An inexpensive and efficient method of sewage disposal for a small community is -

Oxidation ponds: It is a cheap method of sewage treatment Aka waste stabilization pond, redox pond, sewage lagoons, etc. It is an open shallow pool 1 to 1.5 m deep with an inlet and outlet there must be the presence of algae, ceain bacterias, and sunlight. Organic matter oxidized by bacteria to simple compounds such as CO2, ammonia, and water. Algae with the help of sunlight utilize CO2 and other inorganic compounds. Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 825