Science 5 Marks Questions

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 a liquid waste. Most of its water has dissolved and suspended impurities called contaminants. Composition of Sewage: The following components make the sewage:

1. The organic impurities present in sewage are human faeces, animal wastes (like animal dung), urea (as urine), oil, fruits and vegetable wastes, pesticides, herbicides, etc.
2. The inorganic impurities present in sewage are nitrates, phosphates and metals.
3. The nutrients present in sewage are nitrogen and phosphorus.
4. The bacteria present in sewage include those bacteria which cause water-borne diseases such as cholera and typhoid.
5. The other microbes present in sewage are Protozoa which cause a water-borne disease called dysentery.

1. Vermi-composting toilets.
2. Vacuum toilets.
3. Chemical toilets.
4. Composting toilets.
5. Septic tank toilets.

1. Aerated water contains some suspended impurities and the foul odour of the polluted water disappears completely after aeration.
2. Sand filter removes tiny suspended impurities.
3. Chlorine makes the water clear and colourless.
4. Yes, chlorine have a peculiar odour which is not worse than wastewater.

The correct sequence of waste water treatment in treatment plant is:

3. Large objects like plastic bags are removed by passing wastewater through bar screens.

5. Wastewater enters a grit and sand removal tank.

4. Sand, grit and pebbles are made to settle by decreasing the speed of incoming waste water.

2. Water is made to settle in a large tank with a slope in the middle.

1. Sludge is scraped out and skimmer removes the floating grease.

Sanitation and disease are related to each other as lack of sanitation can cause diseases. In our country, a large number of people even today do not have sewerage facilities and thus defecate in open fields, railway tracks, etc. The untreated human excreta thus pollute soil and water sources including the underground water. When this contaminated water is used for drinking, it can cause diseases such as cholera, typhoid, hepatitis, dysentery, etc. which may even lead to death. Therefore, lack of sanitation resulting in drinking of contaminated water can cause health problems.

There are various steps involved in the water treatment plant which involves physical, chemical & biological processes:

• Waste water is passed through bar screens to remove big objects like cans, sticks, rags etc.
• The liquid material is then passed through sedimentation tank where solid waste like faecal matter, sand, grit settles down.
• This solid matter is then removed with the help of a scrapper. This is the sludge.
• A skimmer removes the floatable solids like oil, grease etc.
• The clear water so obtained is called clarified water.
• Air is pumped into clarified water to help aerobic bacteria to grow. The bacteria then consume the unwanted matter still present in clarified water.
• The suspended microbes settle at the bottom & the water is removed from the top.

1. In my opinion, municipality is responsible to maintain sanitation at public places.
2. If all the wastes produced at public places are not disposed of regularly and properly epidemics could break out.
3. Responsibility, sensitivity and awareness towards public hygiene.

The various steps are:

1. Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed.
2. Water then goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.
3. The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water.
4. Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.

3. Typhoid and cholera.
4. In vermi-composting toilets, human excreta is treated by earthworms in a pit.
5. He is intelligent and concious about health.

Every community should have a way of disposing sewage so that people, animals and flies cannot touch it. This is called a sewage system. We know that poor sanitation is the basic cause of a number of diseases. To make our sanitation get better there are different types of sewage systems which can be used such as on-site systems and sewage or effluent systems. Septic tanks, composting pits, chemical toilets, etc., are examples of on-site sewage disposal systems.