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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”