Question 11
(a) Mention any two sources of waste
i)What are biodegradable waste?
(b) State two reasons why waste management is important
(c) Explain briefly the meaning of the following terms
1)Composting
2)Incineration
3)Segregation
(d) Mention how is sewage treated before the disposal Name two medical waste.
Answers
Answer:
(a) Two sources of wastes are domestic and industrial.
i) Wastes which decompose into the soil and do not pose serious challenges to the environment are known as biodegradable wastes.
b) The most important reason for waste collection is the protection of the environment and the health of the population. Rubbish and waste can cause air and water pollution. Rotting garbage is also known to produce harmful gases that mix with the air and can cause breathing problems in people.
c) 1) Composting is defined as the biological degradation process of heterogeneous solid organic materials under controlled moist, self-heating, and aerobic conditions to obtain a stable material that can be used as organic fertilizer.
2) Incineration is a method of treating waste which involves the combustion of the organic substances found in waste materials. The solid mass of the original waste is reduced by around 80 to 85%, while the volume is reduced by between 95 and 96%. When burning waste however, pollutants are created.
3) Segregation is the separation of an individual or group of individuals from a larger group. It sometimes happens to apply special treatment to the separated individual or group. Segregation can also involve the separation of items from a larger group.
Sewage mainly includes human excreta and contains large amounts of organic waste and pathogenic microbes. Thus it is necessary that waste should be made less polluted before discharging into water bodies.
d) The process of sewage treatment is explained in the following steps:
1) Primary treatment- In this treatment, filtration and sedimentation process is applied to remove large and small particles. Filtration process removes the floating debris by passing it through mesh wire screens. Then sedimentation removes the soil and small pebbles. The sediment is known as primary sludge and the supernatant is known as primary effluent. The effluent then enters the secondary treatment.
2) Secondary treatment- In this treatment, large aeration tanks containing primary effluent are constantly agitated with a continuous supply of air. Thus aerobic microbes grow vigorously consuming a major part of the organic effluent reducing Biological Oxygen Demand (BOD) of the effluent. The sewage is then passed into the settling tank where bacteria settle and now it is known as activated sludge. Some of the activated sludge is again passed into aeration tank to serve as inoculum while rest of it enters into large tanks called anaerobic sludge digesters. Here anaerobic bacteria grow to produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide to form biogas. This effluent can then be released into natural water bodies.
Human anatomical waste like tissues, organs and body parts, animal wastes generated during research from veterinary hospitals are some medical wastes.