What Is Sewage Treatment Plant
Sewage Treatment is the process of removing contaminants from wastewater and household sewage water. It includes physical, biological and few chemical processes to remove pollutants. Its aim is to produce an environmentally safe sewage water, called ‘effluent’, and a solid waste, called ‘sludge’ or bio-solids, suitable for disposal or reuse. Reuse is often for agricultural purposes, but sludge is being used as a fuel source more often.
How does a Sewage Treatment Plant work
It works by breaking down solid waste to produce a cleaner and more environment friendly effluent.
The STP has two basic types:
Anaerobic Sewage Treatment
Here the sewage is partly decomposed by anerobic bacteria in a tank without the introduction of air containing oxygen. This leads to a reduction of Organic Matter into Methane, Hydrogen Sulphide, Carbon Dioxide etc. It is widely used to treat wastewater sludge and organic waste as it provides volume and mass reduction of the input material to a larger extent. The methane produced by large-scale municipal anerobic sludge treatment is currently being examined for use in homes and industry, for heating purposes. The effluent produced by this process is highly polluting and cannot be discharged to any watercourse. It should be discharged into the Aerobic layer of the soil (within the top metre of the ground) for the aerobic soil bacteria to continue the sewage treatment via the aerobic process below.
Aerobic Sewage Treatment
In this process, aerobic bacteria digest the pollutants. To establish an aerobic bacterial colony, you must provide air for the bacteria to breathe. In a sewage treatment plant, air is continuously supplied to the Biozone either by direct Surface Aeration using Impellers propelled by pumps which whisk the surface of the liquid with air, or by Submerged Diffused Aeration using blowers for air supply through bubble diffusers at the bottom of the tank. Aerobic conditions lead to an aerobic bacterial colony being established. These achieve almost complete oxidation and digestion of organic matter and organic pollutants to Carbon Dioxide, Water and Nitrogen, thus eliminating the odour and pollution problem above. The effluent produced by this process is non-polluting and can be discharged to a watercourse
Conventional sewage water treatment involves either two or three stages, called primary, secondary and tertiary treatment. Before these treatments, preliminary removal of rags, cloths, sanitary items, etc. is also carried out at municipal sewage works.
Primary Treatment
This is usually Anerobic. First, the solids are separated from the sewage. They settle out at the base of a primary settlement tank. The sludge is continuously being reduced in volume by the anerobic process, resulting in a vastly reduced total mass when compared to the original volume entering the system.
The primary settlement tank has the sludge removed when it is about 30% of the tank volume.
Secondary Treatment
This is Aerobic. The liquid from the Primary treatment contains dissolved and particulate biological matter. This is progressively converted into clean water by using indigenous, water-borne aerobic micro-organisms and bacteria which digests the pollutants. In most cases, this effluent is clean enough for discharge directly to the water bodies
Tertiary Treatment
In some cases, the effluent resulting from secondary treatment is not clean enough for discharge. This may be because the stream it is being discharged into is very sensitive, has rare plants and animals or is already polluted by someone’s septic tank. Therefore, here the sludge is periodically removed by tanker and taken for further processing via aerobic/anerobic processes and then disposed, reused, or discharged safely into the marine environment.
Now that you know what a Sewage Treatment Plant is and how it works, At EPEE Aqua, our expertise and rich experience in water and sewerage infrastructure development has helped us operate and enhance capacity to provide the best solution to meet the needs of our clients while contributing towards our planet with sustainable water infrastructure in response to meet the environmental requirements.
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