Wastewater Treatment Plant

Wastewater is defined as water which carries wastes from homes, industries, businesses or any other sources. It is usually a mixture of water and dissolved or suspended solids. Since water is becoming a scarce commodity, hence it is imperative to evolve technologies which treat them efficiently so that they can be reused. Treatment is also necessary because it helps in the reduction of physical, physiological, radioactive,biological and chemical pollutants.

Types of Wastewater Treatment Plants
Depending on the nature of the wastewater to be treated, wastewater can be classified as:

• Sewage Treatment Plants
• Sludge Treatment Plant
• Industrial Wastewater Treatment
• Agricultural Wastewater Treatment Plant
• Radioactive Wastewater Treatment Plant

Wastewater Treatment Methods
Wasterwater is treated in following stages:

Pre-Treatment
Pre-Treatment is a process which involves the passing of the effluent through the screen chambers to remove large floating solid particles which are settled in the primary sedimentation tanks. In this process apart from pre-chlorination, heavy suspended impurities are also removed.


Primary Treatment
Primary treatment includes chlorination, sedimentation and sludge digestion. Sludge digestion takes place in a sludge digester in which the organic or inorganic wastes and solids removed from sedimentation are are subjected to anaerobic fermentation. Since inorganic suspended solids hinders the performance of the biological oxidation of organic matter hence their removal is necessary. Removal of organic suspended solids present in the effluents reduce the aeration tank volume requirement which provides a primary clarification system prior to aerobic biological treatment process.

Secondary Treatment
In a secondary treatment process bio solids are separated from the water. Here soluble organic matter is biologically oxidized in the presence or the absence of oxygen. The process mainly removes dissolved organic matter and reduces biological oxygen demand. Whole process takes place in a secondary treatment system. A good secondary system has surface overflow rate of 16-80 metre cube/ meter square of the clarification area per day.

Tertiary Treatment
Tertiary treatment is primarily used to recycle water for industrial reuse. It may be also use if the effluent from a secondary treatment plant is not satisfactory. The process used in tertiary treatment system are filtration, demineralization and the reverse osmosis process.


Related Resources
Article: Biological treatment system a versatile aerobic treatment system
Article: Electrocoagulation for Better Removal

Case Study
U.S.A-Small scale waste water treatment plant- Solution for waste water problem
Marquette Waste Water Treatment Plant: Creating Difference