Solids Process Alternatives Evaluation (034-DP-2)
Discussion Paper Summary
One of the key elements of wastewater treatment in the CRD is the treatment and management of wastewater biosolids. This paper explores two solids process alternatives for the Macaulay/McLoughlin treatment plant.
Alternative 1: Anaerobic Digestion with Biogas Production
This alternative would blend primary and secondary sludge prior to thickening on gravity belt thickeners. After thickening, the sludge would be pumped to anaerobic digesters, where pathogens would be reduced and biomass quantity would be reduced. The byproduct of this process would methane, which could be used on site to generate power and heat or upgraded to biomethane and used off-site as an energy source. After digestion, the solids would be dewatered and hauled away for reuse or disposal.
Alternative 2: Thermal Oxidation with Energy Recovery
This alternative would also blend sludge from primary and secondary treatment processes in a sludge tank. After gravity belt thickening, the sludge would be dewatered. Dewatered sludge would then be pumped to an incinerator for thermal oxidation. The heat generated could be used to sustain the oxidation process. The ash would be transported offsite by truck, most likely to Hartland Landfill. Pollution control devices would be used to prevent degradation of air quality during burning.
Findings
The alternative that will be used to develop a preliminary plant layout for the Macaulay/McLoughlin Point plant is Alternative 1: thickening, anaerobic digestion with biogas production, co-generation and dewatering. This alternative was found to present greater opportunity for resource recovery, lower operating costs and a biosolid suitable for reuse.
For a detailed explanation of advantages and disadvantages of the two alternatives, please see the original discussion paper, located in Archived Documents.