Question

Situation (note: Problem 2 is not linked with Problem 1): Assuming the design flow rate of raw wastewater to be treated is 20 MGD in the design year, the dissolved BODs is 380 mg/L, and SS is 360 mg/L. The wastewater generated by the sludge treatment process is about 4 MGD with the dissolved BODs being 1800 mg/L, and SS being 1200 mg/L, and will be returned to the wet well in the pumping station at the beginning of the wastewater treatment train, and will be mixed with the raw wastewater Requirements: You need to (1) identify the treatment train of the wastewater treatment plant, including the sludge treatment process; (2) identify the wastewater quality and quantity after the mixing in the wet well and after primary sedimentation tank (but before being mixed with the return sludge in this problem or the recirculation flow in Problem 3 below); (3) design a completely-mixed activated-sludge process and the secondary settling tank(s) to treat the wastewater using the following conditions: the effluent is to have 20 mg/L of BODs or less. Assume that the temperature is 20°C and that the following conditions are applicable: 1. Influent volatile suspended solids to reactor are negligible 2. Return sludge concentration 12,000 mg/l1 of suspended solids 9,600 mg/l volatile suspended solids. MLVSS 3,500 mg/1-0.8 x total MLSS. 3 4. Mean cell-residence time, c-8 day 5. Kinetic coefficients, Y 0.65 lb cells/b BODs utilized, Ka 0.06 d 6. Effluent contains 18 mg/l of biological solids, of which 85% is volatile and 65% is biodegradable 7. BODs 0.68 x BOD 8. Wastewater does not contain nitrogen and phosphorus. The concentrations of nitrogen and phosphorus in the effluent are 1.0 and 0.5 mg/l, respectively Accomplish your design of the activated sludge process based on the following steps (this will make my grading of your design easier). You can make any assumptions if necessary 2. 3. 4 5. 6 7 Estimate the concentration of soluble BODs in the effluent Determine the treatment efficiency E (both Es and Eovea) Compute the reactor volume Compute the quantity of sludge that must be wasted each day Compute the sludge-wasting rate if wasting is accomplished from the recycle line Estimate the recycle ratio. Compute the HRT, 0 for the reactor Compute the required quantities of nitrogen and phosphorus if the nitrogen requirement is 0.12P, and the phosphorus requirement is one-fifth of the nitrogen requirement Check the specific substrate utilization rate (U), the food-to-microorganism ratio (F/M), and the volumetric loading rate. Compare your result with the design code. 9 10. Compute the oxygen requirements based on BOD and calculate the volume of a 11. Design the secondary clarifies Note: you don't need to include the design of the pumping station, bar rack design, grit removal required, assuming that the oxygen-transfer efficiency for the aeration equipment to be used is 7% and safety factor of 2, Check the air volume chamber, and disinfection tank because the other engineers in the team will do these designs

Answer 1

solutions for questions 1,3,6,9 are solved