CIVE 514 Test 2 2023 PDF

# Wastewater Treatment Plant Design ## Question 1 **For a wastewater flow rate 150 000 m^3/day, design a primary sedimentation tank (rectangular) assuming two tanks in numbers, the surface flow rate to be 48 m^3/m^2.d and detention time of 2 hours, and 3.5 m depth. Length to width ratio, 6:1** ##...

# Wastewater Treatment Plant Design ## Question 1 **For a wastewater flow rate 150 000 m^3/day, design a primary sedimentation tank (rectangular) assuming two tanks in numbers, the surface flow rate to be 48 m^3/m^2.d and detention time of 2 hours, and 3.5 m depth. Length to width ratio, 6:1** ## Question 2 **An activated sludge process is used to treat a wastewater with a flow rate of 2000 m^3/d and BOD5 concentration of 250 mg/L.** **The aeration tank is operated at an MLSS of 3000 mg/L, and HRT of 7 hours.** **The sludge is wasted at 36 m^3/d with solids concentration of 8000 mg/L.** **The effluent BOD5 concentration is 20 mg/L.** **Calculate:** * The volume of aeration tank (m^3) * Sludge Retention Time (days) * Volumetric loading rate (kg BOD5/m^3.d) * F/M ratio of the process (mg BOD5/gMLSS.d) ## Question 3 **A wastewater treatment plant uses a single stage rock-media trickling filter for secondary treatment.** **The wastewater flow rate is 2200 m^3/d with a BOD5 concentration of 300 mg/L.** **Primary clarification removes 35% of the BOD5.** **The filter is 15 m in diameter and 2.0 m in depth.** **Direct recirculation pump operates a 2.78 m^3/min to the filter.** **Wastewater temperature is 20°C.** **Calculate:** * The hydraulic loading rate (m^3/m^2.d) * Organic loading rate (kg BOD5/m^3.d) * Effluent BOD5 concentration (mg/L) * Overall plant efficiency (%) ## Question 4 **Design secondary clarifiers for a wastewater treatment plant using bio towers for treatment of a municipal wastewater.** **The wastewater flow rate is 1800 m^3/d with a BOD5 of 200 mg/L and suspended solids of 200 mg/L.** **The bio-tower uses indirect recirculation and operates at recycle ratio of 2:1. A design Side water depth of 3 m is selected with a maximum overflow rate of 1.8 m/m^2.hr and two (2) clarifiers are used.** ## Question 5 **A grit chamber is designed to remove particles of specific gravity 2.67, with average diameter of 0.25 mm.** **The settling velocity of these particles ranges between 0.018 to 0.025 m/s. A flow through velocity of 0.35 m/s will be maintained by proportional weir.** **Determine the channel dimensions for a maximum wastewater flow of 40,000 m^3/d, assume two (2) chambers and assume detention time of 3.5 minutes and peak factor of 2.5, depth to width ratio of 1.5:1**