Investigation of the performance of chitosan as a coagulant for flocculation of local clay suspensions of different turbidities

Abstract

In the present research, the effectiveness of chitosan as a natural coagulant for turbidity removal was investigated by the use of jar test. Tests were carried out on synthetic turbid water prepared from local clay, with high (314.4 NTU), medium (146.8 NTU) and low (34.2 NTU) turbidity. Experiments were also performed with chitosan as a coagulant aid. Consequence of pH, effect of settling time on residual turbidity was also studied. In present Research New Technique was tried which adopts two sequent treatments that used coagulation, flocculation and sedimentation processes under certain operating conditions. Results show that chitosan produces an appreciable removal of turbidity at approximately neutral pH. With conventional process maximum removal of turbidity was 61.9, 84.1 and 94.0% with residual turbidities of 13.0, 23.3 and 18.8 NTU for low, medium and high turbid water at dose of 1.5 mg/L. In the experiments with chitosan as a coagulant aid, the results were very promising; the residual turbiditities recorded were 8.6, 4.8 and 5.8 NTU for initial turbidities of 34.2, 146.8 and 314.4 NTU. The experimental results of present study proved that the turbidity removal efficiency of new technique was superior than that of conventional process which meets WHO drinking water guidelines. By this technique removal efficiency has increased from 5 to 28% at settling time of 30 minutes with around 75% saving in alum dose. Also sludge produced was less voluminous and readily biodegradable. There was minor change in pH of treated water. Floc formed with chitosan was coarse and readily settleable.