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Influence of sewage sludge application on hydraulic and physical properties of a silty clay loam subsoil Kodsi, Elias G. 1987

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INFLUENCE OF SEWAGE SLUDGE APPLICATION ON HYDRAULIC AND PHYSICAL PROPERTIES OF A SILTY CLAY LOAM SUBSOIL by ELIAS G.  KODSI  B.Sc, American University of Beirut,  1983  A THESIS SUBMITTED IN P A R T I A L F U L F I L M E N T T H E REQUIREMENTS  FOR T H E D E G R E E  MASTER O F  OF  OF  SCIENCE  in T H E F A C U L T Y OF G R A D U A T E STUDIES D E P A R T M E N T OF B I O - R E S O U R C E in cooperation with  ENGINEERING  the  D E P A R T M E N T O F SOIL SCIENCE We accept this thesis as conforming to the  required standard  T H E UNIVERSITY O F BRITISH APRIL, •  COLUMBIA  1987  ELIAS G . KODSI,  1987  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at The University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.  DEPARTMENT OF BIO-RESOURCE in cooperation with the D E P A R T M E N T O F SOIL SCIENCE The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: APRIL, 1987  ENGINEERING  ABSTRACT Turf growers have been farming the Ladner soil in the Boundary Bay area for the last decade. At each harvest, approximately a 2cm layer from the A horizon is taken out with grass. Consequently, the cultivation layer is becoming thinner year after year and the growers are already cultivating the B horizon. The possible improvement of the B horizon structure through sewage sludge application will benefit the  fanners  in the area. A  greenhouse  experiment  was conducted  using a  Ladner subsoil. Treatments  included application rates of 0, 33, and 100 t/ha of composted sewage sludge. The  effect of sludge application on the soil structural stability in relation to  the destructive action of water was evaluated. Soil columns were subjected to periodic 24-hour  simulated  ponding  events.  Adding  sewage  sludge  increased  the  ponding  tolerance of the soil. This was reflected by statistically significant differences in satiated hydraulic  conductivity ('Ks')  between  columns. The significant decrease  the  sludge-amended  of ' K s ' of the  columns  and  control treatment as  the a  control  result of  ponding was responsible for widening the gap between 'Ks' of the control columns and 'Ks' of the sludge-treated  columns. The incorporation of sewage sludge slowed down  the decrease of 'Ks' but could not stop i t The most plausible explanation is that the addition of sewage sludge was effective in increasing the resistance breakdown when subjected  to ponding. Fifty  days after  of aggregates to  the last ponding event,  the  percent stable aggregates averaged 13.7, 26.9, and 48.1% for the 0, 33, and 100 t/ha treatments respectively. In no case was a significant difference in bulk density observed between the treatments. The soil structure deterioration as a result of ponding was not reflected  by the  bulk  density  measurements.  Thus, it was concluded that hydraulic  conductivity and aggregate stability are better idices of soil structural deterioration than  iii  bulk density. A side investigation was carried out to illustrate trends of essential nutrient and heavy metal uptake by bermuda grass. Sludge incorporation at 33 t/ha did not seem to increase nutrient and metal uptake by bermuda grass. However N , Cd, and Zn uptake appeared to increase at 100 t/ha.  iv  TABLE OF CONTENTS ABSTRACT  iii  T A B L E O F CONTENTS  v  LIST O F TABLES  vii  LIST O F FIGURES  ..........  ... viii  ACKNOWLEDGEMENTS  x  1. INTRODUCTION 1.1. INTEREST IN A G R O N O M I C U T I U Z A T I O N 1.2. T H E P R O B L E M 1.3. OBJECTIVES  1 1 1 2  2. L I T E R A T U R E REVIEW 2.1. S L U D G E M A N A G E M E N T 2.1.1. Sludge production 2.1.2. Sludge constituents 2.1.3. Sludge processing 2.1.4. Sludge disposal options 2.2. S L U D G E AS A FERTILIZER 2.3. S L U D G E AS A SOIL CONDITIONER 2.3.1. Aggregate stability 2.3.2. Bulk density 2.3.3. Hydraulic conductivity 2.4. S L U D G E APPLICATION GUIDELINES 2.4.1. Nitrogen 2.4.2. Pathogens 2.4.3. Soil p H 2.4.4. Heavy metals 2.4.5. PCBs  '.  FOR A G R I C U L T U R A L L A N D  3. M A T E R I A L S A N D METHODS 3.1. SOIL A N D S L U D G E CHARACTERISTICS 3.2. E X P E R I M E N T A L DESIGN 3.2.1. Application rates 3.2.1.1. Agronomic rate 3.2.1.2. Conditioning rate 3.2.1.3. Treatments  3.2.2. Soil Packing 3.2.3. Water regime 3.3. SOIL P H Y S I C A L M E A S U R E M E N T S 3.3.1. Hydraulic conductivity 3.3.2. Bulk density 3.3.3. Aggregate stability 3.4. ESSENTIAL NUTRIENT A N D H E A V Y M E T A L U P T A K E E V A L U A T I O N 32 v  3 3 3 3 4 7 8 9 10 12 13 15 15 16 16 16 18 20 20 25 25 25 26 27  27 28 29 29 31 31 ...  3.5. 4.  STATISTICAL ANALYSIS  33  RESULTS A N D DISCUSSION 4.1. A P P L I C A T I O N R A T E 4.2. 4.3. 4.4. 4.5. 4.6. 4.7.  35 35  STATISTICAL DISTRIBUTION HYDRAULIC CONDUCTIVITY A G G R E G A T E STABILITY B U L K DENSITY ESSENTIAL NUTRIENT U P T A K E HEAVY METAL UPTAKE  5.  SUMMARY  AND  CONCLUSIONS  6.  FUTURE RESEARCH  35 38 50 60 60 62 70 72  REFERENCES  73  vi  LIST OF TABLES  Table I: Typical chemical composition of raw and digested sludges 5  (Loehr et a l . , 1979) Table I I : Typical heavy metal content of sludge (Bastian, 1977)  ...5  Table I I I : Recommended cumulative l i m i t s for metals of major concern applied to cropland (U.S. EPA, 1983)  ...........19 21  Table IV: S o i l p a r t i c l e size d i s t r i b u t i o n (Driehuyzen 1983) Table V: Some physical and chemical c h a r a c t e r i s t i c s of the s o i l  21  (Driehuyzen, 1983) Table VI: Chemical composition of the sludge  ..23 24  Table VII: Heavy metal concentration of the sludge Table VIII: Goodness of f i t of normal and log-normal distributions to the hydraulic conductivity data  36  Table IX: Goodness of f i t of the normal and log-normal distributions to the aggregate s t a b i l i t y data  37  Table X: Goodness of f i t of the normal and log-normal d i s t r i b u t i o n s to the bulk density data Table XI: Hydraulic conductivity data f o r the f i r s t ponding event  37 ..43  Table XII: Hydraulic conductivity data f o r the second ponding event .44 • Table XIII: Hydraulic conductivity data f o r the t h i r d ponding event .47 Table XIV: Hydraulic conductivity data f o r the fourth ponding event Table XV: Hydraulic conductivity data f o r the f i f t h ponding event  .48 ..51  Table XVI: I n i t i a l aggregate s t a b i l i t y  3.4  Table XVII: F i n a l aggregate s t a b i l i t y (0 to 5cm depth)  36  Table XVIII: F i n a l aggregate s t a b i l i t y (5 to 10cm depth)  36  Table XIX: I n i t i a l bulk density Table XX: F i n a l bulk density  &  Table XXI: Available metal concentration i n the s o i l  M  vii  1  LIST OF FIGURES  Figure 1: Effect of sewage sludge application on water s t a b i l i t y index  ( Guidi e t a l . , 1983)  14  Figure 2: Effect of sewage sludge application on saturated hydraulic conductivity (Epstein, 1975) Figure 3: Sludge production process flow diagram  14 . . . . . . . . . . . . . . . . . . 22  Figure 4: A simulated 24-hour ponding event  30  Figure 5: Schematic of the falling-head apparatus  30  Figure 6: F r a c t i l e diagram of the 'Ks' data for the 33 t / h a treatment (Third ponding event)  39  Figure 7: F r a c t i l e diagram of the l n ( ' K s ' ) data for the 33 t / h a treatment (Third ponding event) Figure 8: Effect of ponding on hydraulic conductivity  40 41  Figure 9: 95% confidence intervals for the means of the hydraulic conductivity data ( F i r s t ponding event)  45  Figure 10: 95% confidence i n t e r v a l s for the means of the hydraulic conductivity data (Second ponding event)  .45  Figure 11: 95% confidence i n t e r v a l s for the means of the hydraulic conductivity data (Third ponding event)  49  Figure 12: 95% confidence i n t e r v a l s for the means of the hydraulic conductivity data (Fourth ponding event)  49  Figure 13: 95% confidence i n t e r v a l s for the means of the hydraulic coductivity data ( F i f t h ponding event)  5  2  J  J  5  7  «  5 8  Figure 14: Effect of sewage sludge application on hydraulic conductivity Figure 15: 95% confidence i n t e r v a l s for the means of the f i n a l aggregate s t a b i l i t y data (0 to 5cm depth) Figure 16: 95% confidence i n t e r v a l s for the means of the f i n a l aggregate s t a b i l i t y data (5 to 10cm depth)  viii  LIST O F FIGURES  Figure Figure Figure Figure Figure Figure Figure Figure Figure  17: E f f e c t o f sewage sludge a p p l i c a t i o n on the f i n a l aggregate stability 59 18: N i t r o g e n c o n c e n t r a t i o n i n the f o l i a g e o f bennuda g r a s s ...65 19: Phosphorus c o n c e n t r a t i o n i n the f o l i a g e o f bermuda grass ..65 20: P o t a s s i u m c o n c e n t r a t i o n i n the f o l i a g e , o f bermuda grass ..66 21: Cadmium c o n c e n t r a t i o n i n the f o l i a g e o f bermuda grass ...66 22: Copper c o n c e n t r a t i o n i n the f o l i a g e o f bermuda grass ....67 23: N i c k e l c o c n c e n t r a t i o n i n the f o l i a g e o f bermuda grass ....67 24: Lead c o n c e n t r a t i o n i n the f o l i a g e o f bermuda grass 68 25: "Zinc c o n c e n t r a t i o n i n the f o l i a g e of bermuda grass 68  ix  ACKNOWLEDGEMENTS I would like to express my gratitude to Dr. S.T. Chieng for his supervision of my M.Sc. program as well as for his advice and encouragement. also expressed would  Sincere appreciation is  to Dr. J. de Vries for his constant advice and helpful suggestions. I  also like to thank  Dr. K . V . Lo and  Professor  L M . Staley  for  serving as  committee members. Special thanks are due to Mr. Neal Jackson, Mr. Jurgen Pelke, and Dr. M . Bonsu  for  their  technical assistance.  Bio-Resource Engineering Department  Thanks  also to  the  for their enthusiastic  graduate support  students of  the  and to Envirocon  Company for providing the results of the heavy metal analysis of the sludge. Finally, my sincere thanks to my family in Beirut, and to Catherine for their love and patience.  x  1. INTRODUCTION  1.1. INTEREST IN A G R O N O M I C UTILIZATION In  the  past decade strict limitations have  been  imposed on the  disposal of  sewage sludge by incineration, fresh water dilution, and ocean dumping. These methods can adversely affect the environment without providing the potential benefit of resource and energy conservation. Recently, interest in the agronomic utilization of municipal sewage sludge increased. There is a growing consensus  has  that well-managed sludge application systems  to land can be environmentally acceptable if properly designed and operated. Guidelines have been developed to enable the safe use of sewage sludge in land reclamation and biomass production. The agricultural virtues of sewage  sludge can be summarized as  follows (Menzies, 1973): "It is a low-analysis, slow-release organic fertilizer valued mainly as a soil conditioner. Beyond this, and perhaps more important in the long run, the waste is recycled in a useful way back to the land from which it came."  1.2. T H E P R O B L E M Due  to the  nature and  frequency  of fall  and winter rainfall  events in  the  Boundary Bay area, and the inherent characteristics of the Ladner series soil, it is not physically possible to meet the infiltration requirement for all rainfall events assuming a  working subsurface  practices are needed  drainage  system is in place. Consequently, special  management  to enhance the physical and hydraulic properties of this poorly  drained soil. These practices include: i) soil conditioning, ii) use of cover crop, and iii) subsoiling (de Vries, 1983).  1  INTRODUCTION / 2 Turf growers have been farming for the last decade in the Boundary' Bay area. At each harvest, approximately a 2cm layer from the A horizon is taken out with the grass. Consequently, the cultivation layer is becoming thinner year after year and the growers are already farming the B horizon. The mixing of comparted B horizon clods in the cultivation layer is also another problem faced by the farmers in the area. The mixing results from using a chisel plough rather than a paraplough for subsoiling. The chisel plough is inappropriate for the Ladner soil because it tends to pull compacted subsoil clods into the cultivation layer. The  possible improvement of the B horizon structure through sewage sludge  application will benefit the fanners. This applies mostly to the turf growers and other non-food-chain crop farmers who can use sewage sludge with less restrictions than edible food growers.  1.3. OBJECTIVES The main objectives of this study are: 1.  to determine the effects three rates of sewage sludge application on the soil structural stability in relation to the destructive action of water by: a.  monitoring the soil response to periodically simulated ponding events using hydraulic conductivity as an index for ponding tolerance.  b.  determining aggregate stability in water at the beginning and at the end of the experiment  2.  to determine the response of soil bulk density to sewage sludge treatment.  3.  to determine the impacts of sewage sludge application on heavy metal and essential nutrient uptake by a commercially grown turfgrass.  2. L I T E R A T U R E REVIEW  2.1. S L U D G E M A N A G E M E N T Sludge management refers to the processing and disposal of sludge produced at wastewater treatment plants.  2.1.1. Sludge production The  increasing population densities have resulted in a tremendous  increase in  sludge production. For example, experts have predicted that the tonnage accumulated in New  York State will double between 1975 and 1985 (Rajagopal et a l , 1981). In the  case of India, it has been  estimated  that i f the entire  domestic wastes of all the  towns of India are utilized, it can irrigate more than 200,000 hectares of land. In 1977,  Bangkok's production of sewage  sludge  from  cesspools  and septic  tanks was  evaluated to be around 150,000 cubic meters. This volume does not include the sludge from central treatment plants. Thus  it  can be  seen  that  the  potential  sludge  problem  is  omnipresent.  Urbanization trends and tougher pollution control legislation suggest that sludge disposal is one of the most important problems facing wastewater treatment engineers.  2.1.2. Sludge constituents To establish an effective sludge management plan, it is important to know the composition  of the sludge. The constituents  vary  depending  on the origin  of the  sludge, the processing to which it has been subjected, and the amount of aging that has taken place (Metcalf and Eddie, 1979). Since  sludge  is a product  of the food  3  we eat, it contains many of the  U T E R A T U R E REVIEW / 4 elements  present  in our  food:  nitrogen, phosphorous,  potassium, calcium,  iron,  and  others. Typical data on the chemical composition of untreated and digested sludges are shown in table I. Sludge  contains  harmful  contaminants  removed  from  wastewater  by  physical,  biological, and chemical treatments (Dean and Smith, 1973). These contaminants include pathogenic microorganisms, heavy metals, and toxic chemicals. Untreated sludges contain high  concentrations  of  fecal  coliforms,  especially  Escherichia coli.  It  also  contains  smaller quantities of intestinal and respiratory tract organisms, many of which may be disease causing. The human population is not the only contributor of contaminants to the  sewage  stream  (Rajagopal et al., 1981). Industries  and commercial establishments  contribute to the supply of of toxic chemicals and hazardous metals to the wastewater system. Stormwater runoff from  tire wear, lead from  discharging in combined sewers contains zinc and cadmium gasoline, metals  from  gutters,  and  corrosion from  other  metal objects. Table II reports typical values for metals in sludges.  2.1.3. Sludge processing Whatever disposal option is selected by a municipality, the sludge should be processed to: 1. minimize environmental impacts and meet disposal standards established by regulatory agencies. 2. reduce its volume as much as possible in order to decrease the cost of subsequent disposal steps. Sludge processing is achieved by stabilization and dewatering techniques. Sludge stabilization offensive  processes  are  aimed  at  converting raw  (untreated)  sludges  into  a  less  form with regard to odor, putrescibility rate, and pathogenic organism content  LTTERATURE REVIEW / 5 Table I : T y p i c a l chemical composition of raw and digested sludges (Loehr e t a l . , 1979).  RAW ITEM*  T  5k*  vs**  ( % )  Lipids Protein Nitrogen P O, a  K 0 2  Cellulose Si0 pH 2  RANGE  DIGESTED TYPICAL  2.0-7.0 60.0-80.0 6.0-30.0 20.0-30.0 1.5-4.0 0.8-2.8 0-1.0 8.0-15.0 15.0-20.0 5.0-8.0  4.0 65.0  -  25.0 2.5 1.6 0.4 10.0  -  6.0  RANGE  6.0-12.0 30.0-60.0 5.0-20.0 15.0-20.0 1.6-5.0 1.5-4.0 0-3.0 8.0-15.0 10.0-20.0 6.5-7.5  TYPICAL  10.0 40.0 18.0 3.0 2.5 1.0 10.0 7.0  * Expressed as X of t o t a l s o l i d s (TS). * * VS= v o l a t i l e s o l i d s .  Table I I : T y p i c a l heavy metal content of sludge (Bastian, 1977).  METAL*  Silver Arsenic Boron Barium Cadmium Cobalt Chromium Copper Mercury Manganese Nickel Lead Selenium Zinc * Expressed In ppm. ** nd« not detected.  RANGE  nd-960 10-50 200-1,430 nd-3,000 nd-1,100 nd-800 22-30,000 45-16,030 0.1-89 100-8,800 nd-2,800 80-26,000 10-180 51-28,360  MEAN 225 9 430 1,460 87 350 1,800 1,250 7 1,190 410 1,940 26 3,483  MEDIAN 90 • 8 350 1,300 20 100 600 700 4 400 100 600 20 1,800  U T E R A T U R E REVIEW / 6 (U.S.  Environmental Protection Agency (U.S. EPA), 1974). Raw and stabilized sludges  may contain up to 90 to 95% water. Dewatering is a physical process to reduce water  content  to  improve  handling, processing,  transportation,  and  disposal  the  cost  of  sludges. The methods available for sludge stabilization include: 1.  Anaerobic digestion  2.  Aerobic digestion  3.  Composting  4.  Chlorine oxidation  5.  Lime stabilization  6.  Heat treatment  The sludge used in this study was anaerobically digested, dewatered, and then composted. Consequently only anaerobic digestion and composting are discussed here. Anaerobic digestion involves the biological degradation of sewage sludge in the absence of molecular oxygen. The process is carried in a closed tank with an airtight cover.  The  stabilized sludge  is non-putrescible,  reduced. Anaerobic digestion is a two-phase phase, acid formers  and  its pathogen  content  is greatly  process (Peavy et al., 1985). In the first  which consist of facultative  and  anaerobic  bacteria  ferment  the  complex organics to acids and alcohols of lower molecular weight. In the second phase, anaerobic  methane formers  convert the  acids and alcohols primarily to methane and  carbon dioxide. About 50 to 60% of the the organic substrate is metabolized, with less than  10% being converted  to  biomass.  The  residual  organic  material  consists  of a  mixture of microbial tissues, lignin, cellulose, organic nitrogen compounds. Composting  is  defined  as  the  aerobic  thermophilic decomposition  of  organic  solids to a relatively stable humus like material (U.S. EPA, 1978). Sludge compost is a  U T E R A T U R E REVIEW / 7 natural organic product with high humus content similar to peat It has a slight musty odor, is moist and dark in color, can be loaded in trucks, and bears little resemblance to the original material. The processes that have shown successful capabilities for dewatering sludges are (J.M. Montgomery, Consulting Engineers, 1985): 1.  Drying beds or lagoons  2.  Vacuum filtration  3.  Pressure filter press  4.  Belt filter press  5.  Centrifugation  Drying beds or lagoons rely on natural  evaporation and percolation to dewater  the  sludge. The other dewatering devices listed above rely on mechanically assisted physical means to dewater the solids more quickly. For smaller plants where land availabilty is not a problem, drying beds are generally chosen.  2.1.4. Sludge disposal options Sludge disposal is the process of transferring the sludge to the environment so that no additional handling or processing is required. Disposal options fall  into two  general categories: a. Utilization disposal options b. Non-utilization disposal options  Utilization refers to the beneficial use of the sludge or sludge by-products (i.e., soil amendment).  However, wastewater  because it contains  sludge  high levels of metals  may and  not other  be  always  used  toxic substances.  as  a  resource  In this  case,  U T E R A T U R E REVIEW / 8 sludge  options  that  do  not  involve beneficial  use  can  be  adopted.  These  options  include: incineration, landfilling, and dedicated land disposal. The concept of utilizing or recycling sludge nutrients on agricultural land is not only feasible but, in light of the present need  for resource and energy conservation,  this approach is also desirable. In the United States, recent laws encourage agricultural utilization  (U.S. EPA, 1979). The  industrial waste  Clean  pretreatment programs  Water  with  the  Act requires  the  establishment  of  objective of reducing toxic pollutant  loading to municipal treatment facilities. The implementation of pretreatment programs will trend  make more municipal solids suitable for land application. The sludge utilization was given a boost  authorized  the  U.S.  by the  Environmental  Resources  Conservation and  Protection  Agency  to  Recovery Act, which  develop  treatment  and  application rate criteria for sludge application to cropland. The beneficial usage of sewage sludge in agriculture is associated with its value as a fertilizer and as a soil conditioner. These virtues are discussed seperately in this review. However, due to the scope of the thesis more emphasis is put on the value of sludge as a soil conditioner.  2.2. S L U D G E AS A FERTILIZER Information  on  the  response  of  crops  to  sludge  addition  has  been  widely  to tall  fescue  published. A few findings are discussed here. Composted sludge was applied at  four rates (0 to 134 t/ha)  growing on two different soils (loamy sand and silt loam) (Sikora et al., 1980). The results indicated a positive linear relationship between crop yield and sludge application rate for both soils. Day et  al  (1982)  compared the effects  of dried sewage sludge and inorganic  L I T E R A T U R E REVIEW / 9 fertilizers on the yield and quality of hay from Harlem barley. The data showed that dried  sewage  researchers  sludge  may  did not find  be  used  as  an  alternative  source  for  fertilizer.  The  any concern regarding heavy metal toxicity to plants when  sludge is applied at a carefully planned rate. Field  studies with ariaerobically digested sludge were conducted  near  Guelph,  Ontario, using corn and bromegrass as experimental crops (Soon et al., 1978, I). The rates of application supplied 200, 400, 800, and 1600 K g N per hectare per year for 3 years. Bromegrass yields were increaesed by sludge application supplying up to 800 Kg N per hectare. On loam and clay loam soils, there was no further increase in the yield of corn with rates in excess of 200 K g N per hectare. Nitrate concentration in corn stover was increased at rates of 800 K g N per hectare and above (Soon et al., 1978, II). Phosphorus concentration in corn grain and stover was unaffected  by sludge  treatment, however it did increase in bromegrass with increasing sludge rates. The crops exhibited similar responses to large amounts of metal in sludge. Analysis of leachates from the lysimeter experiments indicated nitrate movement through soils which received sludge at rates in excess of 200 kg N per hectare. However there was little, if any, movement of phosphorus to the groundwater.  2.3. S L U D G E AS A SOIL CONDITIONER Soil conditioning implies the improvement of the soil's physical properties by treatment with chemical materials (Schamp et al., 1975). The chemical materials used are  either  chemicals.  inorganic The  salts,  organic  mainly  compounds  calcium range  salts, from  or  high  well-defined  molecular synthetic  mass  organic  polymers  to  UTERATURE REVIEW / 10 complex products whose properties are less clearly understood, frequently waste products. Organic matter stabilizes soil structure through the bonding of organic polymers to  clay surfaces by cation bridges, hydrogen bonding, Vander Waals forces, and  sesquioxides-humus  complexes (Baver et al., 1972). The drying of organic polymers  results in the formation of ah insoluble irreversible matrix. Thus the adhesive bonds formed are not expected to dissolve or break down upon wetting. Since these binding substances  are susceptible  to microbial  decomposition,  organic  matter  must be  replenished and supplied continually if aggregate stability is to be maintained in the long run (Hillel, 1980). This part of the review deals with physical processes in the soil with special reference to sewage sludge application. While the fertilizer values of sludges are now well assessed, studies on the influence of sludge organic matter on the physical properties of soil  are limited  (Guidi  and Hall, 1983). European  experiences of  wastewater sludge as a soil conditioner have been recently published (Catroux et al., 1983). This and other work have shown that sludge can be effective in improving structural and hydraulic properties of soils. The physical properties discussed here are: aggregate stability, bulk density, and hydraulic conductivity.  2.3.1. Aggregate stability  The  enhancement of soil  aggregation is of paramount importance  for soil  productivity. This is especially true for those soils under intensive crop production where the workability, a low tendency to surface crusting, and the resistance to the destructive actions of water and agricultural machinery  are essential to obtain high  yields. A one year study was initiated  on 3 Indiana soil types: a Celina Blount silt  I J T E R A T U R E REVIEW / 11 loam, a Blount silt loam, and Anaerobic  sludge  applied  at  a Tracy sandy 56  t/ha  loam (Kladivko  increased  the  and  mean  Nelson,  weight  1979).  diameter  of  water-stable aggregates in the top 5cm of a soil as much as 4 times over that of the control samples. The data also shows that aggregate stability decreased  over the  winter months in both sludge-amended and control plots, but the sludge-treated plots continued to exhibit more aggregation than their respective controls. A  field  study was established in Italy on a sandy loam soil (Guidi  et al.,  1983). A stability index (WSI) was used to quantify the stability of soil aggregates in water. WSI is defined aggregates  passing  as WSI=  through  a  100x(A/B), where  0.25  mm  mesh  A and  sieve  after  B are 5  and  the  weights of  60  minutes  of  wet-sieving, respectively. According to this method, the index increases as the stability of aggregates increases. The WSI of the control plots tended to be lower, but not always significantly, than  that of the  stability  and  of both  treated  sludge-treated  control plots dropped  plots (Figure 1). The aggregate sharply after  some  months. A  similar behavior has been been observed in Kladivko and Nelson's experiments (1979). The decay of aggregate stability over the  fall  and winter months has been mainly  attributed to: i) the lower biological activity, ii) the decomposition of organic matter during spring and summer, and iii) the destructive action of water. Furrer  and  Stauffer  (1983)  reported  the  results  of  a  field  experiment  Switzerland on a heavy soil. Sewage sludge was applied to meadow plots for  in five  consecutive years at 6 and 24 t/ha. There was no significant difference in aggregation between matter stability.  the  plots fertilized  loading was not  with  high  sewage  enough  to  sludge and mineral fertilizers. The organic trigger  a  significant increase  in aggregate  U T E R A T U R E REVIEW / 12 2.3.2. Bulk density Several studies indicate a decrease in bulk density in soils treated with sewage sludge. The decrease in bulk density is caused by the mixing of organic matter with the mineral soil (Khaleel et al., 1981). Dried  sludge  was  applied  to  a  Hubbard  sand  soil  (Gupta  et  al.,' 1977).  Addition of 450 t/ha annually decreased the bulk density of the sandy soil by 28% in 2 consecutive years. Hall and Coker (1983) reported significant reductions in the bulk density of 3 arable soils as a result of the addition of digested sludge at rates between 100 and 500 t/ha. While Gupta et al. (1977) and Hall  and Cocker (1983) used extremely high  rates of sewage sludge, Kladivko and Nelson (1979) applied the sludge at  moderate  rates that can be used in normal agricultural operations (i.e., 56 and 90 t/ha). Core samples were taken from the 0 to 5cm depth of the soil. Plots where sludge was disked-in exhibited a significant decrease in bulk density because most of the sludge applied was incorporated in the top 5cm of the soil. However, the incorporation of sludge by rototilling did not promote a significant decrease in bulk density because of the dilution effect of mixing the sludge in the upper 15cm rather than in the upper 5cm of the soil. Furrer and Stauffer (1983) conducted field and lysimeter experiments using low application rates (i.e., between 4 and 12 t/ha). In no case was a significant influence of sewage sludge application on bulk density reported.  1ITERATURE REVIEW / 13 2.3.3. Hydraulic conductivity The increased  limited  data  in sludge-treated  available  showed  that  saturated  soils, provided that sufficient  hydraulic conductivity (Ks) organic  material  had  been  used. The addition of anaerobic sludge at 450 t/ha Ks of a Hubbard sand soil by 17% from  3.0x10"  for 2 consecutive years increased 4  to 3.5x10" m / s 4  (Gupta et al.,  1977). In a pot experiment, sewage sludge was incorporated into a Beltsville silt loam subsoil at the rate of 5% on a dry weight basis (Epstein, 1975). The author  found  that Ks increased after the application time, reached a maximum, and then dropped to that of the control (figure 2). This decrease appears to be due to the: i) breakdown of soil aggregates. ii) clogging of soil pores by microbial decomposition products. Though the literature related to the influence of sludge application on physical properties  of  soil  is  limited,  there  is  an  evidence  that  structure  and  hydraulic  characteristics can be improved by sludge treatment. However, most of the significant effects  have been found in studies using high rates of sludge application (i.e., Gupta  et al., 1977, Hall and Coker, 1983). Those rates will ultimately result in heavy metal contamination of the soil and groudwater pollution as a result of overfertilization. The challenge is to apply the sludge at rates high enough  to enhance the soil structure  without causing deterioration of the quality of the environment (Kladivko and Nelson, 1979).  U T E R A T U R E REVIEW  / 14  to-  rn to  LJ  I  5-  Legend o c A CANS +  i i i i i i  i—i—i—i—i—i—i—i—i—i—r  i  i  i  ANS  i  TIME  Figure  1: E f f e c t o f sewage sludge a p p l i c a t i o n a t 38 t / h a on water s t a b i l i t y i n d e x . C= c o n t r o l , CANS= composted a n a e r o b i c s l u d g e , and ANS= a n a e r o b i c sludge ( G u i d i e t a l . , 1983).  E >-  > c_> => o  2  o o o _l  <  Legend  CC  o >X  100  TIME  Figure  (days)  120  O  CONTROL  A  *>7. SLUDGE  i  180  2 : E f f e c t o f sewage s l u d g e a p p l i c a t i o n on s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( E p s t e i n , 1975).  U T E R A T U R E REVIEW 2.4. S L U D G E APPLICATION  GUIDELINES  FOR AGRICULTURAL LAND  The agricultural utilization option assumes that sludge is added rates",  defined  as  the  annual  rate  at  / 15  which  the  nitrogen  supplied  at by  "agronomic sludge  and  available to the crop does not exceed the nitrogen requirement of the crop (U.S. EPA, 1983). In addition, the  application rate must  take into consideration  existing federal,  provincial, and local regulations relative to pathogens, metals, and organics contained in the sludge. Sludge may also be used as a soil conditioner if added at rates greater than  agronomic rates. In this case, increased  monitoring will usually be required for  potential nitrate movement into drinking water aquifers. Exceeding the allowable limits for  cadmium may result in restrictions on crop use (i.e., only non-food-chain  can  be grown).  crops  Guidelines for sludge application on cropland have been developed by the U.S Environmental Protection Agency (U.S. EPA, 1979). The criteria used are based on a management associated pathogens,  rather  with  than  a  performance  applying sludge  heavy  metals,  and  approach  on cropland. The  to  minimize  potential  problems  guidelines address mainly nitrogen,  polychlorinated biphenyls (PCB's)  contained  in sludges.  The following discussion emphasizes these guidelines.  2.4.1. Nitrogen A  major  management.  concern  Following  with  sludge  the  application  of  sludge  application, nitrate  is  formed  on by  land  is  nitrogen  nitrification of  the  ammonium either added in the sludge or released during the mineralization of organic nitrogen. Nitrate is a water-soluble anion that will move downward readily in the soil profile. High nitrate concentration in drinking water may result in health problems for both infants and livestock. The maximum allowable nitrate concentration in groundwater  U T E R A T U R E REVIEW / 16 has  been  established  at  45 mg/1. Nitrate pollution  can be  solved  by adding  the  amount of nitrogen from the sludge that is removed by the crop, plus whatever is volatilized  into the  atmosphere  or  is lost  due  to  denitrification, or considered an  allowable concentration in the groundwater (Vesilind, 1979).  2.4.2. Pathogens Untreated raw sludges contain a variety of pathogens. Any sludge applied to food-chain  crops  must  be  treated  by  a  process  to  significantly  reduce  pathogens.  Typical treatment processes have been discussed in section 2.1.3 . Pathogenic organisms do not enter plant tissues, but problems can result from contamination of the plant surfaces. Root crops and crops which will be eaten raw may not be grown for 18 months after sludge.  the time of application, unless there is no contact between crop and  Animals  should  not  be  grazed  on  the  site  for  one  month  after  sludge  application if the animal product will be consumed by humans.  2.4.3. Soil pH Food-chain crops can be safely grown if the soil pH is 6.5 or greater at the time of planting. The tendency of crops to accumulate heavy metals is significantly reduced as the soil p H increases above 6.5. If the soil p H is less than 6.5, limestone should be added to adjust it to p H 6.5.  2.4.4. Heavy metals From a human health standpoint, cadmium is the sludge-borne metal that has received  the  greatest attention.  Although  Cd is not usually phytotoxic, it is readily  absorbed by plants, can accumulate in edible parts, and enter the food chain (Naylor  U T E R A T U R E REVIEW / 17 and Loehr, 1980). Cd tends to accumulate in the kidneys, and may cause a chronic disease called proteinuria (i.e., increased excretion of protein in the urine). The annual application rate of Cd should not exceed 0.5 Kg/ha on land used for  the production of food-chain crops. For soils with a background pH of 6.5 or  greater, the cumulative Cd loading should not exceed the  levels given in table III.  These regulations were developed from considerations of allowable increases in dietary Cd for a worst case situation, e.g., a vegetarian growing 100% of his food on an acid, sludge-treated  soil. Non-food-chain crops can be grown on soils with a p H of less  than 6.5, provided that the cumulative Cd application rate does not exceed 5 Kg/ha reguardless of the soil cation exchange capacity (CEC). The cumulative metal limits in table III are a function of soil C E C . The use of soil C E C in establishing metal limits does not imply that metals added to soils in sludge are retained by the complex as an exchangeable metals in sludge amended  cation. It has been shown experimentally that nearly all soils are not present as exchangeable  1983). Thus, C E C was chosen as an indicator of soil properties, measured  and  related  to  exchange  soil  components  that  minimize  cations (U.S. EPA, since it is easily  plant  availability  of  sludge-borne metals in soil. In addition to Cd, the cumulative amounts of Pb, Zn, Cu, and N i applied to soils in sludge can be used to determine utilized. Limitations on the  the  number of years that sludge can be  total metal additions to soils are needed  to protect soil  productivity and animal health. The majority of crops do not accumulate Pb, but there is concern regarding the potential ingestion of Pb and other trace elements (Cu, Se, Mo)  by animals grazing on sludge-contaminated  forage  and indirect consumption of  soil. In general, Zn, Cu, and N i will be toxic to crops before their concentration in plant tissues reaches a level that poses a problem to human and animal health.  U T E R A T U R E REVIEW / 18 The  use  encouraged 1975).  application  (e.g.,  1981). Using properties  crops  (e.g., corn, pea,  Sludge  potential  of  cotton, sludge  which  accumulate  beans, berry  for  the  turfgrass, in this  fruits,  production and  manner  while circumventing the  small  tree fruits,  of  biomass  would realize  metals  (Keeney  crops  has  trees) (Abron- Robinson the  problems  heavy  tomato)  of non-food-chain  energy  potential  amounts  et a  is al,  great et al.,  advantages of its beneficial  associated  with the  impacts of  heavy metals on the human food chain. Sludge applications should cease when any single metal concentration  limit is  attained. If the soil p H is maintained at 6.5 or above, cessation of sludge application at the limits presented should enable  the growth of any crop in the future  without  any adverse effects on yield. In addition, soil productivity will be at a level equal to, and most likely greater than, that which existed prior to initiation of sludge appliction.  2.4.5. PCBs PCB's are relatively resistant to decomposition in soils and may be of concern from a human health standpoint. direct  ingestion  by  animals  The principal problem resulting from PCB's is the  grazing  on  forages  treated  with  surface-applied  sludge.  Several studies have shown that essentially no plant uptake of PCB's occurs, although PCB's can be  absorbed  containing concentrations  onto  the  surfaces  of root crops (U.S. EPA, 1983). Sludges  of PCB's greater than  10 mg/kg must  be incorporated  into  the soil when applied to land used for producing animal feed. Dairy cattle are very susceptible  to  partitioned  into  PCB contamination milk  fat,  Since  of  forages,  PCB's  are  since no  PCB's longer  constraints should become less common in the near future.  in  the  diet  manufactured,  are  readily  PCB-related  UTERATURE REVIEW / 19  Table I I I : Recommended cumulative l i m i t s f o r metals of major concern applied to a g r i c u l t u r a l land (U.S. EPA. 1983).  S o i l cation exchange capacity (meq/lOOg) 5 Metal  .  5 to 15 (kg/ha)  15 —  Lead  560  1,120  2,240  Zinc  280  560  1,120  Copper  140  280  560  Nickel  140  280  560  Cadmium  5  10  20  3. MATERIALS AND METHODS  3.1. SOIL AND SLUDGE CHARACTERISTICS The soil was collected from the top 20cm of the B horizon at the Boundary Bay experimental plots (Delta, B.C.). The basic soil mapping unit is the Ladner series (Luttmerding, stone-free  1981).  deposits  This  poorly  which are  drained  underlained  soil  has  developed  from  fine-textured,  by saline sandy materials at depths below  100cm. The material is grayish, partially leached, and contains reddish-brown  mottles.  Some physical and chemical characteristics are given in tables IV and V. The  sludge  was  produced  at  the  Iona  Island  Wastewater  Treatment  Plant  (Richmond, B.C.). Figure 3 illustrates the production process flow diagram. The sludge was composted by Envirocon Company to further  reduce:  1. Pathogen content 2. Water content 3. Heavy metal concentrations The chemical composition of the concentrations  and  maximum acceptable  sludge metal  is given in table  concentrations  VI. Heavy metal  in processed  sludge  are  reported in table VII. Heavy metal concentrations were based on 3 years of monitoring by Envirocon Company. A l l measurements were made according to procedures given in Standard Methods (American Public Health Association (APHA), 1975).  20  MATERIALS AND METHODS / 21  Table IV: S o i l p a r t i c l e s i z e d i s t r i b u t i o n (Driehuyzen, 1983). Particle size 2.0  1.0  0.500  0.250  0.125  (mm)  0.105  0.074  0.0625  0.050  0.002  95.1  93.1  88.8  23.4  -X Passing-  100  100  100  100  99.3  98.3  (Driehuyzen, 1983). CEC Jinlk density pH c hCarbon C l a s s i V: f i c aSome t i o n physical Table and chemical a r a c t e r i s tTotal-N i c s of the s o i l (li/cnO Humic Luvic Gleysol  1.40  (CaCl )  (2)  (JO  5.2  1.8  0.135  2  (meq/lOOg) 22.7  MATERIALS  AND  RAW WASTEWATER-  I i a -ARIF1!  PRIMARY SLUDCE  BIO - CAS PRODI CTION  METHANE  ANAE ROBIC DICE STER  LIQUID DIGESTED SLUDGE  SAND BEDS (DEWATERING)  WINDROW  COMPOSTING  O C X WITH, WOOD CHIPS)  FINAL  Figure  3:  Sludge  PRODUCT  production  process  flow  diagram.  METHODS  /  22  MATERIALS  A N D METHODS  /  23  Table VI: Chemical composition of the sludge.  ITEM **  MEAN (%)  S.D.U)  c.v.U)  RANGE(%)  n  TS  61.6  1.95  3.2  58.3-65.9  10  VS  14.7  1.5  10.3  11.5-17.5  10  NH j-N  0.55  0.1  18.2  0.45-0.70  10  TKN  1.15  0.14  12.2  0.95-1.31  10  TP  0.60  0.07  11.7  0.47-0.73  10  * Mean, s t a n d a r d d e v i a t i o n ( S . D . ) , c o e f f i c i e n t o f v a r i a t i o n range o f d a t a , and number o f samples ( n ) . **  Total total  s o l i d s ( T S ) , v o l a t i l e s o l i d s ( V S ) , ammonia-nitrogen K j e l d a h l n i t r o g e n (TKN), and t o t a l phosphorus ( T P ) .  (C.V.), (NH -N), 3  MATERIALS A N D M E T H O D S / 24  Table V I I : Heavy metal concentration of the sludge.  CONCENTRATION  1  Maximum Acceptable Metal Concentration  Arsenic  less than 20  75  Cadmium  leu than 10  10  Cfvomlnum  lets than 300  Cobalt  lew than 20  150  Copper  less than 750  750  Mercury  less than 3  4  Molybdenum  less than 20  20  Nickel  less than 100  160  Lead  less than 450  450  Selenium  less than 5  Zinc  less than 1,000  1.000  12 1,650  1.  A i l concentrations are in a dry weight basis, in ppm.  2.  B.C. Ministry of Environment: Composted Sewage Sludge maximum allowable concentration for non-restricted land application (Bertrand, 1980).  MATERIALS A N D METHODS / 25 3.2. E X P E R I M E N T A L DESIGN  3.2.1. Application rates The sludge application rates were based  on the guidelines established  by the  U.S. Environmental Protection Agency. The rates included an agronomic rate and  a  conditioning rate.  3.2.1.1. Agronomic rate The agronomic rate is based on the nitrogen and cadmium contents of of the sludge and the nitrogen requirement of the crop grown. Corn was used as a reference crop to derive the agronomic rate because: 1. it, is commonly grown in the area. 2. it has a high annual nutrient utilization. 3. it accumulates very little cadmium, provided lime is added to raise the p H to 6.5 . The advantages of using a crop that has a high annual nutrient utilization are: 1. more sludge nutrients can be recycled. 2. higher levels of organic matter can be added to enhance the soil structural stability without resulting in nitrate pollution of the Equation  3.1  was  used  to  groundwater.  determine  the  agronomic rate based  on  nitrogen  requirement (U.S. EPA, 1983): Np=  Sx[(N03) +  Kv(NH4) +F(No)]x(10)  where: Np= S=  Plant available nitrogen from sludge application, in kg/ha. Sludge application rate, in t/ha (dry weight basis).  (3.1)  MATERIALS A N D METHODS / 26 N03= Kv=  Volatilization factor; use K v = l for dewatered sludge applied in any manner.  NH4= F=  Percent nitrate-N in the sludge, as percent  Percent ammonia-N in the sludge, as percent  Mineralization factor for organic N in the sludge in the first year, expressed as a  fraction. For composted sludge use F=0.1 . No=  Percent organic N in the sludge, as percent In addition to considering the annual rate of nitrogen application, the rate of  cadmium application must be below the prevailing limit i f a food-chain crop is grown. The maximum annual  sludge application rate based on cadmium was calculated  using  equation 3.2 (U.S. EPA, 1983):  Scd= (Lcd/Ccd) (1000 kg/t)  (3.2)  where: Scd= Amount of sludge, in t/ha (dry weight basis), that can be applied based on C d limitation. Lcd= Cd limitation; use Lcd= 0.5 kg/ha/year,  (i.e., U.S. EPA standard as of 1/1/87)  Ccd= Concentration, in mg/kg, of Cd in the sludge. Note that the lowest of the 2 rates, S and Scd. was applied.  3.2.1.2. Conditioning rate The conditioning rate is defined  as a rate of sludge  application in excess of  the agronomic rate and where the improvement of the soil's physical properties is the main objective. In this study, the conditioning rate was arbitrary chosen to be 3 times larger than the agronomic rate.  MATERIALS A N D METHODS / 27 3.2.1.3. Treatments Three treatments were used in this study: 1. Treatment A : no sludge application or control .2. Treatment, B: sludge application at the agronomic rate 3. Treatment C: sludge application at the conditioning rate  Each  treatment  was  replicated  12  times  to  account  for  anticipated  deviations  in  hydraulic conductivity measurements.  3.2.2. Soil Packing The soil was packed in 4-liter paint pails. The pails were painted with latex paint to prevent rusting. Drainage holes were drilled and plastic screening was installed at the bottom of each pail. The soil columns were prepared in 4 steps: 1.  Aggregate preparation: The soil collected was spread on plywood boards and allowed to air-dry for 48 hours at room temperature. Big aggregates were broken down to pea size lumps using a flat shovel. The soil was then raked to insure aggregate size uniformity.  2.  Mixing: The  total  volume of raked  soil  was mixed half a  dozen times to obtain a  homogeneous source for packing. 3.  Sludge addition: Soil  samples  of  equal  weight  (i.e., 4000g  dry  weight)  were  taken  prior  to  packing. For treatments B and C the sludge was thoroughly mixed with the soil samples. 4.  Packing:  MATERIALS A N D METHODS / 28 The soil was packed in layers of 3cm each. Each layer was tamped by dropping on its surface, from a constant height, a 5cm x 5cm wood stick. Thus using the repeated  action  of  gravity  to  achieve  a  realistic, uniform,  and  reproducible  packing. Then, each layer was gently scratched with a wire brush to prevent the formation of low conductivity layers as a result of the packing technique. Bulk density was used as an index for packing uniformity.  3.2.3. Water regime The  soil  columns  temperature between  at  were  incubated  in  a  greenhouse  for  9  months.  The  10 A M . for that period was 21° C and the temperature  average  range was  17 ° C and 28 C. The experiment consisted of 2 phases during which 0  the  treatments were subjected to the same water regime: phase 1: infiltration requirement was always met phase 2: infiltration requirement was not always met  A soil's infiltration requirement is met when rainfall does not result in ponding. This implies that the soil's infiltrability is larger than the rainfall rate. The soil columns were subjected to wetting and drying cycles. Whenever water was applied, the soil surface was protected with cheeze cloth material to reduce the impact of water drops. Phase requirement Spring  and  1:  During  that  was always met summer  rainfall  period  which  lasted  (i.e., 4.4x10"^ m/s events  in  the  3 months,  the  infiltration  based on 2 years return period).  Boundary  Bay  area  (Atmospheric Environment Service, 1982). Water was applied carefully bottle twice a week.  soil's  were  simulated  with a squeeze  M A T E R I A L S A N D M E T H O D S / 29 Phase 2: During this period infiltration  requirement was not  which lasted  always met.  approximately  Ponding, a major  6 months,  the  lowland soil  soil's  problem,  was simulated monthly. Water was applied to the soil columns using a squeeze bottle. Once  a  thin  ponding  layer  was  gradually  established,  water  was  then  applied  continuously for 24 hours using 5mm tubing. A ponding layer of a constant depth was maintained. Figure 4 illustrates the process. The ponding tolerance of the soil columns is defined  within the  context  of this study  as  the  ability of the  soil  columns  to  withstand the destructive actions of surface free water.  3.3. SOIL P H Y S I C A L M E A S U R E M E N T S  3.3.1. Hydraulic conductivity The ponding tolerance  of the soil columns was evaluated  hydraulic conductivity ('Ks') at  the  end  of  each  ponding  by measuring event  The  their satiated term  satiated  hydraulic conductivity is used rather than saturated hydraulic conductivity to recognize that there was air entrapment upon ponding of the were  made  using  the  falling-head  method  (Klute,  soil columns. The measurements 1965).  A  schematic  of  the  falling-head apparatus used in this study is shown in figure 5. A 1cm thick plexiglass plate was lined with a soft rubber pail just  before  measuring  gasket The plate was placed on the top of the  'Ks'. Then, it was  connected  to  a constant head  water  supply and to a manometer using tubing. Weights were put on the top of the plate to insure a tight seal between the rubber gasket and the top of the pail, thus making the apparatus leak-proof. ' K s ' was calculated from Darcy's formula:  'Ks'=  (al/At) ln(Hi/H2)  (3.3)  MATERIALS AND METHODS / 30  OVERFLOW  WATER  A.  WATER SOURCE TPONDING DEPTH (3-4cm)  SAMPLE  COLUMN LENGTH (12-13cm)  c_rt"7,T»Lzr FREE DRAIKAGE FIGURE 4: A s l s u l a t e d 24-hour ponding event.  FREE DRAINAGE Hj» I n i t i a l hydraulic head H " F i n a l hydraulic head 2  Figure 5: Schematic of falling-head apparatus.  MATERIALS A N D METHODS / 31 where  'Ks' is the satiated  hydraulic conductivity (m/s), a is the area of the cross  section of the standpipe (m^), 1 is the length of the soil sample (m), A is the cross sectional area  of the  sample (m^), and t is the  time (s) for the  hydraulic head  difference to decrease from H i (m) to H2 (m).  3.3.2. Bulk density The  bulk density (BD) of the soil columns was determined at the beginning  and at the end of the experiment. B D is the ratio of the mass of the solids to the bulk volume of soil particles plus pore spaces in a sample (Blake, 1965). Three soil samples per column were taken to evaluate the gravimetric moisture content (Gardner, 1965). The column bulk volume was obtained from the volume of the pail occupied by  soil  material. The initial  uniformity.  The  final  bulk density  bulk density  was used  was determined  as an  index for  50 days after  the  soil packing last ponding  event At that time the water content of the columns was below the plastic limit thus allowing: 1.  mixing  of  the  soil  material  to  obtain  a  homogeneous  source  for  moisture  determination. 2.  simultaneous,  non-destructive  sampling at  various depths  for aggregate stability  testing.  3.3.3. Aggregate stability The soil's initial aggregate stability was evaluated three months before the first ponding event  based on 12 samples. To determine  the  final  aggregate stability, soil  samples were collected from the 0 to 5cm and 5 to 10cm depths of each column nine months after  sludge incorporation (i.e., 50 days after the last ponding event). A  MATERIALS  A N D M E T H O D S / 32  total of 48 samples per treatment was taken, half of which was from the 0 to 5cm depth while the other half was from the 5 to 10cm depth. The  method used to determine the stability of soil aggregates in water is a  modified version of the one described by Kemper (1965). Three grams of air-dried aggregates (l-2mm) were placed onto 0.25mm mesh sieves and moistened gently with a water spray device. A mechanical wet sieving machine was used to raise and lower the sieves through a distance of 2.5cm, 40 times each minute. In this manner, the action of flowing  water is simulated. After  10 minutes of sieving, the  sieves were  removed from the water and the oven-dry weight of the aggregates left on each sieve was determined. The soil particle size distribution (table IV) and laboratory dispersion tests showed that no correction was required for particles of diameter  greater  than  0.25mm. The standard procedure is to express aggregate stability (AS) in %: %AS=  (a/b)xl00  (3.4)  where: a=  oven-dry weight of aggregates left on the sieve after 10 minutes of wet sieving  (g). b=  oven-dry weight of aggregates before wet sieving (g).  3.4. ESSENTIAL NUTRIENT A N D H E A V Y M E T A L U P T A K E  EVALUATION  A side investigation was carried out to illustrate trends of essential nutrient and heavy metal uptake by bermuda grass. The soil-sludge mixtures were placed in wooden containers 30cm long, 20cm wide, and 15cm deep. The containers were placed in a greenhouse  along with  the  soil  columns and  were  watered  twice a  week  with  a  calibrated watering can. Two  months  after  sowing,  the  first  grass  cut  was  performed  followed  by  MATERIALS A N D METHODS / 33 biweekly cuts for approximately 4 months. A pair of scissors was used for cutting the grass. Composite samples consisting of 3 consecutive cuts were used to evaluate average  plant  sampling  uptake  period.  of  Four  essential  composite  nutrients samples  and per  heavy treatment  metals were  during  the  taken  during  the  elapsed each  sampling period.The foliage was digested according to the Parkinson and Allen method (1975). The digests were used to run K, Cd, Zn, Cu, Pb, and N i on an ICP-AES and  total  N  and  P on a  Coupled Argon Plasma -  Technicon Autoanalyzer II (i.e., A C P - A E S =  Inductively  Atomic Emission Spectromter. Model: Jarrel-Ash, Atomcomp  series 1110). Note that the number of samples taken did not permit validation of the trends  observed  content of the  through  statistical  soil was evaluated  analyses.  Furthermore,  the  plant-available  to assist in the interpretation  metal  of the results. The  Universal Soil Extract Method was utilized (Melich, 1984). The extracts were used to run the metals on an ICP-AES.  3.5. STATISTICAL ANALYSIS Before  any  statistical parametric  test can  be  carried  out,  it  is  essential  to  establish a statistical frequency distribution that adequately describes the data. Since soil physical properties  are generally well  described by either  the  normal or log-normal  distributions (Warrick and Nielson, 1980), it was decided that only these two will be considered.  The  best  fitting  frequency  distribution  was  determined  by  comparing  coefficients of determination, r , from linear regression of the normal deviate, Z, upon 2  both  the  raw  data  (normal  distribution)  and  distribution) (Lee et al., 1985). The frequency  the  log-transformed  data  (log-normal  that best describes a set of data was  assumed for statistical comparison. Data were analyzed using Analysis of Variance and Newman-Keuls multiple range test as described by Zar (1974). A l l statistical analyses  MATERIALS A N D METHODS / 34 were conducted at the 5% significance level, except when noted. Since the equations describing the mean, coefficient of variation, and deviation  for  log-normal  distributions  are  less  well  known than  those  standard  for  normal  distributions, they are briefly discribed below. The equations are applied to ' K s ' since the  log-normal distribution was assumed  only for the  'Ks' data  (Section 4.2). The  mean for log-normally distributed data ('Ks') may be determined using (Hastings and Peacock, 1975) 'Ks' = exp(X)  (3.5)  where X is the arithmetic mean of the log-transformed 'Ks' data. The appropriate coefficient of variation (CV) expression for log-transformed data is (Hastings and Peacock, 1975), C V = [exp(s )-l]xl00  (3.6)  2  where  s  2  is the  variance  of the  log-transformed  ' K s ' data,  s  2  is calculated using  (Warrick and Nielsen, 1980), s  2  =  l / ( n - l ) Y_ [(In'Ks')i Ui.i.  X]  (3.7)  2  where n is the number of ' K s ' measurements taken. The standard deviation (SD) is defined as as (Topp et al., 1980), SD = exp(s)  (3.8)  where s is the standard deviation of the log-transformed 'Ks' data (i.e., s=(s )^-^ ). 2  Due to the  log-transformation,  the  SD value is a multiplier/division  factor  of 'Ks'  rather than an addition/subtraction factor as is the case for a normal distribution (Lee et al., 1985).  4. R E S U L T S A N D DISCUSSION  4.1. APPLICATION R A T E The agronomic rate was based on a crop nitrogen requirement of 200 kg/ha. This corresponds to a sludge application rate (S) of 33 t/ha (i.e., 2.0% on dry weight basis). The maximum sludge application rate to food-chain crops based on cadmium limitation (S j) is 50 t/ha. Thus, sludge incorporation at 33 t/ha did not exceed the C(  annual cadmium limit recommended  for cropland by U.S. EPA. The conditioning rate  (S') was arbitrary chosen to be 100 t/ha (i.e., 6.1% on dry weight basis). S' can be applied to non-food-chain crops where heavy metal uptake is a lesser concern. The use of composted sewage sludge by the turfgrass Fraser Valley  over  and/or  the  Lower  has a great potential. One characteristic that distinguishes sludge from  chemical fertilizers is that its organic N is released growth  growers in the  a  relatively long period  amount  of  of N application to  and becomes  time. This greatly turfgTass  available to plant  reduces  that can reach  the  frequency  up to 300 kg/ha  (Beard and Rieke, 1969).  4.2. STATISTICAL DISTRIBUTION Tables VIII, LX, and X report the r  2  values of linear regression of the normal  deviate, Z, upon the raw data and the log-transformed that both the  normal and log-normal frequency  data. The r  2  values indicate  distributions adequately  describe  the  soil physical properties. The normal distribution was assumed for the statistical analyses of aggregate stability and bulk density data. The r normal  distribution  describes  well  the  'Ks'  2  values also show that although the  values  for  some  ponding  events,  a  universally good fit for all ponding events is obtained with the log-normal distribution.  35  RESULTS A N D DISCUSSION / 36  Table VIII: Goodness of f i t of normal and log-normal distributions to the hydraulic conductivity data as described by r .  TREATMENT  NORMAL  LOG-NORMAL  FIRST  A B C  0.95 0.95 0.94  0.98 0.98 0.98  SECOND  A B C  0.95 0.97 0.94  0.90 0.97 0.92  THIRD  A B C  0.77 0.70 0.78  0.88 0.91 0.87  FOURTH  A B C  0.96 0.77 0.79  0.94 0.95 0.97  FIFTH  A B C  0.90 0.97 0.97  0.91 0.97 0.98  PONDING EVENT  / 37  RESULTS A N D DISCUSSION  Table IX: Goodness o f f i t o f normal and log-normal  d i s t r i b u t i o n s to  the bulk d e n s i t y d a t a as d e s c r i b e d by r .  TREATMENT  NORMAL  LOG-NORMAL  INITIAL  A B C  0.B7 0.94 0.86  0.86 0.94 0.84  FINAL  A B C  0.93 0.97 0.92  0.93 0.96 0.90  BULK DENSITY  Table  X: Goodness o f f i t o f normal and log-normal d i s t r i b u t i o n s t o 2 the aggregate s t a b i l i t y d a t a as d e s c r i b e d by r .  DEPTH  OtoSe.  5 t o 10cm  TREATMENT  A B  A .  B  NORMAL  0.87  0.J0 0.97 0 95 0.95  LOG-NORMAL  M? 0.91  0.97 0.95 ^  RESULTS A N D DISCUSSION / 38 Conseqently, it was decided to use the log-normal distribution for the statistical tests on the 'Ks 'data. Figures 6 and 7 illustrate fractile diagrams of ' K s ' and ln('Ks') data for the 33 t/ha treatment at the end of the fourth ponding event Figure 6 indicate that the  r  2  value obtained (i.e., 0.75) using the normal distribution is due to lack of fit of the model  rather  than  to  high  random  scatter.  ralationship between Z and ln('Ks') (i.e., log-normally  Figure  7  illustrates  a  strong  linear  =0.96). Not recognizing that the data were  distributed would cause the mean to be poorly estimated  (Warrick and  Nielsen, 1980).  4.3. H Y D R A U L I C CONDUCTIVITY When the soil is subjected to potentially disruptive processes such as ponding, the structure will deteriorate as the aggregates tend to break down. Ponding and the action  of prolonged  water  flow  may cause the  collapse of the  aggregates, as  the  bonding substances dissolve and weaken and as the clay swells and possibly disperses (Hillel, 1980). Rowing water also provides the energy to detach particles and transport them away. The detachement and migration of particles may result in the clogging of pores and hence a reduction in hydraulic conductivity. The surface aggregates are  the  most vulnerable to the destructive action of ponding. The aggregates may collapse as a result of the presence of surface  free  water. The underwater  collapse of the  aggregates promotes the formation of a surface seal that clogs the surface and thus tends to inhibit the  movement  of water  into the  surface  macropores  soil columns. The soil  structure deterioration as a result of repeated ponding events is reflected in figure 8 by the decay of 'Ks' over time. The decrease of ' K s ' appears to be associated with the slaking of the mineral matter fraction of the soil. This was confirmed at the end  RESULTS A N D DISCUSSION  Figure 6 : F r a c t i l e diagram of the 'Ks' data f o r the 3 3 t/ha treatment (Fourth ponding event).  / 39  RESULTS  A N D DISCUSSION /  Figure 7: F r a c t i l e diagram of the ln('Ks') data for the 33 t/ha treatment (Fourth ponding event).  40  RESULTS A N D DISCUSSION / 41  Legend O  A=0 •/ha  +  B=3S t/ho  A  C=100 t/ho  RESULTS A N D DISCUSSION / 42 of  the  factor  experiment to  the  by  determining  aggregate stability in water.  decrease of ' K s ' over  time  is the  gradual  Another contributing  consolidation of the  soil  columns as reflected by an increase in bulk density at the end of the experiment Tables XI to X V report the number of measurements taken, mean, coefficient of variation, standard deviation, and range of ' K s ' data observed for each treatment at the end of each ponding event Figures 9 to 13 illustrate the 95% confidence intervals for the means for each ponding event The low ponding tolerance of the control columns was obvious at the end of the third ponding event This was manifested by a sharp drop of ' K s ' from m/s at the end of the first ponding event to 8.1x10"  1.4x10"  7  m/s at the end of the third  9  ponding event (Tables XI to XIII). Thus the control columns were sealed as a result of three 24-hour ponding events. Whether the soil is sealed or not depends on one's definition  of  conductivity suggested  the  term.  drops  A  below  soil  may  1x10"^  m/s  be  (De  by the Pennsylvania Department  point to which research  considered Tar,  as  1979).  sealed This  when value  its  hydraulic  was originally  of Environmental Resources as a  reference  results can be compared. Field measurements carried out by  the Department of Soil Science at the University of B.C. have indicated that ponded water  in spring infiltrated at  a rate of 2.0x10" ^ m/s  in the  presence of "a low  infiltrability surface layer" or a surface seal (de Vries, 1983). Adding composted  sewage sludge increased  the ponding tolerance  of the  soil.  This was reflected by statistically significant differences in hydraulic conductivity between the  control columns and the sludge-amended  bears  repeating  water-stable  that  the  addition  of  columns. Although mentioned before, it  organic  matter  enhances  the  formation  of  aggregates • through physico-chemical reactions between the organic colloids  and the soil constituents  especially the clay fraction. The drying of organic polymers  RESULTS A N D DISCUSSION  Table XI:  Hydraulic conductivity data f o r the f i r s t ponding  / 43  event.  TREATMENT STATISTICS*  A-0 t / h a  n  12  T  -15.78  •Ks'  (10-  m/s)  7  B«33 t/ha 12  a  1.4  -15.59  C « 1 0 0 t/ha 12  3  -14.96  1.7  3.2  S.D.  1.64  1.44  1.38  C.V. (%)  53.0  37.7  33.2  RANGE ( 1 0 -  7  m/s)  0.6-3.0  0.8-2.7  c  1.7-5.7  * Number of measurements (n), means (X and 'Ks'), standard deviation (S.D.), coefficient of variation (C.V.), and range of data, a-c A different alphabetic character indicates a significantly different 'Ks' at the 5Zlevel.  RESULTS A N D DISCUSSION  / 44  Table XII: Hydraulic conductivity data f o r the second ponding event.  T R E A T M E N T  A»0 t / h a  STATISTICS*  12 -I7.31  X 'Ks'  (IO*  7  m/s)  B»33 t / h a 12  a  0.3  -I5.62  C-100 t / h a 12  b  -14.69  1.6  4.2  S.D.  1.70  1.79  1.49  C.V. (%)  56.9  63.2  41.6  RANGE ( I O " m/s) 7  0.09-0.61  (Tand  0.5-3.9  c  2.2-6.6  * Number of measurements (n), means 'Ks'), standard deviation (S.D.), coefficient of variation (C.V.), and range of data, a-c A different alphabetic character indicates a significantly different at the 52 l e v e l .  RESULTS  A N D DISCUSSION  /  Legend A Lower 9SX confidence limit • Mean V Upper 9SX confidence flmlf  B TREATMENT  Figure 9: 95Z confidence i n t e r v a l s f o r the means of the hydraulic conductivity data ( F i r s t ponding event).  Legend A Lower 93X confidence limit • Wean V Upper 9SX confidence Omit  TREATMENT  Figure 10: 951 confidence i n t e r v a l s f o r the means of the hydraulic conductivity data (Second- ponding event).  RESULTS A N D DISCUSSION / 46 results in the  formation of an insoluble irreversible matrix. Thus aggregates stabilized  through clay-organic complexing are not expected to break down upon wetting. At the end of the second ponding event ' K s ' averaged 3.0x10" ^, 1.6x10" , and 7  4.2x10"  7  m/s for the 0, 33, and 100 t/ha  treatments, respectively (Table XII). Thus,  without simulated rainfall and if the evaporation rate is assumed to be equal to zero for  comparison purpose, ponded water 5cm deep will take around 1, 3, and 19 days  to infiltrate for the 100, 33, and 0 t/ha treatments, respectively. At the end of the last ponding event, 'Ks' values for the 0, 33, and 100 t/ha were 4.4x10" ^, and  3.8x10" 8 m/s,  respectively  depth will disappear  through  1.7x10"  (Table X V ) . Consequently, a ponding layer of 5cm  the sole action of infiltration in 15, 34, and 131 days  for  the 100, 33, and 0 t/ha treatments, respectively. These simplistic comparisons help  to  illustrate  the  increase  in  ponding  tolerance  as  a  result  of  organic  matter  incorporation. Note also that at the end of the last ponding event ' K s ' of the 33 and 100 t/ha treatments plummeted around the ' K s ' of the control columns observed at the end of the  second ponding event (i.e. 3.0x10"  addition of organic matter reduced  m/s). This confirms again that the  the vulnerability of the soil structure to ponding  since the action of 3 additional ponding events was required to decay 'Ks' of the treated columns to around 3.0x10" At  the  difference  end  of the  in ' K s ' between  first the  m/s. ponding event there was no statistically significant  control columns and  the  addition of sludge increased ' K s ' by 21% from 1.4xl0~ On  the  other  hand,  statistical  7  33 t/ha to 1.7xl0"  significance of 'Ks' data was  columns, but 7  the  m/s (Table XI).  observed  between  the  control treatment and the 100 t/ha treatment as ' K s ' increased by 126% from 1.4x10" to 3.2x10" of  7  m/s. These differences  7  are small compared to those observed at the end  subsequent ponding events. For example, at the  end of the second ponding event  RESULTS A N D DISCUSSION  Table  X I I I :  / 47  Hydraulic conductivity data f o r the t h i r d ponding event.  TREATMENT  A=0  STATISTICS*  n  t/ha 12  T  -18.63 •Ks'  (l0-« m/s)  S.D. C.V.  (%)  RANGE d O - "  m/s)  B«33 t / h a 12  3  -16.64  C-100 t / h a 12  b  -16.10  0.81  5.9  10.0  1.27  3.06  1.70  24.4  158.3  57.0  0.6-1 .5  1 .5-50.0  b  5.8-27.0  * Number of measurements (n), means ( X and 'Ks'), standard deviation ( S . D . ) , coefficient of variation ( C . V . ) , and range of data, a-b A different alphabetic character indicates a significantly different •Ks' at the 5Z l e v e l .  RESULTS A N D DISCUSSION  / 48  Table XIV: Hydraulic conductivity data f o r the fourth ponding event.  TREATMENT  *  A-0 t/ha  STATISTICS n  12  X  -I8.90  'Ks'  (10-" m/s)  B»33 t / h a 12  a  -I7.9l  C-100 t/ha 12  b  -16.86  0.62  1.7  4.8  S.D.  1.43  1.91  1.93  C.V. (%)  37.2  72.5  73.9  RANGE ( 1 0 - m/s) t  0.3-1.0  0.6-6.2  c  1.3-17.0  * Number of measurements (n), means (X*and 'Ks'), standard deviation (S.D.), coefficient of variation (C.V.), and range of data, a-c A different alphabetic character indicates a significantly different •Ks' at the 5Z l e v e l .  RESULTS A N D DISCUSSION /  Legend A Lower 9SX confidence limit + Mean v Upper 95X confidence limit TREATMENT  Figure 11: 95 Z confidence Intervals f o r the B e a n s of the hydraulic conductivity (Third ponding event).  V  •  'a  A  Legend  A  A Lower 9SX confidence •mlt  X  a hi  • Mean v Upper 95X confidence Hmll  a  0>>  B TREATMENT  Figure 12: 95Z confidence Intervals for the means of the hydraulic conductivity data (Fourth ponding event).  49  RESULTS A N D DISCUSSION 'Ks'  of the sludge-amended  columns was around  an order of magnitude  / 50  larger  than  that of the control columns. This difference was more or less sustained till the end of the experiment, being larger between the 0 and 100 t/ha treatments than between  the  0 and 33 t/ha treatments. The significant decrease of 'Ks' of the control treatment as a result of ponding was responsible for widening the gap between ' K s ' of the control columns and ' K s ' of the sludge-amended  columns. The addition of organic matter both  at 33 and 100 t/ha slowed down the decay of ' K s ' but could not stop it. The most plausible explanation is that sewage sludge incorporation was effective in increasing the resistance of aggregates to breakdown when subjected to ponding. Figure 14 shows that 'Ks' increased as the  organic matter loading increased.  This trend was validated for each ponding event by statistically significant increases in 'Ks' as the sludge application rate increased. The differences  in 'Ks' between the 33  and 100 t/ha treatments were consistently significant except for the third ponding event due to high random scatter of the 33 t/ha that  some  33  t/ha  columns  maintained  data. The scatter resulted from the  approximately  the  same  ' K s ' value  fact they  exhibited at the end of the second ponding event Figure 10 illustrates the overlap of the 95% confidence intervals for the means of the 33 and 100 t/ha treatments at the end of the third ponding event  4.4. A G G R E G A T E STABILITY The decrease in 'Ks' as a result of ponding was attributed to the slaking of the mineral matter fraction of the soil. To confirm this and furthermore deterioration  of the  and  end  at  the  vulnerable  to  soil structure,  of the  externally  aggregate stability was determined  experiment imposed  Soils vary  destructive  in the  forces  degree  (Hillel,  to  quantify  the  at the begining which  1980). Aggregate  they  are  stability  RESULTS A N D DISCUSSION  / 51  Table XV: Hydraulic conductivity data f o r the f i f t h ponding event.  TREATMENT STATISTICS*  12  n  X 'Ks'  -19.24 (10"« m/s)  S.D. CV.  A=0 t / h a  (%)  RANGE (10-* m/s)  B»33 t/ha 12  3  -I7.89  C-100 t / h a 12  b  -17.09  c  0.44  1.7  3.8  1.58  1.55  1.62  48.5  46.2  50.9  0.2-0.78  0.77-3.2  1.7-7.8  * Number of measurements (n), means (X and 'Ks'), standard deviation (S.D.), coefficient of variation (C.V.), and range of data, a-c A_£ifferent alphabetic character Indicates a significantly different 'Ks' at the 5Z l e v e l .  RESULTS A N D DISCUSSION  Legend *  M«on  V Upper 9SX eonfManct Hmlt  TREATMENT  Figure 13: 95Z confidence Intervals f o r the means of the hydraulic conductivity data ( F i f t h ponding event).  /  52  RESULTS A N D DISCUSSION  Figure 14: E f f e c t of sewage sludge application rate on hydraulic conductivity.  / 53  RESULTS A N D DISCUSSION (AS)  / 54  is a measure of this vulnerability. The concept of aggregate stability was applied  in this study in relation to the destructive action of water. Aggregate ponding 5cm  stability  of  the  soil  averaged  54%  three  months  event (Table XVI). However, the final AS of samples  depth  respectively  averaged (Table  14.9,  XVII).  33, The  statistically significant. Figure  and  58.6%  differences  for in  the final  0,  33,  before  the first  taken from  the 0 to  and  100  t/ha  AS between  the  treatments  15 illustrates the 95% confidence  treatments, were  intervals for the means.  Note that the sludge-amended columns exhibited an average final AS as much as four times over that of the control columns.  Table XVI: I n i t i a l aggregate s t a b i l i t y .  MEAN  S.D.  C.V.  (%)  (%)  (%)  54.0  5.0  9.3  RANGE (%) 47.2  -  60.8  * Mean, standard deviation (S.D.). c o e f f i c i e n t of v a r i a t i o n range o f d a t a , and number o f samples ( n ) .  n 12  (C.V.).  RESULTS A N D DISCUSSION / 55 The final AS of samples taken from the 5 to 10cm depth averaged 12.4, 20.9, and 37.8% for the differences  0, 33, and  100 t/ha  in final AS between  illustrates the  95% confidence  treatments, respectively (Table XVIII). The  the treatments were statistically significant. Figure 16 intervals for the  means.  Note that the  sludge-treated  columns exhibited an average final AS as much as three times larger than that of the control columns. Samples taken from the top 5cm of the soil columns exhibited a higher final AS than  samples  aggregates  taken  mentioned  before,  taken from  from the the  top  drying  is  5 to 10cm depth. This is due 5cm  depth  essential  for  dried the  to  a  lower  stabilization  of  to the water  fact that  content  aggregates  As  through  clay-organic complexing. The final AS of the soil columns averaged  13.7, 26.9, and 48.1% for the 0,  33, and 100 t/ha treatments, respectively (i.e., averages of samples taken from the 0 to 5 and 5 to 10cm depths). This corresponds to an overall decrease in aggregate stability of 75, 50. and 11% for the structure  deterioration  as  a  0, 33, and 100 t/ha result  of ponding  treatments, respectively. The soil  is obvious. The  addition of organic  matter increased the resistance of aggregates to breakdown when subjected to ponding (Figure  17). An agreement was  observed  between  the  AS and  ' K s ' data  as  both  physical properties varied in the same direction. The highest final AS corresponded to the treatment that maintained the  highest ' K s ' throughout  the  experiment, while the  lowest final AS corresponded to the treatment which exhibited consistently the lowest 'Ks'. could  However, due not  be  to  established  experimental as  limitations a relationship between  this would  have  involved  the  destruction  AS and ' K s ' of the  soil  columns at the end of each ponding event Another consideration is that sampling for the initial and final evaluations of AS was performed three months  before and fifty  RESULTS A N D DISCUSSION  / 56  * Table XVII: F i n a l aggregate s t a b i l i t y (0 t o 5 C M depth) . C.V.  S.D.  TREATMENT  MEAN (%)  A»0 t/ha  14.9  B«33 t/ha  33.0  O100 t/ha  58.6  RANGE (%)  (%)  (%)  a  5.9  39.6  7.4 - 30.1  24  b  7.2  21.8  23.2 - 44.9  24  C  9.5  16.2  39.4 - 70.8  24  * Mean, standard deviation (S.D.), c o e f f i c i e n t of v a r i a t i o n  (C.V.),  range o f d a t a , and number o f samples ( n ) .  a-c A d i f f e r e n t alphabetic character Indicates a s i g n i f i c a n t l y d i f f e r e n t aggregate s t a b i l i t y a t the 5Z l e v e l .  Table XVIII: F i n a l aggregate s t a b i l i t y (5 t o 10cm depth) .  TREATMENT  MEAN (%)  S.D.  A-0 t/ha  12.4  a  B«33 t/ha  20.9  b  C-100 t/ha  37.B  c  C.V.  RANGE (%)  (%)  (%)  3.4  27.4  5.9 - 19.7  24  4.1  19.6  13.7 - 31.6  24  13.4  35.4  20.0 - 63.5  24  * Mean, standard deviation (S.D.), c o e f f i c i e n t of variation  (C.V.),  range o f d a t a , and number o f samples ( n ) .  a-c Adifferent alphabetic character Indicates a s i g n i f i c a n t l y d i f f e r e n t aggregate s t a b i l i t y at the 5Z l e v e l .  RESULTS A N D DISCUSSION  7065V  6055>-  5045-  &  m  40-  </)  35-  £ O  30-1  LJ  oor o <  25 H 20-  Legend  15-  A lower 9SX cenf Mence BmJt  10-  + liton V Upper M X confidence limit  50-  l  6 TREATMENT  c  Figure 15: 952 confidence Intervals f o r the means of the f i n a l aggregate s t a b i l i t y data (0 to 5cm depth).  /  57  RESULTS A N D DISCUSSION / 58  706560-  IS >-  555045-  5  40-  00  35-  V +  LU  o  UJ  25  O O <  20-  CC  Legend  15-  A Lower 95X confldoneo ImH  10-  + Moon V tlppor 95X eonrioone* Mmlt  50-  B  TREATMENT  Figure 16: 95% confidence i n t e r v a l s f o r the means of the f i n a l aggregate s t a b i l i t y data (5 to 10cm depth).  RESULTS A N D DISCUSSION  sludge application rate on the f i n a l Figure 17: E f f e c t of aggregate s t a b i l i t y .  /  59  RESULTS A N D DISCUSSION / 60 days after the first and last ' K s ' measurements, respectively.  4.5. B U L K  DENSITY  The  initial  uniformity.  The  bulk  density  packing  (BDi) was  technique  aimed  used at  as  an  achieving  index a  for  realistic,  soil  packing  uniform,  and  reproducible bulk density. B D i averaged 1.21, 1.19, and 1.19 g/cm-* for the 0, 33, and 100 t/ha treatments, respectively (Table X I X ) . The soil packing was fairly uniform as reflected  by the  small coefficients  sludge-amended  columns may  of variation. The slight decrease in B D i of  be due  to mixing of the  composted  the  sludge with the  mineral subsoil. The wetting and and drying cycles resulted in the gradual consolidation of the soil columns. A 23% increase in the final bulk density (BDf) of each treatment was observed  (Table  X X ) . The  gradual  consolidation of the  soil  columns was probably  another factor contributing to the decrease of hydraulic conductivity over time. Statistical comparisons were conducted at the 1% significance level. In no case a significant  difference  in bulk density  structure  deterioration  was  not  hydraulic  conductivity  and  aggregate  was observed  reflected  by  stability  the are  between bulk  the  density  better  treatments. The soil measurements.  indices  of  soil  Thus,  structure  deterioration than bulk density.  4.6. ESSENTIAL N U T R I E N T U P T A K E The effects  of sludge application on the  potassium  in the  t/ha  not  did  foliage of bermuda  seem  to  affect  the  concentrations  grass were nitrogen  of nitrogen, phosphorus,  evaluated.  content  and  Sludge application at 33  (Figure  18).  However,  sludge  incorporation at 100 t/ha increased the level of nitrogen from 1.2 to 1.8% during the  RESULTS A N D DISCUSSION  / 61  * Table XIX: I n i t i a l  TREATMENT  *  (Packing) bulk density .  MEAN <g/cm»)  S.D. (g/cm>)  C.V. (%)  RANGE (g/cm>)  n  A>0 t/ha  1.21  0.02  1.6  1.16 - 1.24  12  B-33 t/ha  1.19  0.03  2.5  1.17 - 1.23  12  C«100 t/ha  1.19  0.02  1.7  1.14 - 1.22  12  Mean, s t a n d a r d d e v i a t i o n ( S . D . ) , c o e f f i c i e n t o f v a r i a t i o n range o f d a t a , and number o f samples ( n ) .  (C.V.),  Table X X : F i n a l bulk density.*  TREATMENT  MEAN (g/cm ) 1  A-0 t A a  S.D. (g/cm>)  C.V. (%)  RANGE (g/cm>)  n  1.49  0.02  1.3  1.47 - 1.52  12  B«33 t/ha  1.47  0.03  2.0  1.45 - 1.50  12  C-100 t/ha  1.46  0.03  2-1  1.41 - 1.49  12  * Mean, s t a n d a r d d e v i a t i o n r a n g e o f d a t a , a n d number  (S.D.),  coefficient o f samples ( n ) .  of variation  (C.V.),  RESULTS A N D DISCUSSION / 62 first sampling period and from 1.5 to 1.8% during the second sampling period. Initially, the  phosphorus  increased differences  concentration  (Figure  19).  between  the  appeared  However, sludge  to  sampling treatments  increase performed and  the  as  the  at  sludge  a  later  control  application stage  treatment.  rate  showed Also,  no  sludge  application did not seem to affect potassium levels throughout the experiment (Figure 20).  4.7. HEAVY M E T A L U P T A K E Sludge application was expected to increase the plant-available metal content of the soil because the pH was not adjusted to 6.5 or greater (i.e., lime was not added). Although mentioned before, it bears repeating that the availability of heavy metals to plants is significantly reduced as the soil p H is increased above 6.5 (U.S. EPA, 1983). Table X X I shows that except for nickel, the available metal concentration increased as the sludge application rate increased. The effects of sludge incorporation on the concentration of heavy metals in the foliage of bermuda grass were evaluated. The following results were observed: 1.  Cadmium: During  the  first  cadmium  concentration  However,  this  difference  between  trend  sampling as  was the  the  period,  sludge  weaker  data  application  during  concentrations  the  exhibited rate  an  increased  increase (figure  the  second  sampling period  of the  0 and  33  t/ha  as  sampling periods  Copper:  the  the  may reflect analytical error. Figure 20 also  shows an increase in cadmium concentration over time for all 3 treatments. 2.  21).  treatments was  negligible. The jump in the concentration of the control treatment between first and second  in  RESULTS A N D DISCUSSION / 63 Sludge application did not seem to affect copper concentration in the foliage of bermuda During  grass (Figure 22). The data were variable indicating no major the  second  sampling  period,  there  was  no  difference  trends.  between  the  concentrations of the 0 and 100 t/ha treatments. 3.  Nickel: Initially, a trend of increasing nickel concentration in the foliage with increasing sludge  application rate  during  the  second  was  observed  (Figure  sampling period as the  23). However, this  nickel concentrations  trend  faded  averaged  31.1,  25.6, and 31.0 ppm for 0, 33, and 100 t/ha treatments respectively. This can be justified  by the  fact  that sludge  addition  did not  affect  the  available nickel  concentration of the soil (Table XXI). Thus, the trend observed initially may be attributed to random variation. 4.  Lead: During the first sampling period there was no appreciable trend observed, only a slight During  increase the  concentrations  in  second  lead  concentration  sampling  averaged  period,  was  recorded  at  this  increase  was  5.5 and 7.3 ppm for the  100  0 and  t/ha  more  (Figure  visible  100 t/ha  as  24). the  treatments  respectively. However, there was no conclusive evidence to suggest a trend of increasing lead concentration with increasing sludge application rate because the lead levels of the 33 t/ha treatment were equal to or smaller than those of the 0 t/ha  treatment. Similarly, other studies have found that the increase in lead  uptake with increasing sludge application rate is minimal as most plants do not accumulate lead (U.S. EPA, 1983). The concern about lead is associated with the potential ingestion of lead by grazing animals. 5.  Zinc:  RESULTS A N D DISCUSSION /  64  Table XXI: Plant-available metal concentration i n the s o i l (ppm).  TREATMENT  pH(CaCl )  Cd  Ni  Cu  Zn  Pb  2  0 t/ha  (1)  5.0  0.6  65  66  32  25  0 t/ha  (2)  5.0  0.6  66  64  33  25  33 t / h a  (1)  5.0  1.3  68  93  77  61  33 t / h a  (2)  4.9  1.6  65  100  93  71  100  t/ha  (1)  5.1  3.5  65  168  216  139  100  t/ha  (2)  5.1  3.3  65  160  200  129  (1), (2)  Replicates.  RESULTS A N D DISCUSSION / 65  FIRST SAMPLING  SECOND PERIOD  F i g u r e 18: N i t r o g e n c o n c e n t r a t i o n i n the f o l i a g e bermuda grass (Dry weight b a s i s ) .  of  0.5  0.4-  FIRST SAMPLING Figure  19:  SECOND PERIOD  Phosphorus c o n c e n t r a t i o n i n the f o l i a g e bermuda grass (Dry weight b a s i s ) .  of  RESULTS A N D DISCUSSION / 66  FIRST SAMPLING F i g u r e 20:  SECOND PERIOD  Potassium c o n c e n t r a t i o n i n the f o l i a g e bermuda grass (Dry weight b a s i s ) .  of  1.6  FIRST  SECOND  SAMPLING PERIOD Figure 21:  Cadmium c o n c e n t r a t i o n i n the f o l i a g e bermuda grass (Dry weight b a s i s ) .  of  RESULTS A N D DISCUSSION / 67  15 -  FIRST  SECOND  SAMPLING PERIOD F i g u r e 22:  Copper c o n c e n t r a t i o n i n the f o l i a g e bermuda grass (Dry weight b a s i s ) .  FIRST SAMPLING Figure 23:  .  of  SECOND  PERIOD  Nickel c o n c e n t r a t i o n i n the f o l i a g e bermuda grass (Dry weight b a s i s ) .  of  RESULTS A N D DISCUSSION / 68  FIRST  SECOND  SAMPLING F i g u r e 24:  PERIOD  Lead c o n c e n t r a t i o n i n the f o l i a g e o f bermuda grass (Dry weight b a s i s ) .  FIRST SAMPLING F i g u r e 25:  PERIOD  Zinc concentration i i r t h e f o l i a g e of bermuda grass (Dry weight b a s i s ) .  RESULTS A N D DISCUSSION / 69 During the first sampling period, zinc concentrations averaged 19.5, 31.0, and 67.0 ppm  for the 0, 33, and 100 t/ha treatments respectively (Figure 25). However,  the gap between the 0 and 33 t/ha treatments was minimal during the second sampling period. The significant increase  in zinc concentration at 100 t/ha was  associated with a large jump in the available zinc concentration of the soil. The zinc concentration of the 100 t/ha treatment remained unchanged throughout experimental period.  the  5. S U M M A R Y A N D C O N C L U S I O N S 1. subsoil.  A greenhouse experiment  Composted  sewage sludge  was was  conducted  using  incorporated  at  soil-sludge mixtures were packed in 4-liter containers. indicator  for  soil  evaluate  the  effect  relation  to  the  a 0,  destructive  action  application  of  periodically simulated ponding events.  water.  on  The  silty  clay loam  33, and  100  t/ha.  The  Bulk density was used as an  packing uniformity. The main purpose of sewage sludge  Ladner  of the  the  soil  soil  structural  columns  Hydraulic conductivity and  experiment  were  was  to  stability in subjected  to  aggregate stability ,  two soil structural attributes relevant to the process of ponding, were used as indices for soil ponding tolerance. 2. The addition of sewage sludge increased the ponding tolerance of the soil. This was reflected by statistically significant differences 5% level between the sludge-amended  columns and the control columns. At the end of  the second ponding event the satiated 1.6x10" , and 4.2x10" 7  7  in hydraulic conductivity at the  hydraulic conductivity ('Ks') averaged  3.0x10" , 8  m/s for the 0, 33, and 100 t/ha treatments, respectively. The  soil structure deterioration as a result of repeated ponding events was reflected by the decay  of ' K s ' over time. At the  end of the  last ponding event the  average ' K s '  values for the 0, 33, and 100 t/ha treatments were 4.4x10" , 1.7x10" , and 3.8x10" 9  m/s, respectively. The addition of organic matter both down the  8  8  at 33 and 100 t/ha slowed  decrease of ' K s ' but could not stop i t The most plausible explanation is  that sewage sludge addition was effective in increasing the resistance of aggregates to breakdown when subjected  to ponding. The final aggregate stability of samples  taken  from the the 0 to 5cm depth averaged 14.9, 33.0, and 58.6%, for the 0, 33, and 100 t/ha treatments, respectively. On the other hand, samples taken from the 5 to 10cm depth exhibited final aggregate stability values of 12.4, 20.9, and 37.8% for the 0, 33,  70  S U M M A R Y A N D CONCLUSIONS / 71 and 100 t/ha treatments, respectively. The differences in AS between the 3 treatments were statistically significant at the 5% level. A trend of increasing hydraulic conductivity with increasing aggregate stability was observed. However, a correlation between the 2 factors could not be established due to experimental limitations. 3. In no case a significant difference in bulk density between was observed. The soil  structure  deterioration  as a result  the treatments  of of ponding was not  reflected by the bulk density measurements. Thus, hydraulic conductivity and aggregate stability are better indices of soil structure deterioration than bulk density. 4. A side investigation was conducted to illustrate trends of essential and heavy metal uptake soil  by bermuda grass. The available metal concentration of the  increased as a result of sludge application. The incorporation of sludge at  "agronomic rate"  (i.e., 33 t/ha)  did not  seem  to increase  uptake by bermuda grass. However, sludge treatment at the 100  nutrient  t/ha)  appeared  experimental plant  to  increase  the  nitrogen,  the  nutrient  and  the  metal  "conditioning rate" (i.e.,  cadmium, and  zinc  uptake  by  the  6. F U T U R E R E S E A R C H 1.  To  conduct  field  experiments  that  incorporate  controlled land  application of  sewage sludge in a comprehensive soil and water management program aimed at enhancing the hydrologic responsiveness of Lower Fraser Valley lowland soils. 2.  To determine the effects of sewage sludge application at moderate conditioning rates on the groundwater quality of lowland soils.  3.  To generate more information about  heavy metal uptake  by crops grown on  Lower Fraser Valley soils treated with sewage sludge. 4.  To check the  feasibility  of using sewage  sludge as an alternative  source or  supplement for chemical fertilizer in the production of turfgrass. 5.  To design a long-term program for the disposal of municipal sewage on land as 1  an alternative for ocean dumping and fresh water dilution in British Columbia.  72  REFERENCES Abron-Robinson, L., Lue-Hing, C , Martin, E.J. and Lake, D.W. 1981. Production of non-food-chain  crops with sewage sludge. U.S. Environmental Protection Agency,  Cincinnati, Ohio. APHA.  1975.  Standard  methods  for  the  examination  of  water  and  wastewater.  Fourteenth edition. American Public Health Association, Washington, D.C. Atmospheric  Environment  Service.  1982.  Canadian  climate  normals,  precipitations  (1951-1980). Environment Canada, Ottawa. Bastian, R . K . 1977. Municipal sludge management: EPA construction grants program. In R.C.  Loehr, ed. Land as a waste management alternative.  Ann Arbor Science,  Ann Arbor, Mich. Baver, L.D., Gardner, W.H., and Gardner.W.R. 1972. Soil physics. Fourth edition. John Wiley and Sons Inc., New York. Beard, J.B. and Rieke, P . E 1969. Producing quality sod. In Hanson, A . A . and Juska, F.V., eds. Agron. 14:442-461. Am. Soc. of Agron., Madison, Wis. Bertrand, R.A. 1980. Agricultural aspects of sludge application to cropland. In Sludge disposal  on  land,  its  future  in  British  Columbia. Ministry  of  Environment,  Province of British Columbia. Blake, G.R. 1965. Bulk density. In C.A. Black, ed. Methods of soil analysis, part 1. Agron. 9:374-390. Am. Soc. of Agron., Madison, Wis. Catroux, G., L'Hermite, P. and Suess, E,(Eds). 1983. The influence of sewage sludge application on physical and  biological properties  of soils. D . Reidel Publ. Co.,  Dordrecht. Day, A.D., Thompson, R . K . and Tucker, T.C. 1982. Sewage  sludge  as a source of  fertilizer for barley hay. Bio-Cycle. 23(2):42-44. Dean, R.B. and Smith, J.E 1873. The properties of sludges. In The proceedings of the joint conference  on recycling municipal sludges and effluents on land, Champaign, 73  / 74 Illinois. U.S. Environmental Agency, Cincinatti, Ohio. Driehuyzen,  M . G . 1983.  Boundary  Bay  water  control  project,  summary,  of  results.  De Tar, W.R. 1979. Infiltration of liquid dairy manure into soil. Transactions  of the  Ministry of Agriculture and Food, Province of British Coulmbia.  ASAE  22:520-528.  de Vries, J. 1983. Entrapment in the viscious circle of inadequate drainage, wet soils, compaction and ways of escape. In Proceedings and related papers of the British Columbia drainage workshop.  AbotsforcL B.C. Ministry of Agriculture and Food,  Province of British Columbia. Epstein, E  1975. Effect of sewage sludge on some soil physical properties. J. Environ.  Qual., 4(1): 139-142. Funer, O.J. and Stauffer,  W. 1983. Influence  properties of soils and L'Hermite, P. and  its contribution  of sewage sludge application on physical to the  humus balance. In Catroux, G.,  Suess, E , eds. The influence  of sewage sludge on physical  and biological properties of soils. D. Reidel Publ. Co., Dordrecht Gardner, W . H . 1965. Water content In C.A. Black , ed. Methods of of soil analysis , part 1. Agron. 9:82-125. Am. Soc. of Agron., Madison, Wis. Guidi, G . and Hall, J.E 1983. Effects of sewage sludge on the physical and chemical properties of soils, in L'Hermite, P. and  Ott, H . , eds.  Processing  and  use of  sewage sludge. D . Reidel Publ. Co., Dordrecht Guidi,  G., Pagliai, M . and  Giachetti, M . 1983. Modifications of some physical  and  chemical soil properties following sludge and compost applications. In Catroux, G., L'Hermite, P. and Suess, E , eds. The influence of sewage sludge application on physical and biological properties of soils. D . Reidel Publ. Co., Dordrecht Gupta, S.C., Dowdy, R . H . and Larson W . E 1977. Hydraulic and thermal properties of a sandy soil as influenced by the incorporation of sewage sludge. Soil Sci. Soc. Am. Proc. 41:601-605.  / 75 Hall,  J.E and  Coker, E G . 1983. Some  effects  of sewage sludge  on  soil physical  conditions and plant growth. In Catroux,G., L'Hermite, P. and Suess, E , eds. The influence  of sewage sludge  application on physical and  biological properties  of  soils. D . Reidel Publ. Co., Dordrecht Hastings, N.A.J. and Peacock, J.B. 1975. Statistical distributions. Butterworths, Toronto. Hillel, D . 1980. Fundamentals of soil physics. Academic Press, Toronto. J.M.  Montgomery, Consulting Engineers.  1985. Water treatment principles and  design.  John Wiley and sons. New York. Keeney,  D.R., Lee, K.W. and  wastewater  sludge  to  Walsh, L M . 1975. Guidelines for  agricultural  land  in  the  applicatio of  Wisconsin.  Technical  bulletin  of soil  analysis, part  88,  Madison Department of Natural Resources, Wis. Kemper,  W.D. 1965. In  C.A. Black, ed. Methods  1.  Agron.  9:511-519. Am. Soc. of Agron., Madison, Wis. Khaleel, R., Reddy, K.R. and M.R. Overcash. 1981. Changes in soil physical properties due to organic waste applications: a review. J. Environ. Qual. 10:133-141. Kladivko, E J . and Nelson, D.W. 1979. Changes in soil properties  from application of  anaerobic sludge. Journal WPCF. 51:325-332. Klute, A . 1965. Laboratory measurement of hydraulic conductivity of saturated soil. In C.A. Black, ed. Methods of soil analysis, part 1. Agron. 9:210-220. Am. Soc. of Agron., Madison, Wis. Larson, W . E , Susag,R.H., Dowdy, R.H., Clapp, C . E and sewage  sludge  in  agriculture  with  adequate  Larson, R . E 1974. Use of  environmental  safeguards.  In  Proceeding, sludge handling and disposal seminar, Ottawa. Environmental Protection Service. Lee,  D . M . , Reynolds, W.D.,Eldrick, D.E. and three  field  methods for measuring  Sci. 65:563-573.  Clothier, B . E 1985. A comparison  of  saturated hydraulic conductivity. Can. J. Soil  / 76 Loehr, R.C., Jewell, W.J., Novak, J.D., Clarkson, W.W. and Friedman, G.S. 1979. 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Environmental  Engineering.  McGraw-Hill Book Co., New York. Rajagopal, K... Lohani, B.N. and Loehr, R.C. 1981. Land application of sewage sludge: the status. Environmental Sanitation Reviews, number 2/3. Environmental  Sanitation  Information Center, Asian Institute of Technology, Bangkok. Schamp, N . , Huylebroeck, J., Sadones, M . 1975. Adhesion and adsorption phenomena in soil  coditioning.  In  B.A. Stewart,  ed.  Soil  conditioners.  Soil  Sci. Soc. Am.,  Madison, Wis. Sikora, L.J., Tester, C.F., Taylor, J.M., Parr, J,F. 1980. Fescue yield response to sewage sludge compost amendments. Agron. J. 72(1):79—84.  / 77 Soon, Y.K.., Bates, T . E , Beuchamp, E G . and Mover, J.R. 1980. Land application of chemically  treated  sewage  sludge:  I.  Effects  on  crop  yield  and  nitrogen  availability. J. Environ. Qual. 7(2): 269-273. Soon, Y . K . , Bates, T . E and Moyer, J.R. 1980. 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Treatment and disposal of wastewater  sludges. Ann Arbor Science,  Ann Arbor. Warrick, A.W. and Nielsen, D.R. 1980. Spatial variability of soil physical properties in the field. In D. Hillel, ed. Application of soil physics. Academic Press, Toronto. Zar, J.H. 1974. Biostatistical analysis. Prentice Hall Inc., Englewood Cliffs, New Jersey.  

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