The Water Resource Centre in Sechelt has a small footprint but a big impact on its British Columbia coastal city, known for beaches and outdoor recreation.

Designed to LEED Gold standards by Vancouver-based PUBLIC: Architecture + Communication, the plant occupies about half the space of the two treatment facilities it replaced, even though it has twice the capacity (1.1 mgd design, 0.6 mgd average flow).

The plant has won numerous design awards, and it won the 2016 Sustainable Communities Award – Water Project from the Federation of Canadian Municipalities and an Architectural Innovation Award from the Architectural Institute of British Columbia in 2018.

The plant incorporates a greenhouse as part of the treatment process and has solar panels with 12-kW capacity, a system that recovers heat from the wastewater, tertiary treatment with membrane filtration, and UV disinfection. It looks like a botanical garden rather than a wastewater treatment plant — and, in fact, it is both.

ODORS CONTROLLED

Sechelt (population 9,500) lies northwest of Vancouver on an isthmus between Sechelt Inlet and Trail Bay. The community’s interest in environmental stewardship is reflected in the Water Resource Centre, which sits next to a residential neighborhood.

The homes next door made odor control important. “The greenhouse functions to fit into the urban environment, but it also contains odors,” says Christine Miller, wastewater supervisor for the District of Sechelt. “There’s an odor control system within the greenhouse. Any odors are picked up and go through a chemical scrubber and then to carbon beds before release. There’s no odor in the community.”

For now, some of the effluent is used for toilet flushing and other in-plant purposes, but most is discharged to the Pacific Ocean in Trail Bay. The long-term plan is to reuse the tertiary-treated water to irrigate parks and golf courses, but the purple-pipe infrastructure is not completely developed.

“We’re working on it,” Miller says. “Whenever a new road is built, we always put in the pipes to prepare for that future reuse.”

COMPACT PROCESS

The Water Resource Centre achieves its relatively small footprint by combining all secondary treatment in sequencing batch reactor tanks that sit under the greenhouse. The process was developed by Organica Water.

After solids and grit removal and aerated primary treatment, the influent moves into four SBR tanks where the activated sludge process includes aeration, settling and decanting. The roots from plants in the greenhouse hang down into the batch reactor tanks to provide media for a diversity of water-cleaning microbes. Fixed-film media for microbes could be added to the tanks to increase treatment capacity if needed in the future. Fine-bubble aerators are at the bottom of the tanks.

The effluent doesn’t flow out of the tanks; it is decanted off the top. “Decanters sit on the surface,” Miller says. “They work kind of like a siphon, drawing off the top of the batch reactor.” The siphoned effluent goes to tertiary membrane filtration and then UV disinfection. The solids that settle to the bottom are ultimately collected by a local company and composted to produce Class A biosolids.

The Water Resource Centre replaced one treatment plant near the present site and another on the edge of the city that now functions as a septage receiving station. The solids are removed there, and the liquids flow to the new facility.

DIVERSE BENEFITS

In its report when the sustainability award was announced, the Federation of Canadian Municipalities described the facility as the first in North America to use plants suspended over treatment tanks in a greenhouse in the SBR process.

The report says the plants make the biological treatment process more efficient, reduce energy usage, save space and control odors. The report also cited the project for the landscaping of the grounds to make them fully accessible to the public, restoring the habitat of a small stream and hosting educational tours.

According to the report, the project’s environmental benefits include reducing suspended solids by 95%, reducing effluent ammonia and fish toxicity, eliminating effluent chlorine, cutting energy consumption by 38% and reducing potable water consumption by 88%.

There were economic benefits as well. The project doubled treatment capacity with minimal increase in operating costs. The $25 million project was funded in part with federal grants, support from the Federation of Canadian Municipalities’ Green Municipal Fund and a contribution from the Sechelt Indian Government District.

HIGHEST QUALITY

The Water Resource Centre is classified by the provincial Ministry of Environment as a Level 4 facility (the highest). It is run by a staff of five certified operators. The facility went online in 2016; the planning began in 2012, when the old plants were at capacity.

“The community was interested in treating the effluent to the highest quality,” Miller says. “That’s what led them to this.”