Wastewater help text

[koay9f]

Tab 1 (the name is escaping me at the moment)

• Try to avoid operating activated sludge processes at Solids Retention Times (SRTs) above 40 days because oxygen demand will be maximized and process performance may deteriorate.

Aerator Performance

• Operate aerobic reactors at lower DO concentration if possible. Aerobic reactors in activated sludge should have DO levels between 0.5 and 2.0 mg/L in most cases. Operating at DO levels above 2 mg/L should be avoided if possible. In most cases, maintaining a DO concentration above 2 mg/L is excessive and a waste of energy.
• When reducing aerator horsepower in service, try to keep the mixing intensity at least 50 HP per million gallons of reactor volume.
• Install variable frequency drives (VFDs) on aeration equipment. This is especially useful for mechanical aerators and positive displacement (PD) blowers. It may not be practical on some types of centrifugal blowers; you should check with the blower manufacturer before installing VFDs. For mechanical aerators and PD blowers, speed typically should be 50% to 100%.
• Use timers to start and stop aerators to conserve energy. Preferably, aerators should have soft starters to protect the aerator motors.
• Use an automatic DO control system to control the amount of aeration equipment in use at any given time. Consider using luminescent or florescent DO probes. DO probes should be placed at strategic locations in the aerobic reactor to ensure good process performance. Don’t use too narrow a DO range so that aeration equipment does not cycle on and off too frequently.
• Oxygen demand at night should be about 60% of daytime oxygen demand due to diurnal organic loading in most municipal wastewater treatment applications. Thus, less aeration equipment may be able to be used at night.
• In extended aeration processes (extended aeration activated sludge and oxidation ditches) not designed for biological nutrient removal, consider turning aerators off 4 to 6 hours per day. It will promote denitrification, save energy, generate alkalinity, and may improve sludge settleability. If hydraulic detention time in the reactor is less than 12 hours, if influent TKN concentration exceeds 40 mg/L, or if effluent ammonia-N limit (monthly average) is 1 mg/L or less, on-off operation may not be feasible.
• Control centrifugal blower air flow rates by automatically adjusting (via a DO control system) blower speed (if appropriate) and/or adjusting blower inlet guide vanes.
• Match oxygen supply to oxygen demand while operating at the lowest acceptable DO concentration.
• Consider replacing coarse bubble diffusers with fine bubble diffusers to increase oxygen transfer rates by about 50%.
• If the activated sludge process is operating well below design loadings, consider taking biological reactors out of service to minimize aeration requirements. If there are concerns about high hydraulic loadings during and after large storm events, pay attention to weather conditions and activate idle reactors as needed to ensure good process performance. Aeration equipment may need to be turned off for some period of time during large storm events to prevent biomass washout.

Like the PH assessments:

[koay9f]

Still keeping with the closable format in PH, but shortening the list

Activated Sludge

• Try to avoid operating activated sludge processes at Solids Retention Times (SRTs) above 40 days because oxygen demand will be maximized and process performance may deteriorate.

Aerator Performance

• Reduce DO Concentration: operate aerobic reactors at lower DO concentration if possible (between 0.5 and 2.0 mg/L for most cases).
• Match oxygen supply to oxygen demand while operating at the lowest acceptable DO concentration by reducing aerator operating time, speed or power supplied (units on).
• Use an automatic DO control system to control the amount of aeration equipment in use at any given time. Consider using luminescent or florescent DO probes. DO probes should be placed at strategic locations in the aerobic reactor to ensure good process performance. Don’t use too narrow a DO range so that aeration equipment does not cycle on and off too frequently.
• Aerator: Consider replacing coarse bubble diffusers with fine bubble diffusers to increase oxygen transfer rates by about 50%.
• Reduce Aerator Speed: install variable frequency drives (VFDs) on aeration equipment.
• Reduce operating time: use timers to start and stop aerators to conserve energy.
• Reduce operating time: diurnal organic loading may allow for reduced aeration at night and turning aeration off can promote denitrification, save energy, generate alkalinity, and may improve sludge settleability.

Add to Field help text: DO - add to the end Operate aerobic reactors at lower DO concentration if possible. Aerobic reactors in activated sludge should have DO levels between 0.5 and 2.0 mg/L in most cases. Operating at DO levels above 2 mg/L should be avoided if possible. In most cases, maintaining a DO concentration above 2 mg/L is excessive and a waste of energy.

Power - add to the end The mixing intensity should be at least 50 HP per million gallons of reactor volume.

Aerator Speed - add to end Installing variable frequency drives (VFDs) on aeration equipment is especially useful for mechanical aerators and positive displacement (PD) blowers. It may not be practical on some types of centrifugal blowers; check with the blower manufacturer before installing VFDs. For mechanical aerators and PD blowers, speed typically should be 50% to 100%.

Aerator Operating Time - add to end However, oxygen demand at night should be about 60% of daytime oxygen demand due to diurnal organic loading in most municipal wastewater treatment applications. Thus, less aeration equipment may be able to be used at night. In extended aeration processes (extended aeration activated sludge and oxidation ditches) not designed for biological nutrient removal, consider turning aerators off 4 to 6 hours per day. It will promote denitrification, save energy, generate alkalinity, and may improve sludge settleability. If hydraulic detention time in the reactor is less than 12 hours, if influent TKN concentration exceeds 40 mg/L, or if effluent ammonia-N limit (monthly average) is 1 mg/L or less, on-off operation may not be feasible.

[koay9f]

Additional help changes: VSS/TSS Ratio of Biomass - replace (and match header to field name) The ratio of biomass in the Volatile Suspended Solids (VSS) to the Total Suspended Solids (TSS). A default value of 0.85 is suggested by Metcalf & Eddy, but should normally be in the range of 0.80 to 0.90. This should not be confused with the ratio of MLVSS to MLSS, which decreases as SRT increases, due to oxidation of the biomass during endogenous respiration.

Influent TSS - replace The Total Suspended Solids (TSS) concentration within the Influent to the activated sludge process. This is primarily used to calculate the mass loading of TSS on the activated sludge process.

Effluent TSS - replace the words before or the "unintential solids wasted" The Total Suspended Solids (TSS) concentration within the effluent from the activated sludge process ...

RAS TSS - replace all Total Suspended Solids concentration in the return activated sludge (RAS). This is used to determine the RAS flow rate and the WAS flow rate for activated sludge. Typically, 40 to 50% of influent TSS, in the range of 4,000 to 15,000 mg/L, but it can be outside this range in some plants.

Plant Control Point - new help text This allows the user to choose between specifying the average Mixed Liquor Suspended Solids (MLSS) concentration for the process and the total Solids Retention Time (SRT) used for calculations.

SRT - new help text The Solids Retention Time (SRT) is the average time the activated sludge solids are in the system. This is an important design and operating parameter for the activated-sludge process.

MLSS - replace The average Total suspended solids concentration in the mixed liquor (MLSS) for the activated sludge process. Calculated based on estimation of heterotrophic biomass growth, cell debris, and inert VSS. Typically, MLSS concentration will be in the range of 1,000 mg/L to 5,000 mg/L. This can be used as a control point for the facility and in this tool is used to calculate the Solids Retention Time (SRT).

Ks - replace Half-saturation coefficient (K.s) or half-velocity constant is the value of soluble substrate concentration at one-half the maximum specific substrate utilization rate. The typical range for this parameter is 25 to 100 mg/L. It impacts substrate (BOD5) utilization and biomass growth.

Do you have an anoxic ...? new help text An anoxic zone is used to remove nitrogen from the activated sludge, this occurs when the sludge is denied sufficient oxygen. This question is used to determine which "Total O2 Requirements" result to show.