Askøy municipality. Environmental status and assessment of municipal waste water with regard to the requirement of secondary treatment in the EU Urban Waste Water Directive

Abstract

Measurements of nutrients available for phytoplankton, chlorophyll-a and secchidepth and control of macroalgae close to municipal waste water discharges gave classification “High” or “Good” environmental conditions in the upper part of the watermasses around Askøy. Investigations of the soft bottom fauna and visual inspection with ROV at the pipe lines ends showed natural environmental conditions except at one station where technical problems had caused a clogged discharge pipe. Good water exchange and minimal effects of the municipal discharges justify the classification of the investigated area as a less sensitive area. Acceptable discharge depths for the planned municipal waste water flows in year 2030 were calculated. By following the recommendations the environmental conditions probably will be even better than today.