What do chlorine and ozone do to the sewage water?
chlorine can be added at various locations in a sewage treatment plant:
- at the end of a sewage plant, chlorine is used to sterilise the treated sewage before it is discharged out from the treatment plant.
- In newer plants with membrane bioreactors, chlorine (as NaOCl) may be used during membrane cleaning to reduce biofouling
in short, chlorine is added to kill bacteria and microorganism at places where they are not desired.
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 water requirement and also for toilet flushing in many housing colonies.
chlorine can be added at various locations in a sewage treatment plant:
- at the end of a sewage plant, chlorine is used to sterilise the treated sewage before it is discharged out from the treatment plant.
- In newer plants with membrane bioreactors, chlorine (as NaOCl) may be used during membrane cleaning to reduce biofouling
in short, chlorine is added to kill bacteria and microorganism at places where they are not desired.
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 water requirement and also for toilet flushing in many housing colonies.
