Pollutants in water consist of a large spectrum of chemicals, pathogens, and physical chemistry or sensory changes. A lot of the chemical substances are toxic. Pathogens can apparently produce waterborne diseases in either human or animal hosts. Alteration of water’s physical chemistry includes acidity, conductivity, temperature, and eutrophication. Eutrophication is the fertilization of surface water by nutrients that were previously scarce. Even many of the municipal water supplies in developed countries can present health risks.