A City of Edmonton utility committee has approved a $217.3-million corrosion and odour control project for its sewer system that could start this year and end by 2026.
The proposed strategy zeroes in on preventing the formation of hydrogen sulfide with chemical treatment, controlling the release of air, and adapting the use of real-time monitoring to reduce community odour impacts and lengthen the life of the sewer network, according to a presentation to the City of Edmonton by EPCOR Water Services Inc. (EWSI) last week.
“The feedback we received indicated a significant impact on residents affected by sewer odour, but it was more concentrated than previously anticipated,” Richard Brown, director of draining, planning and engineering at EPCOR, told the city’s utility committee. “It was consistently described as a persistent nuisance on quality of life.”
EWSI surveyed 1,600 local residents about odour impact. Half of the residents in odour hot spot communities noted that sewer odour negatively impacts their quality of life compared to 21% of respondents in the rest of Edmonton.
Stagnant wastewater leads to anaerobic decomposition, resulting in the production of hydrogen sulfide and other sewer gases leading to odours, according to EWSI’s presentation. At the City’s Duggan pump station, for example, wastewater can be stored in the incoming trunk line for as long as 5 to 15 days. “The water needs to be kept moving to minimize odours”, said Brown.
Brown explained to the committee that odours are pushed out of the sewers when the air inside the sewer is pressurized and there is an opening to the atmosphere.
“Air becomes pressurized when water drops from large heights, or when flow is restricted,” he said.
Hydrogen sulfide also corrodes infrastructure by causing premature asset degradation and failure. The corrosion makes maintenance and inspections challenging, Brown explained.
Additionally, EWSI plans to add containment structures, install one-way flaps, seal manholes, provide controlled release points, add vent stacks with odour filters, and add odour control units as part of the proposed strategy.
The latest strategy proposed by EWSI costs less than the estimates of previously developed odour mitigation plans, which ranged from $350 million to $460 million.
EWSI expects that the capital and operating program will reduce odour intensity in the Steinhauer-Duggan Service Area by 2020, permanently reduce sewer odour intensity in the consistent sewer odour areas (Steinhauer-Duggan, Allendale-Pleasantview and Bonnie Doon Service Areas) by 2025, and appreciably reduce odour city-wide through operational improvements and trunk line cleaning.