PURPOSE: A natural treatment system incorporating an aerobic stabilization pond with constructed wetlands is provided for advance treatment of effluent from conventional wastewater treatment plants. The natural treatment system is suitable to small communities, which are in financial straits. CONSTITUTION: Sand is spread on the bottom of the shallow algal ponds. And water depth of the shallow algal ponds is about 30cm for supplying retention time of 4-5 days. Water depth of the constructed wetlands is about 30cm, and aquatic plants such as water hyacinth, bulrush, dropwort, reed are cultivated in the constructed wetlands. Additionally effluent of the shallow algal ponds and the constructed wetlands is recycled to front part of the shallow algal ponds for improving treatment efficiency.
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