Turbidity reduction in drinking water by coagulation-flocculation with chitosan polymers

Area of Science:

• Water treatment technologies
• Environmental chemistry
• Materials science

Background:

• Turbidity in drinking water harbors microbes and organic matter, necessitating effective reduction for safe consumption.
• Coagulation-flocculation is a key process for water purification, and natural coagulants are sought for sustainable solutions.
• Chitosan, a biopolymer, shows potential as a household water coagulant, but its optimal application parameters require investigation.

Purpose of the Study:

• To evaluate the efficacy of chitosan in reducing turbidity caused by bentonite and kaolinite in model drinking water.
• To determine the influence of chitosan's molecular weight (MW), degree of deacetylation (DD), and functional groups on turbidity reduction.
• To identify optimal chitosan dosage and characteristics for effective household water treatment.

Main Methods:

• Systematic testing of varying chitosan doses, MWs, DDs, and functional groups against bentonite and kaolinite turbidity.
• Measurement of residual turbidity (NTU) to quantify reduction efficiency.
• Analysis of the point of zero charge to understand optimal dosage ranges.

Main Results:

• Higher MW and DD of chitosan correlated with greater turbidity reduction.
• Optimal turbidity reduction (<5 NTU) was achieved at chitosan doses of 1 and 3 mg/L for MW >50,000 or DD >70%.
• Effectiveness varied with clay type, with bentonite showing a broader effective dose range and higher reduction than kaolinite.

Conclusions:

• Chitosan is a viable option for reducing clay-based turbidity in household drinking water, particularly at doses around 3 mg/L.
• Chitosan's performance is influenced by its properties (MW, DD) and the type of clay contaminant.
• Further research into combining chitosan with sedimentation and filtration can enhance its application in low-resource settings.