a new twist on an old test for activated sludge process control estes park pwo seminar october 22,...
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A New Twist on an Old A New Twist on an Old Test for Activated Sludge Test for Activated Sludge Process ControlProcess Control
Estes Park PWO SeminarEstes Park PWO SeminarOctober 22, 2004October 22, 2004
Greg Farmer – Littleton / Englewood Greg Farmer – Littleton / Englewood WWTPWWTP
L/E WWTP Process L/E WWTP Process SchematicSchematic
Aerial ViewAerial View
Phase 2 Construction Phase 2 Construction ProjectProject
Phase 2 Construction Phase 2 Construction ProjectProject
TF/SCTF/SC
40 – 70% of SBOD and 25 – 50% of 40 – 70% of SBOD and 25 – 50% of CBOD is removed in the trickle CBOD is removed in the trickle filterfilter
Aeration basins provide remaining Aeration basins provide remaining BOD removal and flocculationBOD removal and flocculation
SRT < 2 daysSRT < 2 days SVI around 100SVI around 100 Not intended for nutrient removalNot intended for nutrient removal
Typical Activated Typical Activated Sludge Control Sludge Control MethodsMethods Control MLSS InventoryControl MLSS Inventory Dissolved oxygen concentrationDissolved oxygen concentration And RAS/clarifier blanketsAnd RAS/clarifier blankets
To produce a sludge that:To produce a sludge that: FlocculatesFlocculates SettlesSettles CompactsCompacts
Traditional Traditional Performance Performance IndicatorsIndicators Secondary Secondary
clarifier effluent clarifier effluent TSS and BODTSS and BOD
Final effluent TSS Final effluent TSS and BODand BOD
SVI / SettleometerSVI / Settleometer SRTSRT F/MF/M
But, what if……..But, what if……..
What if your secondary clarifiers do What if your secondary clarifiers do not function properly due to hydraulic not function properly due to hydraulic and/or flocculation deficienciesand/or flocculation deficiencies– Too shallowToo shallow– Short circuitingShort circuiting– RAS return problemsRAS return problems– Poor sampling locationPoor sampling location– Thermal CurrentsThermal Currents– Floc shearFloc shear
Final Effluent TSS Final Effluent TSS Secondary Clarifier Secondary Clarifier TSSTSS
TemperatureTemperature
Temperature plays a major role:Temperature plays a major role: Biological activity decreases by Biological activity decreases by
50% for every 10° C drop in 50% for every 10° C drop in temperaturetemperature
Clarifier thermal currents are Clarifier thermal currents are created with as little as a 0.5° C created with as little as a 0.5° C temperature differencetemperature difference
Final Effluent TSS Final Effluent TSS Secondary Clarifier Secondary Clarifier TSSTSS
Aeration Basin Aeration Basin Temperature SwingTemperature Swing
Thermal CurrentsThermal Currents
What Tools Are What Tools Are Available?Available? Does a tool exist that can be used Does a tool exist that can be used
to predict or forecast the correct to predict or forecast the correct MLSS inventory to maintain a MLSS inventory to maintain a healthy biomass?healthy biomass?
This tool must not look at This tool must not look at deficiencies in the secondary deficiencies in the secondary clarifiersclarifiers
Enter the Wally MeterEnter the Wally Meter
Developed by Dr. Eric Wahlberg as Developed by Dr. Eric Wahlberg as the Wahlometerthe Wahlometer
Consider it a “flocculated Consider it a “flocculated settleometer”settleometer”
Determines the “health” of an Determines the “health” of an activated sludgeactivated sludge
Negates the influence of secondary Negates the influence of secondary clarifier inefficiencies on process clarifier inefficiencies on process control decisions control decisions
Wally Meter in ActionWally Meter in Action
Collect a MLSS grab sample 2 times/dayCollect a MLSS grab sample 2 times/day Pour into square Phipps and Bird Pour into square Phipps and Bird
flocculation jar or authentic flocculation jar or authentic “Wahlometer” “Wahlometer”
Mix at 50 rpm for 30 minutesMix at 50 rpm for 30 minutes Record the 5 minute SSVRecord the 5 minute SSV55 reading reading Settle for 30 minutes and record the 30 Settle for 30 minutes and record the 30
minutes SSVminutes SSV3030 reading to calculate SVI reading to calculate SVI Sample subnatant for TSS and/or NTUSample subnatant for TSS and/or NTU
Wally Meter
Wally Meter TermsWally Meter Terms
ESS – Effluent Suspended SolidsESS – Effluent Suspended Solids FSS – Flocculated Suspended FSS – Flocculated Suspended
Solids, SS that remain in the Solids, SS that remain in the subnatant after 30 minutes of subnatant after 30 minutes of settling preceded by 30 minutes settling preceded by 30 minutes of flocculationof flocculation
Clarifier ESS vs. Clarifier ESS vs. Wally Meter FSSWally Meter FSS
How to Use the DataHow to Use the Data
The Wally Meter TSS value is the The Wally Meter TSS value is the lowest possible TSS value that lowest possible TSS value that can be attained in a perfect can be attained in a perfect environmentenvironment
Adjust MLSS to maintain low Adjust MLSS to maintain low Wally Meter TSSWally Meter TSS
Adjust seasonally for temperature Adjust seasonally for temperature changeschanges
The EquationThe Equation
Inventory =Inventory =
(21,000lbs MLSS + ((Avg Wally Meter TSS – 6) * (21,000lbs MLSS + ((Avg Wally Meter TSS – 6) * 500))500))
+(21.5 C – Avg Basin temp.) * Lbs MLSS Inventory +(21.5 C – Avg Basin temp.) * Lbs MLSS Inventory * .1)* .1)
- (5-minute Wally Meter reading – 400) * 20- (5-minute Wally Meter reading – 400) * 20
The EquationThe Equation
Predictive ChartPredictive Chart Spreadsheet
Last 45 DaysLast 45 Days
Final EffluentFinal Effluent
ApplicabilityApplicability
Will the equation work for an Will the equation work for an activated sludge plant? A BNR activated sludge plant? A BNR plant?plant?
Collect data for a period of timeCollect data for a period of time Experiment with equation values Experiment with equation values
to attain a fitto attain a fit