1. Draft a designfor an activated sludge process operating as a CSTR based on the following Monod kinetic parameters:
µmax = 13/day
Ks = 5 mg BOD /liter
Yield = 0.5 mg VSS / mg BOD
kd = 0.2 /day
safety factor = 10
and the following additional assumptions:
average flowrate = 1 MGD of wastewater and S0 = 300 mg/L BOD
MLSS = 4000 mg/liter, and assuming VSS is 75% of the total suspended solids.
The sludge solids will have a degradability represented by 0.5 mg BOD5 / mg SS.
Discharge from the clarifier of this process may not exceed 30 mg/l BOD nor more than 30 mg/liter total suspended solids.
The design items must include SRT, HRT, tank volume, solids production (mass/day and mass/volume of wastewater treated), and required oxygen (mass/day and mass / volume of wastewater treated). All work must be shown, must be legible, and must be logically presented. (Subheadings for each task would be beneficial.) Also provide a summary table of the final results.
2. Municipal waste flowrates typically vary on a daily cycle. For this wastewater, peakflowrate is twice the average flowrate. Using the tank "built" in part 1 above, re-assess what the effluent discharge BOD concentration will be during times of peak flow.
Do not redesign the tank. Recalculate an effluent discharge concentration for the tank you already recommended above.
What other items of your summary table would be impacted, and what would their new values be? Calculate them where possible, discuss qualitative changes if you cannot calculate them.
3. Variations: The influent flow rate or organic loadcould drastically change due to Daily or seasonal flowrate cycles, a sudden change in a local industry process (like emptying a manufacturing tank), or storm events. What parameters in part 1 (above) can be adjusted while the treatment is in process, to improve (decrease) the effluent concentration?