Abstract
Ammonia is a common constituent of mine wastewater that is often collected in large, onsite ponds and treated using biological processes. However, nitrifying bacteria that provide ammonia removal are temperature-sensitive, and under cold conditions become less active and less effective at achieving regulatory requirements. This is compounded by increasingly stringent ammonia discharge regulations that could render some systems non-compliant and necessitate upgrades. An example is Canada’s Metal and Diamond Mining Effluent Regulations (MDMER) that was strengthened in June 2021 and limits the monthly mean effluent concentration of un-ionized ammonia to 0.5 mg/L.
This presentation will examine an innovative biofilm attached growth wastewater treatment system that was pilot tested at a Canadian gold mine from August to December 2021. The study evaluated the ability of Bishop BioCord Reactors to improve the facility’s cold-weather ammonia removal, meet more stringent discharge limits and increase the discharge rate.
The technology offers a simple, low-energy, and easy-to-operate process to upgrade wastewater systems and enhance removal of nutrients and organics. This fixed-film system provides microorganisms with optimal conditions for growth, proliferation and nutrient metabolism on a unique, high-surface area, polymer substrate. The system’s stable biofilm also helps insulate microorganisms within the inner layers and reduces washout, enabling continuous treatment in winter and high-flow conditions.
Full-scale systems can be installed directly into an existing cell, significantly reducing capital costs since additional equipment such as tanks, blowers and pumps are not required to support a sidestream process. Each Reactor is also equipped with a micro-bubble aeration system powered by low-energy compressors, which helps reduce operating costs when compared to blowers.
This presentation will discuss the methodology and results of the pilot system. The containerized system operated in two phases, receiving influent from two cells of the wastewater system to increase ammonia loading to the pilot and demonstrate cold-weather nitrification at variable influents.
The overview will include a summary of the pilot system design and the ammonia removal performance. It was demonstrated that steady-state nitrification was not negatively impacted by the cold-weather conditions observed during the second half of the pilot project, and that average nitrification rates increased from 38 g/day to 55 g/day of ammonia removed during the transition from warm (average 18ºC) to cold (average 7ºC) water conditions and lower to higher ammonia loading conditions. The summary will also discuss how the results were scaled and used to refine full-scale system design.