Question

What is natural alternative to sewage treatment plants

Answer 1

Natural wastewater treatment systems are simple, cost-effective and efficient methods to purify the growing amount of wastewater produced by our society. They can be applied as secondary or tertiary purification treatment, allowing the removal of most of the bacteria, microorganism and the destruction of the organic matter. Among them phytodepuration, lagoon purification and storage in tanks gave good results in terms of yield and are quite diffused all over the world. 
Their extreme simplicity in building, operation and maintenance make these systems competitive with the conventional (sewer) wastewater treatment methods

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Answer 2

Explanation:

Aerobic treatment and fermentation are both biological methods. Physical: Physical methods include sedimentation, aeration and filtration. Sand filters are sometimes used in the oil-water separation process to remove oil and grease particles.