Evaluation of small on-site wastewater treatment systems

Purpose - The purpose of the project was to evaluate and demonstrate new solutions for decreasing the discharges from on-site wastewater treatment plants. Design/methodology/approach - The study evaluated several on-site wastewater treatment plants. Seven of the investigated facilities were package plants, two were urine separating plants with large sand filters, two had storage tanks to collect wastewater separated from toilets and compact sand filters, and, finally, four had chemical precipitation in combination with large sand filters. Findings - All of the systems have shown that they are able to remove more than 90 per cent of the phosphorus and more than 90 per cent of the organic matter. The sorting systems also give very low local emissions of nitrogen. To guarantee that the package plants perform well and manage to fulfil high reduction demands, there is a need for well functioning organisations for supervision and operation. The source separating systems require well-informed and motivated users to achieve low discharges. Originality/value - This study has been followed with great interest by national and local environmental authorities. Such ambitious evaluation of different on-site wastewater treatment systems has never been done before in Sweden. The Swedish Environmental Protection Agency is expected to soon publish new demands for these systems. The results from the project have been an important input for the proposal of new national regulations.