Sustainability of local water supply and sewage system - a case study in a vulnerable environment

Local water supply and sewage systems utilizing soil infiltration systems and septic tanks are common in the Swedish countryside. The effects that infiltration of grey water has on groundwater quality have been investigated in a Swedish holiday village consisting of 269 houses and covering an area of some 160 ha. Boron and linear alkylbenzene sulphonates (LAS) were not found to occur in sufficient quantities to indicate sewage impact on the groundwater. A slight elevation ill the content of nitrate in the groundwater was found compared with data from 1972, with the highest concentration being 4 mg NO3-N/1. The input of nitrogen (N) from sewage is small in comparison with the background levels, while the input of phosphorus (P) constitutes 40% of the total input of this element. The release from grey-water infiltration as a fraction of total leaching was 6% for N and 30%, for P. However, in the groundwater, the level of phosphate was found to be unchanged from background levels. In a bacteriological test two wells out of 118 were found to contain water unsuitable for drinking purposes. About 15% of the available groundwater recharge was used for water supply. The current water and sewage practices appear to be a sustainable. (C) 2000 Elsevier Science B.V. All rights reserved.