An investigation into the use of acid treated sugar cane bagasse ash-based coagulants for water treatment

Abstract

Abstract The aim of the study was to investigate the possibility to use acid treated sugarcane bagasse ash (SCBA) as a coagulant. The effect of type of acid, coagulant dose, time and pH on the coagulation characteristic were investigated. Synthetic turbid water was used for the tests. The coagulants were treated with H2SO4 (SSCBA) and HCl (HSCBA). A 6% m/v solid loading (S/L) of HSCBA reduced turbidity by 97.7% whilst an 8% m/v S/L of SSCBA reduced turbidity by 90.9%. Both coagulants exhibited hindered, transition and compression settling characteristics, however HSCBA had faster settling pattern. Turbidity reduction was best in the 6–10 pH range where there was over 90% turbidity reduction from an initial synthetic turbid water of 110 nephelometric turbidity units (NTU). Both coagulants were tested against natural highly turbid river water, and it was shown that only the HSCBA could reduce turbidity from 1,644 NTU to 2 NTU over 100 min. It was also shown that an overflow rate allowance of 0.01 cm/s could achieve 90% turbidity reduction using HSCBA when type 1 settling used for empirical calculations. The use of HSCBA was also shown to result in an insignificant amount of residual pH, Fe, Cu and Zn in the treated water. This therefore makes the use of HSCBA favorable in that it does not change the chemistry of the treated water.