Effluent from Southshore Water Reclamation Facility approaches drinking water quality

Effluent from Southshore Water Reclamation Facility is discharged to forest wetland

Historically, sewage disposal for Canyon Creek, Widewater, and Wagner, the Southshore Communities in the Municipal District of Lesser Slave River No. 124 Alberta consisted of residential septic tanks and poorly performing disposal fields, which discharged into the soils adjacent to each property. The Municipal District raised concerns that the continued discharge of sewage effluent from disposal fields along the lake shoreline may have an adverse environmental impact and pose risks to public health.

Environmental concerns associated with the septic systems as well as municipal planning restrictions limited further growth in these communities. As a result of the environmental concerns, the Municipal District initiated design and construction of a low pressure wastewater collection system and advanced wastewater treatment for the Southshore Communities. The Municipal District retained Associated Engineering as its Prime Consultant for the feasibility study, preliminary and detailed design, and construction management.

The new wastewater treatment facility is sited in the Lesser Slave Lake watershed. The Municipal District decided that conventional wastewater treatment and direct lake discharge were not adequate to assure the protection of the lake, a major recreational water body. Associated Engineering proposed treating the wastewater to an extremely high standard using membrane bioreactor technology and discharging and polishing the treated effluent in forest wetlands. While many water treatment plants throughout Alberta, including the Southshore Communities’ water treatment plant, use membrane bioreactor technology, this was the first application of this technology for municipal wastewater treatment in Alberta. The membrane bioreactor treatment plant includes a 475 cubic metre flow equalization tank which accepts flows exceeding the plant’s peak day flow of 1,200 cubic metres per day. Flow equalization is followed by screening with 0.75 millimetre screens. Membranes are installed in separate membrane aeration tanks in a non-freezing environment to enable their isolation for automated cleaning. The design of the membrane aeration tanks eliminates the requirement for bi-annual membrane removal for chemical cleaning and removes the concern that membranes cannot be removed during sub-zero temperatures for cleaning needed to restore flow capacity.

External view of Southshore Water Reclamation Facility

Effluent from the membrane process receives ultraviolet disinfection.The high effluent quality enables the use of in-pipe ultraviolet disinfection rather than in-channel units, which significantly reduced construction costs. Effluent is stored in a holding pond. From the holding pond, treated effluent flows to either of two dispersion ponds. Effluent is released continuously from the dispersion ponds to a forest wetland.

The forest wetland incorporates existing terrain, soils, and vegetation to create a system where wastewater can be released year-round. By incorporating existing natural vegetation, only a relatively small area of the existing forest needed to be removed to create the forest wetland. This approach also maintained wildlife habitat values and may lead to enhancements for particular species such as ducks and shorebirds.

Senior Process Engineer, Pat Given, reports, “Effluent from the Southshore facility approaches drinking water quality; typical effluent turbidity is less than 0.1 NTU and coliforms are not detectable.”