A wastewater treatment plant uses an activated sludge process to treat 0.2 m3/s of primary effluent. The concentration of the mixed liquor is 2,000 mg/L MLVSS (Mixed liquor volatile suspended solids), while the RAS (recycled activated sludge) concentration is 10,000 mg/L MLVSS. The substrate concentration in the primary effluent is 210 mg/L BOD5. The F/M ratio is 0.5 mg BOD5/(mg MLVSS-d) and the solids retention time is 8.5 d.  What is the volume of the activated sludge tank?  2.What is the WAS (waste activated sludge) flowrate?  3.What is the flowrate of the secondary treated effluent?  4.What is the RAS (recycled activated sludge) flowrate?  5.What is the hydraulic residence time for the activated sludge tank?

Exercise 4 A treatment plant has the following process diagram. Determine the flow rate expression for each unit. The inflow is Qi. The sludge waste flowrate is Qw. The return flowrate rate is Qr. The mixed liquor return flowrate is Qm. Mixed-liquor return Secondary clarifier Effluent Influent- Anoxic Aerobic Anoxic Aerobic Return activated sludge (e) Bardenpho™ (4-stage) Sludge Exercise 5 Derive the ODE system for above process. There are two species involved in the reaction, as shown below. The process rate for each tank can be simply represented by r1, 12,...15. The gravitational sedimentation is only applied to species X in the clarifier and can be represented by a reaction rate of r5 = 3.5X5. The influent are Xi and S₁. S=X.

A Granulated Activated Carbon (GAC) adsorption laboratory column 10cm in diameter and 3m deep, is found to produce good results in COD removal when operated at a flow of 50L/h. The porosity of the GAC is 0.5 Calculate the following: The application rate in m/h. The residence time, t, in the column. The volumetric flow rate, Vb, in bed volumes per hour, for this residence time. You need to design a GAC system consisting of two columns in series for treating the same water at a rate of 0.5 ML/d. Practical considerations limit the diameter of the columns to 3m. Calculate the minimum required height of the columns.

wet sludge contains 3% solid by weight is pumped to a filter belt press at the rate of 170,000lb/day. the dewatered sludge is 18% by dry weight and the filtrate has total nitrogen concentration of 100 mg/l as nitrogen. assume the belt press has 100% solid capture and specific gravity of the sludge in all forms is 1. Calculate the amount of nitrogen (lb/day) in the filtrate returned? a) 4 b) 9 c) 14 d) 19