Validation of laboratory pilot plants for wastewater treatment by natural pond sedimentation, comparison with a reference plant

A comparison is made between the performance of a three-pond natural sedimentation domestic wastewater treatment plant and two laboratory pilot systems with respectively one and two tanks, using the same raw effluent to validate them as models. A number of physico-chemical and biological parameters were examined. Principal component analysis (PCA) was applied to the reference plant and each of the pilot plants. Field monitoring of the reference plant by weeky sampling for 1 year showed that the first sedimentation pond was the most important in the treatment process. Only slight differences were found, for all the parameters studied except bacteria, between the outflow from the first pond and the outflows from ponds 2 and 3. On the laboratory pilot plants, an initial stabilization period of about 1 month was found necessary to simulate the natural reference plant accurately; the first tank likewise supplied most of the treatment effect. Yields were generally better in the pilot systems operating at 20 degrees C with constant flow rates and controlled light than in the reference plant. Overall, the results obtained show that a natural wastewater sedimentation plant can be accurately simulated by pilot systems, and in particular by a one-tank system. In the future, these model systems should enable us to study the influence, transfer and/or elimination of various micropollutants in this type of ecosystem. Copyright (C) 1996 Elsevier Science B.V.