Explain Biochemical Transformation Occur In

1. Prepare a table comparing the bioreactor configuration, SRT, HRT, recycle ratio, MLR ratio, and design approach for the following: MLE, four-

stage Bardenpho, five-stage Bardenpho, A/O™ AVO™, VIP, and UCT processes.

2. Describe the biochemical transformations occurring in a BNR process that achieves both nitrogen and phosphorus removal. Where do these transformations occur, and how do they interact to allow nutrient removal to occur?

3. Describe the benefits that biological nutrient removal can provide to the operation of an activated sludge system and list the circumstances under which nutrient removal capabilities would be incorporated into an activated sludge system design even though the effluent quality criteria did not require it.

4. Describe the mechanisms that allow denitrification to occur in a supposedly aerobic bioreactor. How can denitrification be increased? What are the impacts of this denitrification on the operational and performance characteristics of the system?

5. Prepare a process schematic of the Phostrip® process. Describe the phosphorus removal mechanisms that operate in this process, indicate how they operate, and how they differ from the mechanisms in other BPR processes. How would nitrification affect the phosphorus removal capability of this process? Why? How would the nature of the elutriant stream influence it? Why?

6. Make a list of all the process design and operational factors that maximize phosphorus removal in a BNR system. Make a similar list of factors that maximize nitrogen removal. Compare the two lists and identify those factors that are similar for the two systems and those that are different. Discuss the impacts of these similarities and differences on the design of a system that removes both nitrogen and phosphorus.

7. Make a list of factors that can affect the characteristics of a wastewater as it enters the first bioreactor in a BNR system and the resulting impact of those characteristics on the performance of a BNR system. Identify which factors are under the control of the process designer and which are under the control of the process operator. What does this analysis indicate about the design and operation of a BNR system?

8. Describe the concept of the organic matter to phosphorus removal ratio. How can this ratio be used as a screening tool to identify the BPR processes to be considered for a particular application?

9. List the factors that affect the size of the initial anoxic zone required for a particular nitrogen removal application. Under what circumstances would a relatively small zone be used? When would a relatively large zone be used?

10. List the factors that affect the size of the anaerobic zone required for a particular BPR application. Under what circumstances would a relatively small zone be used? When would a relatively large zone be used?

11. Derive the equation used to calculate the fraction of nitrate-N recirculated from the aerobic zone of a biological nitrogen removal system to an upstream anoxic zone. Do this for both the MLE and the four-stage Bardenpho systems and explain why the expressions are different.

12. Using the wastewater characteristics in Table E8.4, the stoichiometric and kinetic parameters in Table E8.5, and the temperature correction factors in Table E10.1, design a CAS system with an MLSS concentration of 2750 mg/L as TSS to produce a fully nitrified effluent year round while treating an average wastewater flow rate of 30,000 m'/day. The lowest sustained winter temperature is 13°C and the highest sustained summer temperature is 24°C. Use a diffused air-oxygen transfer system and assume that the in-process oxygen transfer efficiency is 12%. Also assume that the hydraulic characteristics of the CAS bioreactor are equivalent to three tanks-in-series and that the safety factor for uncertainty is 1.0. The diurnal peak loading on the system is twice the average loading. Use this information in selecting the aerobic SRT for the system, but for simplicity, base all decisions about tank volumes and oxygen transfer rates on average loading conditions. Justify all assumptions and decisions.

13. Add an anoxic selector capable of removing all readily biodegradable substrate to the CAS system designed in Study Question 12. Determine its volume and the MLR rate. Justify all assumptions and decisions. Compare the following for the systems with and without the selector: total system volume, aerobic bioreactor volume, oxygen transfer rate and air flow rate to the aerobic zone, and alkalinity that must be added to maintain a residual concentration of 50 mg/L as CaCO,.

14. Use a computer code implementing ASM No. 1 or a similar model to evaluate the effluent nitrate-N concentration and the oxygen requirement in the system designed in Study Question 13. Comment on any differences between the results from Study Question 13 and the simulation results, suggesting possible reasons for differences.

15. For the situation described in Study Question 12, design an MLE system to produce an effluent containing no more than 10 mg/L as N of nitrateN, determining the volume of the anoxic zone and the MLR rate. Justify all assumptions and decisions. Compare the following to the system designed in Study Question 13: total system volume, aerobic bioreactor volume, oxygen transfer rate and air flow rate to the aerobic zone, and alkalinity that must be added to maintain a residual concentration of 50 mg/L as CaCO,.

16. Use a computer code implementing ASM No. 1 or a similar model to evaluate the effluent nitrate-N concentration and the oxygen requirement in the system designed in Study Question 15. Comment on any differences between the results from Study Question 15 and the simulation results, suggesting possible reasons for differences.

17. Add a second anoxic zone to the process considered in Study Question 15, to lower the effluent nitrate-N concentration to 3 mg/L as N. Determine the size of the second anoxic and aerobic zones, and calculate the MLR required. Justify all assumptions and decisions. Compare the following to the system designed in Study Question 15: total system volume; aerobic bioreactor volume; oxygen transfer rate and air flow rate to the aerobic zone; and alkalinity that must be added to maintain a residual concentration of 50 mg/L as CaCO,.

18. Use a computer code implementing ASM No. 1 or a similar model to evaluate the effluent nitrate-N concentration and the oxygen requirement in the system designed in Study Question 17. Comment on any differences between the results from Study Question 17 and the simulation results, suggesting possible reasons for differences.

19. Redo Study Question 17, but in this case, size the first anoxic zone to remove the amount of nitrate-N that can be returned with a MLR rate of four times the influent flow rate. Compare this system to the one designed in Study Question 17 and comment on the differences.

20. Evaluate the possibility of operating the oxygen transfer system in the CAS system designed in Study Question 12 in such a way that 45% of the nitrate-N formed during summer operation is denitrified. At what oxygen transfer rate would the system have to be operated to achieve the desired degree of denitrification? In making your assessment, assume that the reduction in oxygen input will result in an average DO concentration of 0.5 mg/L and that the anoxic growth factor, t^,,, is 0.75.

21. For the situation described in Study Question 12, prepare the design of an A/O™ process operating at a temperature of 20°C at steady-state. Assume that the MLSS concentration is 2,500 mg/L as TSS. If the total phosphorus concentration of the influent wastewater is 8 mg/L as P and the effluent suspended solids concentration is 15 mg/L as TSS, what is the estimated effluent total phosphorus concentration for this process? What is the estimated effluent nitrate-N concentration? State and justify all assumptions.

22. For the situation described in Study Question 12, prepare the design of a VIP process to produce an effluent with minimal ammonia-N and phosphorus concentrations while operating at steady-state at 20°C. Assume that the MLSS concentration is 3,500 mg/L as TSS. If the total phosphorus concentration of the influent wastewater is 12 mg/L as P and the effluent suspended solids concentration is 10 mg/L as TSS, what is the estimated effluent total phosphorus concentration for this process? What is the estimated effluent nitrate-N concentration? State and justify all assumptions.

23. Using a computer code implementing ASM No. 1 or a similar model, systematically investigate the effects of the anoxic SRT and MLR rate on the performance of the MLE process developed in Study Question 15. Also determine the impact of staging the bioreactors on overall process performance. Discuss the implications of your findings to an optimal system design.

24. Using a computer code implementing ASM No. 1 or a similar model, systematically investigate the effects of the distribution of the anoxic SRT between the first and second anoxic zones on the performance of the four-stage Bardenpho process developed in Study Question 17. Adjust the MLR rate to match the nitrate-N need in the first anoxic zone for each size investigated. Also determine the impact of staging the bioreactors on overall process performance. Discuss the implications of your findings to an optimal system design.

25. Using a computer code implementing ASM No. 2 or a similar model, systematically investigate the effects of the anaerobic and aerobic SRTs on the performance of the A/O™ process developed in Study Question 21. Also determine the impact of staging the bioreactors on overall process performance. Discuss the implications of your findings to an optimal system design.

26. Using a computer code implementing ASM No. 2 or a similar model, systematically investigate the effects of the anaerobic and anoxic SRTs on the performance of the VIP process developed in Study Question 22. Adjust the MLR rate to match the nitrate-N need in the anoxic zone for each size investigated. Also determine the impact of staging the bioreactors on overall process performance. Discuss the implications of your findings to an optimal system design.

27. Discuss the impact of solids handling recycles on the performance of a BNR system. What steps can be taken to mitigate these impacts?

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