British Columbia Mine Reclamation Symposia

Engineering approach to mine reclamation with biosolids 2009

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Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation ENGINEERING APPROACH TO MINE RECLAMATION WITH BIOSOLIDS Karin Renken, B.Sc. (Hons. Phys.), M.Sc. (Bio-Resource Eng.) Sperling Hansen Associates Inc., 1401 Crown Street, N. Vancouver, B.C., V7J 1G4, Ph. (604) 986-7723 ABSTRACT Biosolids (treated municipal sewage sludge) used as a soil amendment has been demonstrated to help establish and sustain vegetation on mine tailings and waste rock dumps in B.C. and internationally. This paper outlines an engineering approach to calculate biosolids application rates and suggests monitoring guidelines for operational scale biosolids applications. In addition, a list of general best management practices is presented. Key parameters for biosolids use are related to the site's hydrology, hydrogeology, soil properties, in-situ vegetation, and current and projected wildlife population. The nutrient sensitivity of surrounding waterheds is another key parameter. Biosolids is typically applied at either a fertilizer or a reclamation application rate. Biosolids is applied to vegetated, but nutrient deficient, areas at fertilizer application rates. Biosolids is applied to unvegetated, and organic matter and nutrient deficient areas at reclamation application rates. Application rate calculations are primarily based on the organic matter and nitrogen contents and to a lesser degree on trace element concentrations in the biosolids and the soil to be amended. It is proposed, but not discussed, to base estimations in application rate calculations on the biodegradable C:N ratio instead of the conventionally used Total C:Total N ratio. Algorithms for the determination of fertilizer and reclamation application rates are provided. INTRODUCTION  Biosolids is municipal sewage sludge or septage which has undergone a thorough wastewater treatment process, and which can be safely and effectively recycled on land. In B.C., land application of biosolids is regulated by the "Guidelines for Disposal of Domestic Sewage Under the Waste Management Act" (B.C. MoELP 1983). However, new regulations, entitled "British Columbia Municipal Organic Matter Recycling Regulation" (Regulation), are currently being developed. This paper is a preview of the guidance document for mine and other land reclamation for the latter regulation. '"Land Reclamation' means restoration of productivity to land which has been impaired through processes such as erosion, mining, land clearing, or other activities conducted by people" (B.C. MoELP 1997). Once the Regulation is in effect, only biosolids that meet the following Class A or Class B pathogen reduction requirements can be applied to land without a special authorization under the Waste Management Act (B.C. MoELP 1997): 108 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation Class A: The density of fecal coliform in biosolids shall be less than 1,000 MPN per gram of total solids (dry weight basis). If the density of fecal coliform is more than 1,000 MPN per gram for any one out of five discrete samples, then the density of Salmonella sp. bacteria in the biosolids shall be less than 3 MPN per 4 grams of total solids (dry weight basis). Class B: The density of fecal coliforms (based on at least five discrete samples) shall be less than 2,000,000 MPN per gram of total solids (dry weight basis). The level of pathogen reduction determines which requirements in the Regulation apply for site selection, access and harvest restrictions, and buffer zones. In B.C., general and legal requirements for mine reclamation and closure are specified in the "Health, Safety and Reclamation Code for Mines in British Columbia" (Code) (B.C. MEMPR 1992). According to that Code: 1) All disturbed areas on mine sites, except certain pits and permanent access roads, if required, need to be reclaimed and revegetated as part of the mine closure process unless exempted by the Chief Inspector of Mines or exempted in the Code.  Pit walls constructed in rock, and/or steeply sloping footwalls, and pit floors impounding water, are not required to be revegetated. 2) On all lands to be revegetated, the growth medium (material capable of supporting vegetation growth) shall satisfy land use, productivity, and water quality objectives. 3) Land shall be revegetated to a self-sustaining state using appropriate plant species. 4) Vegetation grown on a mine site must be monitored for metal uptake and where harmful metal levels are found, reclamation procedures must ensure that levels are safe for plant and animal life. 5) The desired land productivity shall not be less than existed prior to mining on an average property basis unless exempted by the chief inspector. 6) The owner, agent, or manager shall undertake monitoring programs to demonstrate that reclamation objectives including land use, productivity, water quality, and stability of structures are being achieved. Sperling Hansen Associates Inc. are in the process of developing a Technical Support Document (TSD), Guidelines, and a Manual of Practice (MOP) for biosolids use in mine and other land reclamation following an engineering approach. The TSD will serve as the basis for the simpler working documents. It includes a comprehensive, and yet concise literature review of practical and theoretical aspects of recycling biosolids on land including: case studies of top soil development and site rehabilitation, nutrients and metals in soil, metal uptake by plants, water quality, and organic contaminants in biosolids. The Guidelines cover the topics of site assessment and design of reclamation and monitoring plans for communication between the biosolids producer, land owner, and regulating governmental agency. The MOP will be a field reference guidebook summarizing the practical aspects contained in the TSD. 109 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation DESIGN OF A RECLAMATION PLAN FOR BIOSOLIDS USE Boundary Conditions As first steps in the design of a reclamation plan for biosolids use, applicable regulations and site permits must be reviewed and a reclamation goal must be clearly defined. In addition, the following information should be compiled: mine location, size, and projected lifespan; land ownership, including surface and mineral rights, and licensed users; geology and description of deposit; proximity to inhabited places; site access; and areas currently available for reclamation. Key parameters or boundary conditions for the design of a reclamation plan for biosolids use are related to the site's hydrology, hydrogeology, soil properties, in-situ vegetation, and current and projected wildlife population. The nutrient sensitivity of surrounding waterheds is another key parameter. To determine the boundary conditions and to identify which areas are similar enough to be treated as one unit in the reclamation plan, a site inspection is required. Areas should be classified based on slope, coarse fragment content or soil texture, elevation, aspect, thickness of soil or overburden cover, vegetative cover, soil color, current and planned future use, or previous history. The boundary conditions that need to be determined will likely include, but may not be limited to, the parameters listed in Table 1. Individual summaries need to be prepared for every disturbed area that is treated as a separate unit in the reclamation plan. Whenever possible, the site characteristics should be described in quantitative terms. Prior to the design of a reclamation plan and as near to the time of biosolids application as possible, biosolids quality parameters, listed in Table 2, need to be determined. Nitrogen in Biosolids In land reclamation, biosolids application rate calculations are primarily based on the organic matter and nitrogen contents and to a lesser degree on the trace element concentrations in the biosolids to be applied and the soil to be amended. Nitrogen (N) is the main nutrient of biosolids and also the major macronutrient which is deficient in most disturbed soils. For several years after biosolids application, the organic matter in biosolids decomposes and releases mineral N. This mineral N is either volatilized, taken up by plants, nitrified, denitrified, leached, immobilized, or adsorpted. The mineralization rate of N in biosolids and soil depends on the C:N ratio, the concentration of heterotrophic bacteria, the; stability of organic matter, the availability of water, the pH and Eh, and temperature. Unfortunately, disagreement exists among researchers concerning the effect of biosolids application rates on the percent of added organic N mineralized (Sopper 1993; Williams et al. 1984). Since the mineralization rate of N is dependent on the C:N ratio, it is proposed to base estimations in biosolids application rate calculations on the biodegradable C:N ratio instead of the conventionally used Total C:Total N ratio. The use of the biodegradable C:N ratio in application rate calculations is intended 110 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation Table 1.    Summary of Boundary Conditions fora Reclamation Site ' 111 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation to accommodate the fact that the rate of decomposition of organic materials varies widely, even if their conventional C:N ratios are the same. For example, organic substrates consisting mainly of lignin (e.g. wood), of cellulose (e.g. paper), or of molecules having a ring structure (e.g. aromatics) break down more slowly than highly proteinaceous materials.  In application rate calculations for land reclamation, the biodegradable C:N ratio should be kept in the range of 14:1 to 18.5:1 to ensure that enough mineral N is available for plant uptake. The biodegradable C:N ratio and its determination is discussed in the TSD. The choice of the most appropriate biodegradable C:N ratio depends on the environmental sensitivity of the site with respect to nitrate inputs. During and after biosolids application, usually some of the ammonium (NH4+) present in biosolids volatilizes as NH3. Volatilization losses depend on the atmospheric partial pressure of NH3, the concentration of NH3 and NH4+ in the liquid phase, the pH, the cation exchange capacity, and temperature. Volatilization losses are especially high in high pH biosolids and soils. Volatilization losses can be substantial after surface application of biosolids (up to 90%). Denitrification of nitrate (NO3-) and nitrite (NO2-) in soil is primarily dependent on the available NO3- and organic C concentrations, the pH and Eh, the soil moisture, and the soil texture and temperature. Denitrification is primarily performed by facultatively anaerobic (functioning with or without O2) bacteria when the soil is anoxic. In B.C.'s Lower Fraser Valley, Paul and Zebarth (1997) found that denitrification losses were significantly higher on manured- than on non-manured plots. The higher denitrification losses were likely due to a higher availability of organic C and denitrifying bacteria. For the same reason, denitrification losses from biosolids-amended sites are expected to be significantly higher than from sites treated with inorganic fertilizers. Denitrification after biosolids application has not been studied as extensively as mineralization or volatilization. Until "good" denitrification guides have been developed, assume that the "missing" N in N balance calculations after biosolids application, has either volatilized or denitrified. Application Rate Calculations The calculation of an appropriate biosolids application rate for mine reclamation is somewhat convoluted as several, interdependent design criteria have to be met. Thus, the most appropriate application rate is usually determined by iteration. In addition, estimations of N mineralization, volatilization, and denitrification rates are only best estimates. Nevertheless, the more land reclamation projects are executed, the easier it will become to correctly predict the behaviour of N after application. To create a friable growing medium with biosolids, biosolids are usually mixed with a mineral substrate that contains fines (< 2 mm) (e.g. tailings, silt or sand). 112 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation In mine reclamation, biosolids are typically applied at either a fertilizer or a reclamation application rate. Biosolids is applied to vegetated, but nutrient deficient, areas at fertilizer application rates. Biosolids is applied to unvegetated, and organic matter and nutrient deficient areas at reclamation application rates. Fertilizer and reclamation application rate calculations differ, but they have some parts in common. To simplify the explanation of the required estimations and calculations, detailed in Tables 3 to 9, they have been broken down into sequences. The sequences for fertilizer and reclamation application rate calculations are as follows: Calculation of Fertilizer Application Rate Step 1: Follow steps outlined in Sequence 1 below. Step 2: Follow steps outlined in Sequence 2 below. Step 3: Follow steps outlined in Sequence 5 below. Calculation of Reclamation Application Rate Step 1: Follow steps outlined in Sequence 1 below. Step 2: Follow steps outlined in Sequence 3 below. Step 3: Follow steps outlined in Sequence 4 below. Sequence 1: Assessment of Boundary Conditions Step 1:   Compile data for the boundary conditions outlined in Table 1. Step 2: Determine the environmental sensitivity of the reclamation site and local drainages with respect to nitrate inputs. Step 3: Compare the measured total trace element concentrations with the suggested maximum concentrations for land reclamation listed in Table 3. If the concentration of one or more elements is greater than the suggested level, a test trial should be conducted or relevant research results should be documented before biosolids are applied on an operational scale. This approach will protect the environment while at the same time recognizing that the use of biosolids will likely enhance site rehabilitation programs. Biosolids test trials are discussed in the TSD and MOP. Step 4:   Determine what types of biosolids are available for reclamation. Step 5:   Determine the quality of available biosolids in terms of parameters listed in Table 2. Step 6: Calculate the "Background Available N" in the soil to be amended as outlined in Table 7. If biosolids have been applied previously, its residual contribution to available N needs to be estimated. Step 7: Compile a list of acceptable organic matter content, and nutrient and total trace element concentrations (target levels) for the site. Average soil nutrient and total trace element concentrations have been compiled in the TSD, although site-specific conditions may require other concentrations. Sequence 2: Estimation of Potentially Leachable N Step 1:   Determine the available N in the biosolids to be applied as demonstrated in Table 6. Step 2: Estimate the potentially leachable N as outlined in Table 8. Repeat the calculations in Table 8 for various application rates until the potentially leachable N is equal to the acceptable level defined in Step 2 of Sequence 1. Remember that denitrification losses may be significant. 113 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation Sequence 3: Determination of Top Soil Mixture - Reclamation Application Rate Step 1:   Refer to Table 9.   If only one type of biosolids is to be used, set all parameter values for "Biosolids 2" in Steps 1, 2, and 3 of Table 9 to zero. Step 2:   Refer to Step 1 in Table 9. Decide on an appropriate biodegradable C:N ratio for the site and calculate the dry weight ratio for the mixture as demonstrated. Step 3:   Refer to Step 2 in Table 9. Define the desired organic matter content and thickness of topsoil after land application. Calculate the desired %C in the top soil mixture based on the formula given. Calculate the dry weight ratio of the components of the top soil mixture based on the final %C content as demonstrated:.  Using the information compiled in Sequence 1, determine the biosolids application rate that meets the design criteria as demonstrated. Step 4:   Follow the steps outlined in Sequence 2 for the biosolids to be applied.   If a mixture of biosolids  is  to  be  applied,  base  calculations  in  Sequence  2  on  the  average  nutrient concentrations in the biosolids mixture. Step 5:   Compare the application rates calculated in Steps 3 and 4.   If the application rate in Step 4 is lower than the one calculated in Step 3, use the application rate calculated in Step 4 in the following step, else skip the next step. Step 6:   Repeat the calculations in Step 2 and Step 3 with modified, but desirable design criteria while keeping the application rate fixed. Step 7:   Based on the available data, calculate the final total trace element and nutrient concentrations using the latest dry weight ratio determined in Step 3. Step 8:   Compare the final total trace element and nutrient concentrations with target levels compiled in Step 7 of Sequence 1. Step 9:   If target levels are not met, repeat the calculations in this sequence with modified, but desirable design criteria until an optimum application rate has been determined. The optimum application rate must not result in exceedances of the acceptable leachable N and should meet most if not all target levels specified in Step 7 of Sequence 1. Remaining nutrient deficiencies may be corrected by additional fertilization. Sequence 5: Determination of Top Soil Mixture - Fertilizer Application Rate Step 1: Refer to Table 9. If only one type of biosolids is used, set all parameter values for "Biosolids 2" in Steps 1, 2, and 3 of Table 9 to zero. Step 2: Refer to Step 1 in Table 9. Decide: on an appropriate biodegradable C:N ratio for the site and calculate the dry weight ratio for the mixture as demonstrated. Step 3: Refer to Step 2 in Table 9. This; step needs to be calculated backwards. Set the desired thickness of topsoil to 150 mm. Using the application rate calculated in Step 2 of Sequence 2 and the information compiled in Sequence 1, enter all known parameter values and all values that can be calculated into the table. Estimate the dry weight ratio by calculating backwards (i.e. calculate the thickness of the mineral component, its wet volume, its wet and dry application rates, and finally the dry weight ratio of the components of the top soil mixture). Step 4: Based on the available data, calculate the final total trace element and nutrient concentrations using the dry weight ratio determined in Step 3. Step 5: Compare the final total trace element and nutrient concentrations with target levels defined in Step 7 of Sequence 1. If target levels are not met, change the design criteria in Step 1 and/or Step 2 of Table 9 to other desirable characteristics. Repeat the appropriate calculations in sequences 2 and 5 until an optimum application rate has been determined. The optimum application rate must not result in exceedances of the acceptable leachable N and should meet most if not all target levels specified in Step 7 of Sequence 1. Remaining nutrient deficiencies may be corrected by additional fertilization. 114 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation 115 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation Table 5.    Estimates of Mineralization Rate (MR) after Biosolids Application 1   Table 6.    Sampling Calculation - Available N in Sample Biosolids 1,2  Table 7.    Sample Calculation - Background Available N in Soil to be Amended  Table 8.    Sample Calculation - Potentially Leachable N for Sample Biosolids used at 50 dry tonnes/ha  116 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation  117 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation MONITORING Following is a brief overview of the proposed monitoring guidelines for operational scale biosolids applications which are summarized in Table 10. Pre-application soil monitoring is necessary to obtain site-specific baseline and design data. Post- application soil monitoring is usually not required, but may be conducted to determine nutrient and trace element concentrations. If the site to be amended is vegetated, vegetation quality, biomass production as well as species composition should be assessed before as well as after application. If the site is not vegetated these assessments must be done at least once and in the first growing season after biosolids application in order: 1) to determine the effects of biosolids application on vegetation quality and biomass production, 2) to identify dominant species for future seed mix or planting stock recommendations, 3) to determine the need for reseeding or replanting, and 4) to determine if weeds pose a problem. Long- term vegetation monitoring is generally not necessary for operational scale biosolids applications, but may be required to prove that vegetation is self-sustaining. When assessing biosolids quality, discrete samples have to be collected to estimate the pathogen reduction level and representative, composite samples should be collected to determine nutrient and trace element concentrations. In B.C., water quality objectives and monitoring programs for mines are typically specified by the B.C. MoELP or the Chief Inspector of Mines. Thus, the water monitoring program, suggested in Table 10, may need to be modified on a case by case basis. MANAGEMENT PRACTICES Management practices for biosolids applications will generally differ for operational scale biosolids applications and test trials. Compared to operational scale biosolids applications, test trials have higher monitoring requirements, and require more planning and tighter quality control throughout project execution. Test trials may be conducted at any time, but are generally limited to the initial start-up phase of a large reclamation project: to quantify design application rates, to determine the best reclamation technology, or to determine if biosolids as a soil amendment is suitable for reclaiming a problematic site. General best management practices for biosolids applications are summarized in Table 11. The design and management of slope applications is discussed in the MOP and TSD. 118 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation  119 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation  PROJECT EVALUATION Revegetation success may either be compared against reference areas or technical standards. With the reference-area approach, monitored parameters on the reclaimed site are compared with the same parameters on a similarly managed and vegetated unmined site nearby that serves as the reference for comparison. With the technical standards method, monitored parameters are compared with an performance standard appropriate for the postmining land use (Vogel 1987). ACKNOWLEDGEMENT I would like to thank the GVRD's Residuals Management Group for giving me the opportunity and support to develop technical documentation for biosolids use. My special thanks goes out to Craig C. Peddie and Dr. Tony Sperling for reviewing this paper. REFERENCES B.C. MEMPR (Ministry of Energy, Mines, and Petroleum Resources). 1992. Health, Safety, and Reclamation Code for Mines in British Columbia. Resource Management Br. Victoria, B.C. B.C. MoELP (B.C. Ministry of Environment, Lands and Parks). 1983. Draft Guidelines for Disposal of Domestic Sludge under the Waste Management Act. 19p. B.C. MoELP. 1997. GVRD Review [Copy] of the Draft British Columbia Municipal Organic Matter Recycling Regulation (July 11, 1997). 35p. Paul, J.W. and BJ. Zebarth. 1997. Denitrification in Manured Soils in the Fraser Valley: How Important is it? In Can. J. of Soil Science. May 1997. PDER (Pennsylvania Department of Environmental Resources). 1994. Interim Guidelines for the Use of Sewage Sludge for Agricultural Utilization or Land Reclamation under The Regulations of the Department of Environmental Resources. Commonwealth of Pennsylvania. 24p. Sopper, W.E. 1993. Municipal Sludge Use in Land Reclamation. Lewis Publishers. Boca Raton. 163p. U.S. EPA. 1993. Final Rules for Use and Disposal of Sewage Sludge. Federal Register. Vol. 58. No.32. 40 CFR Part 503. U.S. EPA. 1994. Land Application of Sewage Sludge. A Guide of Land Appliers on the Requirements of the Federal Standards for the Use or Disposal of Sewage Sludge, 40 CFR Part 503. Vogel, W.G. 1987. A Manual for Training Reclamation Inspectors in the Fundamentals of Soils and Revegetation. U.S. Dept. of Agric. Northeastern Forest Experiment Station. 178 p. Washington State DOE (Department of Ecology).  1993. Biosolids Management Guidelines for Washington State. Draft. Publication Number 93-80. Williams, J.H., G. Guidi, and P. L'Hermite (eds.). 1984. Long-term Effects of Sewage Sludge and Farm Slurries Applications. Elsevier Applied Science Publishers, New York. 120 Proceedings of the 21st Annual British Columbia Mine Reclamation Symposium  in Cranbrook, BC, 1997. The Technical and Research Committee on Reclamation  121

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