Passive approach to wastewater treatment yields fewer GHGs and lower costs

Water

DURATION OF PROJECT: 2016

The Town of Montague, PE, used a passive geotextile dewatering system to turn a sludge problem into a boon for the community.

In 2016, the Town of Montague decided to improve the performance of its wastewater treatment facility while reducing its costs for sludge transportation and disposal.

An overaccumulation of sludge at its wastewater treatment plant was cause for concern for the Town of Montague, a small community of about 2,000 people on Prince Edward Island (the town has since amalgamated into the Town of Three Rivers). The town was diverting over 13 tonnes of sludge annually by the truckload, resulting in about 3,600 kilometres of roundtrip travel every year. Although the facility was still able to meet environmental regulations, the risk of raw, untreated sewage bypassing the facility and being released into receiving waters was mounting. It was time for swift action.

Map of PEI featring Montague

The municipality put in a pumping system to divert pre-treated effluent through strong geotextile bags. The bags sit for up to 28 days, passively filtering the effluent and creating drier and lighter nutrient-rich compost. The compost is then used to fertilize sod fields in the region. This process produces a high-quality dried sludge (Grade A). It also significantly reduces the concentration of suspended solids in the wastewater treatment process, an important measure of water quality. It has also reduced trucking costs for sludge transportation and disposal by $30,000 per year.

Within the first year, the facility had surpassed the town’s projections by dewatering 150,000 more gallons of sludge than anticipated (450,000 gallons in total). With much less sludge to transport for disposal, the town was able to reduce its greenhouse gas (GHG) emissions by 25.8 tonnes of CO₂e annually (equivalent to transporting 150 truckloads). Only four dump trucks are now required to transport the remaining sludge for disposal each year.

9,594 litres

in diesel consumption reduced per year

25.8 tonnes

of CO₂e reduced per year

$31,000

in trucking costs saved in the first year

The town overcame a few challenges to achieve its projected timelines and budget. During construction, the engineers found remnants of an old building under the soil in the construction site, requiring the removal of 30 percent more soil than anticipated. But the town learned perhaps its biggest lesson during the cold winter months as the geotextile bags started to freeze, reducing their capacity for dewatering. Based on its experience, the town recommends weatherproofing the system by ensuring all piping and controls are either buried below the frost line or kept in a greenhouse or heated building.

Thanks to its environmental leadership, today Montague enjoys cleaner wastewater effluent, high-quality compost and lower transportation costs—all while generating fewer GHGs.

The geo bags have been a welcome addition to the Montague treatment system. They are easy to use and provide a more natural, sustainable way to dispose of excess solid by-products.”

—Matt Duffy, Operator, Montague Wastewater Treatment Plant, Town of Three Rivers