krit.club logo

Forests and Wastewater Management - Sanitation and Disease Control

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Forests act as 'Green Lungs' because plants release oxygen (O2O_2) through photosynthesis and absorb carbon dioxide (CO2CO_2), maintaining the atmospheric balance.

•

The forest structure consists of different layers: the Canopy (top layer), Understorey (shrubs and tall grasses), and the Forest Floor (composed of decomposing organic matter and humus).

•

Humus is the dark-colored substance formed by the action of decomposers on dead plant and animal tissues, which restores nutrients like Nitrogen (NN), Phosphorus (PP), and Potassium (KK) to the soil.

•

Sewage is liquid waste containing various impurities: Organic (human feces, oil, urea), Inorganic (Nitrates NO3−NO_3^-, Phosphates PO43−PO_4^{3-}, metals), and Biological (bacteria like Vibrio cholerae).

•

The Wastewater Treatment Plant (WWTP) involves physical, chemical, and biological processes. Physical: Bar screens and grit tanks. Biological: Aeration where aerobic bacteria consume organic waste. Chemical: Disinfection using Chlorine (Cl2Cl_2) or Ozone (O3O_3).

•

Sanitation and disease are closely linked. Poor sanitation and contaminated drinking water are the primary causes of diseases such as Cholera, Typhoid, Polio, Meningitis, and Hepatitis.

•

Alternative sewage disposal systems include Septic tanks (suitable for isolated buildings), Chemical toilets, and Vermi-processing toilets where earthworms treat human excreta into high-quality compost.

📐Formulae

6CO2+6H2O→ChlorophyllSunlightC6H12O6+6O26CO_2 + 6H_2O \xrightarrow[Chlorophyll]{Sunlight} C_6H_{12}O_6 + 6O_2

Organic matter+O2→Aerobic BacteriaCO2+H2O+Energy/Biomass\text{Organic matter} + O_2 \xrightarrow{\text{Aerobic Bacteria}} CO_2 + H_2O + \text{Energy/Biomass}

Sludge→Anaerobic BacteriaBiogas(CH4+CO2)+Manure\text{Sludge} \xrightarrow{\text{Anaerobic Bacteria}} \text{Biogas} (CH_4 + CO_2) + \text{Manure}

💡Examples

Problem 1:

During the wastewater treatment process, why is air pumped into the clarified water?

Solution:

Air is pumped into the clarified water to provide oxygen (O2O_2) for aerobic bacteria to grow.

Explanation:

Aerobic bacteria consume the remaining human waste, food waste, soaps, and other unwanted matter in the water. This is a biological step in the WWTP to ensure the water is safe before being discharged into water bodies.

Problem 2:

How do forests prevent soil erosion and floods?

Solution:

The roots of trees bind the soil particles together, preventing them from being washed away by rain or wind. The canopy acts as a natural buffer that reduces the speed of falling rain droplets.

Explanation:

By slowing down the speed of rainwater hitting the ground, forests allow water to seep into the soil (H2OH_2O infiltration), preventing surface run-off and consequent flooding.

Problem 3:

Identify the chemical used to disinfect water in the final stages of treatment.

Solution:

Chlorine (Cl2Cl_2) or Ozone (O3O_3).

Explanation:

Disinfectants are added to kill harmful pathogens and microbes before the treated water is distributed to the supply system or released into the environment.