Sludge distribution and annual accumulation rate in wastewater stabilization ponds in Northern Greece regions

The designers and the managers of wastewater stabilization pond (WSP) systems need to know the accumulation rate of sludge in WSPs so that the frequency of WSPs sludge removal can be determined. A better understanding of the sludge distribution in WSPs could lead to design improvements to achieve optimal distribution of the sludge for improved efficiency. Therefore, this knowledge needs to be integrated into the pond design, maintenance and management. The first objective of this study was to determine the distribution and accumulation rate of sludge accumulation in full-scale WSP systems consisting of facultative pond and maturation ponds in series, situated in Northern Greece, treating municipal wastewater of rural settlements. The measurements were taken after some years of system operation, without any mainte-nance. The accumulation rates and distri-bution of sludge were determined by measuring the thic-kness of the sludge layer at several locations throughout each pond. The second objective is to assess the relationship between the annual sludge accumulations with organic load treated by the system. Mathematical relationships were derived, correlating the annual sludge accumulation with the mean annual TSS and BOD5 concentration. These equations can be used to calculate the mean annual sludge accumulation at systems of similar climate.