Biological Filtration – Benefits and Challenges Lynn Williams Stephens, PE Agenda

2019 PNWS-AWWA Conference Biological Filtration – Benefits and Challenges Lynn Williams Stephens, PE Agenda

• Background on biofiltration • How to develop a Filter Management Plan • Pilot testing case studies • Toronto: cold weather biological filtration • Lake Oswego: surface water treatment pilot

Brown and Caldwell 2 Biological Filtration Definition

Biological treatment within a filter at a drinking water treatment facility is an operational practice of managing, maintaining, and promoting biological activity on granular media in the filter to enhance the removal of organic and inorganic constituents before treated water is introduced into the distribution system.

2016 AWWA Biological Drinking Water Treatment Committee Slow Sand Biological Filtration

• Historically, biological filtration around for 100’s of years via slow sand filtration • Biofilm layer “Schmutzdecke”

• Relies on microbial activity of bacteria to degrade contaminants

Brown and Caldwell Example of Slow Sand Filtration 4 Current Practices with Rapid Rate Biofiltration Practices

300 15 Facilities with capacity >100 MGD

250

200 7 Facilities with capacity of 50-100 MGD 150

16 Facilities with capacity of

100 10-50 MGD Capacity (MGD) Capacity

0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 Facilities Source: WRF 4459 – Development of a Biofiltration Knowledge Base Overview of Ozonation and Biofiltration

+ O3 =

Brown and Caldwell 6 Overview of Ozonation and Biofiltration

+ O3 =

Cl2

Brown and Caldwell 7 Microbial Oxidation – How does it work?

• Based on redox chemistry • Surface water and groundwater condition

Carbon Source: DOC, etc.

02: -4 charge

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

Brown and Caldwell 8 Microbial Oxidation – Removal of Nitrate and Perchlorate • Based on redox chemistry • Typically surface water or groundwater condition

- NH3 O2 NHNO32

NH3 : +1 charge

- 4NH3 + 7O2 →4NO2 + 6H2O

Brown and Caldwell 9 Application and Benefits • Application • Surface and groundwater • Aerobic and anoxic • Organics – T&O compounds, AOC, DOC, CECs, DBP reduction • Inorganics - ammonia, nitrate, nitrite, iron, manganese, arsenic, perchlorate, selenium • Benefits • Removal of multiple contaminants • Biostability of DWDS • Minimal chemical addition • Minimal energy addition • No waste products Removal of Contaminants by Biofiltration using Inert Media

High Moderate Low >85% 50-85% 15-50% 0-15% Benzo[a]pyrene Acetaminophen Caffeine Atenolol DDT Aldicarb DEET Carbamazepine Fluoxetine Chlorobenzene Erythromycin Meprobamate Formaldehyde Clofibric Acid Diclofenac Primidone Ibuprofen Dimethoate Gemfibrozil Sucralose Molinate Naproxen Geosmin Sulfamethoxazole P-Toluenesulfonic Phenol MIB TCEP Acid Saxitoxin C2 Triclosan Trimethoprim Trichloromethane Source: Dickenson, E., Wert, E., Verdugo, E., Greenstein, K., Brown, J., Schneider, O., Marfil-Vega, R., Summers, R. S. 2017. Simultaneous Removal of Multiple Contaminants Using Biofiltration. Water Research Foundation 4559.

Brown and Caldwell 11 Engineered Rapid Rate Biofiltration

• Media selection • GAC media to increase surface area for biomass • Deep beds • Pretreatment • Ozonation prior to filtration to promote biological oxidation of contaminants • May add external carbon source and phosphate addition to increase biological growth • Underdrain design • Backwash strategy • Disinfection strategy

Brown and Caldwell 12 Backwashing Options for Biological Filters • Probable backwashing intervals at 24 hours • Simultaneous air and water (collapsed pulsing condition), followed by a standard water fluidization; not found to be detrimental to AOC reduction (many utilities) • Non-chlorinated backwash water (most common) • Chlorinated backwash (some still use) • Chlorine does decrease biomass • BOM removal much less affected • Chlorine in air/water improves initial turbidity spike, improves headloss

Source: Hooper, J. 2015. Monitoring Tools for Biological Filtration. ACE Workshop. Backwashing Strategies by 21 Utilities with Biological Filters

Source: Hooper, J. 2015. Monitoring Tools for Biological Filtration. ACE Workshop. Bacterial population roughly doubled when backwashing with unchlorinated water

Source: Hooper, J. 2015. Monitoring Tools for Biological Filtration. ACE Workshop. What are the concerns/challenges?

• Can have increased headloss due to biomass accumulation • Can have reduced Unit filter run volumes (UFRVs) • Design considerations • Promoting bacteria in drinking water • Blackbox

Brown and Caldwell 16 Steps to Understand Biofiltration

1. Define filter objectives 2. Develop Filter Management Plan 3. Develop baseline 4. Reassess Filter Management Plan

Brown and Caldwell 17 Filtration Monitoring and Control Tools

Control

 Filter loading rate/EBCT  Backwash timing/ rates  Filter run time

 Chlorinated vs. unchlorinated backwash  Oxidant dose and type (ozone, chlorine, peroxide)

Brown and Caldwell 18 Filtration Monitoring and Control Tools

Control Operational

 Filter loading  Head loss and rate/EBCT headloss profiling  Backwash timing/  Unit filter run rates volumes  Filter run time  Chlorine demand

 Chlorinated vs. unchlorinated  Visual inspection backwash  Oxidant dose and type (ozone, chlorine, peroxide)

Brown and Caldwell 19 Filtration Monitoring and Control Tools

Control Operational Water Quality

 Desired contaminant  Filter loading  Head loss and removal (organics and/or rate/EBCT headloss profiling inorganics)  Backwash timing/  Unit filter run  Dissolved oxygen uptake rates volumes  Filter run time  Chlorine demand  Organic specific:

 Chlorinated vs.  Biodegradable unchlorinated  Visual inspection dissolved organic backwash carbon (BDOC)  Oxidant dose and  Assimilable type (ozone, organic carbon chlorine, peroxide) (AOC)  Carboxylic acids  Nutrients  Temperature

Brown and Caldwell 20 Filtration Monitoring and Control Tools

Control Operational Water Quality Biological

 Desired contaminant  Filter loading  Head loss and  Adenosine removal (organics and/or rate/EBCT headloss profiling triphosphate (ATP) inorganics)  Backwash timing/  Unit filter run  Heterotrophic plate  Dissolved oxygen uptake rates volumes counts (HPCs)  Filter run time  Extracellular polymeric  Chlorine demand  Organic specific: substances (EPS)  Chlorinated vs.  Biodegradable  Microbial Assessments unchlorinated  Visual inspection dissolved organic (i.e. polymerase chain backwash carbon (BDOC) reaction [PCR])  Oxidant dose and  Assimilable type (ozone, organic carbon chlorine, peroxide) (AOC)  Carboxylic acids  Nutrients  Temperature

Brown and Caldwell 21 Filter Management Plan

Trouble- Monitoring Tool Normal Operations (Baseline) shooting Headloss Continuously Continuously

UFRV Continuously Continuously Operational

Turbidity and/or particle counts Continuously Continuously

Brown and Caldwell 22 Filter Management Plan

Trouble- Monitoring Tool Normal Operations (Baseline) shooting Headloss Continuously Continuously

UFRV Continuously Continuously Operational

Turbidity and/or particle counts Continuously Continuously

TOC/DOC or UV254 Weekly Daily

Water Quality Temperature Continuously Continuously

Carboxylic acids Monthly Weekly

Brown and Caldwell 23 Filter Management Plan

Trouble- Monitoring Tool Normal Operations (Baseline) shooting Headloss Continuously Continuously

UFRV Continuously Continuously Operational

Turbidity and/or particle counts Continuously Continuously

TOC/DOC or UV254 Weekly Daily

Water Quality Temperature Continuously Continuously

Carboxylic acids Monthly Weekly

Dissolved Oxygen Uptake Continuously Continuously Biological ATP Monthly Weekly

Brown and Caldwell 24 Many Successful Utilities with Low Temperatures

Source: WRF 4459 Case Study: Toronto Pilot Study - Biofiltration in Cold Temperatures

Source: Michael J. McKie, Liz Taylor-Edmonds, Susan Andrews, and Robert Andrews. 2018 Water Quality Technology Conference, Workshop: Implementing Drinking Water Biofiltration in Cold Weather Conditions Lake Ontario

Water Temp

Warm Water (>10°C)

Alum, PACl, Lime, PAC, Sodium Hypochlorite Filter Aid Clackamas River Intake Dual Media Filter Washwater

Anthracite Sand FT To Sludge ContactContact BasinsBasins W Lime Lagoons High Service Sodium Hypochlorite Pumps

Carbon Dioxide Clearwell To Distribution • Existing contact basins do not provide System formal flocculation and sedimentation • Seasonal algal taste and odors issue Expansion Treatment Alternative

• Liquid Stream Treatment Process • Ballasted flocculation • Ozonation • Biological filtration

Brown and Caldwell 33 Pilot Plant Configuration

Brown and Caldwell 34 Greatest HPC levels in BAC Filter

100000

10000

1000

100 HPC HPC (CFU/100 mL)

1 Existing Anth Filter GAC Filter BAC Filter Anth Filter Filter Productivity

8,000

7,000

6,000 run) - UFRV Target 5,000

4,000

3,000

2,000

Average UFRV (gal/sf UFRV Average 1,000

0 Existing Anth Filter GAC Filter BAC Filter Anth Filter

3.75 gpm/sf 10 gpm/sf 10 gpm/sf 10 gpm/sf Average BDOC Remaining

1.4

1.2

0.8

0.6 BDOC(mg/L)

0.4

0.2

0 Raw Existing Anth ACTIFLO Ozonated GAC Filter BAC Filter Anth Filter Filter

Brown and Caldwell 37 DBP SDS Testing Results

50 TTHM TTHM Target HAA5 40

HAA5 MCL 30

20 TTHM and HAA5 (ug/L) Potential Formation HAA5 and TTHM

0 Existing Anth Filter GAC Filter BAC Filter Anth Filter Eliminating Prechlorination and adding BAC reduces TTHMs

200 PRECHLORINATION REDUCED 180 Elimination of PrechlorinationPRECHLORINATIONandELIMINATED 160 Biological Filtration

140 µg/L)

Distribution System 120 Locations

100 McCool School #68 Madrid Circle 80 #70 Plumeria St. #8 Apra View 60 #24 Portola St

Distribution System TTHM( System Distribution 40

7/26/2012 9/26/2012 1/26/2014 1/26/2012 2/26/2012 3/26/2012 4/26/2012 5/26/2012 6/26/2012 8/26/2012 1/26/2013 2/26/2013 3/26/2013 4/26/2013 5/26/2013 6/26/2013 7/26/2013 8/26/2013 9/26/2013 2/26/2014 3/26/2014

10/26/2012 11/26/2012 12/26/2012 10/26/2013 11/26/2013 12/26/2013 Summary • Many successful cold water biofiltration plants • From pilot at Lake Oswego WTP, ozonation followed by biological filtration effectively reduced disinfection by-products while achieving effective performance • Non-chlorinated GAC had increased biological activity and improved bed life, but increased headloss • Biological filtration is a process to maximize contaminant removal • Intentional about the biofilter optimization • Develop a Filter Management Plan to increase understanding and to choose monitoring parameters that work for your system Do you want to learn more? • Biological Drinking Water Treatment Committee • Ten State Standards • Anoxic biological treatment • Biologically active filters for surface waters • Aerobic groundwater treatment • Water Research Foundation Biological Filtration Knowledge Area • #4719 – Biofiltration Guidance Manual, expected late 2019/early 2020 Questions? Comments?

Lynn Williams Stephens, P.E. [email protected] (206) 749-2893