Question1. A water treatment plant uses a dual media filter. The two media employed are:
i) Anthracite coal with effective diameter of 1.1 mm, porosity of 0.6, and shape factor of 0.5.
ii) Sand with effective diameter of 0.5 mm, porosity of 0.45, and shape factor of 0.7.
The complete filter depth is 0.8 m with 0.5 and 0.3 meters of anthracite coal and sand correspondingly. Compute the total head loss in the clean filter if the loading rate is 200 m3/m2.day and operational temperature is100C.
Question2. A conventional surface water plant with flocculation, coagulation, sedimentation, and filtration produces filtered water with turbidity less than 0.3 NTU, pH 7 and temperature 10oC on a day when the peak hourly flow is 3.0 MGD. After filtration, the water is chlorinated in a baffled reservoir. For the peak hourly flow rate, t10 is 90 minutes. What is the needed disinfection for the removal of Guardia cysts of the filtered water if free chlorine is employed? The raw water microorganism concentration is <1/100 L.
Note: According to regulations, the free residual chlorine in water entering the distribution system can’t be less than 0.2 mg/L for more than 4 hours and a residual in distribution system should be detectable in at least 95% of the samples tested each month.
Question3. The transmission main from the well field to the community is 2500 ft, the velocity of flow at peak pumping capacity is 3.5 fps, water temperature is 10oC, and pH is 7.5. If free chlorine residual is applied at the well field and is 0.5 mg/L entering the distribution system, what is the log inactivation of viruses?
Question4. As part of their proposed latest research treatment plant, City of St. James is planning to employ five banks of rapid sand filter after their sedimentation tanks. Each bank of sand filters has six filters operated in parallel. Each filter bed has a surface area of 3m X 2m. The design flow rate is 0.044 m3/second. If the design loading rate to filter is 150 m3 /day. m2, compute the following:
i) What total filter surface area should be provided and how many banks of filters need to be operational?
ii) What is the loading rate when one filter is out of service?
Note: Experiments conducted with rapid sand filters at nearby water treatment plants have demonstrated that satisfactory water quality can be received with rates as high as 235 m3 /day. m2.
Question5. A groundwater contains the following constituents to be treated by the lime-soda process to the minimum hardness probable has the subsequent features:
CO2 = 62.0 mg/L HCO3- = 250.0 mg/L as CaCO3
Ca2+ = 80.00 mg/L Cl- = 35 mg/L
Mg2+ = 36.6 mg/L SO42- = 96.0 mg/L
Na+ = 23.0 mg/L
The facility is to treat 50 x 106 L/day of water from this source using lime-soda ash to reduce the hardness.
i) Find out the total hardness, carbonate hardness, and non-carbonate hardness in mg/L as CaCO3.
ii) Find out the lime and soda-ash dosages for softening (units of kg/day). Assume that the lime is 90 percent CaO by weight and the soda ash is pure sodium carbonate.
Question6. A water treatment plant is processing 19,000 m3/day of water. A settling basin for Type- 2 suspension will remove 100 percent of all particles which has a settling velocity of 0.75 m/hour. The basin has an average depth of 3.5 meters and the weir overflow rate is 8m3/m.hour.
Find out:
i) Dimensions of each basin
ii) Detention time
iii) Weir length for each basin.
Suppose there are 3 basins with a rectangular unit in that the length is 3 times the width.
Question7. Why is there a concern for dissolved organics and color in water supply and in water treatment plant?