You have a secondary treatment system that consists of aerobic treatment tank and secondary settling tank. Aerobic treatment tank is assumed to be an ideal continuous stirred-tank reactor. A portion of activated sludge from the secondary settling tank is returned to the aerobic treatment tank. Use this information below to solve Questions 43 through 53. 

What is the net (or active) biomass yield as (g VSS)/(g bsCOD)?

What is the primary difference between removal and disinfection processes in reducing risk of pathogen infection?

Determine cell yield in g VSS/g COD. Present your answer to three decimal places.

How does increasing the concentration of a disinfectant affect the CT value?

During the past summer, when the water temperature was 20°C, I used chlorine dioxide to inactivate viruses, achieving a 2-log10 reduction in 10 minutes. How many minutes would it take to achieve the same 2-log10 reduction of viruses in the winter, when the water temperature is 5°C, using the same concentration of chlorine dioxide? Use the CT table below.

What is NOT the primary characteristic of the lag phase in the bacterial growth curve?

Why is HOCl (hypochlorous acid) generally considered more effective than OCl⁻ (hypochlorite ion) for disinfection? (Choose the two most likely answers.)

Based on the breakpoint chlorination, determine sodium hypochlorite (purity is 7%) dosage rate (kg/day) to apply free chlorine residual of 1.0 mg/L to disinfection of 150,000 m3/day of drinking water.

What was your most significant takeaway from Chapter 3? Why is that?