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