This table might be useful.   Sewage Treatment Plant Selection - Which Sewage Plant is the BEST? Comparision of EN12566-3 Test Results Below is a comparison list of Performance Results during the EN12566-3 Test -  taken from the EN12566-3 PIA Test Centre website. The figures are the average of the 38 weeks testing - the lower the figures, the better the result. It is probably better to avoid plants which have figures in red that are at, or close to, the limit
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