2017 HDR, Inc., all rights reserved.

Transcription

1 Evaluating Operational Factors that Influence Biofiltration Performance in Various Source Waters Samantha Black, EIT, PhD HDR Pete D Adamo, PE, PhD HDR Mike Hughes City of Raleigh 2017 HDR, Inc., all rights reserved.

2 Agenda Biofiltration and WRF Project Overview Upstream Oxidant Addition Microbial Activity Enhancement Upstream Process Modifications

3 01 Biofiltration & WRF Project Overview

4 What is Biofiltration?

5 Microorganism health is important for filter productivity Stressed microorganisms produce extracellular polymeric substances (EPS) EPS accumulates within the biofilter media Accumulation leads to increased head loss and shorter filter run times Source: WRF 4215

6 WRF #4555 Objectives WRF #4555 Objectives 1. Identify biofilter optimization strategies that can increase contaminant removal and/or improve hydraulics 2. Develop a guidance for utilities on when and how to implement strategies

7 16 diverse utilities participated in the WRF project Regional Participants City of Raleigh Greenville Utilities Commission Newport News Waterworks

8 WRF Optimization Strategies Influent Trough Dual Media Filter Underdrains Backwash pumps

9 Raw Water #1 - Upstream Processes Coagulation/Flocculation WRF Optimization Strategies Sedimentation Settled Water Influent Trough Dual Media Filter Underdrains Backwash pumps

10 Raw Water #1 - Upstream Processes Coagulation/Flocculation WRF Optimization Strategies Sedimentation Settled Water Ozone Contactor Influent Trough #2 - Pre- Ozonation Ozone Generator Dual Media Filter Underdrains #2 - Pre-Oxidant: Cl 2, H 2 O 2, MnO 4-, NH 4 Cl 2 Backwash pumps

11 Raw Water #1 - Upstream Processes Coagulation/Flocculation WRF Optimization Strategies Sedimentation Settled Water Ozone Contactor Influent Trough #3 Enhancing Microbial Activity #2 - Pre- Ozonation Ozone Generator Dual Media Filter Underdrains #2 - Pre-Oxidant: Cl 2, H 2 O 2, MnO 4-, NH 4 Cl 2 Backwash pumps

12 Raw Water #1 - Upstream Processes Coagulation/Flocculation WRF Optimization Strategies Sedimentation Settled Water Ozone Contactor Influent Trough #3 Enhancing Microbial Activity #2 - Pre- Ozonation Ozone Generator Dual Media Filter Underdrains #2 - Pre-Oxidant: Cl 2, H 2 O 2, MnO 4-, NH 4 Cl 2 Backwash pumps + #4 Filter Backwashing Air Scour Cl 2, NH 4 Cl, H 2 O 2 Procedure

13 Raw Water #1 - Upstream Processes Coagulation/Flocculation WRF Optimization Strategies Sedimentation Settled Water Ozone Contactor Influent Trough #3 Enhancing Microbial Activity #2 - Pre- Ozonation Ozone Generator Dual Media Filter #2 - Pre-Oxidant: Cl 2, H 2 O 2, MnO 4-, NH 4 Cl 2 Underdrains Backwash pumps + #4 Filter Backwashing Air Scour Cl 2, NH 4 Cl, H 2 O 2 Procedure #5 Filter Media Type

14 Three strategies will be discussed today Utility Pilot or Full-Scale Upstream Oxidant Addition Microbial Activity Enhancement Upstream Process Modifications Backwash Media Type Arlington Water Utilities Pilot/Full Gwinnett County Dept. of Water Res. Pilot/Full Halifax Water Pilot City of Tampa Pilot Southern Nevada Water Authority Pilot/Full Toronto Water Pilot Denver Water Full Fairfax County Water Authority Full City of Raleigh Full Newport News Water Works Full

15 Five metrics were used to evaluate optimization strategies Improvements in organics removal Improvements in inorganics removal Increases in filter run hours Decreases in head loss and/or head loss accumulation rate Decrease in filter effluent turbidity

16 Changes in source water quality were considered At least one year of analytical and operational data Synergy evaluations were conducted to determine how one optimization strategy might affect another Data were normalized to account for source water changes Test filter value Control filter value If normalized value = 1, test filter = control filter

17 02 Results Upstream Oxidant Addition

18 How can upstream oxidants improve biofilter performance? Upstream oxidants added Nondegradable organic carbon becomes more easily degradable More removal using microorganisms is achievable

19 Five upstream oxidants were evaluated Utility Pilot or Full- Scale Ozone Dose (mg/l) Chloramine Dose (mg/l) Permanganate Dose (mg/l) Chlorine Dose (mg/l) Peroxide Dose (mg/l) Halifax Pilot Toronto Pilot Gwinnett Pilot City of Tampa Pilot SNWA Pilot Arlington Pilot/Full Raleigh Full Newport News Full Fairfax Water Full Overall Range Tested

20 Ozone provides hydraulic improvement and turbidity removal Ozone Addition Increased filter run time Decreased effluent turbidity Normalized Filter Run Time (test filter/control filter) mg/l Ozone 3.8 mg/l Ozone 4.0 mg/l Ozone Effluent Turbidity (NTU) Filter Run Time Effluent Turbidity

21 Normalized Headloss (test filter/control) mg/l of Chloramine Headloss Partnership for SDWA turbidity limit 1.0 mg/l of Chloramine Effluent Turbidity 1.5 mg/l of Chloramine Effluent Turbidity (NTU) Chloramine Dosage Actual Headloss (ft) Effluent Turbidity (NTU) Control mg/l mg/l mg/l Chloramine addition significantly decreased headloss

22 Chlorine addition increase filter run time Filter Run Time (hr) % 80% 60% 40% 20% Removal % 0 Control mg/l Chlorine mg/l Chlorine 0% Filter Run Time TOC Removal DOC Removal

23 03 Results Microbial Activity Enhancement

24 Upstream nutrients promote healthy microorganisms Stressed Biomass (Nutrient-Limited) Carbon Nitrogen Phosphorus 100 M 10 M 1 M 1 mg/l 0.1 mg/l 0.03 mg/l Healthy Biomass (Nutrient-Enhanced) *ESEM performed by USEPA ORD

25 Phosphorus was the most commonly studied nutrient Utility Pilot or Full-Scale Phosphorus Ammonia Phosphorus + Ammonia Arlington Pilot/Full mg/l-p 0.5, 1.0, 1.5 mg/l-n 0.5 mg/l-n mg/l-p 1.5 mg/l-n mg/l-p Gwinnett County Pilot 0.1 mg/l-p with and without ph adjustment Raleigh Full 0.1 mg/l, 0.2 mg/l, 0.4 mg/l phosphoric acid with and without ph adjustment Fairfax Water Pilot mg/l-p

26 Ammonia and phosphorus decreased headloss Headloss TOC Removal DOC Removal Normalized Headloss or TOC/DOC Removal (test filter/control) mg/l of Ammonia mg/l phosphorus 1.5 mg/l of Ammonia 1.5 mg/l of Ammonia mg/l phosphorus

27 14 12 Location: PBWTP (Arlington, TX) Media: Sand/GAC Loading Rate: 4.5 gpm/sf Run Time: 24 hours Average Temp: 68 F Normalized Headloss (ft) % decrease in terminal headloss 22% increase in filter run time Hours After Backwash Phosphorus addition decreased headloss & increased filter run time

28 04 Results Upstream Process Modifications

29 Utilities studied the addition of various chemicals Utility Pilot or Full-Scale Chemical & Dose (mg/l) Halifax Pilot Aluminum Sulfate (8 12 mg/l) Arlington Pilot Aluminum Sulfate (16 48 mg/l) Raleigh Full PAC (2 & 3 mg/l) Caustic (Increased 1-2 ph units) City of Tampa Pilot Filter Aid ( mg/l)

30 Caustic increased filter run time in biofilters Normalized Filter Run Time (Hours) Before Caustic Addition Test Filter 1 Test Filter 2 After Caustic Addition

31 Filter Run Time Ozone Dose ph Filter Run Time (hours) D-15 M-16 J-16 O-16 J-17 Date ph (SU) and Ozone Dose (mg/l) Study Period ph Ozone Dose (mg/l) Average Filter Run Time (Hours) Ozone & caustic increased filter run time in downstream filters

32 Biofiltration can reduce upstream alum dose 80% 70% 60% Removal % 50% 40% 30% 20% 10% 0% Alum Dose (mg/l) TOC Removal - Coag/Sed TOC Removal - BAF TOC Removal - Total

33 05 Conclusions

34 Biofiltration can provide various benefits for different utilities Oxidant Addition o Low doses of ozone and chlorine can be beneficial for three purposes: Reduction of EPS More biodegradable organics Particle stability Nutrient Addition o Site-specific benefits of adding phosphorus, but the concentration must be optimized for controlling hydraulics Upstream Process Modifications o Adding caustic/ozone increased filter run time in downstream filters o Minimal impact of varying alum dose on biofilter performance

35 Questions? Samantha Black, EIT, PhD (HDR) Mike Hughes (City of Raleigh) Water Research Foundation Project #4555 Coauthors: Chance Lauderdale (HDR) Christina Alito (HDR) Jen Hooper (CDM) Katherine Dowdell (CDM) Eric Wert (SNWA)