Removal of river water pollutants using indigenous bio coagulants: optimization by central composite design (CCD).

Abstract

Water is one of the most precious natural resource, it is very extensively used by mankind. It is an important and essential component of this universe and plays a vital role in the proper functioning of the Earth’s ecosystems. In an era of increasing environmental concerns, water scarcity admits the draw backs of chemical coagulants and poor sanitary facilities in lowest income earning countries, the need to further develop natural coagulants as alternative environmentally favorable water treatment chemicals. Therefore, this study was conducted to investigate the surface water treatment potentiality of two natural coagulants, cactus(beles) and Moringa stenopetala (seed of shiferaw). To conduct this study natural coagulants were collected from local areas and grab or hand sampling technic was used to collect surface water sample from awetu river. Based on this, coagulation and flocculation treatment process were applied by using jar test apparatus to simulate the results. Design expert (11.0) was used for statistically analyzing the experimental data with ANOVA and to evaluate the optimum condition or value of both process factors with respective responses. So according to the experimentally analyzed result, the optimum conditions and responses obtained from the numerical optimization system for pH, coagulant dosage, stirring speed and stirring time were 2.5, 1.17g, 83.19rpm and 42.1min respectively when cactus powder was used as a natural coagulant. Under this optimum conditions, about 70.22%, 47.10 % and 83.80% for color, COD and turbidity removal efficiency was obtained respectively. And also in the same manner when Moringa stenopetala used as a natural coagulant, the optimum conditions and responses obtained from numerical optimization system for pH, coagulant dosage, stirring speed and stirring time were 10, 0.602g, 30.00rpm and 36.56 minute respectively. Then under this optimum condition, about 99.40%, 56.13%, and 96.56%, for color, COD and turbidity removal efficiency was obtained respectively. The effective results were found using moringa stenopetala.