City selects wastewater thermal hydrolysis option on life cost basis

  • Technology


The small Canadian city of St Thomas has selected a thermal hydrolysis process as part of an upgrading of its wastewater treatment plant that will create a useful biosolids product instead of sending sludge to landfill.

St Thomas, Ontario, has approved plans to use technology from Lystek International in a project to convert the city’s water pollution control plant into a water resource recovery centre. Of seven technology options considered, investing in new anaerobic digesters or the Lystek Thermal Hydrolysis Process were shortlisted. Lystek and the city have announced that the two shortlisted options were comparable in terms of technical, social, and environmental and community aspects. However, an economic comparison showed the Lystek option to be at least 40% more cost effective than anaerobic digestion in a net present value evaluation of capital and operation for 60 years.

The city has a population of around 40,000. The existing 27,300 m3/day plant serves the city and surrounding area and currently uses anaerobic digestion, with the digested sludge being dewatered and transported to landfill.

The Lystek system is based on a physical/chemical process and creates a marketable, federally-registered, Class A biofertiliser known as LysteGro that can be used in agriculture, horticulture and other industries. The system can also be used to produce LysteCarb, which is an alternative source of carbon for biological nutrient removal systems.

The Lystek system being supplied in an approximately $10 million project will form the basis for the city implementing a sustainable long-term biosolids management programme.

‘After much research and analysis, it became clear that the Lystek solution was the best net solution for St Thomas,’ commented Justin Lawrence, Director, Environmental Services and City Engineer for the City of St Thomas, adding: ‘The technical criteria were proven through a peer review of existing installations. The environmental and social benefits are primarily the re-use of bio-nutrients and a greatly improved odor control system. The lower life-cycle capital and operating costs create a significant savings and we can also improve our capacity in the biosolids system. We are confident this decision will pay economic and environmental dividends.’


  • Canada, Lystek International, resource recovery