It is the process of removing the contaminants from sewage to convert it to a composition of clear liquid and solid, which are fit for discharge to the environment or for reuse.
SEWAGE TREATMENT PLANT
- In the most sophisticated treatment, clear potable water can be obtained while leaving only 5 percent to 10 percent of solids after treatment.
- This solid part, called sludge, is further processed to produce what is called biosolid, which has many uses.
- While hoteliers can discharge their sewage to the public sewerage, along with town sewage, for treatment in the city sewage treatment plant and final disposal.
- Many hotels have opted for in-house, Sewage Treatment Plants, where they get fresh water for reuse and may use the sludge as manure for garden activities.
- The fundamental principle of purifying sewage is to completely break down the original organic matter in it by the action of microorganisms (bacteria). These microorganisms digest (eat away) the original organic matter leaving a clear effluent and solids.
The stages in the treatment of sewage are as follows:
- Primary Treatment: This removes the suspended and floating objects by means of strainer, screens, grit chamber, sedimentation tanks, septic tanks, etc. The typical materials that are removed in this stage include large objects such as sticks, rugs, rocks, sand, gravel, fats, oils, grease, etc.
- Secondary Treatment: This treatment is designed to degrade the biological and organic content of the sewage by means of microbial action. The bacteria present in the sewage consume all the organic matter.
- A tertiary process with or without disinfectant: The final treatment is performed at this stage before making eventual disposal of the treated wastewater. Tertiary treatment comprises of many processes and includes filtration, disinfection, and removal of nutrients such as nitrogen and phosphorus which encourage algae formation. Disinfection can be done with chlorine, ozone, and ultraviolet treatment. In many cases, disinfection is done as the last activity (also called effluent polishing). The purpose of disinfection is to destroy residual bacteria in water after secondary treatment, thus rendering it very safe for final disposal.