If Jeff Harris REALLY has a degree in Environmental Engineering...

Last edited by on Fri Feb 15, 2008 8:52 pm; edited 1 time in total

... he SHOULD be able to answer a few simple questions, based on this scenario:

The aeration tank for a completely mixed aeration process is being sized for a design wastewater flow of 4500 m3/d. The influent COD is 150 mg/L. The design effluent COD is 7 mg/L. Recommended design parameters are a sludge age of 10 days and MLVSS of 1400 mg/L. The expected Sludge Volume Index is 100 ml/g. Selection of these values takes into account the anticipated variations in wastewater flows and strengths. The kinetic constants from a bench-scale treatability study are Y = 0.60 mg VSS/mg COD and ke = 0.06 per day.

Jeff, please calculate:
a. the hydraulic residence time and volume of the aeration tank
b. the food/microorganism ratio
c. the sludge production rate
d. the sludge recycle ratio
e. the oxygen requirement.

Subject: Here's another one for Jeff for extra-credit! Fri Feb 15, 2008 8:51 pm

A small southeast Arizona community wishes to construct an activated sludge wastewater treatment plant to treat their wastewater. The plant will be maintained by a part-time operator who will check it a few times each week. The wastewater from the community has an average flow rate of 0.0088 m3/s (0.2 mgd) and an influent substrate concentration of 300 mg/L as COD. Tests on the wastewater indicate the likely concentration of settled sludge from the secondary clarifier will be 12,000 mg VSS/L. The reactor kinetic constants are μMAX = 0.4 hr-1, KS = 75 mg/L as COD, Y = 0.4 g VSS/g COD, and kd = 0.004 hr-1. The design engineer proposes a fully-mixed aeration tank (reactor) with a volume of 25 cubic meters. The design safety factor is to be 20. You have been asked to evaluate this system – the following are specific parameters you have been asked to calculate.

a. What is the hydraulic residence time of the reactor?
b.What is the minimum allowable sludge age?
c.What is the design sludge age?
d.What is the biomass concentration in the aeration tank?
e.What is the COD concentration in the aeration tank?
f.What is the substrate utilization rate (U)?
g.What is the food to microorganism ratio (F/M)?
h.What is the recycle ratio and recycle flow rate?
i.What is the sludge wasting flow rate?
j.What is the sludge production rate?

In addition to these specific parameters, the community wants you to do the following:
k. Provide an evaluation of how this plant will operate.
l.Suggest design changes (if any) to improve the design.

Number of posts : 71 Registration date : 2008-02-03

Lady Zannah is raising her hand to volunteer as a monitor. Bisbee Avenger let me know when to start my stop watch.

Number of posts : 71 Registration date : 2008-02-03

Lady Zannah wrote:: Lady Zannah is raising her hand to volunteer as a monitor. Bisbee Avenger let me know when to start my stop watch.

Let the Sludge Flow begin

Guest

Guest

Looks like old Jeffy boy isn't going to respond to your questions Eric, but I am not surprised. When you don't really have anything to contribute you're better off saying nothing.

Guest

Guest

Numerous people who used to interact with Harris chicken rider

have said that Harris chicken rider

makes it clear that people are not to cross him Hater

or they will be sorry.

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