Coagulation-flocculation process for greywater treatment using Chitosan and Hibiscus Sabdariffa

Abstract

Abstract Greywater means faecal free wastewater from households and buildings. Recycled greywater can be used for daily activities where freshwater is not necessary. Coagulation and flocculation technique in water recycling mostly utilize chemical coagulant alum. However, alum residue in water causes neural diseases and the process produces toxic sludge. Hence, natural coagulant is a safer alternate. Previous studies had proved the efficiency of different types of natural coagulant used individually and as a combination. However, the combination of chitosan and H. Sabdariffa had not been tested. The objective of this research is to investigate the efficiency of chitosan and H. Sabdariffa used alone and combined in greywater treatment. Jar test experiment was conducted using 0.5 L greywater in beakers mixed with the coagulants. The pH and coagulant dosage in each beaker were manipulated to determine the optimum condition. The greywater was then mixed rapidly for 4 minutes at 140 rpm, then slowly for 20 minutes at 30 rpm. Before assessing the final turbidity and Chemical Oxygen Demand (COD), the beakers were allowed to settle for an hour. At pH 4, 0.8 mg/L of chitosan reduced turbidity by 51 % and COD by 60 %. With a dosage of 200 mg/L, H. Sabdariffa demonstrated its best effectiveness at pH 2, resulting in an 88 % reduction in turbidity and a 53 % reduction in COD. When chitosan and H. Sabdariffa were combined, the optimal composition was determined to be 40% chitosan and 60% H. Sabdariffa by weight at pH 4, resulting in a turbidity reduction of 94% and a COD reduction of 56%. The same experiment was carried out using alum at pH 6 and a coagulant dose of 200 mg/l, turbidity and COD were reduced by 96% and 62% respectively. respectively. As a result, the performance of chitosan and H. Sabdariffa have been shown to be comparable to alum in the treatment of greywater, separately and in combination.