Using On-line Monitoring as an Effective Tool for Wastewater Treatment Process Optimization Ontario WEA Wastewater Instrumentation & Data Management Seminar Milton, ON May 30, 2013 Wei Zhang, ASA Analytics, Inc.

Outline Wastewater Water Treatment Process Optimization Issues Applications in Single Unit BNR process –Nitrification –Phosphorus Removal Case Histories Consideration of on-line process analyzer selection

Why On-line Now? Regulations toward TN/TP Technology is more mature More sophisticated treatment processes Direct Benefit – Energy Saving, Chemical Saving

Why Monitor Nutrients? If You Want to Control Process Chemistry, Measure Process Chemistry

Challenges for Today’s BNR/ENR Facing total nitrogen and total phosphorus limitation To provide a fast-response, flexible and reliable system capable of handling highly variable influent nutrient loads Energy Saving and chemical saving To minimize maintenance labor

Nitrification A aerobic biological process to convert ammonia nitrogen to nitrate nitrogen, reducing nitrification and toxicity caused by ammonia. Typical treatment process –Single Stage Nitrification –Multi-Stage Nitrification Process consumes oxygen and alkalinity (reduce pH)

Single-stage Nitrification Influent Ammonia < 30 mg/l On-line monitoring issue: pH, alkalinity, NH 3, NO 2, NO 3 and DO, etc. RAS WAS Aerobic Final Clarifier OH - Primary Eff.

Two-stage Nitrification Influent Ammonia 30~50 mg/l On-line monitoring issue: pH, alkalinity, NH 3, NO 2, NO 3 and DO, etc. OH - 1 st Stage Aerobic 2 nd Stage Aerobic Inter. Clarifier Final Clarifier RAS WAS OH - Primary Eff.

Process Control Indicators DO –4.6 lbs O 2 /lb NH 3 -N removal –Maintain 1~2 mg/l in the aeration basin Alkalinity –7.2 lbs Alkalinity destroyed/lb NH 3 -N removal –Maintain 50~80 mg/l Alkalinity in the aeration basin SRT (RAS Ratio and Temperature) Nitrogen profile through treatment train (increase nitrite as first indication inhibitory of Nitrobacter organisms, or incomplete nitrification)

Nitrogen Transformations Decline in ammonia concentration Increase, then decline in nitrite concentration Increase of nitrate to stable maximum Only AFTER this is any surplus DO produced

Ask Question about Nitrification Process How much oxygen is enough? How much alkalinity is enough?

Nitrification & Energy Saving City of Orlando WWTP (WEFTEC Proceeding 1999) –12 mgd plant with activated sludge process –Using ChemScan analyzer generated nitrogen profile at each aeration basin –Set target setpoint/level of ammonia and nitrate in each tank –Motorized air valves and air blowers in each tank are modulated to maintain the selected nitrogen level. –When ammonia level is higher than setpoint, air valves open to increase nitrification. Conversely, nitrate level higher than setpoint, air valve reducing air…. –If adjustment of air valve can’t maintain desired nitrogen level, further blower adjustment kick-in –ChemScan analyzer is the core part of the process control

Phosphorus Removal TP > 1.0 mg/L –biological phosphorus removal TP < 1.0 mg/L –chemical precipitation, or –combination of chemical & biological

Chemical Phosphorus Removal –Aluminum Al 2 (SO 4 ) 3. (14H 2 O) + 2H 2 PO HCO3 - –» 2AlPO 4 + 4CO 2 +3SO H 2 O –Ferric Iron FeCl3. (6H 2 O) + 2H 2 PO HCO3 - –» FePO 4 + 3Cl - + 2CO 2 + 8H 2 O –Side Reaction Fe 3+ + OH - → Fe(OH) 3 –Ferric (or aluminum) hydroxide is formed, loss of alkalinity

Right Amount of Chemicals US EPA Nutrient Control Design Manual (2009) –Alum to P molar ratio 1.38 : 1 for 75% removal 1.72 : 1 for 85% removal 2.3 : 1 for 95% removal –Iron to P molar ratio 1 : 1 is required with a supplemental amount of 10 mg/l iron added to satisfy the formation of hydroxide.

“Common Practices” –The following methods are often used for determination of “right amount” chemicals –Jar Testing or Bench Testing –Historical Trending –Third Party Laboratory Analysis –Plant’s Lab Analysis –These methods are often labor and time consuming.

Right Solution –Online Phosphorus Analyzer Real time Continuous monitoring SCADA-linked for automatic dosing control Flexible for “feed forward” or “feed back” control –Key – Chemical Saving

Chemical Injection Locations Primary Clarification –Popular location for reducing P loading –Feed forward control loop –A precious control is needed to avoid nutrient deficiency to biological process –Might generate more primary sludge to handle –Monitor locations: raw influent and primary clarifier effluent End of Aeration Basin –Another popular location for “polishing” –Chemical usage are more efficient –Feed back control loop –Monitor location: secondary clarifier effluent or final effluent Both locations

AppliedSpectrometry Associates, Inc. – S. Arant, Donohue & Associates, Inc.

Installations & Case Histories –Kiel, Wisconsin 0.9 mgd Activated sludge process Phosphorus permit limit 1.0 mg/l A cheese factory is the major contribution source Online analyzer data “feed back” to SCADA for ferrous sulfate dosing 20% chemical expense saving

Installations & Case Histories –New London, Wisconsin 2 mgd Activated sludge process plant Phosphorus permit limit 1.0 mg/l Online analyzer data “feed back” to SCADA for ferric chloride dosing control $900 per month chemical expense saving

Installations & Case Histories –Sheboygan, Wisconsin –WWTP servicing population of 50,000 –Current phosphorus limit is 1.0 mg/l –Future phosphorus limit will be 0.05 mg/l –Ferric chloride spending $160,000 annual with current limits –First online phosphate analyzer installed in 2010 –Second online phosphate analyzer just installed –data “feed back” to SCADA for ferric chloride dosing control

Installations & Case Histories –Hite Creek, Kentucky Unpredicted phosphorus load from nearby industrial source Using Alum solution for phosphorus precipitation Plant is able to set up improved alum feed rate for different days of the week to match the expected P load based, using 4 months’ data collected from online analyzer Daily alum dosage reduced from 200 gallon/day to 100 gallon/day

AppliedSpectrometry Associates, Inc. Installations & Case Histories Waupun, WI Ferric to Primary only – total sludge: 5,560 lbs/d, total ferric: 190 gal/d – S. Arant, Donohue & Associates, Inc.

AppliedSpectrometry Associates, Inc. Installations & Case Histories Waupun, WI Multiple Point – total sludge: 5,160 lbs/d, total ferric: 120 gal/d – S. Arant, Donohue & Associates, Inc.

AppliedSpectrometry Associates, Inc. – S. Arant, Donohue & Associates, Inc.

AppliedSpectrometry Associates, Inc. – S. Arant, Donohue & Associates, Inc.

Using Ortho-phosphate to Control Ferric Feed

Advanced BNR/ENR Processes Treatment plant facing discharge limitation on both total N or total P Process involve more than one individual BNR process

BNR Process Schematic Nitrification/Denitrification with chemical phosphorus removal. No supplemental carbon Some simultaneous nitrification/denitrification (SND) Final Clarifier Oxidation Ditch AX Primary Eff. WAS RAS Alum Caustic

Supplemental Carbon Feed Control Chemical feed can be 20~30% of entire operating cost Flow pace is still used in many plants Manual control based on grab sample is imprecise and time consuming Manual control can lead to unnecessary chemical expense and extra BOD discharge Underfeed supplemental carbon – incomplete denitrification Chemical feed control scheme using nutrient parameters are installed in many plants

BNR Process Schematic Post denitrification bio-filter Chemical feed control scheme using nutrient parameter is well developed Denitrification Filter BOD Removal Nitrification Methanol

BNR Process Schematic Modified Ludzack Ettinger (MLE) with supplemental carbon Aerobic Anoxic > 2Q Methanol RAS WAS Final Clarifier Primary Eff.

BNR Process Schematic Bardenpho Process with post denitrification filter Two on-line nutrient analyzers AX Aerobic AX Anaerobic Primary Sludge Final Clarifier Methanol RAS WAS Denitrification Filter

Denitrification Filter Using On-Line Nutrients Signal in Control Scheme (1)

Denitrification Filter Using On-Line Nutrients Signal in Control Scheme (2)

An On-line Nutrient Monitoring Chart

Case Study: Bonnybrook WWTP Calgary, Alberta Orthophosphate 4 Month Average Error 3.0 %Ammonia 4 Month Average Error 3.0 %

Case Study: Bonnybrook WWTP Calgary, Alberta Nitrate 4 Month Average Error 1.7 %TSS 4 Month Average Error 3.3 %

On-line Analyzer Selection Technologies –Ion specific electrode –Spectrophotometers Arrangement/configuration –Single parameter vs. multiple parameters –Single sample location vs. Centralized multiple sample lines Look at the hidden cost –Proprietary reagents vs. generic reagents –some analyzers bundles with service contract

Summary If You Want to Control Process Chemistry, Measure Process Chemistry Proven technology is available that can provide reliable automatic chemical analysis Energy saving and Chemical saving Multi-parameter multi-sample line analyzer system provides online nutrient analysis required for BNR monitoring and control

Contact Wei Zhang ASA Analytics, Inc. Waukesha, Wisconsin (262) Local Contact: Metcon Sales & Engineering, Ltd. Concord, ON (905)