Environmental Engg. Notes for GATE, PSUs preparations - part 4

Hello There,

How have you been? Here is the 4th part of your preparatory content, useful for GATE and PSUs.

• Slow sand filters are more efficient in removal of bacteria than rapid sand filters because, sand used in slow sand filters is finer than in rapid sand filters.
• Air binding phenomenon in rapid sand filters occur due to excessive negative head.
• The percentage of filtered water, which is used for back-washing in rapid sand filters, is about 2 to 4.
• Period of cleaning of slow sand filters is about 2-3 months.
• The rate of filtration of pressure filters is greater than that of rapid sand filters.
• Double filtration is used to increase the filtration capacity of slow sand filters.
• Cleaning is done by scraping and removal in slow sand filters and back washing in rapid sand filters.
• Disinfection of water results in killing of disease bacteria.
• The Disinfection efficiency of chlorine increases by increasing the temperature of water.
• Chlorine demand of water is equal to difference of applied chlorine and residual chlorine.
• The process in which chlorination is done beyond the break point is known as super chlorination and is done as a precautionary measures in cases such as epidemics in a city.
• The percentage of chlorine in fresh bleaching powder is about 30 to 35 percent.
• The treatment of water with bleaching powder is known as hypochlorination.
• The suitable method for disinfection of swimming pool water is ultra violet rays treatment.
• Sulphur dioxide can be used for dechlorination of water.
• In chlorination, with the rise in temperature of water, death rate of bacteria increases.
• As compared to higher pH values, the contact period required for efficient chlorination at lower pH values is smaller.
• Disinfection efficiency is reduced at higher pH value of water.
• In lime-soda process, lime reduces the carbonate hardness and soda reduces the non-carbonate hardness.
• The major disadvantage of using lime-soda softening is that huge amount of precipitate is formed which creates a disposal problem.
• Copper Sulphate is a largely used compound for algae control.
• Activated carbon is used for removing odours.
• As compared to cast iron pipes, steel pipes are stronger.
• The suitable layout of a distribution system for irregularly growing town is dead end system.
• The layout of distribution system in which water flows towards the outer periphery is radial system.

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