City water staff in Belleville, Ontario, have been testing a new odour-control product to break down and control sulfur compounds like hydrogen sulfide and mercaptans that can often fill the autumn air surrounding the city’s wastewater treatment plant (WWTP).
Staff invited the public to engage in a “sniff test” of a product called ProSweet at its St. Paul Street building, as the city considers entering into a $60,000 pilot project to spruce up the neighbourhood’s smell, or at least suppress it. Participants were asked to smell the waste material before, and after, adding the product.
“Everyone noticed a significant difference in the two samples and noted that the H2S [hydrogen sulfide] scent was nearly undetectable,” city staff stated on its social media pages following the event.
One city councillor at the event described the odour suppressant product as resembling the smell of hand soap.
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In wastewater applications, a primary contributor to hydrogen sulfide is the biochemical reduction of inorganic sulfur compounds to sulfide by sulfate-reducing bacteria under anaerobic or low dissolved oxygen conditions.
Products such as ProSweet have become popular as more communities experience vocal contingents — particularly online — rallying against the sulfurous odours at some treatment plants.
“Odour mitigation is one of the priority items to address at the Belleville Wastewater Treatment Plant and there is a specific project included as part of the Master Plan that will be implemented in the near term,” city staff wrote in response to one of many community odour complaints filed in the fall of 2019.
In the Belleville Wet Weather Master Plan, various potential approaches were identified by city staff to address odour from the treatment plant, including improved housekeeping and operational adjustments; implementing an odour treatment system; creating odour modification or masking; and changing the treatment process technology.
Some WWTPs, such as one in Mississippi, have utilized methods such as vanilla-scented misting machines.
“Public complaints about odour can negatively affect an industry’s image in a community. Eliminating the odours eliminates complaints, which is an effective public relations policy with far-reaching benefits,” states ProSweet’s maker, SUEZ Water Technologies & Solutions, in a product statement.
The odour suppressant can either repair the microbial cell membrane to inhibit sulfate transport, or by inhibition of the metabolic pathway in the organism’s use of sulfate as an oxygen acceptor.
SUEZ also says that in previous applications of its technology, not only the public, but also wastewater treatment plant workers, have enjoyed the benefits of less sulfurous odours on the job.
The City of Belleville is serviced by a communal wastewater system that consists of approximately 200 km of gravity sewer, one major pressure sewer, three main larger capacity pumping stations, several smaller capacity sub-area pumping stations, and a single wastewater treatment plant that provides secondary treatment and disinfection to wastewater, prior to the discharging of treated effluent to the Bay of Quinte.
A presentation by J.L. Richards and Associates Ltd. in late 2019 estimated that it may cost about $121 million, over 21 years, for the city to upgrade its wastewater treatment systems.