Wastewater from municipal sources is generally known as sewage. It is usually borne away from households and industries through sewers to be treated at effluent treatment plants. The management of wastewater is of paramount importance for public health and the support of a functioning society. Integrated water management includes measures for the re-use of water after industrial filtration. The main advantages of re-using wastewater are resource efficiency and as a measure to deal with water scarcity.

Wastewater Recycling

The production of clean water from the wastewater of municipal sources is a long-term sustainable solution in areas of the world that experience water shortages. It has the advantage of being less costly than the desalination of seawater. Drought is a key reason for the reclamation of water in Southern Europe. Wastewater that has been treated in an effluent treatment plant may be used for irrigation and other non-potable purposes. This requires the reclaimed water to be treated to a level where it may be used safely in agriculture and industry.

As an example, the paper and pulp industry consumes a great deal water but does not have the same requirements for the quality of the input water. Furthermore, the water within this industry may be re-used several times within the process itself;this being another example of wastewater recycling.

Disinfection of Water

Disinfection has the effect of substantially reducing the number of single-celled microorganisms in the water. Since most wastewater is discharged back into the environment for later collection as drinking and bathing water, disinfection is of paramount importance for public health, as well as for the ecosystems that the water affects.

The method of disinfection must be adapted for the quality and cloudiness of the water. Disinfection of water with a high degree of cloudiness will have a lower degree of success (measured in the successful elimination of pathogens) because the existence of particles that give the water its cloudy appearance also serve to shield microorganisms from disinfection agents. This effect is heightened with a low contact time. Pre-filtration is a measure that lends a greater success to disinfection using water treatment technologies such as ultra-violet light, ozone, chlorine and sodium hypochlorite. After various disinfection processes, the treated water may re-join the water cycle, usually by way of the nearest large body of water, or after being used for agricultural purposes.