WASTEWATER QUESTIONS -

Q1. The new waste discharge permit for an existing conventional activated sludge plant that currently does not nitrify, requires the plant to reduce its ammonia discharge. Plant staff has decided to meet the new permit requirement using nitrification. What operational changes need to be made to begin nitrifying? Estimate the impact on oxygen demand (quantify any change).

Q2. Denitrification is commonly accomplished as a separate process after carbonaceous BOD removal. An alternative is to recycle mixed liquor to an anaerobic stage at the head end of the aeration tank. What potential advantage does the alternative offer? Explain.

Q3. Describe the biological phosphorus removal process, including reactions and required process environment conditions.

Q4. What advantage does the contact stabilization process have over the conventional activated sludge process? Explain why.

Q5. Explain the purpose for recycle flow in the high-rate trickling filter process.

Q6. Identify the unit process that a membrane bioreactor (MBR) replaces. Describe how the MBR process functions.

Q7. Evidence is fairly strong that chlorine, used for wastewater disinfection, combines with organic material in wastewater to form trihalomethane and other disinfection byproducts that are suspected human carcinogens. Despite this health risk, chlorine remains the predominant disinfection method. Explain why.

Q8. Identify two unit process used to thicken waste activated sludge and describe how each process functions.

Q9. A complete-mix, activated sludge process is to be designed based on Monod kinetics.  The design influent flow and BOD₅ are 2.5 mgd and 240 mg/L respectively.  Pilot test results indicate the following activated sludge parameters: μ_max = 3 day^-1, K_S = 60 mg/L, k_e = 0.06 day^-1, Y = 0.70 mg MLVSS / mg BOD₅, and VS% = 85%.

a. Determine the required detention time, θ_i, to produce effluent BOD₅ = 8 mg/L, assuming the MLSS concentration = 3,000 mg/L.

b. Determine the reactor volume.

c. Determine the waste activated sludge produced per day (lb/day).

Textbook - Howe, K. J., Hand, D. W., Crittenden, J. C., Trussell, R. R., & Tchobanoglous, G. (2011). Principles of Water Treatment (1st ed.). Hoboken, New Jersey, USA: John Wiley & Sons.