Sewage Treatment Plant (STP), Preliminary treatment; Upon arrival via the sewer system, the wastewater is
sent through a bar screen & Grit chambers which removes large solid objects such as sticks, rags etc.. Primary Treatment; Primary treatment is the second step in wastewater treatment. It allows for the physical separation of solids and greases from the wastewater. The screened wastewater flows into a primary settling tank where it is held for several hours allowing solid particles to settle to the bottom of the tank and oils and greases to float to the top. Secondary treatment; biological treatment process that removes dissolved organic material from wastewater. The partially treated wastewater from the settling tank flows by gravity into an
aeration tank. Final treatment; Treated water is disinfected and then it is sent out for wastewater reuse activities or for discharging in river/streams. mostly chlorination and/or ultraviolet irradiation is used for disinfection purposes. The Operating Principle of STPs; Conceptually, the process is extremely simple: A small amount of microorganisms converts a large mass of polluted water into clean water. This process also produces a co-product: A vastly reduced, compact solid biomass (the excess microorganisms produced by growth and multiplication of the original population of microorganisms) However, translating this simple principle into a properly designed and engineered STP is a real challenge: It requires sound knowledge of the biology of the microorganisms, chemical and mechanical engineering principles, and an equally large dose of common sense, We need an STP that 1) Achieves the desired results on a consistent and sustained basis. 2) Is robust and reliable, and lasts for at least 10-15 years without major repairs. 3) Needs minimum amounts of money, energy and chemicals to achieve the desired treated water
quality. 4) Is easy to operate and maintain.Benefits of a well-run STP;The primary benefits of a well-run STP are 1) Assured availability of water for various secondary uses 2) Enormous savings in freshwater costs 3) Lesser Environmental Degradation 4) Improved public Health.
Effluent Treatment Plant (ETP), is a process design for treating the industrial wastewater for its reuse or safe disposal to the environment. Treatment Levels & Mechanisms of ETP • Treatment levels:
Preliminary- Physical separation of big sized impurities like cloth, plastics, wood logs, paper, etc.
Primary-Removal of floating and settleable materials such as suspended solids and organic matter.
Secondary-To remove or reduce the concentration of organic and inorganic compounds having two methods Aerobic Process & AnaerobicProcess
Tertiary (or advanced)-Final cleaning process that improves wastewater quality before it is reused, recycled or discharged to the environment.