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

Local water supply and sewage systems utilizing soil infiltration systems a nd septic tanks are common in the Swedish countryside. The effects that inf iltration of grey water has on groundwater quality have been investigated i n a Swedish holiday village consisting of 269 houses and covering an area o f some 160 ha. Boron and linear alkylbenzene sulphonates (LAS) were not fou nd to occur in sufficient quantities to indicate sewage impact on the groun dwater. A slight elevation ill the content of nitrate in the groundwater wa s 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 4 0% of the total input of this element. The release from grey-water infiltra tion 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 b ackground levels. In a bacteriological test two wells out of 118 were found to contain water unsuitable for drinking purposes. About 15% of the availa ble groundwater recharge was used for water supply. The current water and s ewage practices appear to be a sustainable. (C) 2000 Elsevier Science B.V. All rights reserved.