Completion of study on sewage sludge management for St. John’s - Can sewage waste be a resource?

(L-R) Diana Cardoso, Fred Winsor of the St. John’s Harbour ACAP, and Dr. Robert Helleur.

The St. John's Harbour Clean-Up project has started and with it has discussion around the issue of waste management. Diana Cardoso, a former environmental science graduate student at Memorial, recently completed a literature review on biosolids management options for St. John's. The review is part of the St. John's Atlantic Coastal Action Program's (ACAP) St. John's Harbour Clean-Up Project in partnership with the Faculty of Science's Environmental Science Program. Dr. Robert Helleur, Chemistry, assisted Ms. Cardoso with the project.

According to Ms. Cardoso, biosolids are the product generated after the treatment of sewage sludge, which emerges after the treatment of domestic sewage. What to do with the biosolids is a concern. The report first reviewed the St. John's Biosolids Management Plan Report (BMP), which concluded that due to cost, the lack of a composting facility, an incinerator, and other infrastructures capable of working with biosolids, the biosolids should be put into Robin Hood Bay landfill. But, as Ms. Cardoso explains, this has its disadvantages.

“Being a non-environmental landfill, biosolids will increase the leaching problem and create more gas from the landfill, more methane gas, so we've got negative points toward Kyoto. Also, it will reduce the life of the landfill.”

An alternative long-term plan had to be devised. So ACAP asked

Ms. Cardoso to compile a review of the possible methods of dealing with waste water sludge. She looked at different policies and solutions used in Canada, the United States, and in other countries, such as Norway and Japan.

Ms. Cardoso came up with three different solutions for St. John's : composting, reed beds, and gasification.

“With composting, at least you're recycling the biosolids, rather than treating them as waste,” she said. “Where to put the compost would be an issue. You have to find somewhere to use the compost. You either sell it, or use it provincially on golf courses or for reforestation.” Composting, which would involve having an indoor composting facility, could be costly, however.

Reed beds are a type of wetland built on site. The biosolids go on top, every two to three weeks depending on the design. It provides storage, living for eight years or more depending on the design. It is treated slowly and built large enough, so it can last for a long period of time without the solids being removed. The volume of solids can be reduced up to 80 per cent, and they are like a compost.

The third alternative was gasification or pyrolysis, which is a new technology and similar to incinerators. According to Ms. Cardoso's review, gasification is the transfer of energy from a solid to a gas phase by partial combustion of a waste, which uses less oxygen in the burning process, so it starves oxygen and you get less emissions.

Ms. Cardoso hopes her literature review will let the city consider an alternative method to dealing with biosolids. “I'm narrowing it down to a few methods they can focus on.”

Other methods of dealing with the sludge are interesting, as well, but do not pertain to the City of St. John's. One of these is used in Michigan. Cardoso said they put biosolids in a landfill, collect the methane and convert it to electricity. “They sell this electricity and make money, so much so that, the taxes are reduced there.”

Ms. Cardoso believes there are a lot of options for the city other than putting it into a landfill. “Biosolids or sewage sludge should be treated as a resource rather than a waste.”

More has to be done to achieve a clean, serene harbour. “You need a technical review; you need a market analysis, and public acceptance. Getting the public involved is important because if they don't like composting, they're going to be against it the whole way. If your creating a product, it has to be something the public is willing to accept.”

Ms. Cardoso's review is now complete and has been sent to city officials. It is hoped they will take action and decide what to do. “This is a push for the city and the province to do something.”

The Harris Centre in the priority areas and inviting input and dialogue on further opportunities for Memorial University to contribute to economic growth and development in the province.