Wqm 207 – bulking and foam part 2

Bulking and Foaming Problems PART 2

*WQM 207 – Activated Sludge Systems

*Operational Control

*When all else fails for bulking control or poor settling:

*Chemical addition – When is the right time?

*Excessive filamentous growth

*Viscous or non-filamentous bulking

*Operational Control

*What chemicals can be used?

*Polymers – does not increase sludge mass

*Aluminum sulfate (alum)

*Ferric chloride

*Ferrous sulfate -

*Powdered activated carbon

*Talc

*Paper fibers/clay

*Chlorination – the most widespread use

*Designed into new plants

*Retrofitted into older plants

*Common application points:*Directly into aeration basin

*RAS stream (preferred location)

*Operational Control

*RAS Stream Chlorination

*Directly into aeration basin

*RAS stream (most common)

*Operational Control

*Chlorination

*Designed into new plants

*Retrofitted into older plants

*Common application points:*Directly into aeration basin

*RAS stream (most common)

*Operational Control

*Frothing from Nocardia

*Excessive concentrations:

*Lowering MCRT by reducing MLSS

*Chlorinating MLSS and/or RAS MLSS

*Use of water Sprays

*Application of Foaming Agents

*Removal of the scum/Foam should be complete as not to re-enter the treatment process.

*Foaming is also a SAFETY ISSUE

*HAZARD

*Foaming/Froth/Scum will contain grease.

*This makes for a very slippery environment.

*Care must be taken for control and removal of this hazard.

*Numerous Operators have been seriously injured while removing this hazard.

*Settling Examination

*Settling Tests

*Use of a Graduated Cylinder as well as a standard Settle-O-Meter can aid the operator with identification of both foam and bulking conditions.

*Critical timing of the test to simulate actual operations is critical for best results.

*Bulking

*Bulking

*Bulking will take place in the Secondary Clarifier.

*Filamentous Bacteria is the cause.

*Be mindful of why this happens:

*Air or gas in the sludge causes the sludge to float.

*Minor Bulking

*RAS Effects with Bulking

*With bulking, the RAS MLSS concentration will be reduced.

*When this occurs, the concentration is lowered so the rate must be increased.

*System Analysis

*Manipulating the RAS:

*Reduce the MLSS in the Secondary Clarifier

*Reduce SS loading while maintaining RAS BULK withdrawal rate,

The SVI is then increased.

*Process Control

*EVERY POTW (Publicly Owned Treatment Works) is built in “Trains”.

*Multiple treatment tracks so that the facility can stay in operation during periods of maintenance.

*Any maintenance that takes a basin or tank out of service will change the hydraulic loading on the facility, this can disrupt effluent water quality.

*When to make a Change?

*Poor Effluent Water Quality.

*High or Low SVI results.

*Increased number in flagellates or amoeba.

*Decreased number of stalked ciliates.

*All these would inspire a change in process control.

*What about a Good Effluent?

*This is why we look under the microscope.

*If you wait too long to make a change based entirely on effluent water quality, ultimately you will violate your DMR and Permit.

*It takes time through a process to see a change take place. Remember your sludge age or MCRT? Days………….

*Microscopic Analysis Frequency

*Good Operational Effluent: 2 or 3 times per week.

*Poor Operational Effluent: twice per day (morning and afternoon).

*Following a Process Change: daily or twice per day until stabilization.

* WQM 207 Activated Sludge Systems

*Homework:

*Read Chapter 4 “Control of Activated Sludge Bulking and Other Settling Problems”