t h a t f r o m raw sewa; ( S e c t i o n 7 . 4 ) . 6) To e v a l u a t e t h e e f f e c t o f a l k a l i n i t y on t h e r e m o v a l e f f i c i e n c y ( S e c t i o n 7 . 5 ) . The e x p e r i m e n t a t i o n p rog ram i s summar ized i n T a b l e 1. TABLE 1 EXPERIMENTATION PROGRAM T e s t C o n d i t i o n s Chromium PPE Copper PPE Lead PPE N i c k e l PPE Z i n c PPE _ PPE z RS pH 10 .0 A l k : n a t u r a l X X X X X : x X pH 10 .70 A l k : n a t u r a l X X X X X X X pH 11 .40 A l k : n a t u r a l X X X X X X X pH 10 .70 A l k : 180-200 mg/1 as CaCO-X X X X X X X N o t e s : 1) I n d i v i d u a l m e t a l r u n s were a l l p e r f o rmed s t a r t i n g w i t h t h e f o l l o w i n g i n i t i a l m e t a l c o n c e n t r a t i o n s - .5 mg/1, 2.5 mg/1, 5.0 mg/1. 2) M g 2 + do sage : 0 , 8 , 17 , 33 and 50 mg/1. 3) PPE - p r e c h l o r i n a t e d p r i m a r y e f f l u e n t . 4) RS - raw sewage. 5) N a t u r a l a l k a l i n i t y : 120-130 mg/1 as CaCO-. 6) E i n d i c a t e s a c o m b i n a t i o n o f a l l f i v e m e t a l s e a c h w i t h i n i t i a l c o n c e n t r a t i o n o f .5 mg/1. 4. CHAPTER 2 HISTORY OF THE HEAVY METAL PROBLEM 2.1 Tox ic i ty The major areas of concern with respect to the heavy metal problem i n the aquatic environment i s that of t o x i c i t y to b i o l o g i c a l organisms at low concentrations. The build-up of heavy metals i n Vancouver street sediments and i n the r i v e r sediments near Vancouver sewage treatment plant ou t fa l l s has become an area of increasing concern (4,5,12,13) . The factors that contribute to the problem of t o x i c i t y of heavy metals are as fol lows: 1) being elements, heavy metals do not degrade and hence tend to b u i l d up i n the environment (stream sediments). 2) some heavy metals are susceptible to food chain concentration. 3) most heavy metals are toxic to l i v i n g organisms i n f a i r l y low concentrations. The t o x i c i t i e s of the f ive heavy metals used i n th is study (Cr, Cu, Pb, N i , Zn) are summarized i n the fol lowing paragraphs. a) Chromium. The USPHS Drinking Water Standard (19) for hexavalent chromium i s .05 mg/1, although i t does not appear to have any, phys io log ica l effects on humans and i s not retained i n the body. S i m i l a r l y , hexavalant and t r iva l en t chromium have no s ign i f i can t effect on animals at dosages of the order of 25 mg/1 (19). F ish are r e l a t i v e l y tolerant of chromium s a l t s , but lower forms of aquatic l i f e are extremely sens i t i ve . McKee and Wolf (19) conclude that concentrations above 1.0 mg/1 for f i s h and .05 mg/1 for other aquatic l i f e w i l l have toxic ef fec ts . The concentration of radioact ive chromium by algae has been found to be i n the range of 100 to 500 times (19) that present i n the water. 5. b) Coppe r . McKee and Wo l f (19) s t a t e t h a t " C h r o n i c c o p p e r p o i s o n i n g among human b e i n g s has n e v e r been p r o v e d , e ven among p e o p l e i n coppe r i n d u s t r i e s who have a b s o r b e d enough coppe r t h r o u g h t h e i r s k i n t o be c o l o r e d g r e e n " . The USPHS D r i n k i n g Wate r S t a n d a r d s recommend 1.0 mg/1 and t h i s i s p r i m a r i l y f o r t a s t e c o n s i d e r a t i o n s . T o x i c o l o g i c a l s t u d i e s on a w i d e r ange o f c o m m e r c i a l c r o p s i n d i c a t e s t h a t .1 mg/1 o f c oppe r i s b e n e f i c i a l i n i r r i g a t i o n w a t e r ( 1 9 ) . The ma jo r a r e a o f c o n c e r n w i t h r e s p e c t t o c o p p e r t o x i c i t y a p p e a r s t o be w i t h t h e l o w e r b i o l o g i c a l f o r m s . The t o x i c i t y o f c oppe r t o a q u a t i c o r g a n i s m s v a r i e s s i g n i f i c a n t l y w i t h s p e c i e s and w i t h p h y s -i c a l and c h e m i c a l c h a r a c t e r i s t i c s o f t h e w a t e r . McKee and Wo l f (19) i n d i c a t e t h a t .02 mg/1 f o r f r e s h w a t e r and .05 mg/1 f o r s e a w a t e r a r e b e n e f i c i a l c o p p e r c o n c e n t r a t i o n s . S t u d i e s i n d i c a t e t h a t p l a n k t o n c o n c e n t r a t e c oppe r by f a c t o r s o f 1000 t o 5000. c ) L e a d . Lead i s n o t c o n s i d e r e d e s s e n t i a l t o t h e n u t r i t i o n o f human b e i n g s o r o t h e r a n i m a l s and i s a c u m m u l a t i v e p o i s o n t o b o t h . Due t o t h e f a c t t h a t l e a d may e n t e r . the body t h r o u g h f o o d and a i r s o u r c e s as w e l l a s f r o m w a t e r , t h e USPHS D r i n k i n g Wate r S t a n d a r d has been s e t a t .05 mg/1. Mos t a u t h o r i t i e s a g r e e t h a t v5 mg/1 i s a maximum s a f e l i m i t f o r l e a d i n a p o t a b l e . , s u p p l y f o r a n i m a l s . L ead c o n c e n t r a t i o n s a s l o w as .1 mg/1 have been d e l e t e r i o u s t o f i s h l i f e e s p e c i a l l y i n s o f t w a t e r ( 1 9 ) . d) N i c k e l . The t o x i c i t y o f n i c k e l t o man i s b e l i e v e d t o be v e r y l o w . The USPHS has n o t s e t a d r i n k i n g w a t e r s t a n d a r d f o r n i c k e l . A l t h o u g h n o t a g r e a t d e a l o f d a t a e x i s t s , n i c k e l a p p e a r s t o be q u i t e i n j u r i o u s t o p l a n t s e ven a t l o w c o n c e n t r a t i o n s . N i c k e l i s t o x i c t o f i s h and o t h e r a q u a t i c l i f e a t a b o u t . 1 . 0 mg/1 ( 1 9 ) . C o n c e n t r a t i o n s o f n i c k e l s a l t s i n t h e 10-15 mg/1 r a n g e cau sed a 50 p e r c e n t r e d u c t i o n i n t h e b a e g e r i a l i o x y g e n c u t i l i z a t i o n f r o m s y n t h e t i c - s e w a g e ( 1 9 ) . 6. e) Z i n c . Z i n c has no known p h y s i o l o g i c a l e f f e c t s upon man o r a n i m a l s , e x c e p t a t h i g h c o n c e n t r a t i o n s , and t h e USPHS D r i n k i n g Wate r S t a n d a r d o f 5 mg/1 was s e t due m a i n l y t o t a s t e t h r e s h o l d c o n s i d e r a t i o n s . I t i s t owa rd f i s h and a q u a t i c o r g a n i s m s t h a t z i n c , e s p e c i a l l y i n w a t e r l a c k i n g c a l c i u m h a r d n e s s , e x h i b i t s i t s g r e a t e s t t o x i c i t y (19) . I n s o f t w a t e r , c o n c e n t r a t i o n s o f z i n c f r o m 0.1 t o 1.0 mg/1 have been r e p o r t e d t o x i c . Copper a p p e a r s t o have s y n e r g i s t i c e f f e c t on t he t o x i c i t y o f z i n c . Z i n c i s q u i t e t o x i c t o s h e l l f i s h and i t has been shown t h a t t h e y have been a b l e t o c o n c e n t r a t e Zn-65 by a f a c t o r o f 100,000 ( 1 9 ) . ' From t h e above d i s c u s s i o n o f heavy m e t a l t o x i c i t y one m a j o r c o n c l u s i o n c an be drawn - a l l f i v e m e t a l s e x h i b i t an i n j u r i o u s e f f e c t on the a q u a t i c e n v i r o n m e n t and i n c o m b i n a t i o n w i t h one a n o t h e r t h e o v e r a l l e f f e c t i s , i n a l l p r o b a b i l i t y , one o f s y n e r g i s m r a t h e r t h a n a n t a g o n i s m . 2.2 Heavy M e t a l C o n c e n t r a t i o n s i n t h e U rban E n v i r o n m e n t The u se s o f t h e f i v e heavy m e t a l s s t u d i e d a r e numerous and i t i s t h e r e f o r e n o t s u r p r i s i n g t h a t t h e y a r e p r e s e n t i n m e a s u r e a b l e amounts i n t h e combined sewer d i s c h a r g e s f r o m t h e c i t y o f V a n c o u v e r . I n a Wes twa te r R e s e a r c h C e n t r e s u r v e y (13) t h e c o n c e n t r a t i o n s o f e l e v e n t r a c e m e t a l s were d e t e r m i n e d i n samples c o l l e c t e d f r o m Vancouve r s t r e e t s u r f a c e s . T h i s d a t a was compared t o E n v i r o n m e n t a l P r o t e c t i o n Agency ' ( E . P . A . ) d a t a f o r s e v e r a l c i t i e s i n t h e U n i t e d S t a t e s . The d a t a i s shown i n T a b l e 2. The d a t a f o r S e a t t l e i s shown s e p a r a t e l y s i n c e t h i s w e s t c o a s t c i t y ha s a s i m i l a r c l i m a t e t o V a n c o u v e r . As w o u l d be e x p e c t e d , t h e h i g h e s t deg ree o f m e t a l c o n t a m i n a t i o n i s i n t h e i n d u s t r i a l and c o m m e r c i a l a r e a s f o r a l l t h r e e s e t s o f d a t a . H a l l e t a l . (13) a l s o c o n c l u d e d t h a t l e a d c o n t a m i n a t i o n was n o t o n l y a f u n c t i o n o f l a n d use b u t a l s o o f t r a f f i c v o l u m e . A s t u d y by Tanne r e t a l . (25) on t he c h a r a c t e r i s t i c s o f V a n c o u v e r Table 2: Average Trace Metal Concentrations i n Street Surface Contaminants from 8 U.S. Ci t i e s (from Hall et a l . (13)) Study Area Land Use Number of Stations Ag Cd Co Cr Cu Fe Hg b Ni Mn Pb Zn Vancouver, B.C. Industrial 8 0.6 1.5 87 208 780 18,200 62 44 220 1,243 296 (Brunette River Basin) Commercial Residential 6 8 0.7 0.5 2.4 1.2 9 6 5 3 141' 140 212 133 20,400 18,500 117 40 34 46 232 195 1,415 710 702 404 - Green Space 4 • 0.3 ' 1.2 8 9 144 117 16,850 22 27 226 100 246 Overall 26 0.5 1.6 32. 2 163 347 . 18,590 62 35 216 867 415 Seattle, Washington Industrial 1 - 1.4 239 110 27,000 20 490 1,100 480 Commercial 2 - 1.9 206 136 37,000 - 40. 435 4,000 445 Residential 4 - 1.6 244 76 36,500 - 37 455 2,450 497 Overall 7 - 1.5 247 97 35,000 - 35 • 454 2,700 480 United States 0 (8 c i t i e s ) Industrial 38 - 4.1 279 120 28,000 37 590 1,600 360 Commercial 19 - 5.1 226 170 24,000 - 52 400 3,600 520 Residential 22 - 3.1 - 189 91 21,000 - 26 370 1,600 380 Overall 79 - 3.8 - 209 120 24,000 - 34 440 2,000 400 concentrations as mg/kg dry weight of sediment b „ Hg concentrations as ug/kg dry weight of sediment c P i t t and Amy (1973) 8. wastewaters concluded tha t the m a j o r i t y of the sewers c o n t a i n s u f f i c i e n t contaminants to be t o x i c to f i s h . The resea rchers measured heavy meta l and o rgan ic contaminant concen t r a t i ons and i n d i r e c t l y concluded tha t the heavy metals were p a r t i a l l y r e s p o n s i b l e fo r the t o x i c i t y . Due to the t o x i c e f f e c t of heavy meta l s on the a q u a t i c environment, an a rea of prime concern has been the b u i l d - u p of heavy me ta l concen t r a t i ons i n the F rase r R i v e r sediments , e s p e c i a l l y at the o u t f a l l s of sewage t r e a t -ment p l a n t s . A comparison of the heavy meta l concen t r a t i ons i n the sediments of the Iona I s l a n d sewage treatment p l an t to concen t r a t i ons a t four o ther l o c a t i o n s i s presented i n Tab le 3. There i s no b u i l d - u p of heavy meta l s a t the L u l u I s l a n d sewage treatment p l an t o u t f a l l due to the h i g h v e l o c i t y of the r i v e r at t h i s p o i n t and a l s o due to the f a c t t ha t the p l a n t has o n l y been o p e r a t i o n a l for three y e a r s . Around the Iona I s l and sewage treatment p l a n t o u t f a l l there appears to be i nc reases i n heavy meta l concen t r a t ions i n the sediments from 1.25 to 20 t imes the n a t u r a l background c o n c e n t r a t i o n s . G r i e v e and F l e t c h e r (12) i n a study concerned w i t h heavy meta l concen t r a t i ons as a f u n c t i o n of sediment g r a i n s i z e on the F rase r R i v e r D e l t a a l s o found i n c r e a s e s i n copper , l ead and z i n c a t the o u t f a l l of the Iona I s l a n d Sewage Treatment P l a n t . 2.3 Heavy M e t a l Removal Processes At the present time there are a number of d i f f e r e n t heavy meta l removal processes be ing resea rched . The three most f a m i l i a r processes a r e : i ) removal d u r i n g b i o l o g i c a l treatment i i ) carbon a d s o r p t i o n i i i ) l ime c o a g u l a t i o n . 2 . 3 . 1 B i o l o g i c a l Treatment I t i s g e n e r a l l y f e l t tha t the removal of heavy meta l s du r ing b i o l o g i c a l treatment can proceed by e i t h e r of three mechanisms: TABLE 3 A c o m p a r i s o n o f t h e heavy m e t a l c o n c e n t r a t i o n s i n t h e I o n a Dyke s e d i m e n t s t o t h o s e i n f o u r o t h e r l o c a t i o n s a round V a n c o u v e r . L o c a t i o n C iiGhriomium Copper Lead N i c k e l Z i n c (1) I ona Dyke 200 183 55 157 170 (2) L u l u I s ^ S . T . P . O u t f a l l " 18 21 34 4 25 (3) R o b e r t s Bank - 274 39 4 60 (4) Woodward I s . (Ma in Arm) - 39 62 6 50 (5) N o r t h Arm o f F r a s e r R i v e r - 34 40 16 72 (6) A ve rage o f 2 , 3 , 4 , 5 18 30 44 8 52 I n c r e a s e i n I ona Dyke C o n c e n t r a t i o n s o ve r 6 l l x 6x 1 .25x 20x 3.25x C o n c e n t r a t i o n s i n mg/Kg o f s e d i m e n t s . High velocity of river at this point does not allow sedimentation. 10 . i ) P r e c i p i t a t i o n o f m e t a l h y d r o x i d e s o r c a r b o n a t e s w i t h sub sequen t en t r apment i n t he b i o l o g i c a l f l o e . i i ) Some f o r m o f s o r p t i o n by t he o r g a n i c s o l i d s . i i i ) B i o l o g i c a l c e l l u p t a k e . The r e m o v a l e f f i c i e n c y f o r heavy m e t a l s by b i o l o g i c a l w a s t e t r e a t -ment has been s t u d i e d by s e v e r a l r e s e a r c h e r s and a summary o f t h e i r r e s u l t s i s p r e s e n t e d i n T a b l e 4 . The r e m o v a l e f f i c i e n c y appea r s t o be somewhat u n p r e d i c t a b l e . T h i s i s b e s t shown by c o m p a r i n g t h e t h r e e d i f f e r e n t sewage t r e a t m e n t p l a n t s s t u d i e d by B a r t h e t a l . (7) o v e r a 14 day s a m p l i n g p e r i o d . They f o u n d r e m o v a l r ange s o f 37 t o 82%, 16 - 73% , 8-78% and 53-85% f o r h e x a v a l e n t ch romium, c o p p e r , n i c k e l and z i n c r e s p e c t i v e l y . B a r t h e t a l . (6) s t u d i e d t he e f f e c t s o f c o p p e r , chromium, n i c k e l and z i n c , i n d i v i d u a l l y and i n c o m b i n a t i o n , on a c t i v a t e d s l u d g e t r e a t m e n t . P i l o t p l a n t s t u d i e s i n d i c a t e d t h a t a t o t a l heavy m e t a l c o n c e n t r a t i o n o f 10 mg/1 e i t h e r s i n g l y o r i n c o m b i n a t i o n , w o u l d r e d u c e t h e o v e r a l l p l a n t e f f i c i e n c y by abou t 5%. They f u r t h e r c o n c l u d e d t h a t n i t r i f i c a t i o n was i n h i b i t e d by heavy m e t a l s and t h a t t h e r e was no a c c l i m a t i o n o f t he n i t r i f y i n g o r g a n i s m s t o t h e m e t a l s . From t h e p r e v i o u s d i s c u s s i o n two c o n c l u s i o n s can be drawn c o n c e r n i n g heavy m e t a l r e m o v a l d u r i n g b i o l o g i c a l t r e a t m e n t . i ) The r e m o v a l e f f i c i e n c y i s u n p r e d i c t a b l e and t h e r e f o r e c anno t b e d e s i g n e d i n t o t h e s y s t e m . i i ) H i g h m e t a l c o n c e n t r a t i o n s appea r t o have a d v e r s e e f f e c t s on t h e t r e a t m e n t e f f i c i e n c y . 2 . 3 . 2 Ca rbon A d s o r p t i o n Ca rbon a d s o r p t i o n has been u sed as a p o l i s h i n g s t e p t o remove t h e r e f r a c t o r y o r g a n i c s t h a t c o n v e n t i o n a l b i o l o g i c a l t r e a t m e n t p r o c e s s e s f a i l t o remove. I n t he p a s t few y e a r s r e s e a r c h has been c a r r i e d ou t t o a p p l y t h i s TABLE 4 Heavy M e t a l Remova l d u r i n g B i o l o g i c a l Waste T r ea tmen t 1 • - - • R e s e a r c h e r % Rem o v a l C r Cu N i Zn J e n k i n e t a l . (2) 50 -70 . 5ppm* - - 60-80 10-l60ppm* McDermott e t a l . (2) -:• 50-79 .4-25ppm* 30 95-74 2 .5 -20ppm* M o o r e ' e t a l . (2) >99 .05ppm* - - — B a r t h (7) a) 40 b) 82 c ) 37 d) 80 16 73 23 12 78 8 58 85 53 t a) Grand R a p i d s , M i c h i g a n 14 day sample b) R i chmond , I n d i a n a 14 day sample c ) R o c k f o r d , I l l i n o i s 13 day sample d) B r y o n , Oh i o (50 l b . s l u g dose ) ^ i n i t i a l c o n c e n t r a t i o n r ange 12. p r o c e s s t o heavy m e t a l r e m o v a l . Westvaco (22) r e p o r t e d m e r c u r y l e v e l s < 50 ppb when an a c t i v a t e d c a r b o n p r o c e s s was a p p l i e d t o . a . c a u s t i c w a s t e s t r e a m f r o m a p u l p m i l l . A l t h o u g h t h e m e r c u r y . w a s p r e s e n t i n s e v e r a l f o rms ( m e t a l l i c d r o p l e t s , i n o r g a n s a l t s and o r g a n i c f o rms ) t h e r e m o v a l was s t i l l q u i t e h i g h . S m i t h (22) c o n -c l u d e d t h a t c a r b o n a d s o r p t i o n . m i g h t . b e a t t r a c t i v e f o r t h e r e m o v a l o f o t h e r t r a c e m e t a l s f o r t h e f o l l o w i n g r e a s o n s : i ) Ca rbon i s an e f f e c t i v e r e m o v a l agen t even a t v e r y l o w s o l u t i o n c o n c e n t r a t i o n s ; i i ) The r e m o v a l a c t i o n i s r e l a t i v e l y n o n - s p e c i f i c , t h a t i s , t h e c a r b o n . h a s a c a p a c i t y f o r t h e m e t a l i n s e v e r a l d i f f e r e n t f o r m s . i i i ) C a r bon c an be r e g e n e r a t e d and r e u s e d . L i n s t e d t e t a l . (8) i n c a r b o n a d s o r p t i o n p i l o t p l a n t s t u d i e s o b t a i n e d r e m o v a l s o f 9 7 . 1 % , 98 .8%, 96.96%?arid'4"<3,.?2%:for s i l v e r , cadmium, chromium and s e l e n i u m r e s p e c t i v e l y . The mechan i sm o f t h i s i n o r g a n i c r e m o v a l was s p e c u l a t e d t o be c au sed by t h e a d s o r p t i o n o f m e t a l o r g a n i c compounds r a t h e r t h a n t h e a d s o r p t i o n o f t h e m e t a l s a s i n o r g a n i c i o n s . The Orange County Water D i s t r i c t o p e r a t e d a p i l o t p l a n t c o n s i s t i n g o f l i m e c o a g u l a t i o n , ammonia s t r i p p i n g and a c t i v a t e d c a r b o n a d s o r p t i o n t o remove heavy m e t a l s f r o m s e c o n d a r y t r e a t e d e f f l u e n t ( 3 ) . The p i l o t p l a n t o b t a i n e d a v e r a g e r e m o v a l s o f 95%,? '70%?C30%dand :78%_for hexava-lent.;.-- -ch romium, c o p p e r , l e a d and z i n c r e s p e c t i v e l y . I t s h o u l d be n o t e d t h a t i n b o t h o f t h e p r e v i o u s l y m e n t i o n e d p i l o t p l a n t s t u d i e s c a r b o n a d s o r p t i o n was u sed as a p o l i s h i n g s t e p a f t e r t h e g r o s s m e t a l r e m o v a l was p e r f o r m e d by c o a g u l a t i o n and f i l t r a t i o n . 2 . 3 . 3 L ime C o a g u l a t i o n The p r e c i p i t a t i o n o f m e t a l h y d r o x i d e s i s dependent upon t h e 1 3 . c o n c e n t r a t i o n o f t h e m e t a l i o n i n s o l u t i o n and t h e pH o f t h e s o l u t i o n . The f o l l o w i n g e q u a t i o n i n d i c a t e s t h e i n t e r d e p e n d a n c y o f pH, m e t a l c o n c e n t r a t i o n and m e t a l s o l u b i l i t y ; a s pH i n c r e a s e s t h e s o l u b i l i t y o f t h e m e t a l h y d r o x i d e d e c r e a s e s . r M + n i r o H ~ i n = [M(OH) nJ sp T a b l e 5, t a k e n f r o m B r o u z e s ( 1 0 ) , l i s t s t h e s o l u b i l i t y p r oduc t s o f some heavy m e t a l o x i d e s o r h y d r o x i d e s . T h e o r e t i c a l l y , o f t h e m e t a l s s t u d i e d , 3+ C r s h o u l d y i e l d t h e b e s t r e m o v a l when p r e c i p i t a t e d w i t h l i m e a l o n e and t h e 2+ 2+ 2+ r e m o v a l s o f Cu , Pb and Zn s h o u l d be about t h e same. As w i l l be s een i n S e c t i o n 7 t h i s was t h e c a s e . T a b l e 6, r e p r o d u c e d f r o m A rgo and C u l p (11) g i v e s t h e r e s u l t s o f l i m e c o a g u l a t i o n t r e a t m e n t o f a number o f d i f f e r e n t t y p e s o f m u n i c i p a l and d o m e s t i c w a s t e s . I t a ppea r s t h a t f o r t h e m a j o r i t y o f t h e m e t a l s t e s t e d l i m e c o a g u l a t i o n - i s r e a s o n a b l y e f f e c t i v e . TABLE 5 S o l u b i l i t y P r o d u c t s o f C a t i o n i c Heavy M e t a l O x i d e s o r H y d r o x i d e s Compound Ksp SnO 1 x 1 0 - 6 1 Au (OH) - 8.5 x 1 0 - 4 5 T i ( O H ) 3 1 x l O " 4 0 F e ( O H ) . 6 x 1 0 - 3 8 C r ( O H ) - 1 x 10 HgO 3 x 1 0 " 2 6 Cu (OH) . - 19 3 x 10 Zn 4 .5 x 1 0 ~ 1 7 F e ( O H ) - 1.8 x 1 0 - 1 5 P b - 0 ( O H ) 2 1.6 x 1 0 - 1 5 C d ( O H ) 2 2 x 1 0 - 1 4 Mn(OH) - 1 3 2 x 10 J BiOOH 3 x 1 0 - 1 1 BaSO. 4 1 x l O "1 0 B a C 0 3 1.6 x 1 0 ~ 9 A g 2 0 2 x 1 0 - 8 15. TABLE 6: LIME COAGULATION AND RECARBONATION Metal Concentration Before Treatment mg/1 Concentration After Treatment mg/1 F i n a l pH Percent Removal Antimony''" 11 .90 Arsenic 1 11 <10 Barium 1 M..3(sol) 2 11 Bismuth 1 0.0002(sol) . 11 Cadmium Trace 11 -v50 0.0137 0.00075 >11 94.5 Chromium (+6) 0.056 0.050 >11 11 Chromium (+3) 7.400 2.7 •8.7 99.9+ Copper 15.700 0.79 8.7 7 1 8 86 7 0.05 9.5 93 302 Trace 9.1 99+ Gold 1 <.001(sol) 11 90+ Iron 13 2.4 9.1 82 17 0.1 10.8 99+ 2.0 1.23 10.5 40 Lead 1 <.0001(sol) 11 90+ Manganese 2.3 <0.1 10.8 96 2.0 l . l 3 10.5 45 21.0 0.05 9.5 95 Mercury 1 Oxide soluble <10 Molybdenum Trace 8.2 M0 Nickel 160 0.08 8.7 99.9+ 5 0.5 8 90 5 0.5 9.5 90 100 1.5 10.0 99 Selenium 0.0123 0.0103 >H 16.2 Silver 0.0546 0.0164 >11 , 97 1 4 Telurium (<0.001?) 11 (?90+) Titanium 1 4 (<0.001?) 11 (?90+) Uranium"* ? ? Zinc .007(sol) 11 90+ 1. The potential removal of these metals was estimated from s o l u b i l i t y data. 2. Barium and lead reductions and s o l u b i l i t i e s are based upon the carbonate. 3. These data were from experiments using iron and manganese i n the organic form. 4. Titanium and Telurium s o l u b i l i t y and s t a b i l i t y data made the potential reduction estimates unsure. 5. Uranium forms complexes with carbonate ion. Quantitative data were unavailable to allow determination of this effect. 6. Temperature: Ambient 20-25°C. 16 . CHAPTER 3 MAGNESIUM SOLUBILITY Stumm and Morgan (21) s t u d i e d t h e s y s t e m o f Mg-CO.-H-O f r o m two p o i n t s o f v i e w : 1) a s y s t e m w h i c h i s open t o t h e a tmosphe re and i s t h e r e f o r e i n e q u i l i b r i u m w i t h C O - ( g ) . 2) a s y s t e m w h i c h i s c l o s e d t o t h e a tmosphe re ( t h e y c o n s i d e r e d o n l y t h e s o l i d phase and t h e s o l u t i o n p h a s e , t h a t i s , H.CO- was t r e a t e d as a n o n - v o l a t i l e a c i d ) . 2+ A p r e d o m i n a n t s p e c i e s d i a g r a m f o r l o g ( M g ) = 0 and - 3 i s p r e s e n t e d i n F i g u r e 1 f o r t he open Mg-CO.-H-O s y s t e m . A t a p a r t i a l p r e s s u r e o f CG^ c o r r e s p o n d i n g t o t h a t o f t h e a tmosphere ( l o g P _ = - 3 . 5 ) t h e p r e d o m i n a n t s p e c i e o v e r t h e e n t i r e c o a g u l a t i o n r ange o f 10 .0 t o 11 .4 w o u l d be h y d r o m a g n e s i t e (Mg^CO^) ^ ( O H ) 2 3 H 2 0 ( s ) ) i f t h e s y s t e m was a t e q u i l i b r i u m w i t h r e s p e c t t o C 0 2 . 2+ A s o l u b i l i t y d i a g r a m ( - l o g ( M g ) v s pH) f o r t h e c l o s e d M g - C 0 2 ~ H 2 0 s y s t e m i s shown i n F i g u r e 2. I n t h i s c a s e b r u c i t e (Mg(OH) 2 ) i s t h e l e a s t s o l u b l e above pH 9 . The p r e d o m i n a n t s p e c i e unde r t h e c o a g u l a t i o n c o n d i t i o n s i s most p r o b a b l y Mg(OH)^ f o r t h e f o l l o w i n g r e a s o n s : 1) The a l k a l i n i t y i n t h e w a s t e w a t e r w i l l be u sed up i n i t i a l l y t o p r e c i p i t a t e l i m e as CaCO^ and t o p r e c i p i t a t e h y d r o x i d e c a r b o n a t e s ( e . g . h y d r o m a g n e s i t e M g ^ ( C O 3 ) 3 ( O H ) 2 . 3 H 2 0 ) and c a r b o n a t e s o f m u l t i v a l e n t c a t i o n s - 2 p r e s e n t . The CO^ s o u r c e i s g e n e r a l l y l i m i t e d t o t h e i n i t i a l a l k a l i n i t y - 2 b e c a u s e t h e r e i s u s u a l l y i n s u f f i c i e n t t i m e t o c o n v e r t C 0 2 ( g ) t o CO^ . A s suming t h a t t h e r e a c t i o n r a t e f o r M g ( 0 H ) 2 i s n o t s l o w e r t h a n t h e j a r t e s t r e a c t i o n t i m e , M g ( 0 H ) 2 w i l l p r e d o m i n a t e due t o t h e abundance o f h y d r o x -i d e . O t h e r magnes ium fo rms w i l l be p r e s e n t b u t i n l e s s e r amount s . 17 . F I G U R E I P R E D O M I N A N C E D I A G R A M F O R L o g ( M g ) = 0 A N D - 3 ( S T U M M A N D M O R G A N , 1 9 7 0 ) . -2H o - 4H 1- M g C 0 3 - 3 H 2 0 2- Mg 4 (C0 3 ) 3 JOH)2-3H 2 0 3"Mg(0H) 2 ' 1 1 1 1 1 5 7 9 II 13 P H ^ FIGURE 2 SOLUBILITY DIAGRAM. R§jR MAGNESIUM IN WATER AT ATMOSPHERIC CONDITIONS-TOTAL G E M M A T E = IO' 3M. (STUMM AND. MORGAN , 1970) 19. 2) The a f f i n i t y o f n a t u r a l a q u a t i c l i g a n d s o t h e r t h a n OH and CO^ 2 ( e . g . S and P O ^ 3 ) m i g h t f o r m more s t a b l e f o rms t h a n M g C O H ^ . A t t h e p r e c i p i t a t i o n pH t h e s e o t h e r s p e c i e s w i l l u s u a l l y be p r e s e n t i n much l o w e r c o n c e n t r a t i o n s t h a n OH and t h e r e f o r e t h e M g C O H ^ w i l l p r e d o m i n a t e . L a r s o n e t a l . (16) u sed s o l u b i l i t y p r o d u c t c o n s t a n t s o f T r a v e r s and N o u v e l (27) t o show t h e i n f l u e n c e o f t e m p e r a t u r e and pH on t h e s o l u b i l i t y o f magnes ium as shown i n F i g u r e 3. From t h e work o f L a n g l i e r (15) i t has been e s t a b l i s h e d t h a t t h e s o l u b i l i t y c u r v e s i n F i g u r e 3 w o u l d move up s l i g h t l y w i t h i n c r e a s i n g a l k a l i n i t y . T h a t i s t o s ay t h a t t h e s o l u b i l i t y wou l d be i n c r e a s e d w i t h i n c r e a s i n g a l k a l i n i t y . 2+ I n p r a c t i c e , t h e amount o f Mg i n . a q u e o u s s o l u t i o n unde r a g i v e n s e t o f c o n d i t i o n s ( i . e . pH , t e m p e r a t u r e , a l k a l i n i t y , TDS) i s h i g h e r t h a n t h a t p r e d i c t e d f r o m t h e o r y . T h i s comes about f o r s e v e r a l r e a s o n s . 1) The s y s t e m i s n o t a t e q u i l i b r i u m . 2) The f o r m a t i o n o f s o l u b l e h y d r o x o comp lexe s ( e . g . MgOH +) w i l l i n c r e a s e t h e o v e r a l l . m e t a l s o l u b i l i t y . The m e t a l s o l u b i l i t y (M £ ) c a n be e x p r e s s e d by t h e f o l l o w i n g e q u a t i o n : M = [ M 2 + ] + E [ M ( O H ) Z _ n ] t 2 n 3) The p r e s e n c e o f f o r e i g n l i g a n d s (L ^) w i l l f o r m s o l u b l e comp lexe s ( M L ) Z ^ w h i c h w i l l f u r t h e r i n c r e a s e t h e m e t a l s o l u b i l i t y . P P MAGNESIUM SOLUB IL ITY (a s parts per million C a C 0 3 ) BASED ON T H E SOLUB IL ITY PRODUCT C O N S T A N T S OF TRAVERS AND NOUVEL.( 1929) pH VARIATION WITH TEMP. DUE TO C H A N G E S IN H + A C T I V I T Y F I G U R E 3 T E M P E R A T U R E I N F L U E N C E ON M A G N E S I U M S O L U B I L I T Y . ( L A R S O N ET A L , 1 9 5 9 ) ( 1 6 ) 2 1 . CHAPTER 4 RESEARCH RATIONALE 4.1 H i s t o r y o f t h e L ime-Magnes ium P r o c e s s f o r Wate r R e n o v a t i o n The u se o f magnes ium i o n , p r e c i p i t a t e d i n s i t u as MgCOH)^ has been e s t a b l i s h e d as a s u c c e s s f u l c o a g u l a n t f o r t h e r e m o v a l o f d i s s o l v e d , c o l l o i d a l and su spended m a t e r i a l . Thompson e t a l . (26) d e m o n s t r a t e d t h a t MgCO^, p r e c i p i t a t e d w i t h l i m e , w o u l d remove o r g a n i c c o l o u r and t u r b i d i t y f r o m n a t u r a l w a t e r s . B l a c k e t a l . (8) f ound an i n c r e a s e d r e m o v a l e f f i c i e n c y f o r COD, su spended s o l i d s and c o l o u r when u s i n g l i m e and MgCO^ as compared w i t h l i m e a l o n e . B l a c k and Thompson (9 ) showed t h a t cadmium r e m o v a l was g r e a t l y enhanced by u s i n g magnes ium i n c o n j u n c t i o n w i t h l i m e . They a l s o f ound t h a t cadmium was n o t r e l e a s e d i n any s i g n i f i c a n t amounts on c a r b o n a t i o n t o r e s o l u b l i z e t he magnes -ium as MgCO^. Rush (21) showed t h a t a c o m b i n a t i o n o f l ow magnesium and l ow l i m e c o u l d a c h i e v e a b e t t e r d e c o l o u r i z a t i o n o f K r a f t m i l l e f f l u e n t s t h a n 3-5 t i m e s as much l i m e a l o n e . The h y d r a t e d Mg (OH) 2 p r e c i p i t a t e ha s a g e l a t i n o u s n a t u r e and t h e r e m o v a l mechan i sm i s p r o b a b l y some c o m b i n a t i o n o f a d s o r p t i o n , p r e c i p i t a t i o n , c o m p l e x a t i o n , f l o c c u l a t i o n and e n t r a p m e n t . 4 .2 A p p l i c a t i o n o f t h e l ime -magne s i um p r o c e s s t o Vancouve r w a s t e w a t e r s I t has been f a i r l y w e l l documented by H a l l e t a l . (15) t h a t BOD and su spended s o l i d s i n V a n c o u v e r ' s sewage a r e n o t o f p r i m e c o n c e r n due p r i m a r i l y t o h i g h d i s s o l v e d oxygen l e v e l s i n t he F r a s e r R i v e r . As was p r e v i o u s l y d i s c u s s e d , s e c o n d a r y t r e a t m e n t o f w a s t e w a t e r i s d e s i g n e d p r i m a r i l y f o r BOD and su spended s o l i d s r e m o v a l , w i t h t h e u n p r e d i c t a b l e s i d e b e n e f i t o f heavy m e t a l r e m o v a l . I n t he Vancouve r a r e a a more p r a c t i c a l p r o c e s s m i gh t be one a imed a t p r e d i c t a b l e heavy m e t a l r e m o v a l , w i t h t h e s i d e b e n e f i t o f BOD and su spended s o l i d s r e m o v a l . 22 . I t was f e l t t h a t r e s e a r c h was w a r r a n t e d t o see i f a c o a g u l a t i o n t y p e p r o c e s s c o u l d a c h i e v e t h i s e n d . A l i m e - m a g n e s i u m c o a g u l a t i o n was cho sen o v e r j u s t a s t r a i g h t l i m e c o a g u l a t i o n b e c a u s e o f t h e l ow n a t u r a l magnes ium l e v e l s i n t h e s u r r o u n d i n g w a t e r s (< 5, mg/1 (5) ) . I n a r e a s where t h e n a t u r a l magnes ium l e v e l s a r e h i g h , 2+ t h e r e i s a l r e a d y a s o u r c e o f Mg and t h e r e f o r e an enhancement i n r e m o v a l 2+ e f f i c i e n c y c a u s e d by a f u r t h e r Mg a d d i t i o n w o u l d n o t be e x p e c t e d . However , i t was f e l t t h a t f o r low magnes ium w a t e r s s u ch as i n V a n c o u v e r , t h e e f f e c t o f magnesium m i g h t p r o v e s i g n i f i c a n t . 23 . CHAPTER 5 EXPERIMENTAL.METHODS • AND MATERIALS  5.1 S e l e c t i o n o f E f f l u e n t The m a j o r i t y o f t h e r e s e a r c h was c a r r i e d ou t u s i n g p r e c h l o r i n a t e d p r i m a r y e f f l u e n t (PPE) f r o m t h e A n n a c i s I s l a n d Sewage T r e a t m e n t P l a n t . A s e r i e s o f e x p e r i m e n t s was a l s o done on raw sewage (RS) f r o m t h e same p l a n t i n o r d e r t o compare t h e r e m o v a l e f f i c i e n c i e s o f t h e two w a s t e s t r e a m s . E f f l u e n t f r o m t h e A n n a c i s I s l a n d sewage t r e a t m e n t p l a n t was cho sen becau se t h i s p l a n t c o n t r i b u t e s a l a r g e f l o w i n t o t h e F r a s e r R i v e r e s t u a r y and t h e r e a r e a number o f i n d u s t r i a l w a s t e s t r e ams t i e d i n t o i t s sewer s y s t e m . 5;2 S a m p l i n g P r o c e d u r e P r e c h l o r i n a t e d p r i m a r y e f f l u e n t was o b t a i n e d by s a m p l i n g t h e o v e r f l o w a t t h e d i s c h a r g e end o f t h e p r i m a r y s e d i m e n t a t i o n b a s i n u s i n g a p l a s t i c b u c k e t on a r o p e . A samp le o f about 10 I m p e r i a l g a l l o n s was t a k e n e v e r y Monday m o r n i n g w h i c h was a d e q u a t e f o r t h e we.efc.'.s t e s t i n g . I n i t i a l l y , sa one l i t r e sample o f raw sewage was t a k e n f o r an a l k a l i n i t y t i t r a t i o n . As t h e r e s e a r c h p rog ram p r o g r e s s e d , t h e samp le s i z e was changed t o 10 I m p e r i a l g a l l o n s , t o p r o v i d e s u f f i c i e n t sample f o r t h e raw sewage e x p e r i m e n t a t i o n . These s amp le s were t a k e n p r i o r t o t h e comminu to r s as t h i s was t h e most c o n v e n i e n t l o c a t i o n . I n o r d e r t o e l i m i n a t e d i l u t i o n e f f e c t s c au sed by s t o r m w a t e r f l o w s , no s a m p l i n g was done w i t h i n 8 h o u r s o f t h e c o m p l e t i o n o f a r a i n s t o r m w i t h i n t h e sewer c a t chmen t a r e a . T h i s p r e c a u t i o n was deemed n e c e s s a r y b e c a u s e a l a r g e p a r t o f t h e sewage c o l l e c t i o n s y s t em i s c o m p r i s e d o f comb ined s e w e r s . D i l u t i o n was assumed t o be p r e s e n t i f t h e a l k a l i n i t y o f e i t h e r sample was b e l o w t h e n o r m a l v a l u e o f 120-130 mg/1 as CaC0„ . 24. 5.3 Sample S t o r a g e A l l s amp le s were s t o r e d a t 3°C. P r i o r t o a c o a g u l a t i o n t e s t t h e s amp le s we re warmed t o 20°C i n a 35°C i n c u b a t o r w h i c h u s u a l l y t o o k abou t 1% h o u r s . 5.4 C h e m i c a l P r e p a r a t i o n s 5.4.1 Heavy M e t a l S p i k e S o l u t i o n s I n o r d e r t o t e s t t h e heavy m e t a l r e m o v a l e f f i c i e n c y o v e r a r ange o f i n i t i a l c o n c e n t r a t i o n s ( . 5 , 2.5 and 5.0 mg/1 M11"1") a s e t o f s t o c k s o l u t i o n s o f t he v a r i o u s heavy m e t a l s were p r e p a r e d each h a v i n g a c o n c e n t r a t i o n o f 1000 mg/1. A vo lume o f 200 m l was p r e p a r e d f o r each m e t a l f r o m the f o l l o w i n g compounds: Heavy M e t a l Compound C r 3 + C r C l 3 . 6 H 2 0 C u 2 + Cu S0 , . 5H„0 4 2 N i 2 + N i ( N O 3 ) 2 . 6 H 2 0 Z n 2 + Z n S 0 . . 7 H o 0 4 2 The s t o c k s o l u t i o n c o n c e n t r a t i o n was n o t c h e c k e d , b u t f o r e a ch e x p e r i m e n t a s p i k e d sewage sample was a n a l y s e d t o o b t a i n an e x a c t m e t a l i o n c o n c e n t r a -t i o n . 5 .4 .2 A t o m i c A b s o r p t i o n S t a n d a r d S o l u t i o n s The a t o m i c a b s o r p t i o n s t a n d a r d s o l u t i o n s were p r e p a r e d by a c c u r a t e l y d i l u t i n g F i s h e r C e r t i f i e d A . A . s t a n d a r d s t o t h e r ange .05 mg/1 t o 5.0 mg/1. 5 . 4 . 3 L ime D r y r e a g e n t g r ade C a ( 0 H ) 2 was cho sen f o r t h i s s t u d y as t h e p r e f e r r e d method o f l i m e a d d i t i o n . I m m e d i a t e l y p r i o r t o u sage t h e C a ( 0 H ) 2 powder was w e i g h e d a c c u r a t e l y on a S a r t o r i u s M o d e l 2442 b a l a n c e . S e l e c t i o n o f t h e method f o r l i m e a d d i t i o n i s d i s c u s s e d i n A p p e n d i x A . 25 . 5 .4 .4 Magnes ium i o n 4 2+ A 10 mg/1 Mg s o l u t i o n was c a r e f u l l y p r e p a r e d f r om MgSO .7H 0 4 ^ The e x a c t c o n c e n t r a t i o n was n o t o b t a i n e d by a n a l y s i s b e c a u s e i t was f e l t t h a t t h e c h e m i c a l p u r i t y w o u l d be a c c u r a t e enough , c o n s i d e r i n g t h e s m a l l vo lumes 4 2+ u s e d . A c o n c e n t r a t i o n o f 10 mg/1 Mg was s e l e c t e d t o m i n i m i z e d i l u t i o n o f 2+ t he c o a g u l a t i o n t e s t sample (1 m l = 16.7 mg/1 Mg ). The d e c i s i o n t o add magnes ium i n an i o n i c f o r m r a t h e r t h a n as MgCOH)^ i s d i s c u s s e d i n A p p e n d i x A. 5 .4 .5 Sod ium B i c a r b o n a t e 4 A 10 mg/1 as CaCO^ s o l u t i o n o f NaHCO^ was p r e p a r e d and was u sed t o i n c r e a s e t h e a l k a l i n i t y f r o m t h e n o r m a l 120-130 t o a p p r o x i m a t e l y 200 mg/1 as CaCO^ f o r c e r t a i n t e s t s . 5.5 A n a l y t i c a l T e c h n i q u e s 5 .5.1 A l k a l i n i t y A l k a l i n i t y was measured u s i n g t h e p o t e n t i o m e t r i c t i t r a t i o n method d e s c r i b e d i n " S t a n d a r d M e t h o d s " ( 1 ) . 5 . 5 .2 Heavy M e t a l A n a l y s i s A n a l y s i s o f heavy m e t a l c o n c e n t r a t i o n s was done f o l l o w i n g t h e a t o m i c a b s o r p t i o n p r o c e d u r e s d e s c r i b e d i n " S t a n d a r d M e t h o d s " (1) w i t h t h e e x c e p t i o n o f t h e p r e t r e a t m e n t p r o c e d u r e . A d i g e s t i o n c o n s i s t i n g o f a d d i n g lh m l o f HNO^ and 1 m l o f HC1 t o a 50 m l samp le and t h e n b o i l i n g f o r abou t 15 m i n u t e s was u sed i n p l a c e o f t h e more t i m e consuming t e c h n i q u e d e s c r i b e d i n " S t a n d a r d M e t h o d s " ( 1 ) . T e s t s c ompa r i n g t he two d i g e s t i o n p r o c e d u r e s p r o d u c e d i d e n t i c a l r e s u l t s . D i g e s t i o n p r o c e d u r e s f o r samples c o n t a i n i n g l e a d we re s l i g h t l y d i f f e r e n t . I t was f o u n d n e c e s s a r y t o c o n c e n t r a t e t h e samp le s by a f a c t o r o f f o u r i n o r d e r t o i n c r e a s e AA s e n s i t i v i t y . 26. A l l s amp le s e x c e p t z i n c were r u n on t h e J a r r a l l - A s h M o d e l 810 A t o m i c A b s o r p t i o n S p e c t r o p h o t o m e r . Z i n c w a s - r u n on t h e J a r r a l l - A s h M o d e l 500 due t o a v a i l a b i l i t y . T a b l e 7 summar i zes t h e A . A . o p e r a t i n g p a r a m e t e r s . 5 . 5 . 3 pH The pH was measu red on an Accumet M o d e l 810 pH m e t e r w h i c h was s t a n d a r d i z e d d a i l y a t pH 10 . 5.6 L ime-magnes ium C o a g u l a t i o n T e s t P r o c e d u r e The deve l opment o f t h e t e s t p r o c e d u r e i s d e t a i l e d i n A p p e n d i x A . TABLE 7 I n s t r u m e n t O p e r a t i n g P a r a m e t e r s M e t a l Lamp C u r r e n t X-N o n a b s o r b i n g X F lame I n s t r u m e n t C r 10 ma 3579 3520 r e d u c i n g J a r r a l l - A s h 810 Cu 7 ma 3247 N/A s l i g h t l y r e d u c i n g II Pb 10 ma 2320 2316 o x i d i z i n g II N i 8 ma 2170 2204 s l i g h t l y r e d u c i n g it Zn 7.5 ma 2138 N/A o x i d i z i n g J . A . 500 M i s c . 1) S c a l e e x p a n s i o n u sed i n a l l c a s e s . 2) F l a m e : a i r / a c e t y l e n e . 3) Pb samples c o n c e n t r a t e d 4x b y . b o i l i n g . 4) Backg round c o r r e c t i o n n o t r e q u i r e d f o r Cu and Z n . 2 8 . CHAPTER 6 RESULTS AND -DISCUSSION . 6 . 1 . The r e m o v a l e f f i c i e n c y o f - i n d i v i d u a l heavy m e t a l s f r o m PPE - U n f i l t e r e d R e s u l t s 6 .1 .1 Chromium 3+ F i g u r e s 4 , 5 and 6 show t h e r e m o v a l o f C r f r o m PPE w i t h i n c r e a s i n g 2+ pH and a t d i f f e r e n t Mg d o s a g e s ; The a v e r a g e l i m e do sage i s a l s o shown. 2+ A t a g i v e n l i m e d o s a g e , t h e pH t e n d e d t o d rop as t h e Mg c o n c e n t r a t i o n was i n c r e a s e d . The d rop i i i pH was abou t .1 pH u n i t s a t t h e l o w l i m e dosage (pH 10) and abou t .4 pH u n i t s a t t h e h i g h l i m e dosage (pH 1 1 4 ) . T h i s was t h e c a s e f o r a l l f i v e m e t a l s s t u d i e d . 2+ 3+ The e f f e c t o f Mg on C r r e m o v a l was most s i g n i f i c a n t a t t h e l o w -3+ 3+ 3+ e s t i n i t i a l C r c o n c e n t r a t i o n ( [ C r J i ) . A t [Cr ] ^ = .5 mg/1 a r e m o v a l o f 2+ 75% was o b t a i n e d by r a i s i n g t h e pH t o 1 0 . 0 4 . The a d d i t i o n a l 33 mg/1 o f Mg enhanced t h i s r e m o v a l t o 89%. The r e m o v a l was n o t s i g n i f i c a n t l y i n c r e a s e d 2+ 3+ by f u r t h e r Mg a d d i t i o n a t t h i s pH. A t pH 10.68 t h e C r r e m o v a l was 2+ enhanced f r o m 80 t o 91% by t h e a d d i t i o n o f 17 mg/1 o f Mg and w i t h o n l y 2+ m i n o r improvement a t h i g h e r Mg d o s a g e s . A t pH 11 .25 t h e a d d i t i o n o f 2+ 3+ 8 m g / l M g r e d u c e d t h e r e s i d u a l t o a p p r o x i m a t e l y .03 mg/1 C r . T h i s c o u l d o n l y be a p p r o x i m a t e d due t o a l a c k o f A . A . s e n s i t i v i t y a t t h i s c o n c e n t r a t i o n 2+ 3+ r a n g e . F o r Mg a d d i t i o n s >_ 8 m g / l , k t h e C r r e s i d u a l s a t t h e h i g h e r l e v e l s 3+ o f [C r ] . we re a p p r o x i m a t e d a t t h i s same v a l u e . 3+ 2+ A t [Cr ] = 2.5 mg/1 t h e e f f e c t o f Mg i s most s i g n i f i c a n t a t 2+ 3+ pH 10 . 04 . About 17 mg/1 Mg enhanced t h e Cr r e m o v a l f r o m 87 t o 94% and a t h i g h e r p H ' s t h e e f f e c t d i m i n i s h e s . 3+ 2+ A t [Cr ] ^ = 5.0 mg/1 t h e r e m o v a l i s v e r y h i g h and 8 mg/1 Mg a p p e a r s - t o i n c r e a s e t h e r e m o v a l by about 2% o v e r t h e e n t i r e pH r a n g e . An 2+ i n c r e a s e i n r e m o v a l by a Mg a d d i t i o n g r e a t e r t h a n 8 mg/1 d i d n o t o c c u r a> Q- 3 0 2 0 0 C r 3 + R E S I D U A L S ( m g / l ) \ pH 10.04 10.68 11.25 50 .06 .04 ~.03 33 .06 . 0 5 ~.03 17 .08 . 0 5 - . 0 3 8 .10 . 0 6 - . 0 3 0 . 14 .11 .05 1 I 10.0 10.50 pH II.0 I. 50 LIME DOSE (mg/1 163 2 3 6 415 F I G U R E 4 P E R C E N T C r 3 + R E M 0 V A L V s . p H A N D L I M E D O S A G E F O R [ C r 3 + ] . = 0 . 5 0 m g / 1 * M g 2 + D O S A G E ( m g / I ) 100 9 0 8 0 o 7 0 > b u 6 0 or A . 5 0 o ® 4 0 u u. °- 3 0 2 0 10 0 C r 3 * R E S I D U A L S ( m g / l ) 10.04 10.68 11.25 50 .10 . 0 6 ~.03 33 . 15 . 10 ~.03 17 .15 . 1 1 ~.03 8 .26 . 1 3 ~.03 0 .35 .19 .06 1 1 10.0 10.50 pH II.0 5 0 L IME D0SE(mg/l)l 163 2 3 6 415 F I G U R E 5 P E R C E N T C r 3 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ C r 3 + ] . = 2 . 5 0 m g / I * M g 2 + D 0 S A G E ( m g / 1 ) CL 3 0 2 0 10 0 C r 3 * RES IDUALS (mq/ I ) M g >^ 10.04 10.68 11.25 5 0 . 14 . 1 1 - . 0 3 33 . 18 . 0 9 ~ .03 1 7 . 16 .1 1 - . 0 3 8 . 18 .1 1 - . 0 3 0 . 3 0 .19 . 0 7 1 10.0 10.50 pH .0 I 1.50 L I M E D0SE(mg/l) 163 2 3 6 415 F I G U R E 6 P E R C E N T C r 3 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ C r 3 + ] . = 5 . 0 0 m g / I * M g 2 + D O S A G E ( m g / 1 ) 32. 2 + becau se a d d i t i o n a l Mg d i d no t f u r t h e r r e d u c e t he r e s i d u a l a t a g i v e n pH. 6 .1 .2 Copper 2+ F i g u r e s 7, 8 and 9 show t h e p e r c e n t Cu r e m o v a l f r o m PPE w i t h 2+ 2+ 2+ i n c r e a s i n g pH and a t d i f f e r e n t Mg d o s a g e s . The e f f e c t o f Mg on Cu r e m o v a l appea red t o be s i g n i f i c a n t t h r o u g h o u t t h e e n t i r e pH r ange t e s t e d . 2+ The d a t a i n d i c a t e d t h a t , as t h e pH i s i n c r e a s e d , a l e s s e r amount o f Mg i s r e q u i r e d t o a c h i e v e t h e maximum p r a c t i c a l r e m o v a l . The maximum p r a c t i c a l r e m o v a l i s d e f i n e d as t h e r e m o v a l beyond w h i c h t h e r e i s o n l y m i n o r i m p r o v e -2+ ment w i t h i n c r e a s e d Mg d o s a g e s . A t pH 10.01 f o r a l l t h r e e i n i t i a l c oppe r c o n c e n t r a t i o n s , t h e r e i s 2+ s t i l l improvement i n r e m o v a l up t o a t l e a s t 33 mg/1 Mg . Remova l i n c r e a s e s o f 22 t o 46%, 33 t o 54% and 50 t o 69% we re o b t a i n e d f o r i n i t i a l c o p p e r 2+ c o n c e n t r a t i o n s [Cu ] o f . 5 , 2 . 5 , 5.0 mg/1 r e s p e c t i v e l y , as a con sequence 2+ o f a Mg a d d i t i o n o f 33 mg/1. These r e s u l t s i n d i c a t e t h a t t h e e f f e c t o f 2+ Mg i s most s i g n i f i c a n t a t l o w e r i n i t i a l c oppe r c o n c e n t r a t i o n s . T h i s c o n c l u s i o n i s f u r t h e r d e m o n s t r a t e d a t pH 10.56 where r e m o v a l i n c r e a s e s o f 21.5 t o 60%, 54 t o 75% and 63 t o 82% were o b t a i n e d i n o r d e r o f i n c r e a s i n g 2+ 2+ [Cu j ^ a s a con sequence o f a d d i n g 33 mg/1 Mg . The maximum p r a c t i c a l r e m o v a l a t pH 10.56 i s a t 33 mg/1 Mg. The t r e n d o f i n c r e a s e d r e m o v a l w i t h 2+ 2+ i n c r e a s e d [Cu ] - a t c o n s t a n t pH and Mg dosage was f ound t o be t r u e f o r a l l m e t a l s s t u d i e d . 2+ A t pH 11.39 o n l y 8 mg/1 Mg a p p e a r e d t o a c h i e v e t h e maximum 2+ p r a c t i c a l r e m o v a l . A s t h e [Cu ] was i n c r e a s e d f r o m .5 t o 5.0 mg/1 r e m o v a l i n c r e a s e s o f 58 t o 7 0 . 5% , 84 t o 92% and 88 t o 95% were o b t a i n e d r e s p e c t i v e l y . 2+ Cu r e s i d u a l a p p e a r e d t o r e a c h a minimum v a l u e o f .14 - .16 mg/1 2+ a t pH 11.39 and Mg dosage g r e a t e r t h a n 17 mg/1. T h i s c o n s t a n t r e s i d u a l a p p e a r e d t o be i n d e p e n d e n t o f t h e i n i t i a l c o p p e r c o n c e n t r a t i o n w i t h i n t h e r ange s t u d i e d . L I M E DOSE(mg/l) 10.0 168 10.50 216 pH II.0 11.50 3 9 5 2 + F I G U R E 7 P E R C E N T C u ' R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ C u 2 + ] . = 0 . 5 0 m g / I i * M g 2 + D O S A G E ( m g / 1 ) 34. 1 0 0 9 0 8 0 o 7 0 > o © 6 0 or + CM o a. 5 0 5 4 0 3 0 2 0 10 0 1 10.0 1 0 . 5 0 1 r C u ' RES IDUALS ( m g / l ) 10.01 10.56 11.39 5 0 1.04 .56 .14 3 3 1.08 . 5 9 .14 1 7 1.15 . 7 0 .16 8 1.30 .93 .20 0 1.35 1.09 .38 _L_L 11.0 I 1.50 pH L I M E D0SE(mg/l)| 168 216 3 9 5 F I G U R E 8 P E R C E N T C u 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ C u 2 + ] = 2 . 5 0 m g / l i * M g 2 + D O S A G E ( m g / I ) LIME DOSE(mg/l) 10.0 6 8 1 0 . 5 0 216 . 0 I 1.50 pH 3 9 5 F I G U R E 9 P E R C E N T C u 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ C u 2 * ] . " 5 . 0 0 ' m g / I i * M g 2 + D O S A G E ( m g / 1 ) 6 . 1 . 3 L e a d 2+ F i g u r e s 1 0 , 11 and 12 show p e r c e n t Pb r e m o v a l w i t h i n c r e a s i n g pH 2+ 2+ and a t d i f f e r e n t Mg a d d i t i o n s . 1 As was t h e c a s e w i t h Cu , t h e e f f e c t o f 2+ 2+ Mg on Pb r e m o v a l i s most s i g n i f i c a n t a t t h e l o w pH r a n g e . A t pH 9.86 2+ t h e Pb r e m o v a l was i n c r e a s e d - f r o m . a b o u t 40% t o abou t 75% by t h e a d d i t i o n 2+ o f 33 mg/1 Mg . T h i s i n c r e a s e i n r e m o v a l a p p e a r e d t o be i n d e p e n d e n t o f 2+ 2+ i n i t i a l Pb c o n c e n t r a t i o n ( [Pb ]/ ) o v e r t h e r ange s t u d i e d . 2+ A t pH 10 .56 t h e a d d i t i o n o f be tween 17 -33 mg/1 Mg i n c r e a s e d t h e 2+ 2& Pb r e m o v a l by abou t 8% a n d . t h i s a ppea red t o be i n d e p e n d e n t o f [Pb " ] . . 2+ 2+ A t pH 11 .18 t h e e f f e c t o f Mg was m i n i m a l . A t [Pb ] ^ = 2.5 and 5.0 mg/1, t h e a d d i t i o n o f 8 mg/1 i n c r e a s e d t h e r e m o v a l by about 2%. A t 2+ [Pb ] ^ = .5 mg/1 t h e d a t a was i n c o n s i s t e n t and m a y ' i n f a c t be i n e r r o r due 2+ t o samp le c o n t a m i n a t i o n . The r e s i d u a l s o b t a i n e d f o r Mg do sage s o f 0 and 8 mg/1 we re t h e same a t pH 10.56 and 1 1 . 1 8 . ( (F igure 1 0 ) . T h i s i s i n d i s a g r e e -ment w i t h a l l o t h e r r e s u l t s o b t a i n e d f o r any o f t h e f i v e m e t a l s a t any i n i t i a l c o n c e n t r a t i o n . • 6 . 1 . 4 N i c k e l 2+ F i g u r e s 1 3 , 14 and 15 show t h e r e m o v a l o f N i f r o m PPE w i t h 2+ 2+ i n c r e a s i n g pH and a t d i f f e r e n t Mg d o s a g e s . The r e m o v a l o f N i ' i noEeS sed w i t h i n c r e a s i n g pH b u t i t was h a r d l y a f f e c t e d a t a l l by t h e a d d i t i o n o f 2+ Mg . The o n l y r e m o v a l enhancement o f any s i g n i f i c a n c e was f o r t h e h i g h pH 2+ t r e a t m e n t o f t h e samp le w i t h an i n i t i a l N i c o n c e n t r a t i o n o f v5 mg/1. I n t h i s c a s e t h e r e m o v a l was i n c r e a s e d f r o m 45 t o 57% w i t h t h e a d d i t i o n o f 8 mg/1 «pl I 2~t* 2H- 21 o r more o f Mg . As was t h e c a s e w i t h Cu , t h e e f f e c t o f Mg on N i 2+ r e m o v a l i s most s i g n i f i c a n t a t l o w i n i t i a l N i c o n c e n t r a t i o n s . 6 . 1 . 5 Z i n c 2+ F i g u r e s 1 6 , 17 and 18 show t h e r e m o v a l o f Zn w i t h i n c r e a s i n g pH a 4 0 o a> °- 3 0 2 0 IQ 0 P b 2 + R E S I D U A L S ( m g / l ) J 1 M g * * \ 9.86 10.56 11.18 5 0 • 1 1 .07 .025 33 . 14 . 0 8 .05 17 . 15 . 0 9 .03 8 . 19 . 0 9 .09 0 .2 9 . II .10 10.0 10 .50 II.0 II. 5 0 pM L IME D0SE(mg/l)| 144 228 327 F I G U R E 10 P E R C E N T P b 8 * R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ P b 2 + ] . = 0 . 5 0 m g / l « M g 2 + D O S A G E ( m g / 1 ) Q) a. 3 0 2 0 10 0 P b 2 + R E S I D U A L S ( m g / l ) J L 11 9.86 10.56 11.18 5 0 . 51 .15 .13 3 3 — .14 .16 17 . 6 5 . 2 0 — 8 — . 28 .19 0 1.65 — .21 10.0 10 .50 II. 0 11.50 pH LIME D0SE(mg/l) 144 2 2 8 3 2 7 F I G U R E II P E R C E N T P b 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ P b 2 + ] . = 2 . 5 0 m g / | * M g 2 + D O S A G E ( m g / 1 ) 0) o. 3 0 2 0 0 P b 2 + R E S I D U A L S ( m g / l ) M g 2 > \ 9.86 10.56 11.18 50 — .12 .09 3 3 1.20 .15 . 1 1 17 1.30 — — 8 1.50 .33 .13 0 2.93 . 6 4 .21 10.0 10 .50 1.0 11.50 pH L IME D0SE(mg/l) 144 2 2 8 3 2 7 F I G U R E 12 P E R C E N T P b 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ P b 2 + ] . s 5 . 0 0 m g / l * M g 2 + D 0 S A G E ( m g / 1 ) 1 0 0 9 0 8 0 o 7 0 I-o E o, 6 0 cr. + (VI - 5 0 •z 0) o 4 0 CD * o. 3 0 2 0 10 0 T T 10.0 10. 5 0 N i * R E S I D U A L S ( m g / l ) 9.97 10.54 11.40 5 0 .61 .58 .29 8 .61 . 58 .28 0 .63 .61 .37 1.0 . 5 0 pH LIME D0SE(mg/l) 131 9 3 3 9 2 F I G U R E 13 P E R C E N T N i 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ N i 2 + ] = 0 . 5 0 m g / 1 * M g 2 + D O S A G E ( m g / I ) ' 41. LIME DOSE(mg/l) 10.0 31 10.50 I 9 3 1.0 5 0 pH 3 9 2 F I G U R E 1 4 P E R C E N T N i 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ N i 2 + ] = 2 . 5 0 m g / l i * M g 2 + D O S A G E ( m g / 1 ) + A B N O R M A L L Y H I G H p H V A L U E ( I 0 . 9 2 ) 100 9 0 8 0 > 7 0 o E a> 6 0 or ~_ 5 0 5 4 0 o i _ a. 3 0 2 0 1.0 0 T T 11 10.0 TT N i 2 + R E S I D U A L S ( m g / l ) 9.97 10.54 11.40 5 0 1.75 1.25 . 14 33 1.75 1.40 — 17 1.75 1.30 ' — 8 1.65 1.50 . 18 0 1.75 1.40 .28 10.50 5 0 pH LIME D0SE(mg/l) 13 I 9 3 3 9 2 2 + F I G U R E 15 P E R C E N T N T ' R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ N i 2 + ] . = 5 . 0 0 m g / l * M g 2 + D O S A G E ( m g / I ) 43 . 2+ and a t d i f f e r e n t Mg d o s a g e s . 2+ 2+ The r e m o v a l o£ Zn was s i m i l a r t o Cu i n t h a t i t was a f f e c t e d 2+ • by t h e a d d i t i o n o f Mg o v e r t h e e n t i r e r ange o f pH t e s t e d , b u t t h e a f f e c t was most s i g n i f i c a n t i n - t h e l o w pH r a n g e . A t pH 10 .07 t h e i n c r e a s e s i n 2+ r e m o v a l due t o t h e a d d i t i o n o f 50 mg/1 o f Mg were t h e l a r g e s t o f a n y . o f 2+ 2+ t h e 5 m e t a l s t e s t e d . F o r i n i t i a l Zn c o n c e n t r a t i o n [Zn ] o f , .5, r>2a5dand" 5.0 mg/,1 t h e i n c r e a s e s i r i p e r c e n t r e m o v a l were f r o m 20 t o 6 2 , f r o m 40 t o 86 .5 2+ and f r o m 18 t o 77 r e s p e c t i v e l y . A t t h i s pH t h e c o n s t a n t Mg dosage c u r v e s 2+ show no i n d i c a t i o n o f c o n v e r g i n g a t h i g h Mg c o n c e n t r a t i o n s . T h i s 2+ i n d i c a t e s t h a t do sage s g r e a t e r t h a n 50 mg/1 Mg m i g h t be r e q u i r e d i n o r d e r t o r e a c h t h e maximum p r a c t i c a l r e m o v a l . 2+ A t pH 10 .59 t h e maximum p r a c t i c a l r e m o v a l was o b t a i n e d w i t h a Mg. do sage i n t h e 33 -50 mg/1 r a n g e . The i n c r e a s e a v e r a g e d 13;5 p e r c e n t a g e p o i n t s f o r t h e t h r e e i n i t i a l c o n c e n t r a t i o n s . 2+ A t pH 11.36 t h e maximum p r a c t i c a l r e m o v a l f o r [Zn ] . o f 2.5 and 2+ 5.0 mg/1 w a s o b t a i n e d w i t h a Mg do sage o f 8 mg/1. The i n c r e a s e a ve r a ged 2+ 9.0 p e r c e n t a g e p o i n t s . The r e s i d u a l s o b t a i n e d f o r [Zn ] ^ =-.5 mg/1 a t pH 11.36 were a p p r o x i m a t e l y .04 mg/1: Due t o a l a c k o f A . A . s e n s i t i v i t y no ?+2+ s i g n i f i c a n t improvement was nbt iceaBleybyhifehedaddi i t id ionfoMgMg. . 6 .1 .6 Summary The d e g r e e t o w h i c h t h e a d d i t i o n o f magnes ium i o n s i m p r o v e s t h e r e m o v a l o f t e s t e d heavy m e t a l s ha s been shown t o be dependent u p o n . t h e f o l l o w i n g : s p e c i e s o f m e t a l i o n ; c o n c e n t r a t i o n o f imetfala i o n ; and r e a c t i o n s pH.pH. To p r o v i d e some i d e a o f t h e w o r t h o f magnes ium a d d i t i o n , T a b l e 8 2+ summar i zes t h e Mg . a d d i t i o n s . r e q u i r e d t o o b t a i n t h e maximum p r a c t i c a l r e m o v a l f o r e a c h d i f f e r e n t s e t o f e x p e r i m e n t a l c o n d i t i o n s . LIME DOSE(mg/l) 10.0 10.50 pH 5 0 140 212 3 9 5 F I G U R E 1 6 P E R C E N T Z n 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ Z n 2 + ] = 0 . 5 0 m g / I • i * M g 2 + D O S A G E ( m g / 1 ) LIME DOSE(mg/l) 10.0 10.50 pH I 1.0 11. 5 0 1 4 0 212 3 9 5 F I G U R E 17 P E R C E N T Z n 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ Z n 2 + ] . = 2 . 5 0 m g / I * M g 2 + D O S A G E ( m g / 1 ) LIME DOSE(mg/l) 10.0 1 0 . 5 0 II.0 . 5 0 pH 140 212 3 9 5 F I G U R E 18 P E R C E N T Z n 2 + R E M O V A L V s . p H A N D L I M E D O S A G E F O R [ Z n 2 * ] . = 5 . 0 0 m g / I * M g 2 + D O S A G E ( m g / 1 ) TABLE 8 E f f e c t i v e Mg Dosages f o r t h e F i v e Heavy M e t a l s under D i f f e r e n t C o n d i t i o n s o f [M ] . and pH Chromium Copper L e a d N i c k e l Z i n c I n i t i a l C o n c e n t r a t i o n .5 2.5 5.0 .5 2.5 5.0 .5 2.5 5.0 .5 2.5 5.0 .5 2.5 5.0 pH . 10 .0 33 17 <8 + 33 33 33 ^33 ^33 33 8 0 0 >50 >50 50 10.6 17 8-17 <8 + 33 33 33 . 17 17 38 8 8 8 33 17 -33 17 -3 . 11 .4 8 + 8 + <8 + 8 8 8 . 8-17 8 8 0 0 8 8 8 m i n i m a l improvement ( o n l y p r a c t i c a l where opt imum r e m o v a l r e q u i r e d ) 48 . 6.2 The r e m o v a l e f f i c i e n c y o f i n d i v i d u a l m e t a l s i n PPE - F i l t e r e d v s  U n f i l t e r e d R e s u l t s A c o m p a r i s o n o f t h e r e m o v a l e f f i c i e n c i e s o b t a i n e d w i t h f i l t e r e d and u n f i l t e r e d s e t t l e d f i n a l e f f l u e n t i s shown i n T a b l e s 9, 10 and 1 1 . These t a b l e s i n d i c a t e t h a t t h e r e m o v a l e f f i c i e n c y i s o n l y i m p r o v e d about 1 t o 2 p e r c e n t w i t h t h e a d d i t i o n o f a f i l t r a t i o n s t e p (#2 Whatman f i l t e r 2+ p a p e r ) i n t h e p r o c e s s . The o n l y e x c e p t i o n a p p e a r s t o be t h a t o f Zn . The improvement c au sed by f i l t r a t i o n was abou t 8 p e r c e n t a g e p o i n t s a t pH 10 , 4 .4 a t pH 10.6 and 5.4 a t pH 1 1 . 4 . 6.3 The r e m o v a l e f f i c i e n c y o f m i x e d m e t a l s f r o m PPE - U n f i l t e r e d and  F i l t e r e d R e s u l t s A s e t o f e x p e r i m e n t s was p e r f o r m e d on e f f l u e n t t h a t had been s p i k e d t o a p p r o x i m a t e l y .50 mg/1 M n + w i t h each o f t h e f i v e m e t a l s p r e v i o u s l y 2+ t e s t e d . U n f o r t u n a t e l y , t h e Pb was u n d e r s p i k e d t o .125 mg/1 so t h e s e r e s u l t s c o u l d n o t be compared t o t h e i n d i v i d u a l m e t a l r u n s . The r e s u l t s o f t h e s e e x p e r i m e n t s were compared t o t h e r e s u l t s o f t h e .50 mg/1 i n d i v i d u a l m e t a l r u n s p r e v i o u s l y p e r f o r m e d . The c o m p a r i s o n s a r e shown i n T a b l e s 12 , 13 and 14. Of t h e 12 c o m p a r i s o n s shown, t h e o n l y 2+ 2+ t h r e e t h a t d i d n o t compare v e r y w e l l a r e Zn a t pH 10 and N i a t pH 10.6 and 1 1 . 4 . The r e a s o n f o r t h e s e d i f f e r e n c e s i s unknown b u t i t may be r e l a t e d t o t h e s l i g h t d i f f e r e n c e s i n i n i t i a l c o n c e n t r a t i o n s o f t h e i n d i v i d u a l and m i x e d heavy m e t a l e x p e r i m e n t s . T a b l e 15 g i v e s a c o m p a r i s o n o f t h e p e r c e n t a g e r e m o v a l s o f heavy m e t a l s f r o m f i l t e r e d and u n f i l t e r e d s amp le s f o r t h e e x p e r i m e n t s p e r f o r m e d w i t h m i x e d heavy m e t a l s i n PPE . As was t h e c a s e w i t h t h e i n d i v i d u a l m e t a l s , t h e r e appea r s t o be o n l y m i n o r improvement i n r e m o v a l due t o f i l t r a t i o n . 49 . TABLE 9 P e r c e n t Remova l s f o r F i l t e r e d and U n f i l t e r e d Samples o f I n d i v i d u a l Heavy M e t a l s i n P r e c h l o r i n a t e d P r i m a r y E f f l u e n t a t I n i t i a l C o n c e n t r a t i o n = .5-mg/1. pH 10 . 0 Mg Chromium Copper N i c k e l Z i n c L e a d Dose (mg/1) F i l t e r e d U n f i l t e r e d F Unf F Unf F Unf F Unf 0 75 75 22 6 6 31 20 50 44 8.33 84 82 28 9 9 51 47 62 63 16.66 - 86 44 - - 56 47 71 71 33 .33 89 89 46 - - 67 56 73 74 50 . 0 89 89 54 9 9 69 62 78 78 pH 10.6 0 - 80 37 33 13 .4 9 67 78 78 8.33 - 89 48 44 13 .4 13 .4 ate 75 82 82 16.66 - 91 52 50 - - min 81 83 83 33 .33 - 91 60 60 - - nta 81 84 84 50 . 0 - 93 62 60 13 .4 13 .4 o S3 83 86 87 pH 11 .4 0 >95 >95 60 If* 56 42 45 89 90 83 80 8 .33 >95 >95 73 71 55 58 93 91 93 83 16.66 >95 >95 - - - - 93 92 95 94 33 .33 >95 >95 73 73 - - 92 91 95 93 50 .0 >95 >95 75 73 55 57 - - 95 95 5 0 . TABLE 10 P e r c e n t Remova l s f o r F i l t e r e d and U n f i l t e r e d Samples o f I n d i v i d u a l Heavy M e t a l s i n P r e c h l o r i n a t e d P r i m a r y E f f l u e n t a t I n i t i a l C o n c e n t r a t i o n =.2.5 mg/1 pH 1 0 . 0 Mg Dose Chromium Coppe r N i c k e l Z i n c Lead. (mg/1) F i l t e r e d U n f i l t e r e d F Unf F Unf F Un f F Unf 0 88 87 33 33 39 44 40 45 34 8 .33 91 90 47 43 42 39 ated 58 78 _ 16.66 95 94 52 50 - -tamin; 73 81 74 33 .33 93 94 60 53 - - Con 73 85 -5 0 . 0 95 96 61 55 - 42 85 88 80 pH 10 .6 0 93 93 55 54 57 58 75 70 - -8 .33 95 95 63 60 62 63 89 78 89 87 16 .66 96 96 71 70 - - 90 85 92 -33 .33 96 96 77 75 - - 91 89 95 -50 . 0 97 97 77 76 58 - 92 91 94 94 pH 11 .4 0 97 97 85 84 87 94 93 84 95 92 8 .33 99 99 92 92 94 87 96 82 96 93 16 .66 99 99 93 93 - - 96 86 97 -33 .33 99 99 94 94 - - 93 86 -. 94 50 . 0 99 99 94 94 95 96 94 87 98 95 51. TABLE 11 P e r c e n t Remova l s f o r F i l t e r e d and U n f i l t e r e d Samples o f I n d i v i d u a l Heavy M e t a l s i n P r e c h l o r i n a t e d P r i m a r y E f f l u e n t a t I n i t i a l C o n c e n t r a t i o n =5.0 mg/1 pH 10.0 Mg Dose Chromium Coppe r N i c k e l Z i n c L e a d (mg/1) F i l t e r e d U n f i l t e r e d F Unf F Unf F Unf F Unf 0 95 94 56 50 56 60 '31 18 42 8.33 97 97 62 60 63 63 40 18 70 16.66 97 97 68 66 60 60 57 48 74 33.33 97 97 72 69 60 60 70 64 76 50.0 98 97 75 72 60 60 81 77 -pH 10.6 0 97 96 66 63 68 68 85 79 90 87 8.33 98 98 74 73 67 66 89 85 94 94 16.66 98 98 78 75 71 71 94 89 96 -33.33 99 98 83 82 71 68 - 92 98 97 50.0 98 98 84 83 74 72 75 94 98 98 pH 11.4 0 99 99 89 88 95 95 89 96 8.33 99 99 95 95 97 97 OJ 4-1 98 98 97 16.66 99 99 96 96 - - •H 98 93 -33.33 99 99 97 97 - - a o o 99 99 98 50.0 99 99 - 97 97 97 99 99 98 TABLE 12 Compa r i s on o f t h e I n d i v i d u a l M e t a l Remova l s t o t h e Combined M e t a l Removals a t pH 10 .0 (App rox . ) « g 2 + Dose (mg/1) Chromium Copper N i c k e l Z i n c I n d i v i d u a l C o m b i n a t i o n Ind Comb Ind Comb Ind Comb R e s i d u a l Remova l Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem 0 .14 75.0 .14 73.1 .42 22 .38 34.5 .63 6.0 .47 16 .1 .36 20 .26 51 .9 8 .33 .10 82.1 .09 82.7 .39 28 .34 41 .4 .61 9.0 .47 16.1 .24 46.7 .20 63 .0 16 .66 .08 85.7 .09 82.7 .30 44 .34 41 .4 - - .47 16.1 .24 46.7 .18 66.7 33 .33 .06 89 .3 .07 86.5 .29 46 .32 44 .8 - - .47 16 .1 .20 55.6 .10 81 .5 50 .0 .06 89 .3 .07 86.5 .25 54 .34 41 .4 .61 9.0 .47 16 .1 .17 62.2 .12 77.8 I n i t i a l Cone. .56 .52 .54 .58 .67 .56 .45 .54 Avg pH 10 .04 9. 94 10.01 9 .94 9. 97 9 .94 10 07 9. 94 TABLE 13 Compar i s on o f t h e I n d i v i d u a l M e t a l Remova l s t o t h e Combined M e t a l Remova l s a t pH 10 .60 ( A p p r o x . ) „, 2+ Chromium Copper N i c k e l Z i n c Mg Dose I n d i v i d u a l C o m b i n a t i o n Ind Comb Ind Comb Ind Comb (mg/1) R e s i d u a l Remova l Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem 0 .11 80 .4 .04 92.7 .35 33 .26 56 .1 .61 9 .49 15 .5 .16 66.7 .19 61 .4 8 .33 .06 89 .3 .05 90.9 .29 44 .24 60 .58 13.4 .46 20.7 .12 75 .10 80 16 .66 .05 91.1 <.03 >95 .26 50 .23 61.7 - - .40 31 .09 81 .08 84 33 .33 .05 91.1 <.03 >95 .21 60 .25 58 .3 - - .40 31 .09 81 .09 82 50 . 0 .04 92.8 <.03 >95 .21 60 .23 61.7 .58 13 .4 .38 34 .5 .08 83 .3 .07 86 I n i t i a l Cone. .56 .55 .52 .60 .67 .58 .49 .50 Avg pH 10.68 10 .56 10 56 10 .56 10 .54 10 56 10.59 10.56 TABLE 14 Compa r i s on o f t h e I n d i v i d u a l M e t a l Remova l s t o t h e Combined M e t a l Remova l s a t pH 11.4 ( A p p r o x . ) M g 2 + Dose Chromium Copper N i c k e l Z i n c I n d i v i d u a l C o m b i n a t i o n Ind Comb Ind Comb Ind Comb (mg/1) R e s i d u a l Remova l . Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem 0 - . 0 5 91 <.02 >96 .23 56 .20 66 .7 .37 44.7 .30 48 .3 ! .045 90 .045 91 8.33 ^ . 0 3 >95 <.02 >96 - - .19 68 .3 .28 58 .2 .32 44 .8 .040 91.1 .045 91 16 .66 ^ . 03 >95 <.02 >96 .15 71 .175 70.8 - - .27 53 .4 .0.35 92.2 .045 91 33 .33 ^ . 03 >95 <.02 >96 .14 73 .17 71.7 - - .28 51 .7 .040 91.1 .045 91 50 .0 ^ . 03 >95 <.02 >96 .14 73 .165 72.5 .29 56 .7 .32 44 .8 - - .040 92 I n i t i a l Cone. .52 .55 .52 .60 .67 .58 .45 .50 Avg pH 11 . 25 11 .13 11.39 11 .13 11 .40 11 .13 11 . 36 11 .13 55 . TABLE 15 P e r c e n t Remova l s f o r F i l t e r e d and U n f i l t e r e d Samples o f C o m b i n a t i o n s o f Heavy M e t a l s i n P r e c h l o r i n a t e d P r i m a r y E f f l u e n t pH 1 0 . 0 M g 2 + Chromium C o p p e r N i c k e l Z i n c Dose (mg/D F i l t e r e d U n f i l t e r e d F Unf F Unf F Un f 0 75 73 .1 31 . 0 34 .5 16 .1 16 .1 - -8.33 82 .7 8 2 . 7 37 .9 41 .4 17 .9 16 .1 - -16.66 84 .6 82 .7 34 .5 41 .4 17 .9 16 . 1 - -33 .33 88 .5 8 6 . 5 41 .4 44 . 8 - 16 .1 - -50 .0 88 .5 86.5 - 41 .4 - - - -pH 10 .6 0 - 92 .7 54 . 7 56 .1 31 15 .5 80 .0 61 .4 8 .33 >94.5 90 .9 5 8 . 3 60 . 0 31 20.7 81.4 80 . 0 16.66 >94.5 94 .5 6 0 . 0 61 .7 36 .2 31 .0 36.0 84 .0 33 .33 >94.5 94.5 5 8 . 3 59 . 0 37 .9 31 . 0 82 .0 82 . 0 50 .0 >94.5 94 .5 5 5 . 0 61.7 37 .9 34 .5 32.0 8 6 . 0 pH 11 .4 0 >96.3 >96.3 64 . 2 66 .7 46.6 48 .3 - -8.33 >96.3 >96.3 65 . 0 68 .3 46.6 44 .8 - -16.66 >96.3 >96.3 - 70.8 53.4 53 .4 - -33.33 >96.3 >96.3 68 . 3 71 .1 53.4 51 .7 - -50 .0 >96.3 >96.3 70 .0 72.5 44 .8 j 4 4 . 8 -56 . 6.4 The r e m o v a l e f f i c i e n c y o f m i x e d m e t a l s f r o m Raw Sewage - U n f i l t e r e d and  F i l t e r e d R e s u l t s A s e t o f e x p e r i m e n t s were p e r f o r m e d on raw sewage t h a t had been s p i k e d t o a p p r o x i m a t e l y .50 mg/1 M ^ w i t h e a c h o f t h e f i v e heavy m e t a l s . The r e s u l t s o f t h e s e e x p e r i m e n t s were t h e n compared t o t he m i x e d m e t a l r e s u l t s p e r f o r m e d on PPE . Compa r i s on s o f t h e r e s i d u a l s and t h e r e m o v a l e f f i c i e n c i e s a r e shown i n T a b l e s 16 , 17 and 18 . S i n c e no m i x e d m e t a l PPE 2+ 2+ r e s u l t s were o b t a i n e d f o r Pb , t h e i n d i v i d u a l Pb r e s u l t s were s u b s t i t u t e d . The c o m p a r i s o n s f o r t h e e x p e r i m e n t s done a t pH 10.6 and 11.4 ( T a b l e s 17 and 18) i n d i c a t e t h a t t h e two s e t s o f r e s u l t s a r e c o m p a r a b l e i n 8 o u t o f t h e 10 c a s e s . The two s e t s o f d a t a t h a t were n o t c o m p a r a b l e 2+ were i n c o n s i s t e n t i n o p p o s i t e d i r e c t i o n . ( T a b l e 17 - Pb a t pH 10.6 and T a b l e 18 - Z n 2 + a t pH 1 1 . 4 ) . The c o m p a r i s o n o f t h e e x p e r i m e n t s done a t pH 1000 ( T a b l e 16) i n d i c a t e s a s u b s t a n t i a l improvement i n m e t a l r e m o v a l when u s i n g r aw sewage. 2+ A l l m e t a l s e x c e p t N i showed an i n c r e a s e i n r e m o v a l e f f i c i e n c y . The raw sewage sample u sed f o r t h e pH 10 e x p e r i m e n t was a d i f f e r e n t sample t h a n t h a t u s ed f o r t h e pH 10 .6 and 11.4 e x p e r i m e n t s ( w h i c h were b o t h done on t h e same s a m p l e ) . The pH 10 raw sewage may have been c h e m i c a l l y d i f f e r e n t , a l t h o u g h t h e r e a c t i o n pH and r e q u i r e d l i m e dosage were n o t a b n o r m a l . T a b l e 19 compares t h e u n f i l t e r e d and f i l t e r e d r e m o v a l e f f i c i e n c i e s f o r t h e raw sewage e x p e r i m e n t s . The s m a l l i n c r e a s e i n r e m o v a l e f f i c i e n c y c au sed by f i l t r a t i o n i s a p p r o x i m a t e l y a s f ound f o r m i x e d samp le s o f P P E . ( 1 - 2 % ) . 6.5 The E f f e c t o f A l k a l i n i t y on Heavy M e t a l Remova l A s e t o f e x p e r i m e n t s was p e r f o r m e d t o d e t e r m i n e t h e e f f e c t s o f i n c r e a s e d a l k a l i n i t y on t h e r e m o v a l o f heavy m e t a l s f r o m PPE . I t was f e l t TABLE 16 Compa r i s on o f t he Remova l E f f i c i e n c i e s o f C o m b i n a t i o n s o f M e t a l s i n P r e c h l o r i n a t e d P r i m a r y E f f l u e n t (PPE) and Raw Sewage (RS) a t pH 1 0 . 0 . Chromium Copper Lead N i c k e l Z i n c Mg Dose (mg/1) PPE RS PPE RS I n d i v i d u a l RS PPE RS • PPE RS Re s . i dua l Remova l Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem 0 . 14 73.1 .04 93.1 .38 34.5 .19 59.8 1.15 43.6 .28 36.9 .47 L6.1 .43 L7.3 .26 51.9 .08 82.4 8 .33 .09 82.7 - - .34 41.4 - - .75 63.2 - - .47 L6.1 - - .20 53.0 - -16.66 .09 82.7 .04 93.1 .34 41.4 .18 71.4 .60 70.6 .28 i 16.9 - - • 43 L7.3 .18 56.7 .07 84.6 33 .33 .07 86.5 .03 94.8 .32 44.8 .165 73.8 .54 73.5 .24 88.8 - - 42 .5 L8.3 .10 81 .5 .07 84.6 50 . 0 .07 86.5 .03 94.8 .34 41.4 .17 73.0 .45 ' 77 .9 .20 30.7 .47 16.1 • .45 L3.5 .12 77.8 .07 84 .6 I n i t i a l Cone. 152 .58 .58 .63 2. 04 2.14 56 52 .54 .46 ' Avg pH 9.94 9.92 9. 94 9. 92 9.88 9.92 9. 94 9. 92 9. 94 9 92 I n d i v i d u a l Lead d a t a used i n p l a c e o f c o m b i n a t i o n PPE L e a d d a t a . Lead r e s u l t s were c o n c e n t r a t e d 4x . TABLE 17 Comparison of the Removal E f f i c i e n c i e s of Combinations of Metals i n Prechlorinated Primary Effluent (PPE) and Raw Sewage (RS) at pH 10.60. Chromium Copper Lead N i c k e l Zinc M g 2 + PPE RS PPE RS Ind iv idua l RS PPE RS • PP E RS Dose | (mg/1) Residual Removal Res Rem i Res Rem Res Rem Res Rem Res Rem Res Rem Res ii Rem Res Rem Res Rem 0 .04 92.7 .02 96.6 .26 56.1 .30 62.9 .45 77.9 .18 92.1 .49 15.5 .47 9.6 .19 61.4 .11 76. 6 8.33 .05 90.9 c.02 >96.6 .24 60 .28 64.5 .37 81.8 .14 93.9 .46 20.7 .47 9.6 .10 80 .10 78. 7 16.66 < .03 >95 = .02 >96.6 .23 61.7 .29 63.3 .35 82.8 .14 93.9 .40 31 .47 9.6 .08 84 - -33.33 <.03 >95 = .02 >96.6 .25 58.3 .27 65.8 .33 83.8 .12 94.7 .40 31 .43 17. 3 .09 82 .095 79.8 50.0 <.03 >95 = .02 >96.6 .23 61.7 .25 68.4 .28 86.3 .16 93.C .38 ._ 34.5 .45 13.5 .07 86 .08 83 I n i t i a l Cone. 1 .55 • 57 .60 .79 2. 04 2 .28 i .58 .52 .50 .47 Avg pH 10. 56 10 .67 10 .56 10. 67 10. 56 10 .67 10. 56 10. 67 10. 56 10. 67 " i n d i v i d u a l Lead data used i n place of combination PPE Lead data. Lead resu l t s concentrated 4x. oo TABLE 18 Compar i s on o f t he Remova l E f f i c i e n c i e s o f C o m b i n a t i o n s o f M e t a l s i n P r e c h l o r i n a t e d P r i m a r y E f f l u e n t (PPE) and Raw Sewage (RS) a t pH 1 1 . 4 0 . Chromium Copper Lead N i c k e l Z i n c M g 2 + Dose (mg/1) PPE RS PPE RS I n d i v i d u a l RS PPE RS • PPE RS R e s i d u a l Remova l Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem Res Rem 0 <.02 >96 <.02 >96 .20 66.7 .21 73.4 .40 80.4 .195 91.4 .30 48 .3 .35 32. 7 .045 91 .08 83 8 .33 <.02 >96 <.02 *>96 .19 68.3 .195 75.3 .35 82.8 .16 93 .32 44.8 .30 42 .3 .045 91 .07 85.1 16.66 <.02 >96 <.02 >96 .175 70.8 .18 77.2 .13 93.6 .16 93 .27 53.4 .25 51 .9 .045 91 .07 85.1 33.33 < . 0 2 >96 <.02 >96 .17 71.7 .21 73.4 .15 92.6 .085 96.3 .28 51.7 .30 42 .3 .045 91 .09 80.9 50 .0 <.02 >96 <.02 >96 .165 72.5 .16 79.7 .10 95.1 .085 96.3 .32 44.8 .30 42 .3 .040 92 .07 85 .1 I n i t i a l Cone. .55 .57 .60 .79 2. 04 2. 28 C >8 .52 .50 .47 Avg pH 11 .13 1 1 . 16 11 .13 11 16 11 . 18 1 1 . 16 1 1 . 13 11 . 16 11 . 13 11 .16 I n d i v i d u a l Lead d a t a used i n p l a c e o f c o m b i n a t i o n PPE L e a d d a t a Lead r e s u l t s c o n c e n t r a t e d 4x . TABLE 19 E e r c e n t "Removals f o r F i l t e r e d and U n f i l t e r e d Samples o f C o m b i n a t i o n s o f Heavy M e t a l s i n Raw Sewage pH 1 0 . 0 M 2+ Mg Dose (mg / D Chromium Coppe r N i c k e l Z i n c ' F i l t e r e d U n f i l t e r e d F Unf F Un f F Un f 0 93 .1 93 .1 68 .3 69 .8 13.5 17 .3 JO.2 82 .4 8 .33 - - - - - - - -16.66 93.1 93 .1 69.8 71.4 17 .3 17 .3 30.2 84 .6 33 . 33 94.8 94 .8 74.6 73.8 13.5 18 . 31 30.2 84.6 5 0 . 0 94 .8 94 .8 - 73.0 17 .3 13 .5 - 84.6 pH 1 0 . 6 0 96.6 96.6 65 .8 62.9 13.5 9.6 30.9 76.6 8 . 33 ^96.6 >96.6 70.9 64.5 17 .3 9.6 78.7 78.7 16 .66 >96.6 >96.6 70.9 63 .3 17 .3 9.6 30.9 -3 3 . 3 3 >96.6 >96.6 70.9 65 .8 17 .3 17 .3 78.7 79.8 5 0 . 0 >96.6 >96.6 68.4 68 .4 17 .3 13 .5 79.8 83 .0 P H 11 . 4 0 >96.6 >96.6 71.5 73.4 46.1 32.7 75.5 83 .0 8 .33 >96.6 >96.6 75.9 75.3 49 .0 42 .3 80.9 85 .1 16 .66 >96.6 >96.6 79.7 77.2 59 .6 51 .9 S I .9 85 .1 33 .33 >96.6 >96.6 81 78,4 51 .9 42'. 3 81.9 80 .9 50 . 0 >96.6 >96.6 78.5 79.7 50 42 .3 81.9 85 .1 6 1 . t h a t s u c h a d d i t i o n c o u l d be b e n e f i c i a l t o t h e m e t a l r e m o v a l p r o c e s s b e c a u s e t h e r e i s s t o i c h i o m e t r i c a l l y i n s u f f i c i e n t a l k a l i n i t y t o p r e c i p i t a t e a l l t h e 2+ Ca as CaCO^ f o r t h e t h r e e a v e r a g e l i m e d o s a g e s . The s t o i c h i o m e t r i c r a t i o o f a l k a l i n i t y t o l i m e i s 1:1 wherea s t h e r a t i o s f o r t he t h r e e a v e r a g e d l i m e dosages w e r e : 1 : 1 . 6 , 1:2.4 and 1 : 4 . 2 . The e x p e r i m e n t s on t h e i n d i v i d u a l heavy m e t a l s ( [ M n + ] = 2 . 5 mg/1, p e r f o r m e d a t t h e n a t u r a l PPE a l k a l i n i t y o f 120-130 mg/1 as CaCO^, were d u p l i c a t e d w i t h t h e a l k a l i n i t y s p i k e d t o l e v e l s o f 180-200 mg/1 u s i n g sod ium b i c a r b o n a t e . The e x p e r i m e n t s w e r e p e r f o r m e d a t t h e i n t e r m e d i a t e l i m e dosage r a t h e r t h a n t h e h i g h l i m e dosage b e c a u s e t h e r e m o v a l s w e r e so h i g h 2+ (+90%) a t t h e h i g h l i m e dosage ( e x c e p t N i ) t h a t i t was f e l t t h a t i t w o u l d be d i f f i c u l t t o d i s t i n g u i s h s i g n i f i c a n t d i f f e r e n c e s i n r e m o v a l e f f i c i e n c y . The r e s u l t s o f t h e e x p e r i m e n t s a r e p l o t t e d on F i g u r e s 1 9 , 20 and 2 1 . The re does n o t appea r t o be any s i g n i f i c a n t d i f f e r e n c e i n r e m o v a l e f f i c i e n c y * a t l e a s t up t o t h e i n t e r m e d i a t e l i m e do sage . 62. 100 9 0 8 0 o > o 6 * 7 0 6 0 5 0 4 0 3 0 o F 0 pH = 10.7 # A l k a U n i t y = 198 mg /I o A l k a l i n i t y = 120 mg/ I 8 17 3 3 5 0 2 + Mg D o s a g e (mg / I ) F IGURE 19 P E R C E N T C r 3 + R E M O V A L Vs. M g 2 + D O S A G E FOR D I F F E R E N T A L K A LI N I T I E S . 63. F I G U R E 20 P E R C E N T Z n 2 + R E M O V A L Vs. M g 2 + D O S AGE FOR D I F F E R E N T A L K A LI Nl T l E S . 64. F I G U R E 21 P E R C E N T C u 2 + R E M O V A L Vs . M g 2 + DOSAGE FOR D I F F E R E N T A L K A L I N I T I E S 65 . CHAPTER 7 CONCLUSIONS 2+ 7.1 The E f f e c t i v e n e s s o f Mg a t V a r i o u s p H ' s  7 .1 .1 G e n e r a l 2+ a) The e f f e c t o f Mg on t h e r e m o v a l o f heavy m e t a l s i s most s i g n i f i c a n t when u s e d i n c o n j u n c t i o n w i t h l o w l i m e t r e a t m e n t (pH 1 0 . 0 ) . b ) The g r e a t e s t r e m o v a l s were f ound a t h i g h l i m e t r e a t m e n t (pH 11.4) 2+ 2+ 2+ A t t h i s pH t h e e f f e c t o f Mg was s i g n i f i c a n t f o r Cu • and Zn o n l y . • 7 .1 .2 I n d i v i d u a l ; M e t a l s i n PPE 2+ 2+ a) The e f f e c t o f Mg was most s i g n i f i c a n t f o r Zn w i t h m a j o r 2+ 2+ i n f l u e n c e on Cu and Pb r e m o v a l a l s o b e i n g n o t e d . 3+ 2+ b) T h e r e was v e r y good r e m o v a l f o r C r i n t h e ab sence o f Mg due - 3 0 t o i t s l ow s o l u b i l i t y p r o d u c t ( k sp = 1 0 ) . 2+ 2+ c ) The r e m o v a l o f N i was p o o r and t h e e f f e c t o f Mg was i n s i g n i f i c a n t . 7 . 1 . 3 M i x e d M e t a l s i n PPE a) The r e m o v a l o f m e t a l s does n o t appea r t o be a f f e c t e d b y t h e p r e s e n c e o f o t h e r m e t a l i o n s i n s o l u t i o n a t t h e same i n i t i a l c o n c e n t r a t i o n . The r e m o v a l e f f i c i e n c y o f e a ch m e t a l i n t h e m i x t u r e was c o m p a r a b l e t o t h e r e m o v a l e f f i c i e n c y o f t h a t m e t a l when t r e a t e d by i t s e l f . 7 .1 .4 M i x e d M e t a l s i n Raw Sewage a) The r e m o v a l o f m i x e d m e t a l s f r o m raw sewage was c o m p a r a b l e t o t h a t f r o m PPE . The re wa s , h o w e v e r , an i n c r e a s e i n r e q u i r e d l i m e dosage o f 10 -15% t o g e t t o t h e same r e a c t i o n pH. 7.2 R e s i d u a l M e t a l s i n t h e S e t t l e d S u p e r n a t a n t a) F i l t r a t i o n o f t h e s u p e r n a t a n t i n c r e a s e d t h e r e m o v a l e f f i c i e n c y 6 6 . by o n l y 1-2 p e r c e n t a g e p o i n t s . b) S i n c e t h e s u p e r n a t a n t samp le s were c a r e f u l l y p i p e t t e d f r o m b e a k e r s t h a t h a d b e e n s e t t l e d f o r 30 m i n u t e s , t h e s e r e m o v a l s do n o t s i m u l a t e an a c t u a l f l o w t h r o u g h p r o c e s s . F u r t h e r work i s r e q u i r e d t o e s t a b l i s h t h e need f o r f i l t r a t i o n i n t h i s p r o c e s s . 7.3 The E f f e c t o f A l k a l i n i t y on Heavy M e t a l Remova l a) T h e r e i s s u f f i c i e n t a l k a l i n i t y i n t h e w a s t e w a t e r so as t o n o t i n h i b i t heavy m e t a l r e m o v a l up t o a t l e a s t t h e i n t e r m e d i a t e pH. b) The e f f e c t o f a l k a l i n i t y a t t h e h i g h pH c o u l d n o t be r e s e a r c h e d due t o a l a c k o f a n a l y t i c a l s e n s i t i v i t y . 2+ 7.4 The P o t e n t i a l o f Mg f o r F u l l S c a l e T r ea tmen t a) A rough c o m p a r i s o n o f h i g h l i m e t r e a t m e n t v s i n t e r m e d i a t e l i m e 2+ p l u s Mg t r e a t m e n t i s p r e s e n t e d i n A p p e n d i x B. A l t h o u g h f u r t h e r r e s e a r c h i s r e q u i r e d , t h e c o m p a r i s o n i n d i c a t e s t h a t t h e combined t r e a t m e n t m i g h t be c h e a p e r . b) T h i s t ype o f p r o c e s s m i g h t be a p p l i c a b l e i n t h e f o l l o w i n g a r e a s : i . F o r t h e r e d u c t i o n o f heavy m e t a l c o n c e n t r a t i o n s o f i n d u s t r i a l w a s t e s t r e a m s p r i o r t o t h e i r d i l u t i o n i n m u n i c i p a l s e w e r s ; i i . I n c o r p o r a t i o n w i t h i n t h e p r i m a r y t r e a t m e n t p r o c e s s . G r i t r e m o v a l and r a p i d m i x i n g m i g h t be a c h i e v e d s i m u l t a n e o u s l y , so t h a t t h e o n l y m a j o r a d d i t i o n s t o a p r i m a r y t r e a t m e n t f l o w s t r e a m w o u l d be f l o c c u l a t i o n and r e c a r b o n a t i o n . 67 . BIBLIOGRAPHY 1. APHA, AWWA, WPCF. " S t a n d a r d Methods f o r t h e E x a m i n a t i o n o f Water and W a s t e w a t e r " , 1 4 t h E d i t i o n ( 1 9 7 6 ) . 2. A r g o , D.G. and C u l p , G .L . "Heavy M e t a l Remova l i n Was tewa te r T r ea tmen t P r o c e s s e s : P a r t I", Wate r and Sewage Work s , V o l . 1 1 9 : 2 , p. 6 2 , ( A u g u s t 1972) 3. A r g o , D.G. and C u l p , G . L . "Heavy M e t a l Remova l i n Wa s tewa te r T r ea tmen t P r o c e s s e s : P a r t I I " , Water and Sewage Works , V o l . 1 1 9 : 2 , p. 128 , (September 1972 ) . 4. B.C. R e s e a r c h . " W a t e r Q u a l i t y S t u d i e s i n t h e Lower F r a s e r R i v e r " , P r e p a r e d f o r t h e G r e a t e r Vancouve r Sewerage and D r a i n a g e D i s t r i c t , (May 1 9 7 3 ) . 5. B e n e d i c t , A . H . H a l l , K . J . and K o c h , F .A. "A P r e l i m i n a r y Water Q u a l i t y S u r vey o f t h e Lower F r a s e r R i v e r S y s t e m " , Wes twa te r R e s e a r c h C e n t r e , U n i v e r s i t y o f B r i t i s h C o l u m b i a , T e c h n i c a l R e p o r t No. 2, ( A p r i l 1 9 7 3 ) . 6. B a r t h , . E .F . and o t h e r s . "Summary R e p o r t on t h e E f f e c t s o f Heavy M e t a l s on t h e B i o l o g i c a l T r e a t m e n t . P r o c e s s e s " , Journ. WPCF, V o l . 37 , p. 90 ( 1 9 6 5 ) . 7. B a r t h , E .F . and o t h e r s . " F i e l d S u r vey o f F o u r M u n i c i p a l Was tewate r T r ea tmen t P l a n t s R e c e i v i n g M e t a l l i c W a s t e s " , Journ. WPCF, V o l . 37 , p. 1101 ( 1965 ) . 8. B l a c k , A . P . , DuBose, A . T . and V o g h , R .P. " P h y s i c a l - C h e m i c a l T r ea tmen t o f M u n i c i p a l Was te s by R e c y c l e d Magnes ium C a r b o n a t e " , EPA -660/2 -74 -055 (June 1 9 7 4 ) . 9. B l a c k , A . P L and Thompson, C G . " P l a n t S c a l e S t u d i e s o f t h e Magnes ium C a r b o n a t e Water T r ea tmen t P r o c e s s " , EPA -660/2 -75 -006 (May 1 9 7 5 ) . 10 . B r o u z e s , R . J . P . "The Use o f L i m e i n t h e T rea tmen t o f M u n i c i p a l W a s t e -w a t e r s " , R e s e a r c h R e p o r t No. 2 1 , E n v i r o n m e n t Canada . 1 1 . C u l p , R .L. and C u l p , G . L . " Advanced Was tewa te r T r e a t m e n t " , Van N o s t r a n d R e i n h o l d Company ( 1 9 7 1 ) . 12 . G r i e v e , D. and F l e t c h e r , K. " T r a c e M e t a l s i n F r a s e r D e l t a S e d i m e n t s " , G e o l o g i c a l S u r vey o f Canada , P r o j e c t 740062. 13 . H a l l , K . J . , Y e s a k i , J . and Chan , J . " T r a c e M e t a l s and C h l o r i n a t e d H y d r o c a r b o n s i n t h e Sed iment s o f a M e t r o p o l i t a n W a t e r s h e d " , Wes twate r R e s e a r c h C e n t r e , U n i v e r s i t y o f B r i t i s h C o l u m b i a , T e c h n i c a l R e p o r t No . 10 (May 1 9 7 6 ) . 68. 14. H a l l , K . J . A s s i s t a n t P r o f e s s o r , Depar tment o f C i v i l E n g i n e e r i n g , U n i v e r s i t y o f B r i t i s h C o l u m b i a , P e r s o n a l Commun i c a t i o n (December 1 976 ) . 15 . L a n g i e r , W.F. " E f f e c t s o f . T e m p e r a t u r e on t h e pH o f N a t u r a l W a t e r s " , J . AWWA, V o l . 3 8 , p. 179 ( F e b r u a r y 1 9 4 6 ) . 16. L a r s o n , T . E . , L a n e , R.W. and N e f f , C .H . " S t a b i l i z a t i o n o f Magnes ium i n H y d r o x i d e i n t h e S o l i d s C o n t a c t P r o c e s s " , J ; AWWA, 5 1 : 1551 (December 1 9 5 9 ) . 17. L e c o m p t e , A .R . "Wa te r R e c l a m a t i o n by E x c e s s L ime T r ea tmen t o f E f f l u e n t " , T a p p i , V o l . 4 9 , No. 1 2 , p. 1 2 1 - 1 2 4 ( D e c e m b e r 1 966 ) . 18. L i n d s t e d t , JWPCF, V o l . 4 3 , p. 1507. 19 . McKee, M .E . and W o l f , H.W. " W a t e r Q u a l i t y C r i t e r i a " , Second E d i t i o n , P u b l i c a t i o n 3-A, C a l i f o r n i a S t a t e Water R e s o u r c e s C o n t r o l B o a r d . 20. R i a z , M. " Remova l o f Heavy M e t a l s U s i n g G r a n u l a r C o a l " , M . A . S c . D i s s e r t a t i o n , U n i v e r s i t y o f B r i t i s h C o l u m b i a ( Augu s t , 1 9 7 4 ) . 2 1 . R u s h , R . J . "Magnes i um-L ime P r o c e s s f o r D e c o l o u r i z a t i o n o f K r a f t M i l l E f f l u e n t s " , M .A . S c . D i s s e r t a t i o n , U n i v e r s i t y o f B r i t i s h C o l u m b i a ( A p r i l , 1 9 76 ) . 22 . S a b a d e l l , J . E . ( E d i t o r ) . " T r a c e s o f Heavy M e t a l s i n W a t e r - R e m o v a l P r o c e s s e s and M o n i t o r i n g " , E P A - 9 0 2 / 9 - 7 4 - 0 0 1 , p. 57 . 23 . S a r t o r , J . D . and B o y l , G .B . " W a t e r P o l l u t i o n A s p e c t s o f S t r e e t S u r f a c e C o n t a m i n a n t s " , E .P . T e c h n o l o g y S e r i e s , EPA -R2 -70 -081 (November 1 972 ) . 24 . Stumm, W. and Mo r gan , J . J . " A q u a t i c C h e m i s t r y " , W i l e y - I n t e r s c i e n c e , N .Y . , N.Y. ( 1 970 ) . 25 . T a n n e r , G . , T r a s o l i n i , G. and Nemeth, L. "A S t u d y o n Was tewa te r C h a r a c t e r i s t i c s o f G r e a t e r Vancouve r Sewage T rea tment P l a n t s and M a j o r S e w e r s " , R e p o r t EPS 5 -PR -73 -11 (December 1 9 7 3 ) . 26 . Thompson, C . G . , S i n g l e y , J . E . and B l a c k , A . P . "Magnes ium C a r b o n a t e A R e c y c l e d C o a g u l a n t " , J o u r n . AWWA P a r t I, p. 11-19 ( J a n u a r y 1 9 7 2 ) . 27 . T r a v e r s , A . and N o u v e l . "On t h e S o l u b i l i t y o f Magnes ium H y d r o x i d e a t H i g h T e m p e r a t u r e s " , Compt. Rend ( F r . ) 188 : 499 ( 1 929 ) . 69. APPENDIX A TEST PROCEDURE.DEVELOPMENT 1. Introduction Due to the l imi t ed amount of work that has been done using the lime-magnesium process,a test procedure had to be f i r s t developed that would give reproducible r e s u l t s . The test procedure developed by Rush (21) for colour removal from kraf t m i l l effluents was used as a base from which a sa t i s fac tory procedure was developed. An out l ine of the test procedure development i s presented i n the fol lowing sect ion to give some ins ight into the p r a c t i c a l problems that may concern future researchers. 2. Development of the Jar Test Procedure The main factors that were expected to affect trace metal removal included i ) time (of rapid mixing, f l occu l a t i on and se t t l ing ) i i ) mixing speed i i i ) pH s t a b i l i z a t i o n i v ) the a l k a l i n i t y of the sewage 2+ v) tthe dosage and method of Mg addi t ion v i ) 'the dosage and method of lime addi t ion I n i t i a l j a r tests were carr ied out on 600 ml samples of PPE to see i ) the effect of the a l k a l i n i t y of the sewage on pH s t a b i l i s a t i o n , i i ) i f the rapid mix times recommended by Rush (21) would be sa t i s fac tory for heavy metal removal ( i t was f e l t that pH s t a b i l i z a t i o n was'important i n that i t indicated the p r a c t i c a l completion of the p r e c i p i t a t i o n reactions and thus the completion of the rapid mix time). The i n i t i a l j a r tesit's were done as fo l lows: 70. i ) A 600 m l samp le o f PPE was l i m e d t o t h e pH r a n g e 10 .8 t o 11 .3 by a p r e d e t e r m i n e d s l u g d o s e . i i ) The pH was m o n i t o r e d c o n t i n u o u s l y . i i i ) A r a p i d m i x (100 rpm) was m a i n t a i n e d u n t i l t h e pH had s t a b i l i z e d . i v ) The samp le s were t h e n a l l o w e d t o f l o c c u l a t e a t 15 -20 rpm u n t i l an a d e q u a t e f l o e fo rmed f r o m a v i s u a l p o i n t o f v i e w . v ) The s amp le s were t h e n s e t t l e d (0 rpm) and the s e t t l i n g t i m e was mea su red . The p r o c e d u r e o u t l i n e d above was r e p e a t e d f o r s amp le s s p i k e d t o 2+ an a l k a l i n i t y o f 200 mg/1 as CaCO^ and f o r Mg dosages f r o m 0 t o 50 mg/1. The pH s t a b i l i z a t i o n c u r v e s a r e p l o t t e d on F i g u r e 22 , 23 and 24. The c o n c l u s i o n s o f t h i s s e r i e s o f t e s t s a r e as f o l l o w s : 2+ i ) A t t h e n o r m a l a l k a l i n i t y o f t he PPE , an i n c r e a s e i n Mg dosage does n o t appea r t o a f f e c t t h e pH s t a b i l i z a t i o n t i m e ( see F i g u r e 2 2 ) . 2+ i i ) A t t h e e l e v a t e d a l k a l i n i t y , an i n c r e a s e i n Mg dosage i n c r e a s e s t h e pH s t a b i l i z a t i o n t i m e ( see F i g u r e s 23 and 2 4 ) . 2+ i i i ) I n c r e a s e d a l k a l i n i t y a t a c o n s t a n t Mg dosage does n o t i n c r e a s e t h e pH s t a b i l i z a t i o n t i m e ( see F i g u r e s 22 and 2 3 ) . i v ) A r a p i d m i x t i m e o f 15 m i n u t e s w o u l d s t a b i l i z e t h e pH unde r 2+ a l l c o n d i t i o n s e x c e p t t h e c a s e o f h i g h Mg (50 mg/1) and h i g h a l k a l i n i t y (192 mg/1 as C a C 0 3 ) . v ) A f l o c c u l a t i o n t i m e o f 3 m i n u t e s was adequa te f r o m a v i s u a l p o i n t o f v i e w . v i ) The sample s e t t l e d i n 10-15 m i n u t e s . The n e x t s e r i e s o f t e s t s were p e r f o r m e d t o e s t a b l i s h t h e f l o c c u -l a t i o n t i m e . I t was f e l t t h a t a l t h o u g h t h e pH h a d s t a b i l i z e d a f t e r 15 m i n u t e s 0 5 10 15 2 0 T i m e ( m i n u t e s ) i-1 F I G U R E 2 2 p H V s . T I M E F O R P P E A T N A T U R A L A L K A L I N I T Y ( I 3 0 m g / I C a C 0 3 ) . 12 10 No Mg 2+ Rap id Mix x x — x F l o e c u la t i o n A — A S e t t l i n g 10 Ti me ( m i n u t e s ) 15 2 0 F I G U R E 2 3 p H V s . T I M E F O R P P E A T E L E V A T E D A L K A L I N I T Y ( 2 0 0 m g / l C a C 0 3 ) T T T 3 5 m g / I M g T i m e ( m i n u t e s ) F I G U R E 2 4 p H V s . T I M E F O R P P E A T E L E V A T E D A L K A L I N I T Y * 1 9 2 m g / 1 a s C a C 0 3 ) . •74. o t h e r t r a c e m e t a l r e m o v a l mechan i sms ( i . e . e n t r a p m e n t , c o m p l e x a t i o n ) may 2+ r e q u i r e f u r t h e r r e a c t i o n t i m e . To t e s t t h i s t heo r y , a s e r i e s o f Zn r e m o v a l t e s t s were p e r f o r m e d i n w h i c h t h e o v e r a l l r e a c t i o n t i m e ( r a p i d m i x p l u s f l o c c u l a t i o n ) were v a r i e d be tween 15 and 60 m i n u t e s . Z i n c a t 5.0 mg/1 was a r b i t r a r i l y c ho sen as t he heavy m e t a l f o r t h e t e s t s . The t e s t was p e r f o r m e d 2+ a t t h e m i d d l e o f t h e pH r ange ( 10 .6 ) and Mg dosage o f 17 mg/1 was c h o s e n f r o m p r e v i o u s t e s t wo r k . The r e s u l t s o f t h e t e s t s a r e p l o t t e d i n F i g u r e 25 . 2+ The minimum t i m e r e q u i r e d t o r e d u c e t h e Zn r e s i d u a l t o i t s minimum range a p p e a r e d t o be 25 m i n u t e s . A 15 m i n u t e r a p i d m i x t i m e and a 10 m i n u t e f l o c c u l a t i o n t i m e was t h e r e f o r e adop ted f o r a l l f u t u r e t e s t wo r k . As p r e v i o u s l y m e n t i o n e d , s e t t l i n g was c o m p l e t e d f r o m a v i s u a l p o i n t o f v i e w w i t h i n 15 m i n u t e s t h e r e f o r e a s e t t l i n g t i m e o f 30 m i n u t e s was a r b i t r a r i l y c h o s e n . I n t h e i n i t i a l t e s t work a r a p i d m i x t i m e o f 100 ± 5 rpm was u sed and due t o t h e l o n g pH s t a b i l i z a t i o n t i m e s t h a t were d i s c o v e r e d i t was f e l t t h a t t h i s speed w o u l d be s u i t a b l e f o r f u t u r e t e s t i n g . A f l o c c u l a t i o n speed o f 15 -20 rpm was a d o p t e d on t h e r ecommenda t i on o f Rush (21) . S e t t l i n g was done a t 0 rpm. 2+ 3. Dosage and Method o f Mg A d d i t i o n The g e n e r a l l y a c c e p t e d t h e o r y t h a t magnes ium must be added i n i t s i o n i c f o r m so t h a t i t p r e c i p i t a t e s " i n s i t u " f o r opt imum r e m o v a l was t e s t e d . A s e r i e s o f e x p e r i m e n t s were p e r f o r m e d u s i n g l i m e and magnes ium i n t h e f o r m o f MgSO^.7H 2 0 and M g ( 0 H ) 2 . The r e s u l t s a r e shown i n T a b l e 20 . The b e s t 2+ r e m o v a l i s o b t a i n e d when t h e c o a g u l a t i o n i s p e r f o r m e d u s i n g l i m e and Mg r a t h e r t h a n l i m e and M g ( 0 H ) 2 . 4 2+ The magnes ium was t h e r e f o r e added i n t h e f o r m o f a 10 mg/1 Mg 75. 0.6 o> Ul) 0 .5 c o A— o +-• c CP o c-o o + CM Zn 0 .4 o •3 <n CD -0 . 3 [ Z n 2 + ] = 5 mg/1 i [ M g 2 + ] = 17 mg/1 L I M E = 2 l 6 m g / l pH * " l b . 6 S E T T L I N G T IME = 3 0 m i n 1 15 3 0 4 5 O v e r a l l R e a c t i o n T i m e (minutes) 6 0 F I G U R E 2 5 R E S I D U A L Z n 2 + C 0 N C E N T R A T I 0 N V s . O V E R A L L R E A C T I O N T I M E ( R A P I D M I X + F L 0 C C U L A T I 0 N ) TABLE 20 A c o m p a r i s o n o f Heavy M e t a l . R e m o v a l s U s i n g L ime and Mg(OH) and L ime and Mg % Remova l ( U n f i l t e r e d Da t a ) T r a c e M e t a l L ime O n l y L ime and M g ( 0 H ) 2 2+ L imedand Mg C r 92.7 95.6 96.6 Cu 54 57 .1 70 N i 56 5 6 . 3 57 Zn 79 86.2 90 I n i t i a l C o n d i t i o n s I n i t i a l m e t a l c o n c e n t r a t i o n 2.6 mg/1 (ap.prox) L ime Dosage 186 mg/1 ( a ve r a ge ) 2+ Mg Dosage 17 mg/1 s o l u t i o n o f MgSO^.TH^O. On t h e recommendat i on s o f . R u s h . C21), t h e Mg a d d i t i o n was g i v e n a 1 m i n u t e r a p i d m i x t i m e i n o r d e r t o a c h i e v e d i s p e r s a l , p r i o r t o t h e l i m e a d d i t i o n . 4 . Dosage and Method o f t h e L ime A d d i t i o n I n i t i a l l y , t h e l i m e a d d i t i o n was made u s i n g a 10 w e i g h t p e r c e n t s l u r r y o f h i g h p u r i t y r e a g e n t g r a d e C a ( 0 H ) 2 i n d i s t i l l e d w a t e r . T h i s p r o c e d u r e gave p o o r r e p r o d u c i b i l i t y , p r e s u m a b l y due t o s l u r r y s e t t l i n g , and was r e p l a c e d by a d r y r e a g e n t g r ade Ca(OH) a d d i t i o n . W i t h t h e d r y r e a g e n t g r ade Ca(QR)^ a d d i t i o n i t was n e c e s s a r y t o s t i r t h e t e s t b e a k e r f o r about 3 s econd s w i t h a g l a s s r o d i m m e d i a t e l y a f t e r t h e a d d i t i o n t o p r e v e n t t h e Ca(0H)2 f r o m f l o a t i n g on t h e s u r f a c e . 5. L ime -Magne s i um C o a g u l a t i o n T e s t Sequence The p r e l i m i n a r y t e s t work was c a r r i e d o u t t o d e v e l o p a c o a g u l a t i o n p r o c e d u r e t h a t w o u l d p r o d u c e c o m p a r a b l e r e s u l t s f o r t h e r e m o v a l o f f i v e d i f f e r e n t heavy m e t a l s f r o m m u n i c i p a l w a s t e w a t e r . The d e t a i l e d t e s t p r o c e d u r e c o n s i s t e d o f t h e f o l l o w i n g p r o c e d u r e : 1) E v e r y Monday m o r n i n g d u r i n g t h e t e s t p e r i o d , a samp le o f PPE was o b t a i n e d f r o m A n n a c i s I s l a n d Sewage T r e a t m e n t P l a n t and s t o r e d i n t h e 3°C i n c u b a t o r . 2) F o r e a c h r u n a s e t o f 7 - 600 m l samp le s were measured o u t i n t o 1 l i t r e b e a k e r s u s i n g a 1 l i t r e g r a d u a t e d c y l i n d e r . The samp le s were t h e n warmed t o 20-21°C by p l a c i n g them i n t h e 35°C i n c u b a t o r f o r abou t 1% h o u r s . 3) The s amp le s were t h e n s p i k e d t o t h e r e q u i r e d i n i t i a l m e t a l i o n c o n c e n t r a t i o n s u s i n g t h e heavy m e t a l s p i k e s o l u t i o n s . 4) F o r r u n s done a t e l e v a t e d a l k a l i n i t y , t h e samp le s were t h e n s p i k e d w i t h t he a l k a l i n i t y s p i k e s o l u t i o n . 78. 5) One of the samples was - set aside for i n i t i a l metal ion concen-tration (s) analysis. 6) One:of the samples was then used to calculate the lime dosage. The sample was mixed at 100 rpm on a Phipps and Bird Laboratory s t i rrer and the pH was constantly monitored to 10.0, 10.7 or 11.4. The CaCOH^ require-ment was calculated and five doses were measured out. 7) The five remaining samples were st irred on the laboratory s t i rrer at 100 rpm for 1 minute to disperse the metal ion and the a lkal in i ty spike. 2+ 8) With the s t i rrer off, the following additions of the Mg solution were pipetted into the samples: 0.5 ml, 1 ml, 2 ml and 3 ml. These 2+ additions corresponded to 0, 8, 17, 33 and 50 mg/1 Mg respectively. 9) The samples were st irred for 1 minute at 100 rpm and then the CaCOH^ addition was made. 10) The samples were then given a 15 minute rapid mix, a 10 minute f locculation and a 30 minute settle as previously discussed. 11) Since the f i n a l pH measurement and supernatant sampling took about 10 minutes, they were begun after 25 minutes sett l ing. For a l l runs 2+ except those using Pb , two 50 ml samples were pipetted f-romreach beaker. To reduce contamination problems, the supernatant samples were taken in order 2+ 2+ of decreasing Mg dosage. For the Pb runs, two 100 ml samples were required as i t was necessary to concentrate them four times by boi l ing . 12) One of the two supernatant samples was f i l tered through #2 Whatman f i l t e r paper. 13) The metal analysis was then performed by Atomic Absorption Spectroscopy as described in Section 5.2.2. 14) The heavy metal percent removals were then calculated using 79. the following formula: P ^ i - * 100 15) A completed data sheet i s shown in Figure 26. 80 . O b j e c t : ' Cu @ 5.0 mg/1; pH 10.7 Run #: 1 C u 2 + E l o c t e s t : Beake r pH Mg 1 10 .70 0 2 10 .70 8 3 10.65 17 4 10 .60 33 5 10.54 50 S t a r t : 1:14 A - A A n a l y s i s : (810) Sample ABS Cone Remova l 1 f 1.85 63 2 1.35 73 3 1.25 75 4 "...90 82 5 .85 83 1 un f 1.70 66 2 1.30 74 3 1.10 78 4 .85 83 5 .80 84 #6 5.0 #12 ^0 F i g u r e 26: Comple D a t e : 20 J u l y 1976 L ime Do sage : I n i t i a l wt - 1.0376 F i n a l wt .9094 A d d i t i o n .1282 Remark s : C u 2 + s p i k e - 2.9 m l Sample #12 - A c i d s o n l y i n d i s t i l l e d w a t e r 2+ Sample #6 - I n i t i a l Cu A l k a l i n i t y - 120-130 mg/1 d D a t a Shee t 8 1 . APPENDIX B COMPARISON OF EFFECTIVENESS AND COSTS OF HIGH LIME TREATMENT (H . L . ) v s INTERMEDIATE L I M E / M g 2 + TREATMENT ( I . L . / M g 2 + ) B a s i s : .(1) Compa r i s on b a s e d on a 10 mgd p l a n t w i t h w a s t e w a t e r c o n t a i n i n g 3+ 2+ 2+ 2+ 2.5 mg/1 o f C r , Cu , Pb and Zn . N i c k e l ha s been e l i m i n a t e d 2+ b e c a u x e I .L./Mg w o u l d n o t be c o n s i d e r e d as a p o s s i b l e t r e a t m e n t p r o c e s s f o r t h i s m e t a l . (2) S u p e r n a t a n t s o f t he f o l l o w i n g q u a l i t y w o u l d be o b t a i n e d f o r t h e c h e m i c a l dosages shown. The A -A and B-B P o l l u t i o n C o n t r o l o b j e c t i v e s f o r m u n i c i p a l t y p e w a s t e w a t e r s i n B .C. have been shown f o r c o m p a r i s o n . H .L . t r e a t m e n t 2+ I .L ./Mg t r e a t m e n t A -A B-B (400 mg/1 C a ( 0 H ) 2 ) 220 mg/1 Ca(OH) 33 mg/1 M g 2 + C r 3 + .06 .10 .1 .3 C u 2 + .38 .59 .2 .5 Pb .21 .14 .05 .10 r, 2+ Zn .26 .19 .5 5.0 2+ (3) Assume 90% Mg r e c o v e r y and r e c y c l e (Rush) and z e r o r e c y c l e o f t h e l i m e due t o heavy m e t a l c o n t a m i n a t i o n . (4) Assume t h a t i f f i l t r a t i o n i s r e q u i r e d (and t h i s i s v e r y l i k e l y ) , t h a t i t w i l l be r e q u i r e d f o r b o t h p r o c e s s e s . T r e a t m e n t C o m p a r i s o n : ^~~~~^~-£rocess P a r a m e t e r s H.L. I . L . / M g 2 + R e a c t i o n pH 11 .4 10.6 S l udge Volume (minus i m p u r i t i e s ) 400 mg/1 223 mg/1 C h l o r i n a t i o n r e q u i r e m e n t p o s s i b l y n o t ye s C h e m i c a l c o s t s * ( pe r day) $1200 ( l i m e ) $675 ( l i m e ) + $100 ( M g Z + ) = $775 C o s t s n o t e s t i m a t e d a) e x c e s s r e c a r b o n a t i o n c o s t s f o r H1L. t r e a t m e n t . b) e x c e s s s l u d g e h a n d l i n g c o s t s f o r H.L . t r e a t m e n t . M i s c e l l a n e o u s 2+ s l u d g e s e t t l i n g f o r I .L./Mg may be a p r o b l e m Dow C h e m i c a l - M g C l 2 @ $8 .20/cwt ( b u l k ) Domtar - L ime @ $ 6 2 . 5 0 / t o n (22 t o n l o t s ) The above c o m p a r i s o n i n d i c a t e s t h a t I .L./Mg t r e a t m e n t m i g h t be be cheape r when t r e a t i n g i d e n t i c a l w a s t e s t r e ams t o s i m i l a r s u p e r n a t a n t q u a l i t y . 

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