The Municipality of North Grenville

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1 A solution is required to increase the peak flow capacity of the Kemptville WPCP, a conventional activated sludge process, within a small footprint while maintaining good effluent quality. Location: Kemptville WPCP Challenge: Increase average and peak flow capacity within the small footprint available for plant expansion Solution: Full-scale Pilot demonstration of the BioMag TM technology to assess the feasibility of treating anticipated future flows within the existing secondary treatment tankage Results: Potential to double the existing secondary treatment capacity while maintaining excellent effluent quality and deferring a plant expansion The Municipality of North Grenville BioMag TM Process Pilot Demonstration At The Kemptville WPCP The Kemptville Water Pollution Control Plant (WPCP) is a conventional activated sludge (CAS) plant with tertiary treatment owned and operated by the Municipality of North Grenville in Ontario. The WPCP has an approved rated average day flow (ADF) capacity of 4,510 m 3 /d and peak flow capacity of 11,370 m 3 /d. The existing treatment processes include screening, grit removal, primary clarification, biological treatment, secondary clarification, flocculation, filtration, and ultraviolet (UV) disinfection. Sludge management is provided by waste activated sludge (WAS) co-thickening in the primary clarifiers and anaerobic digestion of the co-thickened sludge. A full-scale demonstration was conducted over the period of July to September 2013 to assess the feasibility of converting the existing secondary treatment train at the Kemptville WPCP to a BioMag treatment process. Background The Kemptville WPCP Optimization and Expansion Class Environmental Assessment (Class EA) was completed in It evaluated a number of alternatives to address future wastewater servicing needs to accommodate population growth in the serviced area. The recommended design concept that emerged from the study was to expand the existing CAS treatment system using a staged approach: Stage 1A Construct Influent Equalization Facility. Stage 1B WPCP Expansion to an ADF of 9,020 m 3 /d. Stage 2 WPCP Expansion to an ADF of 11,800 m 3 /d.

2 Magnetite is recovered from the waste activated sludge and reused. The BioMag treatment system pilot project was a great success in demonstrating increased capacity in the secondary clarifiers at the wastewater treatment plant. Karen Dunlop, Director of Public Works, Municipality of North Grenville Plant Constraints/Issues Currently, the Kemptville WPCP is operating at approximately 50 percent of its rated ADF, however historic peak flows have exceeded the peak flow capacity of the treatment system. An influent equalization facility was recommended in the Class EA to attenuate projected peak flows and minimize the required footprint for clarification and tertiary filtration. In spite of this, the expansion would still require a significant increase in footprint and acquisition of land. Compact Footprint Solution to Increase Capacity Following the completion of the Class EA, XCG Consultants Ltd. (XCG) identified and investigated the opportunity to use the relatively new BioMag treatment system at the Kemptville WPCP to treat average day and peak flows greater than the existing rated capacity of the secondary treatment system. The BioMag technology has been identified by the manufacturer, Evoqua Water Technologies (Evoqua), as a small footprint process, ideally retro-fitted within a treatment facility s existing bioreactors and secondary clarifiers to provide an overall increase in secondary treatment capacity and improve effluent quality, potentially reducing or eliminating the need for upstream flow equalization and land acquisition. The BioMag TM Process The BioMag process is a patented ballasted activated sludge and flocculation process that involves the addition of magnetite ballast to the mixed liquor to improve sludge settleability. The BioMag technology is relatively new in wastewater treatment applications and focuses specifically on the secondary treatment components of an activated sludge wastewater treatment plant. The increased specific gravity of the biological floc when embedded with magnetite improves its settleability, allowing the secondary clarifiers to operate at higher loading rates and mixed liquor suspended solids (MLSS) concentrations while maintaining adequate settling and thickening. Magnetite is magnetic in nature and can therefore be recovered. The WAS is first sent through a shear mill to shear and extract the magnetite from the floc. The WAS then flows through a rotating drum with fixed magnets where the magnetite is recovered from the WAS. In steady state operation, magnetite is added to the system by mixing mixed liquor with virgin magnetite in the ballast feed tank. BioMag Demonstration Activities A full-scale demonstration of the BioMag system was undertaken. XCG was retained by the Municipality to review the results of the demonstration and assess the feasibility of converting PAGE 2

3 BioMag TM Process Schematic the existing secondary treatment train at the Kemptville WPCP to a BioMag treatment process. The demonstration program involved temporary integration of the BioMag process into the Kemptville WPCP at full-scale. One secondary treatment train was removed from operation. Magnetite was added to the online bioreactor and a magnetite recovery system housed in a trailer was temporarily installed on site. The pilot system and associated equipment, materials, and services for the demonstration were provided by the developer of the BioMag process, Evoqua. There are currently no installations of the BioMag technology in Canada, therefore this innovative and costeffective solution received funding through the Ontario Ministry of the Environment s Showcasing Water Innovation (SWI) grant program 1. Magnetite is a fine powder (dark material in photo) that is embedded into the floc and allows for increased operating mixed liquor concentrations. A Long-Term High Solids Test was conducted to simulate the operating conditions that would be experienced by a full-scale BioMag installation at the Kemptville WPCP. This was accomplished by diverting all primary effluent flow to the test treatment train which had been retrofitted with the BioMag process. Secondary Clarifier Stress Testing was conducted to determine the peak day and peak hour process capacity of the test secondary clarifier when operating as a BioMag treatment system. PAGE 3

4 Increasing the ADF capacity for the secondary clarifiers from 4,510 m³/day to 9,000 m³/day with the BioMag treatment system allows more options when deciding how to increase capacity while keeping a small footprint at the wastewater treatment plant. Mike Finley, Superintendent of Environmental Services, Municipality of North Grenville. Demonstration Results The BioMag demonstration at the Kemptville WPCP was capable of meeting the target secondary effluent performance targets of 10 mg/l, 10 mg/l, and 0.3 mg/l for cbod5, TSS, and TP, respectively, based on the results of the Long-Term High Solids Testing. This was achieved at an average demonstration operating MLSS concentration, excluding magnetite, of 7,000 mg/l. The ballasted mixed liquor exhibited excellent settleability, with an average sludge volume index (SVI) value of 50 ml/g. The results of the secondary clarifier stress testing indicate that the secondary clarifiers are capable of treating peak flows resulting in equivalent surface overflow rate (SOR) and solids loading rate (SLR) values that are significantly higher than the typical design guideline values for a nitrifying CAS facility. Secondary Clarifier Stress Test Operating Conditions Parameter Peak Hour SOR (m 3 /m 2 /d) BioMag Demonstration Operating Conditions Typical CAS Design Guideline Values (1) 55.8 < 37 Peak Hour SLR (kg/m 2 /d) 476 < 170 Notes: 1. MOE Design Guidelines (2008) for an activated sludge process with nitrification requirement and chemical addition for phosphorus removal. Based on the results of the full-scale pilot demonstration, conversion of the existing Kemptville WPCP process to a BioMag treatment system is a technically feasible option. The BioMag system can be easily integrated into the existing process, provides additional capacity within the existing bioreactor and secondary clarifier tankage, and produces secondary effluent that consistently meets the demonstration targets. Based on the results of the Long-Term High Solids Testing, clarifier stress testing, and process modeling, it is estimated that conversion of the existing secondary treatment train to BioMag could provide an increase in the ADF capacity of the Kemptville WPCP secondary treatment train from its current rated ADF capacity of 4,510 m 3 /d up to 9,000 m 3 /d. The estimated conceptual capital cost associated with converting the two existing secondary treatment trains to a BioMag process is $2.7 million and is considered to be accurate to within -25 to +40 percent. This is approximately 25% less than the estimated cost to expand secondary treatment using the CAS process. The estimated incremental operational and maintenance costs associated with conversion from a CAS process to a BioMag process is $79.78 per 1,000 m 3 of wastewater treated, or $29,120/yr per 1,000 m 3 /d of average flow treated. Next Steps Following the completion of the BioMag demonstration, the Municipality of North Grenville is reviewing the demonstration summary report with consideration to the recommendations of the Kemptville WPCP Optimization and Expansion Class EA completed in Based on the results of this review, the Municipality may choose to re-open the Class EA study and evaluate the BioMag technology as an alternative design concept as part of the Municipal Class EA process. PAGE 4

5 It is estimated that the existing bioreactors and secondary clarifiers at the Kemptville WPCP can treat up to double the existing flow capacity when operating as a BioMag TM process. Future Research The duration of the demonstration test was limited to a period of approximately 10 weeks, therefore the long term implications of a retrofit of the BioMag process on the life expectancy of the mechanical equipment or the maintenance requirements could not be demonstrated. Before widespread implementation of the BioMag process in Ontario WPCPs is considered, it is recommended that the following items be investigated further and/or confirmed: The long-term impact, if any, of ballasted mixed liquor and activated sludge on equipment, such as pump impellers, and piping to determine if the presence of the magnetite ballast will result in premature wear and increased maintenance cost. The long-term impact, if any, of the presence of magnetite in the secondary effluent on tertiary filter performance. The impact of the magnetite on the accuracy of existing magnetic flow meters and selection of flow metering technology. The long-term impact of the presence of residual magnetite in the WAS on anaerobic digester performance and the potential for accumulation of magnetite in reactor dead-zones. The impact of residual magnetite in biosolids used for land application. Potential Applicability of the BioMag TM Process at Other Ontario WPCPs The BioMag process could have widespread application in Ontario. The BioMag process has the potential application for: Increasing wastewater treatment plant capacity without construction of new bioreactor and/or secondary clarifier tankage by increasing the biomass that can be retained in an existing secondary treatment plant. Providing for the discharge of a nonacutely toxic effluent by allowing nitrification in an existing bioreactor. Increasing the wet weather flow treatment capacity of an existing wastewater treatment plant by allowing operation at higher surface overflow and solids loading rates than are possible in a conventional plant. For more information on this project contact: XCG Consultants Ltd Bristol Circle, Suite 300 Oakville, Ontario L6H 6Z7 P: E: toronto@xcg.com 1 This project received funding support from the Government of Ontario. Such support does not indicate endorsement by the Government of Ontario of the contents of this material. PAGE 5