MIXING SURFACE WATER AND GROUNDWATER IN A SMALL NORWEGIAN WATERWORK. INFLUENCE ON WATER QUALITY AND CORROSION IN THE DISTRIBUTION SYSTEM
Asketjern/Blaker waterwork (ca. 5,500 persons) was until 1985 supplied with acid, soft surface water with a high humus concentration. The distribution system consists mainly of asbestos cement and cast iron pipes, and severe corrosion occurred. pH near 11 was measured at end points of asbestos cement pipes. There was no treatment for corrosion control. From 1985 12-14 % hard groundwater was mixed with surface water at the waterwork. This paper deals with a laboratory study performed before the use of the groundwater and a study of water quality before and after the mixing of the two waters for the purpose of revealing any possible reduction of corrosion after the use of groundwater. The laboratory study indicated minimum 50 % groundwater to reduce the corrosion of the asbestos cement pipes to a minimum level and to give an acceptable water quality with respect to water hardness and corrosivity, but an increase in turbidity is observed. “Complete abstract not presented.”