What are the primary causes and sources of water pollution at beaches?
The majority of beach closings in the United States are due to indications of the presence of high levels of harmful microorganisms found in untreated or partially treated sewage. Most of this sewage enters the water from combined sewer overflows, sanitary sewer overflows, and malfunctioning sewage treatment plants. Untreated storm water runoff from cities and rural areas can be another significant source of beach water pollution. In some areas, boating wastes and malfunctioning septic systems can also be important local sources of beach water pollution. Combined sewer systems are designed to carry both raw sewage and storm water runoff to sewage treatment plants. During heavy rainstorms, these systems can become hydraulically overloaded and discharge a mixture of raw sewage and polluted runoff from streets into local waterways. The discharges pollute water around the outfalls and at downstream beaches. Heavy rainfall can also hydraulically overload separate sanitary sewer systems whic
