Sewage treatment

From ArticleWorld

Sewage treatment is the process of removing the majority of the contaminants found in waste-water or sewage. The result is suitable for disposal liquid effluent and a sludge. The process itself is difficult and needs to be done in a controlled manner with actions ranging from simple to complex.

Description

Sewage is the liquid waste collected from baths, toilets, kitchens, public bathrooms and so on. Sewers are used to dispose of it. A common practice nowadays is to separate the water drains from different areas of the house in greywater and blackwater. Greywater can be recycled and purifying it is easier to do. A sewerage system that transports liquid waste to a treatment facility is defined as being a combined sewer system (because it usually incorporates storm water discharges as well). This practice is not being built anymore. Separate sewage systems are provided for the wastes and the storm water. The building where sewage treatment is done is named “sewage treatment plant”.

Treatment

Several stages are done for sewage treatment to be done:

• Primary Treatment – It is sometimes named mechanical treatment because of the use of machines during the operation. Primary treatment refers to reducing oils, grease, solids, sand, fat, grit and other such substances. First of all the large objects are removed, followed by sand and grit. The final two steps are the maceration, screening and sedimentation.
• Secondary Treatment – This step is aimed towards damaging biological content removing. In most sewage treatment plants the aerobic biological processes are being used. Bacteria and protozoa will consume the biodegradable organic contaminants and the result of the secondary treatment will be sludge and cleaner liquids.
• Tertiary Treatment – This is the final steps and it is used to make sure the effluent quality of the liquid meets the standards of not being dangerous to the environment it will be discharged in. Depending on the are a number of Tertiary Treatment solutions can be used. Examples can be given in effluent polishing, lagooning, several types of filtration, wetlands, nutrient removal and others. If disinfection is also used it will always be the last step taken in the process.