Thanks very much for the ...

Thanks very much for the response and comments. These seem to reinforce our view that oil should be avoided. At the moment we are not considering to implement a new process step for active oil removal, rather prevention of oil entering the effluent stream. The question was aimed to assess whether we are being overly cautious and also to gain an understanding of the wider industry practice. The question of a "threshold" concentration is an interesting one. The number of 10ppm (or 20ppm) has been mentioned - although I understand that these at most are guidelines and will depend on the specifics of the effluents chemistry and the treatment system in question. We are likely to recommend further laboratory studies to establish the actual influence of oil on our filters as the concerns over its effect seems to be substantial enough to warrant this. A related but difficult issue is the fate of the oil in the treatment train – this will of course have a direct relevance to the question of how it will affect the sand bed filters. The effluent in our case is high pH, which I think could potentially cause additional problems (frothing?). Andras Paksy