Boat Harbour Remediation, Wastewater Treatment Study

Boat Harbour was originally a tidal estuary connected to the Northumberland Strait in Pictou County, Nova Scotia (Province). The Province constructed the Boat Harbour Effluent Treatment Facility (BHETF) in1967 to treat effluent from a pulp and paper and other industrial sources. This reconstruction converted the natural tidal estuary into a closed effluent stabilization lagoon. The Province has ceased the reception of new effluent to the BHETF by January 31, 2020 and committed to the subsequent remediation of Boat Harbour to restore it to the tidal estuary. GHD, on behalf of Nova Scotia Lands Inc. as part of the Boat Harbour Remediation Planning and Design Project, conducted a pilot test to evaluate GHD's proposed water treatment strategy for the remediation of Boat Harbour. The analysis of dredged slurry from the Boat Harbour illustrates that metals, dioxins and furans, petroleum hydrocarbons are among the chemicals of concern which need treatment. The objectives of the pilot study was to evaluate sludge removal by hydraulic dredging, removal in dry, and evaluation of water treatment using Geotube® dewatering, alkaline precipitation of metals, coagulation and flocculation, media filtration and activated carbon adsorption. The results of this study showed that Geotube® dewatering with the help of an aluminum chloride hydroxide based coagulant and an anionic acrylamide based polymer could reduce the concentration of dioxines and furans (D&Fs) as well as heavy metals from dredged slurry significantly. It was found that further treatment of Geotube® effluent as well as bulk water using media and GAC adsorption vessels could reduce the concentration of COCs even further to the levels below assessment criteria. The analysis of final effluent showed that the concentration of all D&Fs compounds measured below their detection limits. This paper summarizes the findings of water treatment part of the Boat Harbour pilot study.