Replacement Effluent Treatment Facility Design
An 'Effluent Treatment Facility' is a system designed to take the total industrial effluent generated by the kraft pulping process and treat it. The quality of effluent is regulated through the Environment Canada Pulp and Paper Effluent Regulations (PPER).
The Pulp and Paper Effluent Regulations were created to protect fish.
Between 1985 and 2015, Canada wide the quality of pulp and paper effluent released directly into the environment improved significantly. Find out more from Environment Canada. Additionally, the full regulations are available online under the Fisheries Act.
Determining the Recommended Approach
Alternatives for the treatment technologies were evaluated against several criteria. An Activated Sludge Treatment (AST) system is the recommended approach. More information on how the recommended type of facility was determined is available here.
An AST requires a discharge (or outfall), we began by looking for a recommended outfall location. The first step was screening out areas where it shouldn't be located.
A series of models were created to evaluate the flow dynamics, dispersal rates, settling rates, water chemistry and temperature profiles of the effluent discharge location options.
Studies showed that if the outfall was inside Pictou Harbour, for example close to the Mill property, the slow currents and other environmental factors inside the Harbour could result in eutrophication. Eutrophication is the creation of conditions that stimulate the growth of plants and algae that will consume oxygen in the water which will harm aquatic species.
The Northumberland Strait was chosen as the outfall location, due to flow conditions including depth of water, currents, wind, density, and temperature. In this dynamic location, modelling predicts there will not be an accumulation of nutrients.
Locating the Marine Outfall
Knowing we needed to reach the Northumberland Strait, we looked at how to get there. There are a lot of constraints - things we want to avoid - including available commercial, recreational, and Aboriginal fisheries sensitivities, bird and shoreline sensitives, and other socio-economic sensitivities. A route was proposed out through Pictou Harbour to reach the Northumberland Strait that balances these constraints. Engineering constraints however put the team back to the drawing board. A new alternative route, still working to balance potential impact on the environment, minimize construction risks, and balanced cost, is now proposed. The new route would follow Highway 106 from NPNS to Caribour Harbour, and out into the Northumberland Strait.
Throughout the project a key consideration has been to develop a solution that does not impact Boat Harbour in the future tidal state, as identified in consultation with Pictou Landing First Nation. All project modelling considered a future tidal state with the removal of the existing dam at Boat Harbour.
Going beyond the PPER regulations, the outfall is designed to follow the Canadian Council of Ministers of Environment (CCME) Marine Guidelines. All applicable effluent parameters meet background conditions within 100 m of the diffuser.
Once the effluent is treated on the mill site in the ETF, a pipeline will carry the treated effluent to the outfall location. The outfall itself is a multi-port diffuser. By having a six-port diffuser, there is better mixing and therefore less potential for environmental impact. Based on the design completed to date, it's anticipated that the pipeline will be approximately a 36" diameter pipe made out of HDPE material. An HDPE pipe is strong and has some flexibility to allow for the undulating ocean bottom profile. There will be no need for bends in the pipe, reducing risk for leaks and breakages.
In the recommended design, a rock mattress will be placed under the outfall pipeline on the bottom of Pictou Harbour, and then covered in armour-stone for protective cover.
Options for how to design and operat an ETF were considered and are detailed here.