In-situ Reduction of Sludge Volume by Microbial Digestion

Notre-Dame-de-l'Île-Perrot will conduct a pilot project to assess the potential for using microbial digestion to reduce the volume of sludge produced in the aerated ponds at its water treatment plant. A microbial consortium of bacterial strains and enzymes will be injected into 5 of the town’s 8 aerated ponds. The microorganisms considered for this project have proven able to hydrolyze and oxidize various biomaterials similar to municipal biosolids (liquid manure, biomass waste) and the project will test their use on the municipal sludge that has accumulated at the bottom of the aerated ponds. The project’s objective is to reduce the ponds’ drainage frequency, which will reduce the town’s sludge pumping, dehydration, transportation and disposal costs. The project’s environmental objectives are: • Reduce organic sludge volume by at least 40% after 3 months and at least 80% after one year to reduce the amount of sludge disposed of in landfill. • Reduce greenhouse gases (GHGs) from sludge treatment and transportation. • Reduce GHGs at the source. It is generally recognized that aerated ponds account for 10 to 15% of all greenhouse gases generated by a municipality. • Increase the organic quality of the remaining sludge (better redox potential, reduced toxic content, increased nutrient bioavailability (nitrogen, phosphorus and carbon). • Improve effluent water quality (COD, BOD5, SS, phosphorous, nitrogen and coliform bacteria). The project also aims to decrease the need for pond aeration, which will reduce energy requirements and prolong the service life of the aeration system’s mechanical equipment, thereby reducing the community’s operating costs. Odour from the aerated ponds should also be reduced, which will improve the quality of life for citizens residing near the water treatment plant. The project is supported by the MRC of Vaudreuil-Soulanges waste management plan (PGMR) and the Communauté métropolitaine de Montréal waste management plan (PMGMR). It is also aligned with Quebec’s waste management policy (Politique québécoise de gestion des matières résiduelles), which targets elimination of organic waste disposal in landfill, including municipal biosolids, by 2020. The use of municipal biosolids as fertilizer is a preferred alternative to landfill under this policy, so eliminating sludge contaminants could limit contamination when the fertilizer is applied to farms and forests. (Project description from original funding application)