Environmental Engineering: Water Treatment Please consider each of the following points: a. Determine the required residence time for each reactor of 3 equal volume CSTRs in series given a zero-order reaction with a reaction rate constant, k = -5 mg/L hr. The influent concentration is 125 mg/L and 95% conversion is required across the three-reactor system. What is the total reactor system residence time? b. Determine the required residence time for a single CSTR given the same conditions.  c. Determine the required residence time for a PFR given the same conditions. d. Why are all three residence time the same?

Underneath a conventional plug flow reactor and a plug flow reactor with tapered aeration that both use sludge recycle, sketch graphs of DO, DO Uptake, S, and Xa, versus distance from the inlet of the reactor

Four standard concrete cylinders of 6-inchdiameter cross section were tested underuniformly increasing axial compressive loads 28days after casting concrete. The maximummeasured loads were 121,000 lbs, 116,700 lbs,128,800 lbs, and 119,100 lbs. What is the averagecompressive strength of this concrete in ksi?

The treated waste water is being discharged into a river that has a temperature of 15°C. The BOD rate constant determined in the laboratory for this mixed water is 0.12 per day (base e) at 20°C (Temperature coefficient, 1.047). What fraction of maximum oxygen consumption will occur in first four days?

3. A first order decay reaction is occurring in a single CFSTR. Dividing the reactor into two smaller CFSTRs that are operated in series (effluent from one serving as the influent to the other) reduces the overall mixing and therefore makes the flow more PFR-like. Because reaction efficiency is greater in a PFR than a CFSTR, we might expect that dividing the reactor would improve the efficiency. To test that hypothesis, consider a system receiving an influent with C = 100 mg/L of a reactant that undergoes a first order decay reaction with a rate constant of 0.1 min ¹. Assume that the system has a total hydraulic detention time of 1 hour, but that it can be operated in three different ways: as a PFR, a CFSTR, or as two CFSTRs in series with the detention time split equally between the two. Find the effluent concentrations for the three possible operating modes

Environment aerobic.