Algal Growth Control Within Natural Water Purification Systems: Macrophyte Light Shading Effects

Natural water purification systems including oxidation ponds and surface flow wetlands are commonly used to treat wastewater in tropic regions, however, the water quality of the effluent fluctuated and often failed to comply with regulatory water criteria due to algae bloom. Separation of algae is inevitable to produce high effluent quality and to comply with local effluent standards. Algal growth control measures including emergent and floating macrophytes as well as back cloth physical light shading and algaecide application were studied and were aimed to reuse the effluent for water resource conservation and groundwater recharge. The results demonstrated that emergent and free-floating macrophytes light shading on algal growth control were viable in both batch experiments and field-scale hybrid natural water purification systems such as surface flow wetlands. Water quality parameters including COD, turbidity, SS were positively correlated with the algal concentrations and could be used as indictors of the trophic status of aquatic systems. Emergent macrophytes assisted control algal growth by preventing sunlight from reaching the water column in surface flow wetlands. Results of this study can be used by similar hybrid natural water purification systems to control algal activity and to prevent effluent deterioration.

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