of the Recommended Effluent Treatment Facility
Water reductions, through the implementation of cooling towers, will be required to reduce peak summer indirect cooling water volume. The replacement effluent treatment facility is designed to process up to 85,000 m3/day of effluent that is created through the kraft pulp mill process. An activated sludge treatment (AST) process has been designed to remove solid materials (TSS), organic loads (BOD/COD), and chlorinated compounds (AOX).
Effluent will be collected at the mill’s existing pump station and fed into a new primary clarifier for suspended solids removal by gravity. The solids are primarily wood fibers and lime. Prior to being fed to the primary clarifier the pH of the effluent will be adjusted to improve treatability. Following the primary clarifier, the clarified effluent is cooled and then enters the biological treatment system. Indirect heat exchangers and cooling towers will be used to cool the effluent prior to the biological treatment.
Biological treatment consists of an anoxic zone followed by aeration basins using coarse bubble submerged aerators assisted by mixers. Biological solids will be removed using two gravity clarifiers, which collect and recycle most of the biomass back to the inlet of the biological treatment system as activated sludge to maintain treatment operations. The treated effluent from the secondary clarifiers will discharge to the Northumberland Strait via a pumped marine outfall to a multi-port diffuser.
As a contingency, a separate spill containment system will be incorporated to protect against process upsets, spills or other unforeseen events. Liquid collected in the spill containment area will be treated or recovered.
Waste sludge from both the primary and secondary clarifiers will be collected and dewatered. It is anticipated that the resulting material will be fed, along with bark and wood waste, to the mill’s biomass boiler. Liquid from the dewatering of the sludge is sent to the inlet of the biological treatment stage for further processing.