The total volume of a primary settling tank is 2500 m3 and the waste water flow is 25 x 106 litres per day. The detention time in settling tank is
Detention time, t = V/Q
Acceptable lower limit of bacteria removal through activated sludge process is
Bacteria and organisms are removed by mechanical means during waste water treatment.
Match List-I (Treatment process) with List-ll (Classification) and select the correct answer using the codes given below the lists:
If the efficiencies of BOD removal of first-stage and second-stage trickling filters are each 65,0%, then what is the overall BOD removal efficiency of these filters?
Overall BOD removal efficiency
= 65 + (100 - 65) x (65/100)
= 65 + 22.75 = 87.75%
A septic tank of 7 m3 in volume serves for 5 people. If the rate of accumulation of sludge is 70 litres per capita per year and sludge is removed when it occupies 50% of its volume, what is the cleaning interval of septic tank?
The volume of sludge at the time of cleaning
= 0.5x7 = 3.5 m3
= 3500 litres
Rate of accumulation of sludge
= 5 x 70 = 350 litre/year
Cleaning interval = 3500/350 = 10 years
Where does sloughing occur?
With continuous growth of microbes on the surface of filte ring media, the inner layer organisms die due to deficiency of food and loose contact with the surface of media. The shearing stress of flowing sewage remove these layers of organisms. This is called sloughing in trickling filters.
The maximum efficiency of BOD removal is achieved in which of the following?
What does the biological layer sticking to the trickling filter consist of?
What is the most generally adopted detention period (approximately) for a septic tank under the Indian conditions?
Which one of the following describes the short- circuiting occurring in a sedimentation tank?