Drinking water in the US and developed nations of the world is treated to remove contamination of foreign materials, both mineral and organic. Contaminants can be present in almost any water source and can be observed in water supplies obtained from mountains, rivers and soil, with even greater contamination potentials coming from domestic sewage and industrial waste.
Cryptosporidium and giardia are examples of microscopic parasites prevalent in surface water. These parasites cause gastrointestinal diseases and have caused large outbreaks of illness. One example of this was a 1993 outbreak in Milwaukee, WI where 400,000 people became sick. Surface water is most vulnerable but poorly constructed and shallow wells are also at risk.
One of the requirements for removing or inactivating these types of parasites is to enhance the coagulation capabilities in water treatment facilities. Impurities in waste water are primarily anionic or negatively charged. Cationic (positively charged) additives have been developed to neutralize these charged anionic contaminants. By introducing optimal quantities of cationic additives that will cause this system to reach a neutral charge, it is possible to improve the efficiency of removing contaminants via sedimentation or filtration. Zeta potential measurements provide a tool that quantifies the optimal concentration of the oppositely charged additives required to enhance coagulation of contaminants from a water supply.