Drinking Water Treatment and Disinfection Elsevier饮用水处理和消毒.pptVIP

Giardia and Cryptosporidium filtration is best large size resistant cyst and oocyst Enteric viruses disinfection is ultimate barrier filtration and coagulation also help via adsorption to particles dependent on surface charge of virus Water Distribution Systems * Drinking Water Treatment – Chapter 25 Class Objectives Be able to define the possible components of a water treatment train and their functions Be able to differentiate between rapid and slow filtration Identify the components of a water treatment train that are best for a virus. A protozoa. List the possible detrimental effects of microbial biofilms in water distribution systems Differentiate between dissolved organic carbon and assimable organic carbon Describe the AOC test Where does drinking water come from? Rivers Streams Lakes Aquifers Drinking water treatment processes Water treatment processes provide barriers between the consumer and waterborne disease One or more of these treatment processes is called a treatment process train Typical Water Treatment Process Trains Chlorination Filtration (sand or coal) In-Line Filtration involves a coagulation step (additive that allows aggregation of suspended solids, e.g., alum, ferric sulfate, and ferric chloride, polyelectrolytes) Direct Filtration involves a flocculation step where the water is gently stirred to increase particle collision thereby forming larger particles Conventional Treatment involves a sedimentation step which is the gravitational settling of suspended particles Filtration Processes Used Rapid filtration used in United States fast filtration rates through media (sand or anthracite) backwashing needed Slow sand filtration common in United Kingdom and Europe slow filtration rates through media (sand and gravel) removal of biological layer needed higher removal rates for all microorganisms 99 99–99.9 90 Cryptosporidium 99 97–99.9 58–99 Giardia 99.999 10–99 88–95 Enteric viruses 99.999 50–98 76–83 Fecal coliforms 99.999