Breaking a Paradigm: Benefits of Chlorine and other Oxidants on Biofiltration Pete D Adamo, PE, PhD Chance Lauderdale, PE, PhD

Transcription

1 Breaking a Paradigm: Benefits of Chlorine and other Oxidants on Biofiltration Pete D Adamo, PE, PhD Chance Lauderdale, PE, PhD 2014 HDR, Inc., all rights reserved.

2 Where we are heading 1. Background and Quick Survey of Oxidants and Biofilters 2. Breaking Paradigms Chlorine and Biofiltration 3. Observations at Newport News Water Works 4. Observations at Arlington, TX 5. Conclusions and Ongoing Research

3 Project Background and a Quick Survey of Oxidants in Biofilters

4 Biofilters are both simple and complex Biofilm Granular media Microbial Aggregates (loose biofilm) Particles

5 The benefits of ozone as a pre-oxidant are well characterized T&O DBPs Filter Performance CEC CT AOC

6 However too much AOC or a nutrient imbalance can lead to excess microbial growth and poor filter hydraulics Filter Media Particle Filter Media Particle Impeded Flow Filter Media Particle

7 Filter productivity may decrease after conversion to biofiltration WRF TC #4215

8 WRF 4555 focused on identifying robust optimization strategies that yielded enhanced and reliable effluent water quality Filter Media Particle Filter Media Particle Improved Flow Filter Media Particle

9 WRF 4555: Optimization Strategies & Targeted Studies 1) Enhancing Microbial Activity 2) Upstream Coagulation/ Sedimentation 3) Pre-Oxidants 4) Filter Backwashing Strategy Nitrogen/ Phosphorus Supplementation Trace Metals Floc Carryover Physical/Chemical Effects Effects of Pre-Oxidants (Single or Multiple Synergies) Acceptable Residual Levels Backwash Duration, Air Scour Dechlorinated Back Wash 5) Filter Media GAC/Anthracite, Filter Caps

10 Oxidants, like peroxide, applied to the filter influent can decrease headloss WRF TC #4215

11 While ozone has distinct benefits to biofilter hydraulics, diminishing return may prevent achievement of hydraulic goals. WRF TC #2725

12 The benefits of free chlorine on filter performance are well documented

13 Breaking Paradigms Chlorine and Biofiltration

14 But, you don t chlorinate a biofilter + = Chlorine Granular Media Filter Biofilter WRF TC #4346

15 Chlorinated Filters v. Biological Filters Technologies at odds Chlorinated filters o Particle/colloid conditioning o Minimization of biological fouling o Control nuisance organisms o Dissolved metals removal o Disinfection byproduct formation o No biological treatment benefits! Biological filters o Biological treatment benefits o Biological fouling potential o Optimization often needed for metals removal, hydraulics, and particle conditioning objectives

16 Chlorination and Biofiltration Surprising synergies? Minimize/mitigate DBP formation Optimize filtration and hydraulics Achieve biological treatment objectives

17 Case Study 1: Full-Scale Demonstration of Chlorinated Biofilters at NNWW

18 Lee Hall WTP Process Schematic Sodium Permanganate (as needed, dose varies) Alum ( mg/l) ph adjustment (caustic or sulfuric acid) Polymer (0.1 mg/l) Ozone ( mg/l) Raw Water Average Turbidity 2.7 NTU Average TOC 6.7 mg/l Lee Hall Reservoir Contact Basin Copper Sulfate (as needed, dose varies) Rapid Mix Flocculation / Dissolved Air Flotation Ozonation Ozonation Lime (target ph = 7.5 s.u.) Chlorine ( mg/l) Ammonia ( mg/l) Zinc Orthophosphate ( mg/l) Fluoride ( mg/l) Distribution System Clearwell Water from RO plant Dual-media Biofiltration

19 Historically, Lee Hall has suffered from shortened run times during summer months Run Time

20 NNWW Improving Filter Hydraulics with Seasonal Growth Issues in Full-Scale Testing Algae issues in Water Supply Ozonated feed from full-scale Chlorine Filter Characteristics: 36 Anthracite 12 Sand No Cl Residual

21 Chlorine Enhancement Results

22 UFRV (normalized) Filter run times were greatly improved with low doses of chlorine, while limited impact on organics removal was observed 6 60% % 20% TOC/DOC Removal % 0 Control mg/l Chlorine mg/l Chlorine UFRV TOC Removal DOC Removal 0%

23 Manganese removal and DBP-FP were not impacted by chlorine addition Condition THM THM-FP (mg/l) ppm Cl Influent < ppm Cl Effluent <1 216 Control - Influent <1 271 Control - Effluent <1 347

24 Testing in 2017 Filters fed low doses of chlorine continue to perform better

25 Case Study 2: Pilot-Scale Demonstration of Chloramines at Arlington, TX

26 AWU Understanding the impacts of chloramine on biofilter performance (pilot) Water supply fed up to 1.5 mg/l chloramine Ozonated feed from full-scale Chloramine ph Nutrients Zebra Mussel Overgrowth Filter Characteristics: 40 GAC from full-scale 12 Sand

27 Headloss Accumulation Rate (ft/hr) Chloramine addition drastically reduced filter headloss Headloss Accumulation Rate Control 0.5 mg/l of Chloramine 1.0 mg/l of Chloramine 1.5 mg/l of Chloramine

28 Percent DO Consumed (%) Slight DO consumption increased with chloramine addition (nitrification); no difference in TOC/DOC removal was observed 100% 50% 90% 45% 80% 40% 70% 35% 60% 50% 40% 30% 20% 10% 30% 25% 20% 15% 10% 5% TOC/DOC Removal % 0% Control 0.5 mg/l of Chloramine1.0 mg/l of Chloramine1.5 mg/l of Chloramine 0% DO Consumption TOC Removal DOC Removal

29 Normalized media ATP - Test Filter/Control Filter Media ATP was pushed deeper in GAC bed mg/l Chloramine 1.0 mg/l Chloramine 1.5 mg/l Chloramine Total ATP Equal to Control Normalized ATP (24" Deep) Normalized ATP (8" Deep)

30 Turbidity Chloramines had some but limited impact on turbidity breakthrough & TTHM-FP Influent Control 0.5 mg/l of Chloramine 1.0 mg/l of Chloramine 1.5 mg/l of Chloramine Effluent

31 Conclusions and Ongoing Research

32 The synergistic benefits of chlorination and bio filtration merit additional investigation Can chlorination help with biological and particulate fouling? Can we develop guidance to allow others to easily investigate and optimize? Can we predict/modify particulate fouling based on charge/zeta, particle size, ph, etc? What are the downstream water quality and stability impacts of biofilter chlorination? Can we further optimize media selection/design to provide even further robustness over our current strategies?

33 Acknowledgements HDR Christina Alito, Rob Hoffman CDM Smith Kate Dowdell, Pat Evans SNWA Holly McNaught, Julia Lew, Joseph Paul, Mary Murphy, Janie Zeigler, Brett Vanderford, Eric Dickenson, Mac Gifford Dalhousie University Graham Gagnon, Leili Abkar University of Texas at Austin Mary Jo Kirisits, Sarah Keithley Vendors Hach (Vadim Malkov), LuminUltra (Dave Tracey), ManTech (Rob Menegotto) Participating Utilities Arlington Water, Aurora Water, Denver Water, Fairfax County, City of Tampa, Gwinnett County, Newport News, City of Raleigh, Toronto Water, Halifax Water, Halton

34 Contact: Pete D Adamo, Ph.D., P.E. pdadamo@hdrinc.com Leadership Diversity Expertise

35 Breaking a Paradigm: Benefits of Chlorine and other Oxidants on Biofiltration Chance Lauderdale, PE, PhD (PI, HDR) Mark Titcomb (NNWW) Jennifer Hooper, PE (Co-PI, CDM Smith) Eric Wert, PE, PhD (Co-PI, Southern Nevada Water Authority) Christina Alito, PE, PhD and Kelsey Kenel (HDR) Kate Dowdell (CDM Smith) 2014 HDR, Inc., all rights reserved.