FJERNELSE AF KVÆLSTOF FRA REJEKTVAND / Removal of Nitrogen from Sludge Supernatant Liquid
Supernatant liquid from digesting tanks is rich in ammonia. Treatment of supernatant liquid by stripping and absorption was investigated technically and economically under Danish conditions. In a pilot plant, 50 % of the ammonia was removed in one tower. The ammonia was absorbed in sulphuric acid whereby ammonium sulphate was formed. Technical and economical assessments showed that under Danish conditions stripping of sludge liquid is normally not profitable in domestic wastewater treatment plants. However, stripping can be advantageous under special circumstances such as sewage treatment plants with pre-precipitation and in case of plants with land constraints.