Waste stabilization ponds and land treatment seepage, which are generally used for very small communities, are being used less frequently due to their specificity and their lack of suitability in certain cases (ground characteristics, available space, fragile receiving bodies, etc.)
This article gives the choice criteria for the proposed new series for 5 communities sized between 50 and 400 p.e. (person equivalents), together with a detailed description of the facilities:
-septic tank + covered infiltration bed
-horizontal settling-digestion tank + covered infiltration bed
-settling-digestion tank (Imhof tank) + trickling filter + infiltration bed
-pond + covered infiltration bed
-reed bed filters
in addition to the design of the infiltration beds and discussion of the investment costs.
All the series had to achieve the following effluent quality levels:
COD = 90 mg/l, BOD5 = 30 mg/l, TSS = 30 mg/l, N-NK = 40 mg/l
For the time being, the difficulties encountered are of a technical nature and concern the infiltration beds' feeder devices which do not produce a flat water jet that gives even spreading.