How many stages are there in sludge digestion process?
Explanation: The sludge digestion process consists of acid fermentation, acid regression and alkaline fermentation.
The form of sludge which is free from pathogenic bacteria is
Explanation: The digested sludge is free from pathogenic bacteria. It has the behavior of rich humus soil.
The BOD of supernatant liquor in a sludge digestion process is ____ ppm.
Explanation: The range of BOD of supernatant liquor in a sludge digestion process is between 2000 and 3000 ppm. It is a form of sludge that is obtained in the sludge digestion process.
Which of the following is correct regarding pH in different stages of the sludge digestion process?
Explanation: The pH value in Alkaline fermentation stage is 7.5 whereas in Acid regression and Acid fermentation stage, the pH>7, having the least in acid fermentation stage.
Which of the following is incorrect about aerobic digestion in the sludge digestion process?
Explanation: The residual energy in aerobic digestion is very less in comparison to anaerobic digestion.
The color of digestive sludge is
Explanation: The color of digestive sludge is black. It has an inoffensive odor.
Which of the following is correct regarding anaerobic digestion in the sludge digestion process?
Explanation: Anaerobic digestion is a low energy process which contains low amount of biomass and where both facultative and anaerobic bacteria solubilize the organic matter.
The maximum temperature at which thermophilic microorganisms remain active in sludge digester is
Explanation: The maximum and minimum temperature at which thermophilic microorganisms remain active in sludge digester are 60oC and 40oC respectively.
Which of the following is obtained in the secondary tank in two stage sludge digester?
Explanation: In two stage sludge digester, the partially digested sludge is obtained in primary tank, whereas digested sludge is obtained in the secondary tank along with supernatant liquor.
The high rate sludge digestion tanks are used when the capacity of the tank is ____ million liters per day.
Explanation: High rate digesters are used when the capacity of tank is 4 million litres per day. Complete mixing and uniform feeding of raw sludge takes place in high rate digesters.
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