Environmental Engineering
The main disadvantage of oxidation pond is that

BOD removal is very low
None of these
Maintenance and operation cost are high
Large area is required for construction

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Environmental Engineering
Scour valves are provided

At every summit of rising mains
At street corners to control the flow of water
At every depression and dead ends to drain out the waste water that may collect there
At the foot of rising main along the slope to prevent back running of water

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Environmental Engineering
The major disadvantage of lime soda process of water softening is that

It is unsuitable for turbid and acidic water
It is unsuitable for softening the water of excessive hardness
Huge amount of precipitate is formed which creates a disposal problem
The effluent cannot be reduced to zero hardness

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