Important Questions Test: Waste Water Story - Class 7 MCQ

because using pesticides on plants is no way useful to reduce water pollution and use of unleaded petrol in cars is related to air pollution. 

So, statement (1) and (4) is correct.

It was declared in 22 March, 2005.

Eucalyptus is an efficient biomass producer, it can produce more biomass than many other tree species. Growing Eucalyptus in low rainfall areas may cause adverse environmental impacts due to competition for water with other species.

The impurities present in sewage water may consists of organic or inorganic substances .

Waste that originates from kitchen is known as sludge.

A skimming tank is a chamber so arranged that the floating matter like oil, fat, grease etc., rise and remain on the surface of the waste water.

Sludge is a semi-solid byproduct that is produced during wastewater treatment processes. It is composed of both organic and inorganic materials that settle out during sedimentation, often containing a mixture of water, microorganisms, and solid waste materials.

Treatment of Sludge:

The most common method for treating sludge is anaerobic digestion. Here’s how the process works:

1. Anaerobic Digestion:
   • In this process, sludge is placed in a sealed container known as an anaerobic digester, where bacteria break down the organic material in the absence of oxygen.
   • The digestion process produces biogas (methane and carbon dioxide) as a byproduct, which can be captured and used for energy generation.
   • Anaerobic digestion reduces the volume of sludge, stabilizes it, and reduces odors. The end product is a digested sludge, which can sometimes be further treated for use as fertilizer.

This method is preferred because it reduces the volume of waste, produces useful byproducts like biogas, and minimizes environmental impacts.

Other Methods of Treatment:

• Dewatering: Sludge is often dewatered to reduce its water content, making it easier to handle and transport.
• Incineration: Sometimes, dried sludge is burned to reduce its volume, though this can be energy-intensive and release pollutants if not controlled properly.
• Composting: In some cases, treated sludge can be composted to be used as a soil conditioner.

The function of sedimentation in wastewater treatment is primarily

Settling Suspended Particles: Sedimentation allows suspended particles, such as silt, sand, and organic matter, to settle at the bottom of a tank due to gravity and then decant can be taken out which will be free of these impurities.