Effect of Mixing Natural Coagulant with Alum on Water Treatment

Abstract

Coagulation chemicals such as Aluminium are widely used in water treatment. Water treatment using chemicals can be very costly and the use of high level of alum in water can caused hazard disease like Alzheimer. As an alternative, coagulant from natural substance (i.e. Dolichos Lablab) mix with alum is used for coagulation in water treatment. It is more environmental friendly and effective in term of cost. The use of natural coagulant can reduce the dosage of alum in water treatment. This research aims to analyse the effect of mixing different types of natural coagulant with alum and which will give the better result in turbidity removal at its optimum mixing ratio. Natural coagulant mixes with alum were added to the jars containing one litre of raw water were compared to a jar containing raw water added with Alum only which acted as a reference. Different ratios (1:1 and 1:2) of natural coagulant to alum were prepared. Turbidity and colour were measured and the results obtained were evaluated. It was found that by using the ratio of alum to Dolichos Lablab of 1:2 has better turbidity removal of 71.27% from 2200 NTU to 632 NTU of 5 ml/L respectively for the synthetic water. As for lake water, it is shown that the mixture of alum to dolichos lablab at ratio 1:1 and 6:6 ml/L has highest turbidity removal of 95.51% from 12.8 NTU to 0.575 NTU.