Activated Sludge 11.1 Flashcards
During increased flow from storms, what problems can arise? (Combined Sewer System)
- Reduced wastewater time in treatment units (hydraulic overloading)
- Increased amounts of grit and silt which lower the volatile content of solids
- increased organic load during initial washout of accumulated sewer deposits
- Rapid changes in wastewater temp and solids content
What could happen if a long deactivated lift station is brought back online or a blockage cleared?
- Large volumes of septic wastewater could cause a shock load on the treatment process
What are required water quality indicators
- Chemical Oxygen Demand (COD)
- Suspended Solids
- Nitrogen
What factors could have changed if the desired effluent quality is not achieved?
- Higher COD or BOD load applied to the aerator (influent load)
- More difficult to treat wastes
- Unsuitable MLSS concentration in the aerator
- Lower or Higher rate of WAS
- Unsuitable RAS rate
- Higher solids concentrationts in digester supernatant returned to plant flow or return too rapid
- drop of oxygen levels
- increase or decrease in wastewater temp
What two major variables affect the way an activated sludge plant is operated?
- Dischargers to the collection system
- in-plant operational variables
Besides storm flows, what other variables in the collection system can affect the operation of an activated sludge plant?
- wastes discharged
- maintenance activities
Besides the operator, who should be present during the start up of a new activated sludge plant? Why?
- design engineers
- vendors
- OTHER nearby operators
- specialists
- equipment manufacturers
- contractors
- To make sure that any equipment breakdowns are not caused by improper startup
Where can record data for suspended solids and volatile content be collected from?
- Primary effluent
- aerator mixed liquor
- return sludge
- final clarifier or secondary sedimentation tank effluent
Where can record data for BOD, COD, or TOC2 (total organic carbon) be collected?
- Plant influent
- Primary effluent
- Final clarifier or secondary sedimentation tank effluent
How long can results be given on a COD test?
4 hours
What disadvantages does a BOD test have in terms of operational control?
- Procedural errors can cause a large variation in results
- 5 days of waiting are required before results are available
- Only a portion of the load on the activated sludge process is measured by the test
Where can record data for Dissolved Oxygen (DO) be collected?
- Aerator
- Final Clarifier or secondary sedimentation tank (inside the effluent weir)
- Final effluent
Where can record data for Settleable Solids be collected?
- Influent
- Mixed liquor settleability test
- Digester supernatant
- Final effluent
Where can record data for temperature be collected?
- Influent
- Aerator
- Final effluent
Where can record data for pH be collected?
- Influent
- primary effluent
- aerator (measure immediately off aerator)
- Final effluent
Where can record data for clarity (secchi disk) or turbidity (turbidimeter) be collected?
Final clarifier
Where can record data for Chlorine demand be collected?
Final clarifier effluent
Where can record data for Coliform Group Bacteria be collected?
Plant effluent
What record data for meter readings and calculations should be collected?
- daily flow
- pounds of solids under aeration
- pounds of COD or BOD to aerators
- pounds of solids in effluent
- RAS rate
- WAS rate
- air to aerators (diffused air system); hours operated at various speeds (mechanical aeration)
- Sludge age
- pounds of solids in sludge to digester
- pounds of solids in digester supernatant
- power cost
What daily observations must be made for daily records?
- odors
- Influent (color and level of inflow)
- Primary Clarifier (Scum and color)
- Aeration tank (Turbulence, color, and amount of surface foam/scum)
- Secondary Clarifier (Effluent clear or turbid, type of solids on surface and influent)
- RAS: Color and Odor
- Equipment & Motors
- Condition of receiving waters both upstream and downstream of discharge point
Why should aerator pH be measured in the aerator instead of the lab?
pH can change rapidly outside the aerator
What are two methods to supply oxygen from the air to bacteria?
- Mechanical Aeration
- Diffused Aeration
What is the formula to determine Sludge Age?
(Suspended Solids under aeration, lbs)/(Suspended solids added, lbs/day)
Define High-Rate activated Sludge
- Highest loading of F/M ratio
- age ranges 0.5-2.0 days
- lower quality effluent
- more easily upset; requires tighter control
