Water resources and environment are polluted due to untreated wastewater release and can cause irreparable damages to environment. Industrial wastewaters containing particular pollutants can double this damage.  Although, wastewater can be naturally treated in environment, nature is not normally able to fully treat human-produced wastewaters in case of increasing wastewater volumes because of short limited time availability. Therefore, human has resulted that time of treatment is to be reduced by using different methods of treatment so that the environment is protected from damage.

There are a wide variety of approaches to treat wastewater ranging from  natural to innovative and advanced methods. Wastewater treatment plants are different in size; some are small package-based for house-hold purpose while others are large and mainly used for urban and industrial wastewater treatment purposes. Consulting engineers select and propose  the optimum and appropriate alternative, in terms of economical, technical, and environmental factors by quality and quantity analysis of particular wastewater