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Abstract
A demonstration plant for ecologically engineered
wastewater treatment was constructed in 1989 as an aquaculture inside a
greenhouse, i.e. a mesocosm, designed for operation in a Nordic climate,
at N.Lat. 60, in Sweden. Located on the Baltic Sea coast in Trosa, Stensund
Folk College was used as a model community, with 100 person equivalents
(p.e.), for the purpose of developing a recycling concept for the wastewater
resourses of nitrogen, phosphorus and heat energy. After 4 years of operation,
results show that the wastewater from 34 p.e. (0.18m3 per day per person)
has been treated in the aquaculture, from January 1990 to January 1994.
Based on the total wastewater flow from 100 p.e., the nutrient uptake in
the aquaculture was 10% of the nitrogen and 8% of the phosphorus. Source
separation of phosphorus, i.e. the phosphorus not used, amounted to 34
%, coming through an increased awareness to using phosphorus-free cleaning
agents. The aquaculture's reduction of pathogenic bacteria and organic
material gave a treated effuent close to swimming water quality. Metals
were reduced by anaerobic treatment, with 48-73 % reduction of the seven
identified metals. Energy balances showed a small net energy import during
winter, and 19% of the greenhouse's available energy was heat pumped. The
costs of aquaculture wastewater treatment still exceed conventional costs,
as long as aquaculture products are not counted. |
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