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Charlotta Jernå har studerat Civilingenjör Naturresursteknik
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Master’s thesis about liquid composting of blackwater in Hölö, Södertälje

Published: 30 June 2022

Charlotta Jernå has studied Natural Resource Engineering, specializing in environment and water at Luleå University of Technology. She has now published her Master’s thesis. The study aimed to evaluate the liquid compost in Södertälje, which is part of the municipality's nutrient recirculation system.

Since 2012, there is a facility for treatment of blackwater in Södertälje. The blackwater comes from cesspits and is sanitized by liquid composting (auto-thermal aerobic digestion) and addition of urea. After the treatment, the blackwater can be used as fertilizer and spread on arable land.

The degree project can be briefly summarized in two parts. The first was to evaluate the facility in terms of mass flows and gas emissions. Calculations would be made on available data, mainly analysis results from annual sampling. The variation in the data contributed to great uncertainty in the calculations and no certain conclusions could be drawn.

The second part was about investigating possibilities to include more substrates and developing a sampling plan for bucket toilet waste. The amount of substrate could be increased mainly by ensuring delivery from cesspits. The water content of the substrate could be lowered by connecting cesspits in which waste from bucket toilets is collected.

Supervisor at LTU was Inga Herrmann and Annelie Hedström was the examiner. The thesis was carried out in collaboration with Telge Återvinning and the Environmental Office in Södertälje municipality. After the studies, Charlotta Jernå will continue at Telge Återvinning for further work with the liquid compost and other projects.

Annelie Hedström

Annelie Hedström, Professor

Phone: +46 (0)920 492309
Organisation: Urban Water Engineering, Architecture and Water, Department of Civil, Environmental and Natural Resources Engineering
Inga Herrmann

Inga Herrmann, Associate Professor

Phone: +46 (0)920 492528
Organisation: Urban Water Engineering, Architecture and Water, Department of Civil, Environmental and Natural Resources Engineering