Reference no: EM132232247

Question 1: Implementing enhanced biological phosphorus removal. A small community, population 2,000, has a new discharge permit which includes a 1.0 mg/I phosphorus limit. The plant currently includes primary sedimentation and an aerobic nitrifying activated sludge system. The following are plant parameters.

a) Activated Sludge HRT = 8 hours
b) Operating SRT = 10 days
c) Influent BODs = 180 mg/I

The plant is considering modifying the biological process to a UCT configuration to achieve enhanced biological phosphorus removal and meet the phosphorus limit. A test was performed using sludge from another biological phosphorus removal plant containing polyphosphate accumulating organisms (PA0s). The sludge from the other plant was anaerobically mixed with this plant's primary effluent for a 2-hour period. No significant phosphorus release was observed. What does this indicate about the potential for biological phosphorus removal? What might be the problem, what is a potential solution, and what might be design criteria for additional work to include in the plant modification?

Question 2: Nitrification and denitrification. An activated sludge WWTP with a flow of 10 MGD is planning for a new ammonia limit of 1 mg/I for the period May-October each year. The TKN-N (Total Kjeldahl Nitrogen) of the influent wastewater averages 60 mg NA and the alkalinity of the municipal water supply is 60 mg/I as CaCO₃. Approximately 30% of the influent TKN-N is removed in primary treatment, but a flow of 0.02 MGD at 600 mg/I NH₄-N is recycled.

If 85% of the ammonia nitrogen removed in the activated sludge process is converted to NO₃; what might be a 50% NaOH dose required to maintain adequate alkalinity? What NaOH dose would be required if the process were modified with to an MLE configuration such that 70% of the NO₃- produced were denitrified?

Qualitatively, what impact will the type of aeration system have on a chemical dosage? What is the advantage of a plug flow system versus complete mix for a nitrifying system?

Question 3: The oxygen demand in an activated sludge process. For the Madison configuration above, the following average data was obtained for the aeration system with off-gas testing over a 1-day period:

Point	alohaF	air flow (scfml)	D.O. conc (mg/l)
1-1,2	0.34	1300	0.2
2-1,2	0.46	850	0.9
2-3,4	0.54	580	1.2
2-5,6	0.60	410	2.2
3-1,2	0.68	310	2.4
3-3,4	0.72	230	2.8
3-5,6	0.72	245	4.5

Assume the testing is at elev 750 ft, the mixed liquor temperature is 20 deg C, the beta coefficient for salinity is 0.98, and the saturation 0.0. concentration is 10.6 mg/I for the 16 ft deep tanks.

What is the estimated actual oxygen uptake rate (AOTR) for each point in the process if the clean water, standard oxygen transfer efficiency (CWE) of the diffusers is 32%

If coarse bubble diffusers were being used, and the CWE was 8%, but alphaf would improve to 0.8 throughout the length of the tank what would be the ratio of the total air requirement for the fine bubble configuration versus the coarse bubble configuration?