Based on the results of a step input tracer test, the flow pattern in a disinfection...

 

Transcribed Image Text:

Based on the results of a step input tracer test, the flow pattern in a disinfection reactor can be repre- sented as a CFSTR with a 15-min hydraulic detention time and a plug flow reactor with a 5-min detention time, in series. Hypochlorous acid (HOCI) is being added at the reactor inlet, at a dose of 8 mg Cl/L. When the influent is chlorinated in a separate, batch test, 1.5 mg/L Cl is consumed before the first data point is analyzed, which is at 1=30s. For the next 30 min, the Cl2 concentration in solution decays approximately according to the rate expression rc = -0.02 -0.15c where rc, is in mg Cl/L-min and cc, is in mg Cl/L. (a) Sketch the effluent tracer curve that you think led to the inferred reactor arrangement. (b) Suggest a reason for the nearly complete consumption of added Cl at low doses in the batch test. (c) What is the value of 710 that would be used to compute the CT product for this system? (d) What is the value C that would be used to compute the CT product for this system? (e) The plant owners are considering installing a baffle that would convert the CFSTR portion of the system into two equal-sized CFSTRS in series. Would such a change increase, decrease, or have no effect on the values of C and T that would be used to compute the CT product? Explain your reasoning in a few sentences. Based on the results of a step input tracer test, the flow pattern in a disinfection reactor can be repre- sented as a CFSTR with a 15-min hydraulic detention time and a plug flow reactor with a 5-min detention time, in series. Hypochlorous acid (HOCI) is being added at the reactor inlet, at a dose of 8 mg Cl/L. When the influent is chlorinated in a separate, batch test, 1.5 mg/L Cl is consumed before the first data point is analyzed, which is at 1=30s. For the next 30 min, the Cl2 concentration in solution decays approximately according to the rate expression rc = -0.02 -0.15c where rc, is in mg Cl/L-min and cc, is in mg Cl/L. (a) Sketch the effluent tracer curve that you think led to the inferred reactor arrangement. (b) Suggest a reason for the nearly complete consumption of added Cl at low doses in the batch test. (c) What is the value of 710 that would be used to compute the CT product for this system? (d) What is the value C that would be used to compute the CT product for this system? (e) The plant owners are considering installing a baffle that would convert the CFSTR portion of the system into two equal-sized CFSTRS in series. Would such a change increase, decrease, or have no effect on the values of C and T that would be used to compute the CT product? Explain your reasoning in a few sentences.