Cumberland High Performance Wastewater Lagoon and Wetland Upgrade

The Village of Cumberland is planning to upgrade its wastewater lagoon system in order to meet regulatory requirements and increase its capacity to service a population of up to 7000 people. The wastewater treatment lagoons were built in 1968 and do not have any phosphorus removal or disinfection. This system has been out of compliance with provincial regulation since the 1990’s. The project is aligned with the village’s Strategic Plan, which established a goal to develop an environmentally sustainable method to treat liquid waste produced by the Village.

The two phase upgrade will implement a combination of both engineered and natural assets to achieve higher levels of treatment. The first phase consists of specific improvements to the lagoon-based system. This includes adding a second influent trash screen to reduce bypass flow in wet weather, adding phosphorus removal by means of chemical coagulation, and removing the coagulated and fine suspended solids by means of a dissolved air flotation (DAF) system. Subsequent disinfection of the wastewater with parecetic acid, a less toxic chemical than chlorine, will run in parallel with dewatering of DAF solids using geotube membranes. This first phase will allow the system to meet all regulatory requirements while providing a treatment capacity of 910 m3/day, thus allowing the village to grow to 4,500 people.

The second phase will consist of adding a second DAF unit, which will double the capacity to 1800 m3/day, allowing the system to service up to 7,000 people. This final phase also includes building an engineered wetland that will use a biochar media reed bed to remove emerging contaminants such as pharmaceuticals. The restoration and augmentation of the existing wetland adjacent to the lagoons will provide a final polishing function before the effluent is discharged into the receiving creek. Plan operators will regularly monitor the performance of the upgraded lagoon, DAF, reed bed and wetlands.

The upgraded lagoon system will improve the quality of wastewater by reducing carbonaceous biochemical oxygen demand (CBOD5) by 65%, total suspended solids (TSS) by 91% phosphorus by 95%, nitrogen by 98%, and fecal coliforms by 99%. The initiative will also help protect an important downstream ocean shellfish farming area and declassify the receiving creek from the designation of "sewage outfall". The use of disinfected effluent for the automatic washdown of the influent screens will reduce the facility’s potable water use by 80%. Although the proposed upgrades will triple the facility’s energy consumption, lagoon systems have lower energy requirements compared to mechanical systems designed to treat equivalent flows. The use of wood-sourced biochar for the reed bed will sequester 1.5 tonnes of C02e/year. The enhanced treatment capacity will allow the village to grow and result in an increased municipal revenue stream. In terms of community benefits, the project will improve public health by ending unacceptable discharge effluent and creating new public walking trails.

The knowledge value of this initiative to small municipalities with non-compliant lagoon-based systems is the combination of engineered and natural assets to enhance wastewater treatment and restore natural habitat.