Q. What is the cost-benefit relationship regarding sewage treatment as a strategy to fight water pollution?
To treat sewage is greatly cheaper for society. The non-treated sewage pollutes lakes, rivers and the sea being a cause of diseases transmitted through water. For the society the costs of these diseases are lot higher than the cost of the sewage treatment.
One of the major economical systems to treat sewage is the aerobic treatment system, reservoirs kept much oxygenated for aerobic bacteria to decompose organic material.