In primary treatment, the suspended solid pollutants in the sewage will be removed, and most physical treatments can only meet the requirements of primary treatment. After the primary treatment, 30% BOD can be removed from the wastewater. It doesn’t meet the emission standard. Primary treatment is a pre treatment of secondary treatment.
In secondary treatment, colloid and dissolved organic pollutants (BOD, COD) in the waste water will be removed, and the removal rate can be higher than 90%. The organic pollutants meet emission standards. Use pH meter to monitor whether the emissions of organic pollutants are up to standard.
In tertiary treatment, non biodegradable organic pollutants, N, P and other soluble inorganic substances that lead to eutrophication of water bodies are further processed. Main methods are biological nitrogen and phosphorus removal method, coagulant sedimentation method, sand filtration method and activated carbon adsorption method.