Industrial contributions constitute as much as 20% of the 700 000 m3 .d−1 of sewage discharged to the Saronikos gulf through the sewerage system which serves the Greater Athens area. The main industrial discharges originate from food, textile, pulp and paper, chemical, tanning and metal processing and electrical industries. In the majority of the cases the pretreatment is inadequate and the existing emission standards are violated. This results in increased concentrations of toxic metals in the sewage. The impact of these toxic discharges on the marine environment and the sewage treatment works have been investigated. Increased concentrations in the water column and the sediments have been reported but there are no indications of accumulation of toxic metals in the body of benthic organisms. The impact on the imminent operation of the treatment works for the sewage of Athens, have been investigated with the aid of pilot and bench scale studies. The results did not indicate a serious inhibition of the sensitive digestion and nitrification processes. However due to the high concentrations of the heavy metals, with average values approaching threshold values, it is important that appropriate action is taken to control industrial discharges through a revised and rational regulatory framework.

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