Problem 3A 2,000 m3 water tower has been taken out of operation to install a chlorine monitor. When the watertower was put out of operation, its chlorine concentration was 2.0 mg/L. After ten hours, the chlorinecontent was determined to be 1.2 mg/L. Considering that the tank is a completely mixed batch reactor andthat there is a first order decay.a) Calculate the reaction decay rate in day-1.b) What mass of chlorine (in kg) must be added to the tank to raise the chlorine level back to itsoriginal concentration?

An ideal continuous stirred tank reactor (CSTR) has an influent containing Chemical X at a concentration of 150 mg/l and a flow rate of 100 gpm (380 liters/min). Chemical X undergoes a first-order decay reaction having k = 0.40 hr –1 . Determine: 1a. The required detention time and volume of the CSTR if the effluent concentration contains 20 mg/l of Chemical X. Express the volume in both gallons and liters. 1b. Use a spreadsheet to perform the necessary calculations and then use the spreadsheet's graphing tools to plot two graphs; i. Pollutant removal efficiency, 1e, on the vertical or y-axis versus hydraulic detention time on the horizontal or x-axis. ii. Effluent concentration, CX1 , on the vertical or y-axis versus hydraulic detention time on horizontal or x-axis. Analyze and comment on the significance of the graphs. 1c. How many times larger must a CSTR be than a PFR to achieve 80 percent pollutant removal or conversion? 1d. How many times larger must a CSTR be than a PFR to…

(a) Prove that for a first order decay reaction (k1= 2 days-1) taking place in reactors of identical size at steady state, it does not matter if you use a CMFR followed by a PFR or a PFR followed by a CMFR (i.e. show that the final treated effluent concentration, in mg/L, is approx. the same in each scenario). Assume the volume of each reactor is 15 L and the reactors in series will be used to treat a wastewater containing 5 mg/L of contaminant “C” at a flowrate of 10 L/day. (b) Does this remain true if a second order decay reaction was taking place? If not, which sequence of reactors is more efficient (i.e. removes more of the contaminant)? Assume the same reactor volumes, flow rate and contaminant concentration as in part (a), and k2 = 2 Lmg-1day-1 . You must show your derivation of the expression for a PFR with 2nd order decay.

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

A CMFR is working at a steady state. The volume of the reactor and flow rate are 10m3 and 2.5m3/h respectively. The influent pollutant concentration is 10mg/L. Calculate the pollutant concentration in the reactor when the pollutant is going first order decay with reaction rate constant k=0.3/h

Subject environmental engineering

A waste stream flows at 2,000 liters/day with a concentration of 60 mg/l of hazardous chemicalA. The chemical undergoes a first-order decay reaction with k = 0.01/sec. Complete performanceanalyses of the three common ideal chemical reactors to determine the effluent concentration ofchemical A for the following conditions:1. CSTR, V = 500 liters2. PFR, V = 14 liters3. Batch Reactor, V = 500 liters (i.e., 4 batches of waste processed per day to handle thetotal daily volume of 2,000 liters) with a reaction time τ = 10 min.Compare and contrast the performance of each reactor type.

It is found in a water sample that it has insufficient alkalinity and therefore soda ash (Na,CO3) is added in water. Calculate the amount of CO2 produced per day in kg if 10 MLD of water needs 333 mg/1 dose of alum. (Assume no reaction takes place before soda-ash addition).

A 90-m³ basement in a residence is found to be contaminated with radon coming from the ground through the floor drains. The concentration of radon in the room is 1.5 Bq L- (becquerels per liter) under steady-state conditions. The room behaves as a CMFR, and the decay of radon is a first-order reaction with a decay rate con- stant of 2.09 x 10-s. If the source of radon is closed off and the room is vented with radon-free air at a rate of 0.14 m. s, how long will it take to lower the radon concentration to an acceptable level of 0.15 BqL-¹?

A medium containing 50 g/L of S (substrate) is continuously fed into a completely mixed reaction vessel at a certain liquid flow rate. The working volume of the reactor is maintained at a constant liquid volume of 10 L by overflowing. The following table shows the steady state concentrations of X (biomass or cell), S, and P (product).   X (g cells/L)    S (g/L)    P (g/L) 2.0                  30.0       18.0 3.0                  20.0        27.0 4.0                  10.0        36.0 4.5                   5.0         40.5 4.8                   2.0         43.2   If cell growth follows the Monod equation, no cell death occurs at steady state, and the product formation is growth-associated, determine (1) μmax, (2) Ks, (3) Yx/s, and (4) Yp/s.