Heavy Metal Potential of Domestic Biological Wastewater Treatment Plant Sludge

The use of sludge as fertilizers helps to the recycling of nutrients to the environment due to its beginning from wastewater and therefore relatively high content of nutrients and organic matter. However, wastewater does also contain hazardous compounds like heavy metals and micro pollutants which eventually are separated to the sludge during the treatment processes at the wastewater treatment plant. In order to improve the sludge quality, source tracking is a relatively cheap and effective way to find and eliminate hazardous compounds and prevent them from ending up in the sludge. The aim with this thesis was to investigate the fertilizer potential in sludge from wastewater treatment plant. The sludge is analyzed in terms of nutrient and heavy metal contents as well as physiochemical parameters. In order to determine the potential as fertilizer, the quality of the sludge is compared with other fertilizer alternatives, other sludge types and regulations for sludge use in agriculture. The work with sludge quality improvements in Gaborone is also investigated. Sludge from different stages along the treatment processes were collected in order to see differences in quality related to the treatment. The results shows that the samples of primary an aerobically treated sludge tend to have higher heavy metal content than the secondary sludge. The quality of the dry sludge samples indicates lower nutrient content than both the primary and secondary sludge, but similar heavy metal content. The analysis of dry sludge from indicates a low nutrient value and high heavy metal content in comparison to other selected fertilizer options and sludge from other. The processes for removal of nutrients from the wastewater are an important factor for the nutrient content in the sludge. Keywords wastewater; fertilizers; nutrients; sludge treatment

Evaluation of Harvested Rainwater Quality As a Drinking Water Source in Urban Land Uses in Western Province Sri Lanka

Increasing of population around the world has imposed considerable strains on the water resources. Hence, regulatory authorities have faced significant challenges to expand their water supply schemes not only due to financial constraints but also due to limited water resources. Consequently, there has been a growing interest, especially in developing countries, in harvested roof run off as an alternative source of drinking water. However, in determining the end use and the potential success of such an option, the possible problems associated with water quality need to be analyzed and the feasibility of using rainwater as a source of water for household use should be determined. Therefore, this research study was focus on evaluating roof runoff as a drinking water source in different urban land uses where different urban activities are present. For this purpose, a roof runoff samples were collected from three selected land uses namely industrial, commercial and residential. The samples have collected from each land use with three selected roofing materials which are common to the area. This is to evaluate the roof runoff quality based on the variability of land use pattern as well as the variability on roofing materials. All the collected samples have tested for a range of water quality parameters namely, pH, alkalinity, Hardness, Turbidity, TS, COD, Nitrogen (Ammonia), chloride and biological contaminations. Both uni-variate and stacked area analysis techniques were used in the analysis of test results. Based on the outcomes, recommendations are provided to use harvested roof runoff as a drinking water source in urban land uses in Sri Lanka. Keywords urban land uses; drinking water quality parameters; rainwater harvesting