Chapter 18 Wastewater Story Solutions
Question - 1 : - Fill in the blanks:
(a) Cleaning of water is a process of removing ………. .
(b) Wastewater released by houses is called ………. .
(c)Dried …….. is used as manure.
(d) Drains get blocked by …….. and …… .
Answer - 1 : -
(a) pollutants
(b) sewage
(c) sludge
(d) cooking oils and fats
Question - 2 : - What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas?
Answer - 2 : -
Sewage is wastewater released by homes, industries, hospitals, offices and other users.
Sewage is harmful if discharged untreated into rivers or seas because sewage is a complex mixture of suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes.
Question - 3 : - Why should oils and fats be not released in the drain? Explain.
Answer - 3 : -
Oils and fats should not be thrown down the drain. They get hard and block the pipes. In an open drain, the fats clog the soil pores reducing its effectiveness in filtering water.
Question - 4 : - Describe the steps involved in getting clarified water from wastewater.
Answer - 4 : -
Step 1: When wastewater passes through bar screens, large objects like rags, sticks, cans, plastic packets are removed.
Step 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.
Step 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 scraper.
Step 4: Air is pumped into clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soap and other unwanted matter that still remains in clarified water.
After several hours, the suspended microbes settle at the bottom of the tank as activated sludge. The water is then removed from the top.
What is sludge? Explain how it is treated.
Answer - 5 : -
Solids like faeces which settle at the bottom of tank and are removed with a scraper are called sludge. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.
Question - 6 : - Untreated human excreta is a health hazard. Explain.
Answer - 6 : -
Human excreta may cause water pollution and soil pollution. Both the surface water and groundwater get polluted. Groundwater is a source of water for wells, tubewells, springs and many rivers. Thus it becomes the most common route for water borne diseases. They include cholera, typhoid, polio, meningitis, hepatitis and dysentery.
Question - 7 : - Name two chemicals used to disinfect water.
Answer - 7 : -
(i) Chlorine
(ii) Ozone.
Question - 8 : - Explain the function of bar screens in a wastewater treatment plant.
Answer - 8 : -
When wastewater passes through the bar screens, large objects like rags, sticks, cans, plastic packets, napkins are removed under the filtration process.
Question - 9 : - Explain the relationship between sanitation and disease.
Answer - 9 : -
Sanitation is the hygienic means of promoting health through prevention of hazards of wastes as well as the treatment and proper disposal of sewage wastewater.
Poor sanitation is a major cause of diseases worldwide and improving sanitation is known to have a significant beneficial impact on households and across communities. So poor sanitation and contaminated water is the cause of a large number of diseases.
Question - 10 : - Outline your role as an active citizen in relation to sanitation.
Answer - 10 : -
An active citizen has many responsibilities regarding sanitation. An active citizen should do the following to maintain proper sanitation:
- Surroundings should be clean (both inside and outside).
- Sewage system in the home should be properly managed.
- Some leakage or other problem in the sewage system should be reported to the municipality.
- If the sewage of any particular house makes the neighbourhood dirty, we should request them to be more considerate about health of others.