A simple method for small scale wastewater treatment plants for the thickening of sludges: mesh filter and foam filter

Abstract

The ultimate disposal of wastewater sludge (biosolids) continues to be one of the most difficult and expensive problems in the field of wastewater engineering. Wastewater treatment plants generate different sludges, like primary settled sludge, waste activated sludge, chemical sludge and anaerobic sludge, according to their operating systems. These excess sludges have to be managed by reducing their volume and stabilizing them before their ultimate disposal. Generally used volume reduction methods are thickening and dewatering that are usually coupled with conditioning. Sludge thickening and dewatering require either a big capital investment or a big surface area. Moreover, most of the mechanical dewatering technologies use polymers to condition the sludge before dewatering. These polymers have high cost rendering the mechanical dewatering uneconomical. Small-scale wastewater treatment facilities play an important role in the aquatic environment in many countries. Although sludge treatment is essential for overall wastewater treatment, it is difficult and non-economical for small-scale treatment plants to use mechanical equipments. Considering these points, there is therefore a need for alternative technologies for high performance and easy to operate small-scale wastewater treatment facilities. In this study, mesh filter and foam filter are used as a liquid-solid separator instead of the conventional equipments like gravity sludge thickener, dissolved air flotation or centrifuge. By this way, it is possible to reduce the water content of the sludge as mechanical devices and make thickening process economical.