A New Twist on an Old Test for Activated Sludge Process Control Estes Park PWO Seminar October 22, 2004 Greg Farmer – Littleton / Englewood WWTP

L/E WWTP Process Schematic

Aerial View

Phase 2 Construction Project

TF/SC 40 – 70% of SBOD and 25 – 50% of CBOD is removed in the trickle filter 40 – 70% of SBOD and 25 – 50% of CBOD is removed in the trickle filter Aeration basins provide remaining BOD removal and flocculation Aeration basins provide remaining BOD removal and flocculation SRT < 2 days SRT < 2 days SVI around 100 SVI around 100 Not intended for nutrient removal Not intended for nutrient removal

Typical Activated Sludge Control Methods Control MLSS Inventory Control MLSS Inventory Dissolved oxygen concentration Dissolved oxygen concentration And RAS/clarifier blankets And RAS/clarifier blankets To produce a sludge that: Flocculates Flocculates Settles Settles Compacts Compacts

Traditional Performance Indicators Secondary clarifier effluent TSS and BOD Secondary clarifier effluent TSS and BOD Final effluent TSS and BOD Final effluent TSS and BOD SVI / Settleometer SVI / Settleometer SRT SRT F/M F/M

But, what if…….. What if your secondary clarifiers do not function properly due to hydraulic and/or flocculation deficiencies What if your secondary clarifiers do not function properly due to hydraulic and/or flocculation deficiencies –Too shallow –Short circuiting –RAS return problems –Poor sampling location –Thermal Currents –Floc shear

Final Effluent TSS Secondary Clarifier TSS

Temperature Temperature plays a major role: Biological activity decreases by 50% for every 10° C drop in temperature Biological activity decreases by 50% for every 10° C drop in temperature Clarifier thermal currents are created with as little as a 0.5° C temperature difference Clarifier thermal currents are created with as little as a 0.5° C temperature difference

Final Effluent TSS Secondary Clarifier TSS

Aeration Basin Temperature Swing

Thermal Currents

What Tools Are Available? Does a tool exist that can be used to predict or forecast the correct MLSS inventory to maintain a healthy biomass? Does a tool exist that can be used to predict or forecast the correct MLSS inventory to maintain a healthy biomass? This tool must not look at deficiencies in the secondary clarifiers This tool must not look at deficiencies in the secondary clarifiers

Enter the Wally Meter Developed by Dr. Eric Wahlberg as the Wahlometer Developed by Dr. Eric Wahlberg as the Wahlometer Consider it a “flocculated settleometer” Consider it a “flocculated settleometer” Determines the “health” of an activated sludge Determines the “health” of an activated sludge Negates the influence of secondary clarifier inefficiencies on process control decisions Negates the influence of secondary clarifier inefficiencies on process control decisions

Wally Meter in Action Collect a MLSS grab sample 2 times/day Collect a MLSS grab sample 2 times/day Pour into square Phipps and Bird flocculation jar or authentic “Wahlometer” Pour into square Phipps and Bird flocculation jar or authentic “Wahlometer” Mix at 50 rpm for 30 minutes Mix at 50 rpm for 30 minutes Record the 5 minute SSV 5 reading Record the 5 minute SSV 5 reading Settle for 30 minutes and record the 30 minutes SSV 30 reading to calculate SVI Settle for 30 minutes and record the 30 minutes SSV 30 reading to calculate SVI Sample subnatant for TSS and/or NTU Sample subnatant for TSS and/or NTU Wally Meter

Wally Meter Terms ESS – Effluent Suspended Solids ESS – Effluent Suspended Solids FSS – Flocculated Suspended Solids, SS that remain in the subnatant after 30 minutes of settling preceded by 30 minutes of flocculation FSS – Flocculated Suspended Solids, SS that remain in the subnatant after 30 minutes of settling preceded by 30 minutes of flocculation

Clarifier ESS vs. Wally Meter FSS

How to Use the Data The Wally Meter TSS value is the lowest possible TSS value that can be attained in a perfect environment The Wally Meter TSS value is the lowest possible TSS value that can be attained in a perfect environment Adjust MLSS to maintain low Wally Meter TSS Adjust MLSS to maintain low Wally Meter TSS Adjust seasonally for temperature changes Adjust seasonally for temperature changes

The Equation Inventory = (21,000lbs MLSS + ((Avg Wally Meter TSS – 6) * 500)) +(21.5 C – Avg Basin temp.) * Lbs MLSS Inventory *.1) - (5-minute Wally Meter reading – 400) * 20

The Equation

Predictive Chart Spreadsheet

Last 45 Days

Final Effluent

Applicability Will the equation work for an activated sludge plant? A BNR plant? Will the equation work for an activated sludge plant? A BNR plant? Collect data for a period of time Collect data for a period of time Experiment with equation values to attain a fit Experiment with equation values to attain a fit