British Columbia Mine Reclamation Symposium

Successful trials lead to commercial scale reclamation with bio-solids : an update on GVRD bio-solids.. Duthie, David; Peddie, Craig Cameron, 1956-; Salahub, Donna 1994-02-17

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th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  SUCCESSFUL TRIALS LEAD TO COMMERCIAL SCALE RECLAMATION WITH BIO-SOLIDS - AN UPDATE ON GVRD BIO-SOLIDS APPLICATION TO COPPER MINE SPOILS. David Duthie, Residuals Program Manager, GVRD Craig Peddie, Senior Staff Engineer, GVRD Donna Salahub, Contracting Engineer Greater Vancouver Regional District Sewerage & Drainage Department 4330 Kingsway, Burnaby, B.C. V5H 4G8  ABSTRACT In May of 1993, at the Seventeenth Annual Mine Reclamation Symposium, the GVRD described the implementation of two demonstration projects on copper mine spoils in Princeton , B.C., using hydraulic application and several methods of solids spreading on a range of substrate materials and terrain conditions. This discussion reports on the results and conclusions of that work. Vegetation in the first growing season was spectacular on plots at the Granby Tailings Pile. Application rates of between 55 and 180 dry tonnes/ha resulted in establishing a crop of mixed grasses and legumes yielding between 1700 kg/ha and 5800 kg/ha on literally barren ground. At the highest application rate, organic matter was raised from zero to nearly three percent, one-half the typical level of Princeton rangeland. No indication of nitrate leaching was observed in the soil profile although mass balances indicated higher volatilization man expected. No measurable increases of metals levels in the resultant soils were observed., Two plots received second applications and tillage trials in September of 1993. Hydraulic application to steep slopes of waste rock heaps at the Similco Mine proved successful in promoting a vegetative cover. The bio-solids coating adhered to the rock and resisted washing down the slope. Areas with existing vegetation showed significant benefit from the fertilizer values. The use of graders proved difficult for controlling lift thickness in flat applications resulting in a sealing effect on available soil substrate but better vegetation was established on scarified areas. For all plots, there were no indications of nutrient movement beyond the applied areas.  192  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  Wood wastes were incorporated into some of the test plots at the Granby site and were found to be very useful in nutrient management and developing soil structure. The unqualified success of these developmental projects has provided strong justification and the technical "know-how" to embark upon a program of commercial-scale operations. The GVRD has applied for permits to reclaim approximately 40 ha at each site in 1994 to commence ongoing programs.  INTRODUCTION The Greater Vancouver Regional District has committed to annually recycle 100,000 tonnes of processed sewerage sludge by the end of the decade, in economical and environmentally safe beneficial uses. The Residuals Program has undertaken considerable research activity to develop engineered nutrient formulations of processed sewerage sludge (bio-solids) for both fertilizer and soil building applications. Excellent results have been demonstrated in the fertilizing of rangeland, poplar tree plantations and evergreen forest areas and in establishing soil and vegetation on disturbed land including landfill cover, tailings piles and waste rock heaps. Reclamation of disturbed land with a soil amendment of biosolids, or treated wastewater sewage sludge, is well proven in trial and commercial scale operations in the United States and Europe. Biosolids have been applied to the acid spoils of the Palzo tract in southern Illinois, to Philadelphia coal mines, to a high elevation gold mine in Montana and to the Palmerton Superfund site in Pennsylvania. In the United States this work has successfully returned over 1500 hectares of disturbed land to productivity. In 1992, the Greater Vancouver Regional District, in conjunction with the Town of Princeton and Similco Mines Ltd., carried out trials on abandoned copper tailings and waste rock piles to demonstrate the use of biosolids in reclamation. The biosolids were trucked from the Annacis Island Wastewater Treatment Plant hi Vancouver to the sites, located near Princeton for application to flat portions of the abandoned tailings site and to all aspects of the waste rock piles. The primary focus of the trials was to demonstrate! building a viable soil in situ with biosolids. The variety of application rates and methods used were described in a paper given at the 1993 Mine Reclamation Symposium. This year's paper highlights the excellent results achieved with respect to improved soil fertility, vegetation establishment and environmental monitoring.  193  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  RESULTS AND DISCUSSION The biosolids application trials have been evaluated on the basis of several criteria including the facility to create a soil in-situ, the extent and uniformity of vegetative cover established, the quality and quantity of the vegetation, and the results of a thorough environmental monitoring program. Each of these are discussed in detail below. Soil Building Criteria and Results The trial results clearly demonstrate the soil building capacity of biosolids. Tailings, for example, are comprised of sand and silt fractions characterized in Table 1.  Table 1  Similco Soils and Granby Tailings Characteristics  While typical levels of organic matter measured on rangeland soils adjacent to the tailings pile were 6%, the low organic matter level of 0.1% in the tailings by comparison reflects an absence of soil development subsequent to placement of the tailings. Similarly, mineral nitrogen or nitrogen that is immediately available for plant growth in the ammonium and nitrate forms is less than 1 ppm. Typical levels for these forms in fertile soil are 50 to 100 ppm. The reserve pool of organic nitrogen which is slowly released over the growing season, or seasons is the difference between total nitrogen and available nitrogen. Optimum values for soil organic nitrogen are between 0.2 and 0.4%, or about 2000 to 4000 mg/kg. The reserve pool of nitrogen is only 57 mg/kg in the tailings and 174 mg/kg at the Similco site indicating that these sites have severe deficiencies of organic nitrogen. Fertility analyses of the tailings showed similar nutrient deficiencies for phosphorus, zinc, boron and manganese. At the Similco site iron, boron, zinc and manganese were deficient.  194  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  Figure 1  Post Application Fertility  The improvement in soil fertility is best shown in the charts in Figure 1 and Figure 2. Here, macro and micro nutrient levels are compared with background levels, for the tailings plots. The graphs show the positive effect of the addition of biosolids to the soil fertility for two different application rates. At these application rates, soil organic matter was increased from 0.1% to 1.0% and 2.4%, and soil total nitrogen was increased from 50 mg/kg to 1245 mg/kg and 2100 mg/kg (0.12% and 0.21%). Micronutrient levels were generally unproved by the addition of biosolids, as shown in the charts. The final organic levels are less than the 6% organic matter typical for this region, but much improved over the background levels. The total nitrogen levels approach the 0.2 to 0.4% levels considered optimum for fertile soils.  195  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  Figure 2  Post Application Fertility  Biosolids contain a variety of beneficial, soil building microorganisms. During the growing season, much of the ammonium in the biosolids/soil layer was nitrified, confirming the biosolids' contribution of beneficial bacteria to the soil. Both the ammoniacal and nitrate forms of nitrogen are desirable and immediately available for plant uptake. The fact that this conversion occurred is normal, expected, and confirms that a viable soil has been established. Vegetation Establishment Criteria and Results The tailings plots were seeded in the fall with a reclamation and nurse crop seed mix. The nurse crop mix was designed to germinate and establish quickly, modifying the germinating microenvironment for the reclamation seed. The nurse crop is expected to die out over subsequent years leaving the final reclamation vegetation varieties. Species from both crop mixes were established in the first year, with the fall rye from the nurse crop forming the predominant species. The visual results were dramatic and spectacular as a healthy, thick crop established itself on the otherwise devoid tailings. The establishment of this vegetative cover within one growing season is shown in the before and after photographs (Photographs 1 & 2). The yield on the plots was measured and varied with the application rate, as shown hi Table 2.  196  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  Table 2  Granby Tailings Crop Yields  The quantity or productivity of vegetation established on the tailings exceeded what was measured on the adjoining rangeland, or normal productive levels for this area. The goal of achieving a sustainable cover equal or exceeding normal productive levels for the area, was achieved within one growing season. The yield on the reclaimed tailings varied between 1700 and 5800 kg/ha, exceeding the 900 kg/ha yield measured on nearby range by a factor of two to six times. Seeded control areas on the tailings supported almost no growth, confirming the soil model criteria used to design for a productive vegetative stand. Only limited vegetation was established on the flat portions of an unreclaimed waste rock pile due to problems experienced in applying biosolids. The graders used had difficulty spreading the biosolids evenly over the site, resulting in areas receiving little or no biosolids while other areas received an excessive application. This plot is expected to fill in with vegetation over time. Plans for future work on this type of terrain are based on spreading the biosolids with manure spreaders, followed by ripping to distribute the biosolids and fines in the soil profile. These two operations are expected to improve the reclamation success. Vegetation also established to a limited degree on the slopes of the waste rock piles. Here, on a previously unreclaimed dump face with no overburden, vegetation has developed by the end of the first growing season. Although fall seeding was successful on the tailings, it was less successful on the slopes at Similco. Although we can only speculate on the cause it appears that the seed was lost over the winter due to wind and water erosion. Future trials will incorporate the seed in the biosolids spray rather than using a post-application technique. Other slopes seeded in the spring following the biosolids application, consistent with normal seeding practice at Similco, fared much better. Two sloped dump faces, which already had vegetation growing on them, showed a marked  197  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  increase in cover quality after they were also treated with biosolids. No yield measurements were made on the slopes because of the difficult terrain, however, similar results from biosolids application trials on rangeland in the area can be used to estimate the yield increases. These rangeland trials were comprised of biosolids applications at one half, the same and two times the application rate used on the waste rock slopes. The yield was 2.9 times, 4 times, and 7.2 times that of the control area. Mean values for vegetation quality analysis results are shown in Table 3 below. These are compared with results for vegetation samples from control plots and some typical norms for alfalfa to compare with Plot 1. The plant mix on the other plots is too complex to provide meaningful comparisons but plant tissue metal concentrations are typically below levels considered phytotoxic and below levels considered toxic to livestock. Higher copper levels were measured on one tailings plot applied with biosolids (Plot 3a) and on two control plots (no biosolids). Although 3a received the highest application rate, the fact that both controls also exhibited high copper uptake suggests that the result is spurious. Sample cleanliness or weed uptake is a more likely explanation than to suggest it relates to application rate. The alfalfa crop on Plot 1 would be considered protein deficient but exhibits normal levels of copper, molybdenum and zinc. Overall, there did not appear to be any significant change in plant tissue metals content attributable to the biosolids applications.  198  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  ENVIRONMENTAL IMPACTS The key objective of the monitoring program is to ensure that the application has no adverse impact on the environment. All biosolids applications to land are regulated under the Ministry of the Environment, Lands and Parks. While guidelines have been established to ensure public safety and environmental quality for agricultural applications, land reclamation guidelines are still under development. As a result, the Approval for the trial projects required extensive monitoring for nutrient leaching, metals concentrations in the biosolids/soil layer and metals uptake in the vegetation. Biosolids contain both immediately available, inorganic nitrogen, and slow release organic nitrogen. Reclamation use of biosolids is intended to build a soil while providing sufficient mineral nitrogen to quickly establish a self sustaining vegetative cover. In providing a pool of nitrogen which will last for several years, there is potential in the first year for an excess of available nitrate nitrogen to develop. The rate of mineralization of organic nitrogen is highly dependent upon complex soil biology and climactic conditions and is still quite unpredictable. Nitrate, because of its solubility in water, can move with water percolating into the sub-soil. Unlike the ammonium ion which is largely tied up by cation exchange in these alkaline soils, nitrate is the most likely of the two plant available nutrients to move freely into the sub-soil. Leaching into ground water or surface water systems, however, also depends; on site conditions, precipitation and the location of aquifers and streams. Each biosolids application is designed to minimize nitrate leaching and these trials were designed to extend our knowledge of nutrient dynamics and to confirm predictive models being developed for nitrogen mineralization and movement in the soil. On the tailings, soil samples were taken to a depth of 150 centimeters and analyzed for all forms of nitrogen, before and after the trials. As expected, the soil samples from the upper 30 cm profile into which the biosolids were tilled showed increases in all forms of nitrogen. All soil samples taken from all plots below 30 cm showed no increase in nitrogen levels. The field soil sampling indicated that no leaching of nitrate nitrogen had occurred on the tailings plots. Considering me late fall application where the most severe combination of winter moisture and lack of early vegetative cover created a worst case scenario, these results have been very promising. We will continue to monitor these plots through the next growing season and we are carrying out several supporting studies with the University of British Columbia. Column tests in this program have confirmed field observations that very little water moves through the tailings and that leaching is unlikely. Other work is attempting to refine the predictive model for both volatilization and mineralization. These trials have indicated that, a least in the dry belt climate of Princeton,  199  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  ammonia losses to volatilization were far greater than predicted and that mineralization of organic nitrogen has proceeded more slowly than commonly believed. The approval for the trial projects also required extensive soil monitoring for total metals. Biosolids contain trace levels of arsenic, lead, mercury and cadmium. In addition, biosolids contain copper, nickel, zinc, and other metals which are also micronutrients required by plants. The approval required establishing a background level of metals prior to the biosolids application followed by post application monitoring. Table 4 below, shows that total metal levels on the biosolids sites changed very little, if at all. The addition of biosolids had the effect of diluting the naturally occurring high copper levels in the upper soil profile. No metal accumulation was observed in the tillage zone nor were there any signs of metal movement or accumulation below the tillage.  200  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  SUMMARY AND FUTURE PROJECTS The trials are essentially completed and the results are favorable. Plans are being put into place for full scale projects at each of these two sites. Some additional work is planned to evaluate the potential for excessive copper and molybdenum uptake in vegetation. The Greater Vancouver Regional District has applied for permits for the Similco and Granby tailings sites. The total area which will likely be permitted will be about 500 ha. Plans are in place to apply biosolids to approximately 80 hectares for 1994, including the bulk of the abandoned Granby tailings. The reclamation work at Similco will consist of soil building in unreclaimed areas and lighter applications of biosolids to increase productivity and provide some additional soil building for already reclaimed areas.  References: GVRD Applications for Approvals GVRD First, Second Third, Progress Reports to the MOE, 1993,1994 MOE Draft Guidelines USEPA 503's USEPA Process Design Manual GVRD Application for a Permit - Similco R.L. Westerman, 1990, Soil Testing and Plant Analysis, Soil Sc. Soc. of America, pp. 613-615  201  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  Photograph 1: Grandby Tailings “Before”  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  Photograph 2: Grandby Tailings “After”  th  Proceedings of the 18 Annual British Columbia Mine Reclamation Symposium in Vernon, BC, 1994. The Technical and Research Committee on Reclamation  202  


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