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.
The wastewater that is polluted by human activities if without treatment is poured into the freshwater resources that ultimately mingle into marine water will definitely going to affect the water and marine life in it. Because of pollution, the oxygen level drops in the water. So less oxygen will be available to the aquatic life and because of this there will be less growth. Moreover it has been found that some species have even become the distinct species because of rising water pollution.
Hence it is very crucial to address the water problem at every level of its consumption and use. |
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| Wastewater treatment processes are designed to achieve improvements in the quality of the wastewater. The various treatment processes may reduce : |
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| 1. Suspended solids (physical particles that can clog rivers or channels as they settle under gravity) |
| 2. Biodegradable organics (e.g. BOD) which can serve as “food” for microorganisms in the receiving body. Microorganisms combine this matter with oxygen from the water to yield the energy they need to thrive and multiply; unfortunately, this oxygen is also needed by fish and other organisms in the river. Heavy organic pollution can lead to “dead zones” where no fish can be found; sudden releases of heavy organic loads can lead to dramatic “fishkills”. |
| 3. Pathogenic bacteria and other disease causing organisms These are most relevant where the receiving water is used for drinking, or where people would otherwise be in close contact with it. |
| 4. Nutrients, including nitrates and phosphates. These nutrients can lead to high concentrations of unwanted algae, which can themselves become heavy loads of biodegradable organics to the treatment processes. This type of treatment should ideally take place at the industrial plant itself, before discharge of their effluent in municipal sewers or water courses. |
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| There are three major steps to treat the waste water: |
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Primary (mechanical) treatment is designed to remove gross, suspended and floating solids from raw sewage/Effluent. It includes screening to trap solid objects and sedimentation by gravity to remove suspended solids. This level is sometimes referred to as “mechanical treatment”, although chemicals are often used to accelerate the sedimentation process. Primary treatment can reduce the BOD of the incoming wastewater by 20-30% and the total suspended solids by some 50-60%. Primary treatment is usually the first stage of wastewater treatment. |
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Secondary (biological) treatment removes the dissolved organic matter that escapes primary treatment. This is achieved by microbes consuming the organic matter as food, and converting it to carbon dioxide, water, and energy for their own growth and reproduction. The biological process is then followed by additional settling tanks (secondary Clarifier) to remove more of the suspended solids. About 85% of the suspended solids and BOD can be removed by secondary treatment. |
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Tertiary treatment is simply additional treatment beyond secondary Tertiary treatment can remove more than 99 percent of all the impurities from sewage or Effluent.
The typical tertiary treatment includes disinfection, Sand filtration & Adsorption with activated carbon filter. |
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