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Abstract
Centralised treatment of domestic sewage coming from A Coruña city (250000 inhabitants) and several medium and small size villages (up to 15000 inhabitants) together with industrial estate effluents was planned. The area population is about 380000 inhabitants and the overall effluent will reach about 600000 equivalent inhabitants. The characteristics of different streams will determine the treatment alternatives and pre-treatment requirements for individual streams. Domestic sewage from A Coruña showed medium to high organic content (741 mg l-1 of COD), while domestic sewage from small villages (Lorbé, Oleiros) and industrial estates (Sabón, A Grela) showed a high variability in organic content, with COD concentration ranging from 100 to 4000 mg l-1 or more. About 50-65% COD corresponded to suspended solids, although some industrial effluents showed lower values. Characterized industrial effluents had lower concentration of nutrients (nitrogen and phosphorus) and higher concentration of sulphate and alkalinity than domestic sewage. Anaerobic biodegradability was about 80% for domestic sewage, and ranged from 20 to 100% for industrial estate effluents. Furthermore, some industrial streams showed high microbial toxicity. The results indicate that anaerobic treatment of these effluents is of interest. However, specific pre-treatment for some individual streams or the adoption of minimisation and prevention measures in order to reach total or partial detoxification is suggested.