notes of waste managment of class 7
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Answer:
Waste Water Story Class 7 Notes Science Chapter 18
Water, Our Lifeline. Water is needed by all forms of life. ...
Sewage. It is wastewater released by homes, industries agricultural fields and other human activities. ...
Composition of Sewage. ...
Water Freshens Up: An Eventful Journey. ...
Sewerage System. ...
Manholes. ...
Treatment of Polluted Water. ...
Wastewater Treatment Plant (WWTP)
Explanation:
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The organic impurities present in sewage are human faeces, animal wastes , urea , oil, fruits and vegetable wastes, pesticides, herbicides, etc
The bacteria present in sewage include those bacteria which cause water-borne diseases such as cholera and typhoid.
The pipes which carry away wastewater or sewage from houses and other buildings are buried under the ground. An underground pipe which carries away dirty drainage water and waste matter is called sewer. The provision of drainage at a place by laying sewers under the ground is called sewerage. Actually, sewerage is an underground network of interconnected pipes called sewers that carries the sewage from the place where it is produced to the sewage treatment plants, where it is processed.
Treatment of wastewater involves physical, biological and chemical processes depending on the nature of contaminants.
The water rich in a lather, mixed with oil and other pollutants that go down the drains from sinks, showers, toilets, laundries is dirty. It is called wastewater
The water which is unfit for human consumption becomes the source of many water-borne diseases which ultimately lead to loss ( of human life. It is estimated that one billion human beings do not get safe drinking water. So, realising the urgency we celebrate 22nd March as World Water Day to bring awareness amongst people for safe water, fit for human consumption.
It is wastewater released by homes, industries agricultural fields and other human activities. It also includes rainwater that has run down the street during a storm or heavy rain and it is liquid waste. Most of its water has dissolved and suspended impurities called contaminants.
The organic impurities present in sewage are human faeces, animal wastes (like animal dung), urea (as urine), oil, fruits and vegetable wastes, pesticides, herbicides
The inorganic impurities present in sewage are nitrates, phosphates and metals
The nutrients present in sewage are nitrogen and phosphorus
The bacteria present in sewage include those bacteria which cause waterborne diseases such as cholera and typhoid
The other microbes present in sewage are Protozoa which cause a water-borne disease called dysentery
In a house, there are two sets of pipes, i.e. one set of pipes brings clean drinking water into the house and the other set of pipes takes away wastewater from houses. For proper sanitation, a well-maintained sewage system is required
The pipes which carry away wastewater or sewage from houses and other buildings are buried under the ground. An underground pipe which carries away dirty drainage water and waste matter is called sewer. The provision of drainage at a place by laying sewers under the ground is called sewerage. Actually, sewerage is an underground network of interconnected pipes called sewers that carries the sewage from the place where it is produced to the sewage treatment plants, where it is processed
A place where wastewater or sewage from houses and other buildings is brought for processing is called wastewater treatment plant.
Treatment of wastewater involves physical, biological and chemical processes depending on the nature of contaminants.
1. Physical Process (Screening)
The bar screens first remove the large rubbish objects like rags, sticks, cans, polybags, napkins, sanitary towels, etc., from the wastewater.
After passing through the bar screen, wastewater is taken to a tank called grit and sand removal tanks. In this, sand and grit settle down slowly at the bottom of the tank as water passes slowly through this tank. The settled sand and impurities are removed from the tanks from time to time.
2. Biological Process
The first sedimentation tank is sloped towards the centre. Solid like faeces settle at the bottom and is called sludge which is removed by a scraper. Oils and grease float at the surface of the water are removed by a skimmer. The biogas produced (by anaerobic bacteria) in the process can be used as fuel or can be used to produce electricity. Here, water gets cleared of rubbage, oil, grease, etc and we get clarified water which is sent to aeration tank now. In the aeration tank, the watery waste already contains bacteria (aerobic) in it. The compressed air bubbles are passed through this waste to provide 02 to the bacteria to increase bacterial activity which ultimately digests human waste, food waste, soaps and other unwanted and harmful matter still remaining in the wastewater leaving behind fairly pure water.
3. Chemical Process
The water after aeration tank is allowed to stand in a second sedimentation tank. Here, the microbes present get settled at the bottom at the tank in the form of activated sludge which is about 97% water. At this stage, water has very low level of organic matter suspended matter and does not contain many harmful things. It is safe for human consumption