Sewage disposal
The used or we can say wasted liquids water from various areas has to be treated before it accumulates and causes nuisance and population to the environment. The various waste water includes water used by home and then released the wasted water, water from the industries or we can say industrial waste like these all the waste water is to be treated for the purpose to avoid epidemic diseases and for good environment. The sewage collected is taken to land or water where it does not create mosquitoes breeding centers. This should be in down-stream and should not damage or pollute the drinking water. It should be also taken care the disposed water is not making and problem to the society. So given below are the few useful terms to understand the sewage disposal easily and properly.
(a) Refuse- It is the waste water which is rejected, which includes sewages, sullage, garbage’s etc.
(b) Sewage- It is the liquid waste from the community including discharge from latrines, canals, industries waste.
(c) Sullage- It is the liquid discharges from the home which is mostly a waste and does not smell bad.
(d) Storm water- It is the rain water from roofs, wastes and building.
(e) Garbage’s- It is dry refuse and it includes decayed fruits, grass, leaves, paper pieces, sweeping, vegetables etc.
(f) Sewer - The underground conduits and drains through which sewage is conveyed is known as sewer. The sewers are available in lengths of 600 mm, 750 mm and 900 mm including the internal depth. Glazed earthen ware sewer pipes are cheap. They are resistant to acid and corrosion. They are hard and durable. They are impervious and can be easily cut.
How is sewage treatment Necessary?
It is necessary to maintain public health and hygiene. It prevents the possible contamination of water. It prevents atmosphere pollution i.e. bad odour. It reduces nuisance caused by flies, mosquitoes and insects. It encourages aquatic life.
STAGES OF SEWAGE TREATMENT
Primary treatment
1. Screening and skimming chamber-removal of fats, oils and floating matters.
2. Grit chamber –grits such as stone and sand particles are removed.
3. Primary setting tank-removal of organic matter.
Secondary treatment
4. Trickling filter – output from primary setting tank is made in contact with air and due to aerobic condition, fine dissolved matters are established to flocks.
5. The secondary setting-dispersed for irrigation and chlorination (0)
6. Sludge digestion tank- sludge from primary setting tank and secondary setting tank are stabilized which is accompanied by aerobic action through aerobic bacteria.
BOD & COD
(a) BOD (Biological oxygen demand)- It indicates the amount of oxygen in mg/liter for the complete oxidation of organic materials in sewage. BOD is less for mild sewage.
(b) COD (Chemical oxygen demand) - It is the amount of carbon in various types of organic matters. COD test is a test for oxygen consumed from chemical oxidizing agent like potassium di-carbonate in acid medium for oxidation of organic matters.
Aerobic and Anaerobic Decomposition
(a) Aerobic decomposition is caused by aerobic bacteria in presence of oxygen.
e.g., trickling filter
(b) Anaerobic decomposition is caused by anaerobic bacteria in the absence of oxygen.
e.g., Septic tank and sludge tank.
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