Characterization of the drinking water sludge for agricultural usage

Abstract

Water treatment plants generate large quantities of sludge resulting from treatment processes. “Konduwatuwan” water treatment plant located in Ampara in Sri Lanka, generates a huge amount of sludge annually and is disposed directly to the adjacent environment. Concerns have been raised by various authorities regarding the potential risk of the sludge on human and environmental health. This study was conducted to characterize the sludge and to evaluate the potentials to utilize it for soil application in agriculture. Physical and chemical parameters were analyzed using sludge samples in the laboratory. The result showed that the average moisture, total solid, ash and organic matter contents present in the sludge were 79.44%, 20.55%, 60.73% and 39.27% respectively and the monthly mean values of ash and organic matter contents did not significantly vary with time during the study period. The pH, electrical Conductivity, levels of cadmium, chromium, iron, lead and nitrogen were promising in the sludge when compare with aluminium based water sludges used for comparison in this study. Further, the levels of pH, electrical conductivity, nitrogen and phosphorous present in the sludge were within the suitable range for land application and the concentrations of cadmium, chromium and lead were far below the threshold values for composting according to Sri Lankan standards. Thus, the sludge can be utilized for the cultivation of non-food crops. However, further studies are recommended to investigate the effects of sludge on long-term application over the metal loading on cropping lands.