Sewage Water Treatment

Ozone in Sewage Water Treatment

Sewage water, whether it is municipal or from a small residential colony, poses a great health hazard and cannot be disposed off in any other water body like river, lake or sea nor can it be dumped on any land. It can lead to sever health problem to the community and also contaminate the sub-surface water and the surrounding land where it is dumped. This sewage contains harmful chemicals some of which are non-biodegradable and will cause severe environmental degradation. This water has to be treated to the safe level before disposing off. The treatment generally consists of solid particle removal, followed by oxidation in a bio-reactor. The water has to be further treated for disinfection before final disposal.

Ozone plays a vital role in the process of sewage water treatment. It forms a part of the tertiary treatment of the sewage water. The primary treatment consists of stabilization followed by formation of colloidal particles and removal of these along with suspended solids in a filtration process.


The secondary treatment is normally in a bio–reactor where oxidation takes place with the help of aerobic bacteria. The water still has to be clarified, filtered and disinfected. The earlier conventional use of chlorine is today less desirable due to the formation of harmful by-products. This is replaced by ozone with added advantage of giving further reduction of colour, odour while disinfecting at the same time. Ozone is also used for the reduction of BOD (Biological Oxygen Demand) and COD (Chemical Oxygen Demand). However, the primary function of using ozone in the tertiary treatment is to disinfect. A minimal dose of ozone does this job better than high dosage of chlorine. Sometimes, ozone is also used at the primary stage in addition to the tertiary stage.

The ozone treated water is considered environmentally safe for disposal. In fact, in most of the cases, the ozone treated sewage water is recycled for various uses like gardening, cooling tower make-up water requirement and also for toilet flushing in many housing colonies.