Wastewater Disposal to Water Environments

Disposal into a lake, ocean or stream requires taking into account the ability of the receiving water to assimilate wastewater. The natural purification capacity of the environment is limited. Even while wastewater is disposed to the ocean, the area surrounding the outfall could be satisfactorily polluted and the pollutants (involving pathogens) could be washed towards the beaches. The effects of improper disposal of biodegradable substances became a source of public outrage within the early 1800s. The flush toilet was becoming popular and sewage was discharged straight within the nearest waterway. The receiving waters were fast polluted. Fish in the receiving waters died and the water had an extremely offensive odour. While there are many reasons why we no longer discharge untreated sewage into the environment, (involving disease transmission, sediment buildup...) one of the purpose is directly associated to the fact that sewage contains much which is biodegradable. Here mainly focus on effect of oxygen demanding compounds on streams. DO content is one of the most hugely used indicators of whole ecological health of a body of water, e.g. fish require 4 to 5 mg/l to survive.

Nutrients (nitrogen and phosphorus) promote the growth of algae within the receiving water. In lakes and sensitive water environments, a removal of nutrients might be needed. In additional, if the wastewater contains high stages of heavy metals and toxic chemicals, these might have to be erased before wastewater disposal. Over the years the needs for disposal into water environments has become stricter as the impact of pollutants is better appreciated. It could be expected in which this trend towards more stringent discharge needs will continue.