ACTIVATED-SLUDGE PLANT FACING GRAPE HARVEST PERIOD - A CASE-STUDY

Most of municipal activated sludge plants located in wine production r egions receive winery wastewaters during the grape harvest period whic h lasts usually only a few weeks. A drastic increase in organic pollut ion (COD, BOD) during this period generates a temporary overloading, r esulting very often in biological problems such as decreased sludge se ttleability, sludge flee disintegration, increased SS concentration in treated effluent and in the worst case a complete plant failure. In o rder to work satisfactorily even during those temporary overloading pe riods, the plant has to be oversized. This strategy is rather costly, because such a plant has to run below its nominal capacity during a ma jor part of the year. An original solution has been proposed and succe ssfully tested at a municipal wastewater treatment plant in Eguisheim, France. The proposed technique is based on the addition of a mineral material with a low particle size, whose presence positively influence s the physical behaviour of the sludge and will allow the nominal capa city of the plant to be surpassed without any important modification. The modification of the sludge structure around the added powdered mat erial improved significantly the sludge settleability (DSVI< 160 ml/g) and enabled the plant to treat organic pollution several times higher than the nominal level. Copyright (C) 1996 IAWQ. Published by Elsevie r Science Ltd.