List of top Water & Wastewater Treatment and Management Questions

A person consumes 2.5 liters of water per day. The water quality test indicated that the supplied water has a Pb concentration of 0.6 mg/L. If the weight of the person is 75 kg, the exposure level for Pb for this person from this drinking water source is _________mg/kg/day (rounded off to 2 decimal places).

One million liters per day (MLD) of wastewater with a soluble BOD of 200 mg/L is treated in an activated sludge process. The BOD of treated wastewater is 20 mg/L. The observed yield coefficient of the biological system is 0.35.
The daily biomass generation in the system is _____________kg (an integer value).

An industry discharges 2 million liters per day (MLD) of wastewater with a temperature of 45°C and a pH of 2, whereas the neighboring industry produces 3 MLD of wastewater with a temperature of 30°C and pH of 8. If both the wastewaters are mixed and carried through a pipeline, then the resultant pH of mixed wastewater is ___________ (rounded off to 2 decimal places).
Neglect buffering capacity of the system and the temperature effect on pH.

A Class-A pan was setup adjacent to a lake for measuring evaporation losses in the lake. The depth of water in the pan at the beginning of a certain week was 250 mm. In that week, there was a rainfall event with 10 mm depth. Water depth in the pan at the end of the week was 240 mm. The pan coefficient is 0.8.
The estimated lake evaporation during the week was |_________mm (an integer value).

With respect to particle settling in wastewater treatment systems; the correct statement(s) is/are

The processes of removal of particles in a rapid sand filter with their description is given in the table.

Process	Description
(i) Straining	P: Removes only particles in the water large enough to get caught in the pores of the filter
(ii) Sedimentation	Q: Larger and heavier particles do not follow the fluid streamline around the sand grain and settle on the grain
(iii) Interception	R: Particles that do follow the streamline, but are too large and are caught because they brush up against the sand grains
(iv) Diffusion	S: Very small particles are experiencing Brownian motion and may collide with the sand grains by chance

Select the correct match.

Crown corrosion of reinforced cement concrete sewer is caused by ______