Pushpakumara, T.D.C., and W.G.T. Sandakelum. 2021. “Heavy Metal Potential of Domestic Biological Wastewater Treatment Plant Sludge: Research Article- DOI: 10.23953/cloud.Ijaaeee.503”. International Journal of Advanced Alternative Energy, Environment and Ecology, July, pp.90-113. https://cloudjl.com/index.php/AlternativeEnergy/article/view/30.