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Trussell Technologies, Inc. Pasadena, CA 1

Final Report

Development of an Innovative IPR Treatment Train to Maximize Recycled Water Recharge and Minimize Blending Requirements

Date: February 27, 2015

To: Kira Alonzo, Metropolitan Water District of Southern California

From: Fredrick W. Gerringer, D.Env., P.E., BCEE

Subject: Final Report for Foundational Actions Funding Program Agreement No. 139824: Development of an Innovative IPR Treatment Train to Maximize Recycled Water Recharge and Minimize Blending Requirements

1 EXECUTIVE SUMMARY

This project investigated the efficacy of using ozonation, biofiltration and soil aquifer treatment (SAT) on a nitrified and partially denitrified wastewater effluent for indirect potable reuse treatment. Treatment was optimized for maximum total organic carbon (TOC) removal to facilitate compliance with California’s groundwater recharge regulations limiting the TOC of wastewater origin in groundwater to 0.5 mg/L. Testing included granular activated carbon (GAC) and anthracite coal filter media, transferred ozone dose and TOC concentration (O3:TOC) ratios of 0.75 to 1.50, empty-bed contact times (EBCT) of 10 to 39 minutes for biofiltration and hydraulic retention times (HRTs) of 28 days and 56 days for SAT. This project also investigated the impact of this treatment train on other water quality parameters, such as bromate, N-nitrosodimethylamine (NDMA), trace organic chemicals (TOrCs) and total coliform bacteria. This comprehensive study defined the limits of TOC reduction achievable by the full treatment train of ozonation, biofiltration and SAT while identifying other water quality and operational factors important to the full-scale implementation of this treatment train. Optimal operating conditions of an ozone system with an O3:TOC ratio of 1.00, a biological activated carbon (BAC) filter with an EBCT of 39 min, and SAT with a minimum HRT of 56 days were able to reduce the TOC concentration by 79%, which would significantly reduce the blend water required for compliance with the TOC requirement of the groundwater recharge regulations. Additionally, sequential addition of chlorine and ammonia in the ozone influent was shown to minimize bromate formation, NDMA and total coliform concentrations after SAT were below the detection limit, and significant TOrC removal was provided by this treatment train. The most important next step before considering implementation of the tested treatment train would be to perform a cost-benefit analysis to determine if the capital, operations and maintenance costs associated with treatment would be offset by cost savings from the purchase of blend water and by improving water supply reliability.


2 INTRODUCTION

Upper San Gabriel Valley Municipal Water District is investigating options for using recycled water for groundwater recharge. The objective of this project is to optimize the indirect potable reuse treatment of a nitrified and partially denitrified secondary effluent using ozonation, biofiltration, and SAT. The primary driver for this optimization is the California groundwater recharge regulation that limits the municipal wastewater contribution to no greater than 0.5 mg/L of TOC over a 20-week running average. Satisfying this regulation with reclaimed water that has a TOC concentration higher than 0.5 mg/L requires blending with other water sources, such as storm water or imported water. Minimizing the TOC content of the water through the optimization of ozonation, biofiltration and SAT will reduce the blending needed to comply with the wastewater TOC limit. This achievement would lower the costs associated with purchasing water for blending with recycled water and would effectively increase the amount of water available for groundwater recharge.

2.1 Participating Entities and Roles

The following list provides the entities participating in the project and their respective roles:

Upper San Gabriel Valley Municipal Water District: Project sponsor.

Trussell Technologies, Inc.: Conducted pilot testing and analyzed results.

Stetson Engineers, Inc.: Provided project management support.

2.2 Experimental Approach

The pilot plant was located at Los Angeles County Sanitation Districts’ (LACSD’s) San Jose Creek Water Reclamation Plant (SJCWRP) near Whittier, California (Figure 1). This study used a WEDECO advanced oxidation process (AOP) pilot unit for ozonation, a Leopold filter pilot and an Intuitech filter pilot for biofiltration, and Trussell Technologies soil columns for SAT. Additional details regarding the pilot plant feed water and the pilot equipment are discussed below.


Figure 1. San Jose Creek Water Reclamation Plant in Whittier, CA.

2.2.1 Feed Water

SJCWRP has two sides, east and west, that treat municipal wastewater separately using primary treatment, secondary treatment with nitrification and denitrification, and tertiary treatment with filtration and disinfection with free chlorine and chloramine. SJCWRP West provided unfiltered secondary effluent for this study.

The first two months of startup overlapped with a WateReuse Research Foundation (WRRF) project entitled, “Equivalency of Advanced Treatment Trains for Potable Reuse.” In April and May of 2014, microfiltration (MF) treated the secondary effluent before ozonation and biofiltration. MF significantly reduced turbidity but only reduced TOC and ultraviolet light absorbance at 254 nm (UVA) by approximately 15%. These changes to water quality were expected to have a minimal effect on biofiltration data and little impact of the study results since the MF pilot unit was removed from the treatment train at the end of May 2014 and Test 1 did not begin until three weeks later.

2.2.2 Pilot Equipment

This project used a WEDECO AOP pilot unit, a Leopold biofiltration pilot unit, an Intuitech biofiltration pilot unit, and two of Trussell Technologies’ soil columns. The WEDECO and Leopold pilot units were operating since June 2013 as part of a WRRF pilot study of direct potable reuse. The WRRF project required treatment by the Econity MF pilot unit before


ozonation until the end of May. After May, the MF pilot unit was no longer part of this treatment train. The soil columns were operating since August 2013 using ozonated secondary effluent. However, the water source for the soil columns was changed to ozone and biofiltration effluent to suit the needs of this project. More details about the pilot equipment are provided below.

2.2.3 WEDECO AOP Pilot Unit

Ozone was generated using a WEDECO AOP pilot unit (Charlotte, NC), housed inside a shipping container (Figure 2). This pilot unit included an oxygen generator, ozone generator, , two different ozone dissolution systems (side stream injection and direct gas injection with plug flow reactor), ozone destruct system, ultraviolet light (UV) reactor, hydrogen peroxide chemical feed system for advanced oxidation with ozone or UV, and respective instrumentation and controls. The ozone generator had a capacity of 3.2 lbs/day. The maximum applied ozone dose for the side stream ozone system was 13 mg/L for a water flow of 20 gpm. A series of contactors after the side stream injector provided 35 gallons of residence volume, or 2 minutes and 20 seconds of HRT at a flow of 15 gpm.

Figure 2. Interior of WEDECO AOP pilot unit.


2.2.4 Leopold Filter Pilot Unit

Leopold (Zelienople, PA) provided a filter pilot unit with blowers, pumps, a control panel and automatic backwashing for biofiltration (Figure 3). The single filter column, designated Filter Column 1 (FC-1) had a cross-sectional area of 4 ft2 and contained 5 ft of used Calgon F-300 GAC from a filter that was in need of regeneration at Upper Occoquan Service Authority in Centreville, VA. This pilot unit was operating with this GAC since June 2013 and was not expected to have any significant adsorptive capacity remaining. A startup period was not required for this pilot unit because it already had a mature biofilter from the ongoing WRRF project. Online instruments included flow, head loss across the filter media, influent and effluent turbidity, and influent and effluent dissolved oxygen. Data from these instruments were stored in comma delimited text files for analysis. Filter backwashes could be triggered manually or automatically based on head loss across the filter media, runtime and turbidity. The BAC filter was also capable of performing hydraulic bumps, which resemble backwashes of short duration that could mitigate gas binding in the filter media.


Figure 3. Leopold biofiltration pilot unit.

2.2.5 Intuitech Biofiltration Pilot Unit

A pilot unit (Figure 4) consisting of four filter columns with individual feed pumps was leased from Intuitech (Salt Lake City, UT). Each 6-inch diameter filter operated independently of the others, although they shared the air scour and backwash systems. When in automatic mode, backwashing was initiated on high runtime, run volume, headloss, or effluent turbidity limits entered in the equipment process screens. Online instrumentation included flow, head loss across the media, and effluent turbidity. Data from these instruments were stored on the pilot unit and downloaded weekly to monitor performance.


Figure 4. Intuitech biofiltration pilot unit with four filter columns.

Filter Column 2 (FC-2) and Filter Column 3 (FC-3) of the Intuitech filter pilot were filled to a depth of 6 feet with custom municipal reactivated FILTRASORB 300 GAC (Calgon Carbon, Pittsburgh, PA). This reactivated GAC had a lower iodine number than virgin GAC of the same type (500 mg/g versus 900 mg/g, respectively). Therefore, it was expected to take less time to exhaust the adsorptive capacity of the GAC. Filter Column 4 (FC-4) and Filter Column 5 (FC-5) were filled to a depth of 6 feet with anthracite coal with an effective size of 1.0 to 1.1 mm and an uniformity coefficient of 1.5 (George L. Throop, Pasadena, CA).

2.2.6 Soil Columns

Soil aquifer treatment were modeled using two soil columns operating in series (Figure 5) at Trussell Technologies’ workshop in Pasadena, CA. Soil Column 1 (SC-1) had a diameter of 8 inches and Soil Column 2 (SC-2) had a diameter of 6 inches. Soil was collected from a quarry located in the same aquifer as the spreading grounds that would be used for groundwater recharge by Upper San Gabriel Valley Municipal Water District. The soil was sieved to remove material larger than 2 mm before it was loaded into columns that were partially filled with water. The columns were tapped with a rubber mallet to improve compaction and release trapped air as 10 feet of soil were added to each column by the handful.


Figure 5. Soil columns in Trussell Technologies’ workshop in Pasadena, CA. SC-1 (8-inch diameter) and SC-2 (6-inch diameter) were used in this study. Both columns contained 10 feet of soil and were wrapped in plastic to minimize algae growth.

Effluent from the Leopold pilot unit was collected from the pilot plant at SJCWRP, transported to the workshop, stored in a refrigerated reservoir, and pumped into the bottom of SC-1. The effluent from the top of SC-1 was then pumped into the bottom of SC-2. Each soil column operated in an upward flow configuration with an individual HRT of 28 days and a combined HRT of 56 days since SC-1 fed SC-2. The flow rates for SC-1 and SC-2 was kept at 0.29 gal/day and 0.16 gal/day, respectively.

Before soil column testing started, the soil columns were flushed with effluent from the Leopold filter pilot to remove water from a previous soil column study. Flushing was accomplished by pumping the Leopold filter effluent into the bottom of the columns at a flow rate of 1.74 gal/day for SC-1 and 0.96 gal/day for SC-2 for 10 days. These flow rates provided a 5-day HRT for the columns and two volume exchanges were achieved over the 10-day flushing period.


2.2.7 ECONITY MF Pilot Unit

ECONITY (Torrance, CA) provided the MF pilot unit (Figure 6), which used a pressurized PVDF membrane module with a nominal pore size of 0.1 m and a surface area of 969 ft2 (PF-90M, ECONITY, Torrance, CA). The MF unit operated at flux of 30 to 40 gfd. Operation of the MF pilot included daily chemical-enhanced backwashes with a 200-mg/L chlorine solution and monthly clean-in-place with a 1000-mg/L chlorine solution.

Figure 6. Econity MF pilot unit.

2.3 Water Quality Analyses

Pilot plant data was collected using online instrumentation and water quality grab samples. Table 1 shows important parameters each pilot unit measured continuously. These data were downloaded and graphed weekly to help evaluate process performance. The soil columns did not have any online instrumentation. The collection frequency of water quality grab samples depended on the parameter being measured and the sample location. Table 2 shows the sampling frequency for TOC, UVA, turbidity, pH, bromide, bromate, NDMA, TOrC and total coliform bacteria. TOC, UVA, turbidity, and total coliform bacteria were measured in Trussell Technologies’ laboratory in Pasadena, CA. NDMA and bromate were measured because they


were potential disinfection byproducts of the ozonation of wastewater effluent, and bromide was measured because it is a precursor in the formation of bromate. Total coliform bacteria was measured using the membrane filtration method (SM 9222b). Eurofins Eaton Analytical (Monrovia, CA) measured NDMA, bromate, and bromide. TOrCs, such as pharmaceuticals and personal care products (PPCPs), artificial sweeteners, and fire retardants (Table 3), were analyzed at LACSD’s laboratory using a modified version of the United States Environmental Protection Agency Method 1694.

Table 1. Pilot unit parameters measured continuously by online instrumentation.

Monitoring Location

Pilot Unit

Wedeco Leopold Intuitech

Influent

Flow Dissolved oxygen

Flow Temperature Flow

UVT Turbidity

Effluent UVT Dissolved oxygen

Turbidity Turbidity

Other

% ozone in feed gas EBCT Filtration rate

% ozone in off-gas Head loss Head loss

Applied ozone dose Run time Run time

Dissolved ozone residual

Table 2. Sampling frequency for TOC, UVA, turbidity, pH, bromide, bromate, TOrC and total coliform bacteria.

Sample Location

Analyte

TOC UVA Turbidity pH Bromide Bromate TOrC Total

Coliform

Ozone Inf 2/week 2/week 2/week 1/week 1/test 1/test 1/test 1/test

Ozone Eff 2/week 2/week 2/week 1/week --- 1/test 1/test 1/test

FC-1 Eff 2/week 2/week 2/week 1/week --- --- --- 1/test

FC-2 Eff 2/week 2/week 2/week 1/week --- --- 1/test 1/test

FC-3 Eff 2/week 2/week 2/week 1/week --- --- 1/test 1/test



SC-1 Eff 1/week 1/week 1/week 1/week --- --- --- 1/test

SC-2 Eff 1/week 1/week 1/week 1/week --- --- --- 1/test


Table 3. List of TOrCs analyzed by LACSD’s laboratory.

Chemical Name Chemical Type Method Reporting Limit (ng/L)

4-Nonylphenol PPCP 25

4-tert-octylphenol PPCP 5

Acesulfame-K Artificial Sweetener 50

Acetaminophen PPCP 10

Atenolol PPCP 10

Atorvastatin (Lipitor) PPCP 10

Azithromycin PPCP 10

Bisphenol A Used in resins 10

Caffeine PPCP 10

Carbamazepine PPCP 10

Carisoprodol PPCP 10

DEET Pesticide 10

Diazepam PPCP 10

Diclofenac PPCP 10

Dilantin (Phenytoin) PPCP 10

Erythromycin-H2O PPCP 10

Fipronil Pesticide 2

Fluoxetine PPCP 10

Furosemide PPCP 10

Galaxolide PPCP 50

Gemfibrozil PPCP 10

Ibuprofen PPCP 10

Iohexol PPCP 100

Iopromide PPCP 10

Meprobamate PPCP 10

Metoprolol PPCP 10

Naproxen PPCP 10

Nonylphenol diethoxylate Surfactant 25

Nonylphenol monoethoxylate Surfactant 25

Octylphenol monoethoxylate Surfactant 25

Octylphenol diethoxylate Surfactant 25

Primidone PPCP 10

Propranolol PPCP 10

Sucralose Artificial Sweetener 40

Sulfamethoxazole PPCP 10

TCEP Flame Retardant 10

TCPP Flame Retardant 20

TDCPP Flame Retardant 20

Tonalide PPCP 50

Triclocarban PPCP 10

Triclosan PPCP 10

Trimethoprim PPCP 10


2.4 Test Conditions

The pilot study was separated into 5 testing periods (Table 4). The EBCT of FC-1, which was operating as a biofilter for the WRRF project since June 2013, was set at 19 minutes for the entire pilot study. An EBCT of 19 minutes was used because the flow set point for the Leopold pilot unit had to be entered in whole numbers. A flow of 8 gpm provided an EBCT of 19 minutes, which was as close as the Leopold pilot unit could get to an EBCT of 20 minutes. FC-2 and FC-4 had EBCTs of 20 minutes, and FC-3 and FC-5 had EBCTs of 10 minutes. The HRTs of SC-1 and SC-2 were 28 days for the duration of testing. As noted in Table 4, Test 4 was not completed because of pilot equipment failures. Bromide, bromate, NDMA, TOrC and total coliform bacteria samples were not collected, but other general water quality samples (e.g., TOC, UVA and turbidity) were collected during Test 4 and are discussed in this report.

Table 4. Pilot test conditions for the ozone system, filter columns, and soil columns.

Test Details

Testing Period

Startup Test 1 Test 2 Test 3 Test 41 Test 5

Dates Start 28-Mar 19-Jun 7-Jul 28-Jul 25-Aug 9-Oct

End 19-Jun 7-Jul 28-Jul 25-Aug 9-Oct 21-Oct

Average Transferred O3 Dose (mg/L)

4.2 4.7 6.2 7.9 8.2 5.0

Target O3:TOC ratio 0.75 0.75 1.00 1.25 1.50 1.00

Filter Column EBCT (min)

FC-1 19 19 19 19 19 19

FC-2 20 20 20 20 20 20

FC-3 10 10 10 10 10 10

FC-4 20 20 20 20 20 20

FC-5 10 10 10 10 10 10

Soil Column HRT (d)

SC-1 28 28 28 28 28 28

SC-2 28 28 28 28 28 28 1 Test 4 was not completed due to time restrictions caused by pilot equipment failures.

The O3:TOC ratio was the primary variable that changed between tests. During Test 1, the target O3:TOC ratio was 0.75, which corresponded with an average transferred ozone dose of 4.2 mg/L. At the maximum target O3:TOC ratio of 1.50 (Test 4), the transferred ozone dose averaged 8.2 mg/L. Adjustments to the transferred ozone dose were made at least once per week using data from TOC grab samples. At the beginning of each test, the transferred ozone dose was adjusted to satisfy the new O3:TOC ratio based on the most recent TOC data.

During startup and Tests 1 to 4, ozone was added to either MF-filtered secondary effluent (startup and Test 1) or secondary effluent without filtration (Tests 2, 3 and 4). The startup period was used for the startup, commissioning and optimization of the Intuitech filter pilot and to allow the biofilter to ripen on the reactivated GAC and anthracite coal filter media. Five-


gallons of effluent from FC-1 were collected every two weeks and transported to the workshop to feed the soil columns. Water remaining in the reservoir feeding SC-1 was drained and replaced with fresh filter effluent. Figure 7 shows the process flow diagram for the pilot plant from startup through the end of Test 4. This configuration coupled with changes in the ozone dose allowed for the following evaluations to be performed:

1. Comparison of GAC vs anthracite coal for biofiltration. 2. Importance of O3:TOC ratio on biofilter performance. 3. Effect of longer EBCT on biofiltration performance. 4. Comparison of 28-day HRT vs 56-day HRT for SAT after ozone and biofiltration.

Figure 7. Process flow diagram showing the configuration of the pilot plant during startup and Tests 1 to 4. FC-1 is the filter column of the Leopold pilot unit and FC-2, FC-3, FC-4 and FC-5 are the filter columns of the Intuitech pilot unit.

The configuration of the unit processes was modified during Tests 5 to see the effect of extended EBCTs (Figure 8). During Test 5 the ozone pilot unit was feeding ozonated secondary effluent to FC-1. Effluent from FC-1 was then supplied to the remaining filter columns. All filter columns operated at the same EBCTs as the previous tests.


This approach allowed the simultaneous comparison of 19-minute, 29-minute and 39-minute EBCTs for the biofilters. Effluent from FC-2, which had a total EBCT of 39 minutes, was the water source for the soil columns. That sequence of unit processes was important to determine the lower limit of TOC removal by biofiltration and the additional benefit of SAT when TOC was already significantly reduced by biofiltration. Here is a complete list of the evaluations made during Tests 5:

1. Comparison of GAC and anthracite coal for biofiltration. 2. Importance of O3:TOC ratio on biofilter performance. 3. Effect of extended EBCTs on water quality. 4. Comparison of 28-day HRT vs 56-day HRT for SAT after ozone and biofiltration. 5. The effect of a 39-minute EBCT on overall TOC removal.

Figure 8. Process flow diagram showing the configuration of the pilot plant during Test 5. FC-1 is the filter column of the Leopold pilot unit and FC-2, FC-3, FC-4 and FC-5 are the filter columns of the Intuitech pilot unit.


The comparison of GAC to anthracite, the evaluation of the importance of the O3:TOC ratio and the effect of EBCT on biofilter effluent water quality was similar to Tests 1 to 3. The 28- to 56-day lag in sample collection from the soil columns means soil columns samples from previous tests were collected during Tests 5. For example, the duration of Test 3 was July 31 to August 28. The 28-day HRT through the soil columns resulted in water from Test 3 being collected at the SC-1 effluent during late September and at SC-2 effluent during late October. Test 5 samples from the effluent of SC-1 were collected on November 25. Soil column operation was extended until the end of December to permit the collection of SC-2 effluent for Test 5 (56-day HRT).

2.5 Bromate Formation Control

Ozonation of water containing bromide can form bromate, which has a maximum contaminant limit (MCL) of 10 g/L. During the WRRF pilot study, the bromate concentration after ozonation exceeded the MCL with O3:TOC ratios of about 0.9. The corresponding TOC reduction by biofiltration at an EBCT of 21-min was approximately 40%. During this study, higher O3:TOC ratios were tested to improve TOC removal by biofiltration, which was expected to cause higher bromate formation. The WRRF pilot study also showed bromate was not removed by BAC, and bromate removal during SAT has not been established. Therefore, this study considered the chloramine-ammonia method (Wert et al., 2007a) as a possible approach to minimize bromate formation during ozonation. The chlorine-ammonia method adds free chlorine to oxidize bromide to bromine, and then adds ammonia to transform bromine into bromamine. Bromamine effectively sequesters the bromide because bromamine does not react with ozone to form bromate (MWH, 2005; Wert et al., 2007a).

The chlorine-ammonia method was evaluated using the same configuration as Test 5. Ozone concentration was adjusted to have a minimum ozone concentration-time (Ct) of 2.5 using different chlorine and ammonia residuals (Table 5). The Ct value was chosen to meet the requirement for 1.0-log Crypto inactivation credit as listed in the US EPA table for ozone disinfection (US EPA, 2010). Sodium hypochlorite was added 30 seconds upstream of the ammonia injection point, which was added as ammonium sulfate. The reaction between ammonia and bromine is very fast and was facilitated by a static mixer located before the side stream for ozone injection (Figure 9).

Table 5. Test conditions for the chlorine-ammonia method of bromate formation control.

Cl2-NH3 Experiment

Target O3 Ct (min-mg/L)

Cl2 residual (mg/L)

NH3-N residual (mg/L)

1 2.5 0 0

2 2.5 0 0.5

3 2.5 1 0

4 2.5 1 0.7

5 2.5 2 0

6 2.5 2 0.9

7 2.5 4 0

8 2.5 4 1.3

9 2.5 8 0

10 2.5 8 2.1


Figure 9. Process flow diagram of the WEDECO AOP pilot unit showing chlorine and ammonia injection points.

Chlorine residuals were measured after the pump located right after chlorine injection point, using the Hach DPD free chlorine reagent powder pillow kit (Hach method 8021). Ammonia residuals were measured after the static mixer before ozone injection using the Hach AmVer™ Salicylate Test 'N Tube™ kit (Hach method 10023). When the desired chlorine and ammonia residuals were achieved, influent samples were collected. After 4-5 minutes, effluent samples were collected to account for the residence time in the ozone system. Table 6 shows all the parameters measured during chlorine-ammonia testing.

Table 6. Parameters measured from the ozone influent before any chemical addition and the effluent of the ozone contactors during chlorine-ammonia testing.

Cl2-NH3 Experiment

Bromide Bromate NDMA TOC

O3 Ct Inf Eff Inf Eff Inf Eff Inf Eff

1

2

3

4

5

6

7

8

9

10

P um p I nl et

NH4

O3

Mixer

NaOCl Pump

Mi x er Sample


3 COST SUMMARY

Table 7 compares the original budget in the Agreement with the actual expenses for each task through January 31, 2015 (including costs incurred by Stetson Engineers). Other than two tests that were not completed during Task 4 (see Section 4 for more details), the tasks were completed successfully. Task 5 is still ongoing and will be finished during the first quarter of 2016. To date, Upper San Gabriel Valley Municipal Water District has been reimbursed by the Metropolitan Water District of Southern California for eligible costs incurred during 2014 quarter one and quarter two.

Table 7. Original budget vs actual expenses by task, including the amount remaining for each task and the project as of January 31, 2015.

Task No. Task Name Original Budget Actual Expenses

Amount Remaining

1 Comprehensive Literature Review $10,000.00 $9,969.95 $30.05

2 Development of a Test Plan $16,000.00 $15,974.00 $26.00

3 Procurement of Pilot Equipment and GAC $108,000.00 $107,996.38 $3.62

4 Pilot Testing of O3/BAC and Soil Columns $136,000.00 $136,032.50 -$32.50

5 Project Management and Reporting $30,000.00 $29,359.80 $640.20

Totals $300,000.00 $299,332.63 $667.37

4 SCHEDULE SUMMARY

Table 8 compares the planned schedule in the Agreement and the actual schedule highlighting any differences that occurred. Other than Test 4 final sampling and Test 6, all the other tasks were accomplished. Test 1 sampling was delayed because the performances of the Intuitech filter columns were still stabilizing. Test 1 samples were collected on July 7 instead of May 23, as initially planned. For this reason the duration of each test was reduced from 30 days to 21 days. Test 2 samples were collected on July 31 and no problems were encountered during this testing period. Collection of Test 3 samples was delayed until August 25 due to technical problems at the site. Test 4 samples were scheduled to be collected on September 8, but were not collected due to time restrictions caused by pilot equipment failures that occurred during the months of August and September. Also on September 24, a plant power outrage caused damage to the ozone generator, which required repair by the equipment vendor. The generator resumed operation the first week of October when Test 5 commenced. No problems were encountered during Test 5 but testing period was shorter than initially planned, lasting only 12 days. Test 6 was not performed because the technical problems during the month of September delayed the start of Test 5 and the budget for Task 4 only covered pilot testing through the end of October.


Table 8. Planned schedule vs actual schedule.

2016

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1

Planned scheduleActual scheduleNot performed

In progress

Not completed because of pilot system failureduring Test 4

No problem encountered



Intuitech filter columns stabilization was longer than initially anticipated


Sample collection was postponed for technicalproblems at the site

Test 3

Test 4

Test 5

Test 6

Collection was delayed because filter columns were stabilizing

Test 5 was shorter because of pilot system failure during Test 4

Not completed because of pilot system failure

5Project Management

and Reporting

Test 14a

Test 24b

4c

4d

4e

4f

Development of a Test Plan

Procurement of Pilot Equipment and GAC

Pilot Testing of O3/BAC and Soil Columns

1

2

3

4

2014 2015Task no.

Task Name Notes

Comprehensive Literature Review

5 PROJECT RESULTS AND ANALYSIS

Water quality analyses included TOC, UVA and turbidity data, but only TOC data are used to evaluate treatment train performance in this report. This approach was taken because the California groundwater recharge regulations limit the TOC content of wastewater origin to 0.5 mg/L, making TOC the most important of these water quality parameters. However, tables with average TOC, UVA and turbidity data are in the Appendix for reference. The average O3:TOC ratios for each test varied slightly from the target O3:TOC ratios as shown in Table 9. The discussion in the following sections will reference the target O3:TOC ratios.

Table 9. Target O3:TOC ratios compared to the average O3:TOC ratios for each test.

Test

O3:TOC Ratio

Target Average

1 0.75 0.77

2 1.00 0.97

3 1.25 1.30

4 1.50 1.47

5 1.00 0.88


5.1 Comparison of GAC vs Anthracite Coal for Biofiltration (Tests 1 to 5)

One of the purposes of the pilot test was to compare GAC and anthracite filter media at different O3:TOC ratios and the same EBCT. These comparisons evaluated TOC data using the Intuitech filter columns with different filter media and the same EBCT: FC-2 (GAC) vs FC-4 (anthracite) at a 20-min EBCT and FC-3 (GAC) vs FC-5 (anthracite) at a 10-min EBCT. As shown in Figure 10, both GAC filters exceeded the performance of the anthracite filters in terms of TOC percentage removal, with FC-2 removing approximately 45% more than FC-4 and FC-3 removing 30% more than FC-5. The difference in performance is due to the adsorptive capacity of the GAC and its ability to regenerate biologically compared to the anthracite filters (Thiel et al., 2006). The results are in line with other pilot studies that compared TOC removal efficiencies in GAC and anthracite columns. Seip (2014) found TOC removal at an EBCT of 12.7 minutes ranged from 20 and 81% in the BAC columns and an average of 0% from the biological filters with anthracite media.

Figure 10. TOC removal during testing with FC-2, FC-3, FC-4 and FC-5. No TOC data is shown for September 29 to October 6 because the ozone system was offline for repairs.

TOC removals during Test 5 were lower than they were during the previous tests because these filter columns were operating downstream of FC-1, which removed an average of 33% of TOC. Removal after FC-1 was expected to be lower because much of the easily metabolized TOC


would already be gone, leaving behind organic matter that was less susceptible to biological treatment. A more detailed discussion of TOC removal during Test 5 is provided in Section 5.5.

5.2 Importance of O3:TOC Ratio on Biofilter Performance (Test 1 to 4)

The effect of the ozone dose was determined by monitoring changes to TOC removal by BAC as the target O3:TOC ratio increased from 0.75 to 1.50 during the Tests 1 to 4 (Figure 11). These data showed the O3:TOC ratio had no impact on TOC removal through FC-1. The trends for the remaining filters indicated improved TOC removal as the ratio increased from 0.75 to 1.00. However, increases above 1.00 caused a decline in TOC removal by those filters. Ozone residual measurements showed no evidence of an ozone residual entering any of the filters, minimizing the possibility of an ozone residual affecting biofilter performance. These results indicated the optimal O3:TOC ratio for maximizing TOC removal for FC-2, CF-3, FC-4 and FC-5 was approximately 1.00. It is not clear why this was different than FC-1, which had older GAC that had been operating in another pilot study for 9 months before this project began.

Figure 11. Average TOC removal by the filter columns at different O3:TOC ratios.

5.3 Effect of EBCT on Biofiltration Performance (Tests 1 to 4)

The effect of EBCT was investigated by comparing the Intuitech filter columns with the same filter media and different EBCT: FC-2 vs FC-3 for GAC and FC-4 vs FC-5 for anthracite


(Figure 12). Increasing EBCT from 10 to 20 minutes had little to no effect on TOC removal for the anthracite columns. However, the same increase in EBCT increased TOC removal by BAC about 20%. These results indicated EBCTs for anthracite filters exceeding 10 min would not be beneficial, but higher EBCTs for BAC could achieve higher TOC removal.

Figure 12. Comparison of the average TOC removals by the columns with the same filter media but different EBCTs.

5.4 Comparison of 28-Day HRT to 56-Day HRT for SAT after Ozone and Biofiltration (Tests 1 to 5)

FC-1 effluent produced the water that fed the soil columns for evaluating SAT performance after 28-day and 56-day HRTs. FC-1 was chosen to feed the soil columns because it already had a mature biofilter with exhausted GAC from 9 months of operation before this pilot study began. SC-1 provided the first 28 days of SAT and was followed by SC-2, which provided the next 28 days of SAT. Combined, the HRT through both soil columns was 56 days. TOC removal during Test 2 could not be calculated because a sampling error did not allow the measurement of the influent TOC for SC-1. As shown on Figure 13, SC-1 removed an average of 48% of TOC during Test 1 and 35% of TOC during Tests 3, 4 and 5. TOC removal by SC-2 was initially low (6% in Test 1) but gradually increased to 26% in Test 5. These results suggest there was a maturation process occurring as the microorganisms in SC-2 adjusted to the quality of the water it was receiving. The decline of TOC removal by SC-1 from Tests 1 to 3 also left relatively more


TOC for SC-2 to remove, which could account for the increased percent removal by SC-2 during later tests. In spite of the increasing TOC removal by SC-2, most of the TOC removal occurred in SC-1, which is consistent with research showing SAT achieved most of its TOC reduction within days rather than weeks (Rauch-Williams et al., 2010; Drewes and Fox, 1999; Fox et al., 2006).

Figure 13. TOC reduction by the soil columns during Tests 1, 3, 4 and 5.

While TOC removal by SC-1 and SC-2 varied between these tests as described above, the overall removal after a 56-day HRT ranged from 50 to 60%. Tests 1, 3 and 4 had target O3:TOC ratios of 0.75, 1.25 and 1.50, respectively, and the increasing O3:TOC ratio did not have a consistent effect on the overall TOC removal. Test 5, which had a total BAC EBCT (39 min) that approximately doubled the BAC EBCT of the other tests (19 min), showed the best combined TOC removal by the soil columns. This result is attributed to the improving TOC removal by SC-2 because the performance of SC-1 did not improve during Tests 3 to 5.

5.5 The Effect of a 39-Minute EBCT on Overall TOC Removal (Test 5)

During Test 5, FC-1 and FC-2 were operated in series to produce a BAC effluent with a combined EBCT of 39 minutes. This water was fed to the soil columns to evaluate the impact of a longer EBCT on overall TOC removal by the treatment train of ozone, BAC and SAT. The most relevant comparison would be Tests 2 and 5 because they operated with the same O3:TOC ratio for the ozone system. However, there was a sampling error for the TOC measurement of SC-1 influent during Test 2, which prevented this comparison from being


made. However, comparing Test 5 to Tests 1, 3 and 4 still permits the evaluation of the effect of the longer EBCT on overall TOC removal.

TOC removal by the full treatment trains ranged from a low of 65% in Test 3 to a high of 78% during Test 5 (Figure 14). TOC removal by ozonation (3 to 6%) and FC-1 (31 to 39%) was fairly constant throughout testing. As shown in Figure 13 and discussed in Section 5.4, TOC reduction by the soil columns varied from 50 to 60%. When combining removals for the whole treatment train in Tests 1 to 3, TOC reduction varied from 65 to 69%. These results showed no trend that correlated with the increase in the O3:TOC ratio from 0.75 in Test 1 to 1.50 in Test 4. However, TOC removal during Test 5 was 78%, which was noticeably higher than the previous tests. This better performance was attributed to the improved TOC removal by SC-2 (Figure 13) and the additional TOC removal from the extra 20 min of EBCT provided by FC-2 (Figure 14). TOC removal by FC-2 did not match FC-1 (26% vs. 35%) even though they had similar EBCTs (20-min vs. 19-min), but the longer EBCT further reduced TOC without affecting the TOC-removal efficiency of the soil columns. Ultimately, that resulted in a final product TOC concentration for Test 5 that averaged 1.4 mg/L compared to final product TOC concentrations that ranged from 1.7 to 2.0 mg/L.

Figure 14. Total TOC removal for the complete treatment train in each test.

5.6 Disinfection byproducts (DBPs)

NDMA and bromate were ozonation DBPs measured on the last day of each testing period. Bromide concentration in the ozone influent was also sampled because bromate forms when ozone reacts with bromide. NDMA was measured regularly in the effluent of FC-2 and FC-3 to


evaluate the effect of EBCT on BAC removal of NDMA. Special sampling for NDMA in the effluents of FC-1, SC-1 and SC-2 was conducted as part of Test 2 to evaluate the fate of NDMA through the soil columns. During Test 5, NDMA was also collected from FC-1 effluent because it was operating before FC-2 and FC-3 to test the effect of longer EBCTs on BAC performance.

5.6.1 NDMA

One of the most concerning DBPs formed during ozonation of wastewater is NDMA (Stalter et al, 2010). NDMA has been classified by the US EPA as likely a human carcinogen (US EPA, 2008) with a cancer risk of 10-6 at 0.7 ng/L in drinking water (US EPA, 2001). The California notification level for NDMA is 10 ng/L. The exact mechanism of NDMA formation during ozonation is still unknown. Some studies have shown NDMA formation due to the oxidation of dimethylamine (DMA) and dimethylsulfamide (DMS) (Andrzejewski et al., 2008; Schmidt and Brauch, 2008; von Gunten et al., 2010).

NDMA concentrations for Tests 1, 2, 3 and 5 are shown in Figure 15, with a blue line representing the California Division of Drinking Water (DDW) notification limit of 10 ng/L. Figure 16 shows the percentage of NDMA removed by FC-2 (20-min EBCT) and FC-3 (10-min EBCT) for Tests 1, 2, 3 and 5 and the percentage of NDMA removed by FC-1 (19-min EBCT) for Tests 2 and 5.

Figure 15. NDMA concentrations in the secondary effluent, ozone effluent and BAC effluent of FC-1, FC-2 and FC-3. The blue line shows the DDW notification limit of 10 ng/L. The concentration in the effluents of FC-2 and FC-3 were below the detection limit for Test 5.


Figure 16. NDMA percent removal by FC-2 and FC-3 during Tests 1, 2, 3 and 5 and by FC-1 during Tests 2 and 5. The maximum NDMA removal that could be demonstrated for FC-2 and FC-3 during Test 5 was limited to 86% by the NDMA concentration in FC-1 effluent (14 ng/L) and the detection limit (2 ng/L).

During Test 5, cumulative EBCTs after FC-1, FC-2 and FC-3 were 19 min, 39 min and 29 min, respectively. NDMA concentrations in the secondary effluent varied from 50 to 95 ng/L, and concentrations after ozonation increased from 40 to 300 ng/L with no linear correlation between the O3:TOC ratio and NDMA formation (R2 = 0.01). For Test 1, the ozone effluent NDMA concentration was 390 ng/L, and FC-2 and FC-3 removed 92% and 98% of that, respectively. In Test 2, the ozone effluent NDMA concentration was 130 ng/L and removal by FC-1, FC-2 and FC-3 was 38%, 70% and 61%, respectively. SC-1 treated FC-1 filtrate, removing 95% of the remaining NDMA to lower the concentration to 4.1 ng/L after the 28-day HRT in the soil column. After another 28 days of SAT in SC-2, the NDMA concentration was below the detection limit of 2 ng/L. The attenuation of NDMA by SAT could have significant implications regarding the design of indirect potable reuse projects that include surface spreading for groundwater recharge by allowing treatment facilities to rely on SAT to remove a significant amount of NDMA from the treated water after spreading.

For Test 3, FC-2 and FC-3 reduced the NDMA concentration of 340 ng/L by 98% to 8.0 ng/L and 6.4 ng/L, respectively. For Test 5, FC-1 reduced the ozone effluent NDMA concentration of 160 ng/L to 14 ng/L, a decrease of 91%. FC-2 and FC-3, which were operating downstream of FC-1 to test EBCTs above 20 min, demonstrated at least 86% removal by lowering the NDMA concentration below the 2-ng/L detection limit. These data indicated BAC has the potential to reduce NDMA concentrations below the 10-ng/L notification limit and possibly below the detection limit depending on the initial NDMA concentration and the EBCT for the BAC process.


5.6.2 Bromate

Bromate is a potential human carcinogen with an MCL in drinking water of 10 g/L based on an annual average (US EPA, 2011). It can form during ozonation of bromide-containing waters through a series of reactions involving ozone and secondary oxidants such as hydroxyl and carbonate radicals (von Gunten, 2003). Research has shown bromate formation concentration increases with ozone dose (Wert et al., 2007b, Zimmermann et al., 2010), while formation is influenced by several factors: low pH and lower temperature are associated with lower bromate formation (MWH, 2005, Croue et al., 1996).

Figure 17 shows bromide concentrations in the secondary effluent and bromate concentrations after ozonation. Previous sampling never detected bromate in the secondary effluent so its initial concentration was assumed to be 0 µg/L. The average concentration of all bromide sampling was about 90 µg/L. For Tests 1 and 2, the bromate concentration was below the MCL and the O3:TOC ratios were 0.75 and 1.00, respectively. During Test 3, the O3:TOC ratio was 1.25 and the bromate concentration of 11 µg/L exceeded the MCL. During Test 5, the bromide concentration and the O3:TOC ratio was the same as Test 2 but bromate formation was 20 µg/L. Concentrations exceeding 10 µg/L indicate potential compliance challenges so bromate formation control testing by the chlorine-ammonia method was conducted

Figure 17. Bromide and bromate concentrations during Tests 1, 2, 3 and 5. The blue line depicts the bromate MCL of 10 µg/L.


5.6.3 Bromate Formation Control

The approach used for the chlorine-ammonia method to minimize bromate formation was described in Section 2.4. Figure 18 shows bromate formation after the sequential addition of sodium hypochlorite and ammonium sulfate at an average O3:TOC ratio of 0.94 and an average bromide concentration of 95 µg/L. Three of the four samples with this bromate formation control strategy had concentrations below the 10 µg/L MCL, showing the chlorine-ammonia method to be an effective approach to limiting bromate formation in a nitrified wastewater effluent. Due to the inconsistency of the results (i.e., high bromate with a 3 mg/L total chlorine residual), additional study would be required to develop a larger database for determining the total chlorine residual required to achieve sufficient bromate formation control to satisfy the bromate MCL under expected water quality conditions.

Figure 18. Bromate formation after chlorine-ammonia addition. The green line shows the bromate MCL of 10 µg/L.

5.7 TOrCs

Recent studies have suggested post-ozone activated carbon adsorption is effective in further removing TOrCs and reducing toxicity attributed to ozonation (Göbel et al., 2007, Reungoat et al., 2011, Stalter et al., 2011). TOrC monitoring during Tests 1, 2, 3 and 5 was performed before and after ozonation and in the effluent of FC-2 and FC3. FC-1 effluent was also analyzed


during Test 5 because FC-1 treated the water before FC-2 and FC-3 to test the effect of extended EBCTs on BAC performance. Tables 10 to 13 show TOrCs that were detected in the ozone influent and the effluent of subsequent unit processes. TOrCs that were never detected in the ozone influent are not listed in these tables but can be found in the Appendix in Tables A5 to A8, which display all the results for the TOrC analyses. No Test 4 TOrC data are available because pilot equipment problems prevented sample collection during that test. The columns with anthracite coal (FC-4 and FC-5) were not included in this portion of the study.

Table 10. Summary of TOrCs not removed by ozonation and BAC filtration during Test 1.

O3 Influent O3 Effluent FC-2 Effluent (20-min EBCT)

FC-3 Effluent (10-min EBCT)

4-Nonylphenol 4-Nonylphenol

4-tert Octylphenol 4-tert Octylphenol

Acesulfame-K Acesulfame-K Acesulfame-K Acesulfame-K

Atenolol

Azithromycin

Carbamazepine

Carisoprodol Carisoprodol Carisoprodol Carisoprodol

DEET DEET DEET DEET

Diclofenac

Dilantin (Phenytoin) Dilantin (Phenytoin)

Erythromycin-H2O

Fipronil Fipronil

Fluoxetine

Furosemide

Galaxolide Galaxolide Galaxolide Galaxolide

Gemfibrozil

Ibuprofen

Iohexol Iohexol Iohexol Iohexol

Meprobamate Meprobamate Meprobamate Meprobamate

Metoprolol

Nonylphenol diethoxylate

Nonylphenol monoethoxylate

Octylphenol monoethoxylate

Primidone Primidone Primidone Primidone

Propranolol

Sucralose Sucralose Sucralose Sucralose

Sulfamethoxazole

TCEP TCEP TCEP TCEP

TCPP TCPP TCPP TCPP

TDCPP TDCPP TDCPP TDCPP

Tonalide

Triclocarban

Triclosan

Trimethoprim





4-Nonylphenol 4-Nonylphenol 4-Nonylphenol



Atenolol

Azithromycin

Carbamazepine

Carisoprodol Carisoprodol Carisoprodol

DEET DEET DEET DEET

Diclofenac


Erythromycin-H2O

Fipronil Fipronil Fipronil

Fluoxetine

Furosemide

Galaxolide Galaxolide Galaxolide

Gemfibrozil

Ibuprofen



Metoprolol

Naproxen

Nonylphenol diethoxylate Nonylphenol diethoxylate

Nonylphenol monoethoxylate Nonylphenol monoethoxylate

Octylphenol monoethoxylate Octylphenol monoethoxylate


Propranolol


Sulfamethoxazole Sulfamethoxazole

TCEP TCEP TCEP TCEP

TCPP TCPP TCPP TCPP


Tonalide Tonalide

Triclocarban Triclocarban

Triclosan

Trimethoprim





4-Nonylphenol

4-tert Octylphenol

Acesulfame-K Acesulfame-K

Atenolol

Azithromycin

Carbamazepine

Carisoprodol Carisoprodol Carisoprodol

DEET DEET DEET DEET

Diclofenac


Erythromycin-H2O

Fipronil Fipronil

Fluoxetine

Furosemide

Galaxolide Galaxolide

Gemfibrozil

Ibuprofen



Metoprolol

Nonylphenol diethoxylate

Nonylphenol monoethoxylate

Octylphenol monoethoxylate


Propranolol


Sulfamethoxazole

TCEP TCEP TCEP TCEP

TCPP TCPP TCPP TCPP


Tonalide

Triclocarban

Triclosan


Table 13. TOrC Concentrations (ng/L) measured during Test 5. EBCTs shown in the column headings represent the total EBCT at the effluent of the filter column.




4-Nonylphenol 4-Nonylphenol 4-Nonylphenol



Atenolol

Azithromycin

Carbamazepine Carbamazepine

Carisoprodol Carisoprodol Carisoprodol Carisoprodol Carisoprodol

DEET DEET DEET DEET DEET

Diclofenac

Dilantin Dilantin Dilantin Dilantin

Erythromycin-H2O

Fipronil

Fluoxetine

Furosemide

Galaxolide Galaxolide Galaxolide

Gemfibrozil

Iohexol Iohexol Iohexol Iohexol Iohexol

Meprobamate Meprobamate Meprobamate Meprobamate Meprobamate

Metoprolol Nonylphenol diethoxylate Nonylphenol monoethoxylate Octylphenol monoethoxylate

Primidone Primidone Primidone Primidone Primidone

Propranolol

Sucralose Sucralose Sucralose Sucralose Sucralose

Sulfamethoxazole Sulfamethoxazole Sulfamethoxazole Sulfamethoxazole

TCEP TCEP TCEP TCEP TCEP

TCPP TCPP TCPP TCPP TCPP

TDCPP TDCPP TDCPP TDCPP TDCPP

Tonalide

Triclocarban

Triclosan

Trimethoprim


Tables 10 to 13 indicate ozone removed to the detection limit an average of 59% of the TOrCs in the ozone influent. During Tests 1 to 3, FC-2 (20-min EBCT) and FC-3 (10-min EBCT) completely removed 38% and 31%, respectively, of the TOrCs in the ozone effluent. Total TOrC removal below the detection limit for Tests 1 to 3 was 70% for ozone and FC-2 and 67% for ozone and FC-3. Reduction in TOrC concentrations below the detection limit was slightly improved by higher EBCT during Tests 1 to 3, which tested EBCTs of 10 and 20 min. The same trend was not evident during Test 5, which tested EBCTs of 19, 29 and 39 min, suggesting complete removal of the more easily biodegradable chemicals was achieved with a 20-min EBCT. However, an analysis of Tables A5 to A8 in the Appendix showed longer EBCTs provide better removal of TOrCs not completely removed by ozone or BAC.

5.8 Total Coliform Bacteria

Total coliform bacteria are commonly used as an indicator of pathogenic bacteria with a wastewater origin. This parameter was measured at every step of the treatment train to determine its removal by ozonation, potential regrowth by biofiltration, and fate during SAT. Total coliform concentrations are shown in Figure 19, with log removal values (LRVs) for each unit process listed in Table 18. Positive LRVs indicate removal and negative LRVs indicate regrowth. Ct values (mg-min/L) calculated from the ozone residuals in the contactor on the day of total coliform sampling were 1.5 for Test 1, 0.95 for Test 2, 1.7 for Test 3 and 2.0 for Test 5.

Figure 19. Total coliform bacteria concentrations in the ozone influent and effluent of each subsequent unit process. The concentration after SC-2 was only measured during Test 1 because the feed to SC-2 (SC-1 effluent) was always below the detection limit.


Table 18. Total coliform bacteria LRV for the unit processes in each test. Positive LRVs indicate removal and negative LRVs indicate regrowth. The LRV for SC-2 could not be calculated in Test 1 because the concentration of total coliform bacteria after SC-1 was below the detection limit. Measurements in SC-2 effluent were not made after Test 1 because the concentration in the SC-1 effluent was always below the detection limit.

Test O3 Eff FC-1 FC-2 FC-3 FC-4 FC-5 SC-1 SC-2

1 2.01 0.53 0.04 0.04 0.07 -0.35 ≥2.41 ---

2 2.61 -0.90 -0.08 -0.99 -1.41 -1.41 ≥4.09 NM

3 2.73 -1.11 -0.73 -1.15 -0.64 -1.04 ≥3.29 NM

5 3.56 0.10 0.03 0.11 0.05 0.14 ≥2.13 NM

NM = not measured

LRVs for ozone disinfection ranged from 2.01 to 3.56. After ozonation, there was approximately 1 log of regrowth of total coliform bacteria through the filters during Tests 2 and 3, but an average of no regrowth during Test 1. Test 5, which placed FC-1 before the other filter columns, showed small declines in total coliform bacteria concentrations through each filter. These results show no specific pattern to the total coliform bacteria concentrations after biofiltration that could be linked to the variables examined in this study (i.e., media type, EBCT.or O3:TOC ratio. Notably, total coliform concentrations after SC-1 were always below the detection limit, even with total coliform concentrations in the source water (FC-1 effluent) exceeding 104 CFU/1000 mL during Test 2. The concentration in SC-2 effluent was below the detection limit in Test 1. In the subsequent tests, SC-2 effluent was collected but not analyzed because the SC-1 effluent samples were always below the detection limit.

6 CONCLUSIONS

The primary objective of this project was to investigate the effect of several variables on TOC removal by a treatment train of ozone, biofiltration and SAT that treated a nitrified and partially denitrified secondary effluent. These variables included the O3:TOC ratio, filter media type (GAC vs. anthracite), biofilter EBCT, and the HRT of SAT. The main driver for this optimization was TOC minimization to reduce the amount of blend water that would be required to satisfy the California groundwater recharge regulation that limits the municipal wastewater contribution to no greater than 0.5 mg/L of TOC in the groundwater over a 20-week running average. Unless treatment prior to groundwater recharge includes reverse osmosis membranes, satisfying this requirement is typically not possible without blending with other water sources, such as storm water runoff or imported water. However, storm water runoff is only available in California during the raining season (typically November to April) and imported water is expensive and unreliable. Therefore, maximizing TOC removal before accounting for blending with other source waters is necessary to reduce the cost of this indirect potable reuse strategy.


This research demonstrated biofiltration was better at TOC removal when using GAC media than it was with anthracite media. Additionally, the average TOC removal during Tests 1 to 4 was increased from 34% to 44% when the EBCT was lengthened from 10 min to 20 min. A longer EBCT of 39 min during Test 5 was able to increase the average TOC removal by BAC to 51%. Anthracite media did not have the same sensitivity to EBCT, with TOC removal averaging 23% and 24% at EBCTs of 10 and 20 min. Over the range of O3:TOC ratios tested during this study (0.75 to 1.50), there was not a consistent affect on biofilter performance, regardless of filter media type. However, the step increase from 0.75 to 1.00 did show a significant improvement in TOC removal for all filters, whereas further increases had no effect. These results suggested a O3:TOC ratio of 1.00 would provide optimal TOC removal. For SAT, the first soil column (28-day HRT) reduced the TOC in the feed water by an average of 38% and the second soil column (also 28-day HRT) reduced the TOC another 16% for a total average removal of 55%. The overall TOC reduction by the full treatment trains of ozone, BAC (20-min EBCT) and SAT ranged from 65 to 69%. When the EBCT of the BAC was extended to 39-min, TOC removal by the full treatment train increased to 78%.

Other benefits of the treatment train included significant removal of TOrCs, with most of the measured chemicals below the analytical method detection limit in the BAC effluent. While not studied here, additional TOrC attenuation could be achieved during SAT. Ozone was demonstrated to form significant NDMA, but BAC removed most of it and SAT further dropped the NDMA concentration below the detection limit of 2 ng/L. Bromate formation was shown to exceed the MCL of 10 g/L under certain circumstances, but the chlorine-ammonia method was effective at lowering formation enough to comply with the MCL. Additionally, the treatment train was able to remove all of the total coliform bacteria present in the source water, demonstrating excellent disinfection capabilities.

Considering the data generated by this study, the optimal design criteria to maximize TOC removal for a treatment train of ozone, BAC and SAT treating the secondary effluent at SJCWRP would be an ozone system operating at an O3:TOC ratio of 1.00, a BAC filter with an EBCT of 39 min, and SAT with a minimum HRT of 56 days. However, a cost analysis would need to be performed to determine if an EBCT of that length would be justifiable or if a shorter EBCT would be better.

This research demonstrated the technical feasibility of an indirect potable reuse treatment train of ozone, BAC and SAT and developed some basic design criteria for these unit processes. These results could be applied to reuse of wastewater effluent from SJCWRP or more generally to other wastewater treatment facilities producing a wastewater effluent of similar quality. Pilot testing would be recommended at other facilities to confirm treatment train performance and optimize operations as necessary.

One important task to be performed before considering the implementation of the treatment train tested in this study is an analysis to determine if the capital, operation and maintenance costs of a treatment facility with the suggested design criteria would be offset by reducing the cost of purchasing or otherwise securing the quantity of blend water necessary to satisfy the 0.5 mg/L limit for TOC of wastewater origin required by California’s groundwater recharge regulations. Another benefit for consideration would be improved water supply reliability since recycled water is a local supply with a higher resistance to drought than water to Southern California from Northern California or the Colorado River. The cost analysis should compare various source waters and treatment options for surface spreading, including Title 22 treated water, secondary or tertiary effluent followed by ozonation, and secondary effluent followed by ozone and BAC.


All of these options would be followed by SAT, although the upstream treatment and source water could affect the efficiency of SAT.

A policy change that could reduce blend water requirements is relaxing or eliminating the 0.5 mg/L limit for TOC of wastewater origin. This regulation is the primary driver of needing to reduce the TOC concentration, but it does not consider whether or not the TOC resembles organic matter in wastewater effluent. For example, ozonation alone has the ability to significantly remove the wastewater “fingerprint” of a wastewater effluent, as demonstrated by the excitation-emission matrix (EEM) spectra images before and after ozonation shown in Figure 20. Convincing DDW to modify the wastewater TOC rule would likely require a significant research effort, but those expenses would likely be offset by lower implementation costs for indirect potable reuse by surface spreading if this regulation was changed.

Figure 20. EEM images of secondary effluent before and after ozonation. The peaks associated with humic acids (HA), fulvic acids (FA) and proteins and soluble microbial products (SMP) are typical of wastewater effluents and were almost entirely removed by ozonation.

7 REFERENCES

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Drewes, J. E.; Fox, P. Behavior and characterization of residual organic compounds in wastewater used for indirect potable reuse. Water Sci. Technol.1999, 40, 391-398

Fox, P.; Houston, S.; Westerhoff, P.; Nellor, M.; Yanko, W.; Baird, R.; Rincon, M.; Gully, J.; S., C.; Arnold, R.; Lansey, K.; Quanrud, D.; Ela, W.; Amy, G.; Reinhard, M.; Drewes, J. Advances in Soil Aquifer Treatment Research for Sustainable Water Reuse; American Water Works Association Research Foundation: Denver, CO, 2006.


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MWH. Water Treatment: Principles and Design, 2nd Edition, Wiley, 2005.

Rauch-Williams, T.; Hoppe-Jones, C.; Drewes, J. E. The role of organic matter in the removal of emerging trace organic chemicals during managed aquifer recharge. Water Res. 2010, 44, 449-460.

Reungoat, J., Escher, B.I., Macova, M., Keller, J., 2011. Biofiltration of wastewater treatment plant effluent: effective removal of pharmaceuticals and personal care products and reduction of toxicity. Water Res. 45 (9), 2751-2762.

Schmidt CK and Brauch HJ. (2008) N,N-dimethylsulfamide as precursor for N-nitrosodimethylamine (NDMA) formation upon ozonation and its fate during drinking water treatment. Environ. Sci. Technol. 2008 Sep 1;42(17):6340-6.

Seip N. D. Study of Pilot-scale Filtration at Minneapolis Water Works, TVM4905 Water Supply and Wastewater Systems, Master’s Thesis, Norwegian University of Science and Technology, Department of Hydraulic and Environmental Engineering, March 2014.

Stalter, D., Magdeburg, A., Weil, M., Knacker, T., Oehlmann, J., 2010. Toxication or detoxication? In vivo toxicity assessment of ozonation as advanced wastewater treatment with the rainbow trout. Water Res. 44, 439-448.

Stalter, D., Magdeburg, A., Wagner, M. and Oehlmann, J. (2011) Ozonation and activated carbon treatment of sewage effluents: Removal of endocrine activity and cytotoxicity. Water Res. 45(3), 1015-1024.

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US EPA (2001) Integrated Risk Information System

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US EPA 2010 Code of Federal Regulations, Protection of Environment, Title 40 Volume 22, Chapter 1, Parts 141-143. July 1, 2010. http://www.gpo.gov/fdsys/pkg/CFR-2010-title40-vol1/content-detail.html

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von Gunten, U., Salhi, E., Schmidt, C.K., Arnold, W.A. (2010) Kinetics and mechanisms of N-nitrosodimethylamine formation upon ozonation of N, N dimethylsulfamidecontaining waters: Bromide catalysis. Environ. Sci. Technol. 44(15), 5762-5768.

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Zimmermann, S.G., Wittenwiler, M., Hollender, J., Krauss, M., Ort, C., Siegrist, H., von Gunten, U. (2010) Kinetic assessment and modeling of an ozonation step for full-scale municipal wastewater treatment: Micropollutant oxidation, by-product formation and disinfection. Water Res. 45 (2), pp. 605-617.


APPENDIX

Table A1. Average TOC (mg/L) data from grab samples collected during testing period.

Test O3 Inf O3 Eff FC-1 FC-2 FC-3 FC-4 FC-5 SC-1 SC-2

1 6.1 5.9 4.0 3.7 4.1 4.8 4.8 2.1 2.0

2 6.6 6.5 4.6 3.5 4.2 4.8 4.9 2.3 2.0

3 6.0 5.6 3.7 3.2 3.7 4.2 4.3 2.2 1.9

4 5.7 5.6 3.9 3.2 3.9 4.5 4.6 2.2 1.7

5 6.1 5.8 3.9 2.9 3.3 3.7 3.7 1.9 1.4

Table A2. Average UVA (cm-1) data from grab samples collected during testing period.


1 0.131 0.061 0.064 0.045 0.052 0.060 0.057 0.045 0.046

2 0.130 0.063 0.055 0.034 0.048 0.052 0.052 0.048 0.040

3 0.137 0.057 0.053 0.039 0.046 0.051 0.051 0.042 0.034

4 0.123 0.074 0.059 0.038 0.052 0.067 0.068 0.041 0.033

5 0.125 0.064 0.037 0.027 0.033 0.039 0.040 0.040 0.025

Table A3. Average turbidity (NTU) data from grab samples collected during testing period.


1 0.70 0.34 0.20 0.18 0.18 0.17 0.17 0.30 0.16

2 1.48 0.89 0.63 0.24 0.26 0.22 0.25 0.34 0.13

3 0.97 0.36 0.39 0.19 0.23 0.22 0.21 0.26 0.21

4 0.78 0.39 0.25 0.24 0.24 0.25 0.27 0.28 0.20

5 0.68 0.30 0.19 0.15 0.15 0.17 0.16 0.23 0.14

Table A4. Average pH data from grab samples collected during testing period.

Test O3 Inf O3 Eff FC-1 SC-1 SC-2

1 7.0 7.0 7.1 8.1 7.9

2 7.2 7.2 7.1 7.9 7.9

3 7.2 7.2 7.1 7.8 7.9

4 7.3 7.3 7.2 7.9 7.4


5 7.2 7.1 7.2 7.3 7.0

Table A5. TOrC concentrations (ng/L) measured during Test 1. All the “less than” values are below method reporting limit.

COMPOUND NAME Sec Eff O3 Eff FC-2

(20-min EBCT) FC-3

(10-min EBCT) 4-Nonylphenol 128 20 <25 <25

4-tert Octylphenol 12 6 <5 <5

Acesulfame-K 200 51 200 223

Acetaminophen <10 <10 <10 <10

Atenolol 34 <10 <10 <10

Atorvastatin <10 <10 <10 <10

Azithromycin 63 <10 <10 <10

Bisphenol A <10 <10 <10 <10

Caffeine <10 <10 <10 <10

Carbamazepine 365 <10 <10 <10

Carisoprodol 105 39 10 23

DEET 299 56 13 34

Diazepam <10 <10 <10 <10

Diclofenac 236 <10 <10 <10

Dilantin (Phenytoin) 261 33 <10 <10

Erythromycin-H2O 37 <10 <10 <10

Fipronil 59 11 <2 <2

Fluoxetine 44 <10 <10 <10

Furosemide 142 <10 <10 <10

Galaxolide 5,500 380 62 96

Gemfibrozil 36 <10 <10 <10

Ibuprofen 20 <10 <10 <10

Iohexol 2,750 1,220 1,420 1,690

Iopromide <10 <10 <10 <10

Meprobamate 303 131 49 102

Metoprolol 324 <10 <10 <10

Naproxen <10 <10 <10 <10

Nonylphenol diethoxylate 120 <25 <25 <25

Nonylphenol monoethoxylate 153 <25 <25 <25

Octylphenol diethoxylate <25 <25 <25 <25

Octylphenol monoethoxylate 36 <25 <25 <25

Primidone 184 39 19 29

Propranolol 56 <10 <10 <10

Sucralose 28,700 19,400 7,210 13,200

Sulfamethoxazole 1,220 <10 <10 <10

TCEP 756 735 60 130



(20-min EBCT) FC-3

(10-min EBCT) TCPP 3,110 2,770 281 655

TDCPP 913 838 26 62

Tonalide 250 <50 <50 <50

Triclocarban 52 <10 <10 <10

Triclosan 122 <10 <10 <10

Trimethoprim 14 <10 <10 <10



(20-min EBCT) FC-3

(10-min EBCT) 4-Nonylphenol 195 45 50 <25

4-tert Octylphenol 26 24 <5 <5

Acesulfame-K 736 240 288 374


Atenolol 100 <10 <10 <10



Bisphenol A <10 <10 <10 <10

Caffeine <10 <10 <10 <10


Carisoprodol 68 33 <10 17

DEET 733 217 14 44

Diazepam <10 <10 <10 <10

Diclofenac 293 <10 <10 <10



Fipronil 76 24 <2 3


Furosemide 676 <10 <10 <10

Galaxolide 7,900 880 <50 84

Gemfibrozil 651 <10 <10 <10

Ibuprofen 32 <10 <10 <10

Iohexol 4,390 2,380 1,220 1,950

Iopromide <10 <10 <10 <10


Metoprolol 479 <10 <10 <10

Naproxen 15 <10 <10 <10

Nonylphenol diethoxylate 148 149 <25 <25



(20-min EBCT) FC-3

(10-min EBCT) Nonylphenol monoethoxylate 250 278 <25 <25


Octylphenol monoethoxylate 76 52 <25 <25



Sucralose 35,400 26,000 7,160 12,600

Sulfamethoxazole 1,310 25 <10 <10

TCEP 461 450 49 116

TCPP 3,420 3,160 229 591

TDCPP 812 908 23 74

Tonalide 340 100 <50 <50

Triclocarban 117 23 <10 <10

Triclosan 301 <10 <10 <10

Trimethoprim 29 <10 <10 <10



(20-min EBCT) FC-3

(10-min EBCT) 4-Nonylphenol 98 <25 <25 <25

4-tert Octylphenol 8 <5 <5 <5

Acesulfame-K <50 <50 105 86


Atenolol 29 <10 <10 <10



Bisphenol A <10 <10 <10 <10

Caffeine <10 <10 <10 <10


Carisoprodol 234 57 <10 19

DEET 115 10 10 18

Diazepam <10 <10 <10 <10

Diclofenac 237 <10 <10 <10



Fipronil 49 3 <2 <2


Furosemide 118 <10 <10 <10

Galaxolide 5,800 130 <50 <50



(20-min EBCT) FC-3

(10-min EBCT) Gemfibrozil 18 <10 <10 <10

Ibuprofen 12 <10 <10 <10

Iohexol 1,860 601 394 857

Iopromide <10 <10 <10 <10


Metoprolol 320 <10 <10 <10

Naproxen <10 <10 <10 <10

Nonylphenol diethoxylate 58 <25 <25 <25

Nonylphenol monoethoxylate 118 <25 <25 <25


Octylphenol monoethoxylate 39 <25 <25 <25



Sucralose 34,200 17,800 6,880 12,700

Sulfamethoxazole 853 <10 <10 <10

TCEP 549 434 51 139

TCPP 3,790 3,120 218 748

TDCPP 865 826 21 63

Tonalide 190 <50 <50 <50

Triclocarban 43 <10 <10 <10

Triclosan 125 <10 <10 <10

Trimethoprim <10 <10 <10 <10

Table A8. TOrC concentrations (ng/L) measured during Test 5. All the “less than” values are below method reporting limit. EBCTs shown in the column headings represent the cumulative EBCT at the effluent of the filter column.


(19-min EBCT) FC-2

(39-min EBCT) FC-3

(29-min EBCT) 4-Nonylphenol 114 101 <25 26 <25

4-tert Octylphenol 8 <5 <5 <5 5

Acesulfame-K 94 <50 63 104 103

Acetaminophen <10 <10 <10 <10 <10

Atenolol 48 <10 <10 <10 <10

Atorvastatin <10 <10 <10 <10 <10

Azithromycin 31 <10 <10 <10 <10

Bisphenol A <10 <10 <10 <10 <10

Caffeine <10 <10 <10 <10 <10

Carbamazepine 257 <10 17 <10 <10

Carisoprodol 98 16 24 10 18



(19-min EBCT) FC-2

(39-min EBCT) FC-3

(29-min EBCT) DEET 194 13 32 11 20

Diazepam <10 <10 <10 <10 <10

Diclofenac 228 <10 <10 <10 <10

Dilantin (Phenytoin) 273 10 24 <10 12

Erythromycin-H2O 12 <10 <10 <10 <10

Fipronil 42 <2 6 <2 <2

Fluoxetine 40 <10 <10 <10 <10

Furosemide 180 <10 <10 <10 <10

Galaxolide 5,000 <50 100 58 130

Gemfibrozil 27 <10 <10 <10 <10

Ibuprofen <10 <10 <10 <10 <10

Iohexol 11,600 2,670 2,540 649 1,490

Iopromide <10 <10 <10 <10 <10

Meprobamate 316 64 83 40 76

Metoprolol 311 <10 <10 <10 <10

Naproxen <10 <10 <10 <10 <10

Nonylphenol diethoxylate 107 <25 <25 <25 <25

Nonylphenol monoethoxylate 131 <25 <25 <25 <25

Octylphenol diethoxylate <25 <25 <25 <25 <25

Octylphenol monoethoxylate 43 <25 <25 <25 <25

Primidone 215 13 17 15 19

Propranolol 56 <10 <10 <10 <10

Sucralose 32,500 14,200 16,700 7,370 12,900

Sulfamethoxazole 1,450 <10 12 13 29

TCEP 636 488 448 58 149

TCPP 2,880 2,170 2,210 259 844

TDCPP 759 711 623 20 71

Tonalide 140 <50 <50 <50 <50

Triclocarban 62 <10 <10 <10 <10

Triclosan 76 <10 <10 <10 <10

Trimethoprim 11 <10 <10 <10 <10

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