Collections > Electronic Theses and Dissertations > Chitosan Coagulation for Household Water Treatment in Developing Countries

Providing safe drinking water for underserved populations is still a challenge. Almost 800 million people around the world consume untreated or improperly treated water. Household water treatment is a critical and immediate intervention to provide safe drinking water where there are no improved sources of drinking water or water treatment systems do not function properly. The purpose of this research was to determine the efficacy of chitosan as a novel coagulant for water treatment in the home and determine whether characteristics of chitosan, especially molecular weight and degree of deacetylation, influence the performance of chitosan for removal of turbidity and microbes (bacteria and viruses) from water. Effects of water quality parameters such as pH, turbidity and salinity on chitosan coagulation efficacy were also evaluated. Zeta potential during coagulation and antimicrobial effects of chitosan in water were examined to give insight into potential mechanisms of chitosan action. The jar test method was used to evaluate the effects of chitosan characteristics on removal of turbidity and representative microbes (E. coli and bacteriophage MS2) from water. Overall, this research suggests that chitosan is an effective natural coagulant to use for household water treatment. Chitosan efficiently removed kaolinite or bentonite turbidity at low optimum chitosan dose of 3 mg/L. It also exhibited 3 -5 log10 removal of E. coli bacteria and bacteriophage MS2 at chitosan doses of 3-10 mg/L. The chief mechanisms of turbidity and microbial removal by chitosan include interparticle bridging and charge neutralization. The antimicrobial activity of chitosan appeared to play a minor role in microbial removal. Raw water qualities such as pH, salinity and turbidity had minimal effects on chitosan’s efficacy. Chitosans with intermediate molecular weight and high degree of deacetylation are the best candidates for turbidity and microbial removal, and there is a range of effective doses; chitosans exhibit high removal of turbidity and microbes, including bacteria and viruses, across a range of raw water qualities.