The most difficult challenge facing any water treatment facility is sewage treatment odour control. Whatever benefits the plant may bring are often overshadowed by the stigma of the odours it emits. Even government regulations cannot properly determine the performance indicators needed to make these plants neighborhood friendly. These odours could waft into parks and other public spaces ruining the experience for the people. It’s not just the residents who have a valid cause for concern. If sewage treatment odour control is not exercised properly, it could affect the morale of the plant employees which may impact job performance. It may cause various stakeholders to complain and bring enormous pressure to the plant management and municipal leadership to resolve the issue.
What causes odours at wastewater treatment plants?
The foul smell that comes from sewage is generally caused by the anaerobic breakdown of organic compounds. The product of this reaction is the formation of hydrogen sulfide which gives off an offensive, nauseating smell similar to the odour of rotten eggs, ammonia, or garlic. Because hydrogen sulfide is not water soluble, it is dispersed in the air, hence the foul smell.
Other organic compounds responsible include amines and mercaptans which contain sulfur or nitrogen and these produce smells that are detectable by the human nose even at extremely low concentrations.
What intensifies odours?
Odours become intensified with higher temperatures. This is why more complaints are usually experienced in the summer months than at any time of the year. Even performing plant maintenance can play a role in increasing the challenge of sewage treatment odour control.
Sewage Treatment Odour Control Using Metal Salts
A new study involving common commercial chemicals or metal salts has been undertaken to address the odour issues emanating from the treatment of sewage sludge. Although this is not a new method in reducing odours, the novel way with which it is used may prove to be game changing.
Researchers from University of British Columbia’s Okanagan campus have embarked on a study to develop a new way of using common, inexpensive chemicals to enhance sewage treatment odour control.
The study is led by Cigdem Eskicioglu, as associate professor with UBC Okanagan’s School of Engineering. According to Professor Eskicioglu, the process of using microorganisms to obtain energy and nutrients from sludge using anaerobic digestion can be very toxic, corrosive, and produce extremely odorous sulfuric gases like hydrogen sulfide. Having to invest resources to create a more robust sewage treatment odour control solution in these plants becomes an expensive proposition.
Eskicioglu and her associates have put together unique combinations of commercial chemicals or metal salts in the fermentation process to determine the effect on odour control and the results have been nothing short of dramatic.
By changing the doses and point of insertion in the fermentation process, metal salts have substantially reduced the foul smell at minimal cost without sacrificing the benefits of anaerobic digestion in the treatment of sewage.
“Not only were we able to reduce the production of sulfuric gases by 93 per cent, to the point that they became nearly imperceptible, but we unexpectedly discovered that pathogenic fecal coliforms in the digested sludge were reduced by 83 per cent,” says Timothy Abbott, an associate of Eskicioglu. “Digestion performance and biogas production remained completely intact and the leftover material was much safer for eventual use in applications such as agricultural fertilizers.” He added.
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