Exclusion of aquatic animals and removal of suspended solids from the water to be treated are essential prior to the application of disinfectants. Pathogens are known to adhere to organic and inorganic matter and removal of suspended solids can significantly reduce loading of pathogenic agents in water. Removal of suspended solids can be achieved by filtration or settlement of suspended material. The most suitable filtration system will depend on the initial quality of water, volumes to be filtered, capital and operating costs and reliability.