Application Note
Chlorine Measurement In Wastewater And Regulated Discharge Requirements
Homes, industry, schools, and businesses all generate sanitary waste, or sewage. Sewage treatment is a multistage process that cleans up wastewater before discharge or reuse. In the final step of the treatment, disinfectants are added to kill disease-causing organisms. Common disinfectants are chlorine gas and sodium hypochlorite. Chlorine dosage levels are designed to leave almost no residual in the wastewater after treatment.
Industrial plants are also a source of non-sanitary wastewater. Many industries discharge large amounts of cooling water into lakes and rivers. To reduce the biofouling in cooling towers and heat exchangers, the cooling water is often treated with chlorine. Small amounts of chlorine are present in the wastewater discharge.
Federal and state agencies regulate the amount of chlorine allowed in water discharged into lakes, rivers, and oceans. Limits are between 0.01 to 0.30 ppm of chlorine. Chlorine is closely regulated because even small amounts are harmful to the environment. Typically, dischargers are required to monitor their waste streams and report chlorine levels to a regulatory agency. Agencies can require either continuous or grab-sample testing.
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