Treatment of 1,4-Dioxane Using Advanced Oxidation at Artesian Water Company’s Llangollen Wellfield

John Civardi, PE 1 , Andrew Prosser, EI 2 , J. Margaret Gray, PE1, Jason Marie, PE1, Kathryn Greising, EIT1

1Hatch Mott MacDonald, 111 Wood Avenue South, Iselin, NJ 08830-41122Artesian Water Company, Inc., 664 Churchmans Road, Newark, DE 19702

Abstract

The Artesian Water Company (Artesian) Llangollen Wellfield has a capacity of 2.2 MGD. Treatment was limited historically to aeration, chlorination, and pH adjustment. In 2000, bis(2-chloroethyl) ether (BCEE) was discovered in three of the wells. Subsequently, granular activated carbon (GAC) treatment was provided for the removal of BCEE. Recently, 1,4-dioxane was detected in one of the wells at levels of concern, and Artesian removed the well from service. Monitoring wells at a nearby landfill found 1,4-dioxane as high as 300 µg/L. The Delaware Department of Public Health requires that levels above 3.5 µg/L of 1,4-dioxane be reported. Artesian conducted a treatability study, which found that using UV-hydrogen peroxide and quenching the hydrogen peroxide with the existing GAC, was the most cost-effective treatment option to remove 1,4-dioxane. The full-scale treatment system includes two UV reactors, each with 144 lamps, which are sized to provide 2-log (99%) reduction of 1,4-dioxane. This paper describes critical components associated with the treatability study, bench studies, design, and initial operation.

Key words: 1,4-dioxane, UV Hydrogen Peroxide, GAC

Project Background

Artesian Water Company, Inc. (Artesian) is the oldest and largest investor owned public water utility on the Delmarva Peninsula. Its Llangollen wellfield consists of four public supply wells (Well 2, Well 6, Well 7, and Well G-3R) and one aquifer storage and recovery (ASR) well that are all screened in the Potomac Formation. The wellfield began operation in the 1950s and had a water supply withdrawal allocation of 3.8 MGD in the late 1960s. As a result of groundwater contamination in the region originating from two nearby Superfund sites, the Army Creek

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Landfill and the Delaware Sand and Gravel Pit, the wellfield allocation has been limited to 2.2 MGD.

In 2000, bis(2-chloroethyl) ether, or BCEE, was discovered in the wellfield. The wells also contained trace quantities of additional organic compounds such as benzene and 1,2-dichloroethane, as well as inorganic contaminants such as iron, radium, and chromium.

Upon detection of BCEE, Artesian ceased operation of the Llangollen wellfield and immediately began planning for the design and installation of granular activated carbon (GAC) treatment. The Delaware Division of Public Health set an advisory level of 0.96 µg/L for BCEE in October 2000. The GAC system was installed downstream of an existing aerator and prior to chemical injection. The water flows from the wells, through the aerator, into a wet-well and is then pumped through the GAC units. After the GAC units, the water is injected with fluoride, lime, a corrosion inhibitor, and chlorine prior to entering the public water supply system. The GAC system consists of three sets of dual GAC pressure vessel contactors that contain a total of 120,000 pounds of GAC, with one set of GAC contactors designated for the treatment of the ASR well.

When the GAC system was first placed into service in 2001, the GAC experienced breakthrough after approximately two years of operation. Over time the breakthrough frequency increased, and in the period from 2010 to 2013, breakthrough occurred approximately every four to six months when the wellfield was operating at its full capacity of 2.2 MGD. Based on the increased frequency of breakthrough, the annual GAC change out cost has increased from the initial $60,000 per year to $240,000 per year. In addition, Artesian has been unable to regenerate the carbon since it contains trace levels of mercury, chromium, radium, and several other inorganic compounds.

In the winter of 2013, at the request of Delaware’s Division of Public Health, Artesian tested its Llangollen wellfield for 1,4-dioxane. EPA has classified 1,4-dioxane as a group B2 probable human carcinogen. Damage to the liver and kidneys has been observed in rats chronically (long-term) exposed in their drinking water. Well G-3R, the largest producing well in the wellfield, tested positive for elevated levels of 1,4-dioxane. As a result of this discovery, Artesian immediately removed Well G-3R from service, reducing the wellfield production capability from 2.2 MGD to 1.2 MGD. Since Artesian provides over 20 MGD from its wells, the loss of nearly 5 percent of supply was significant. Artesian acted quickly by conducting a treatability study to identify a treatment solution so that Well G-3R could be returned to service.

Treatability Study

A treatability study was performed to identify the most cost-effective treatment method for removing 1,4-dioxane that could be integrated into the existing treatment facility. Given the complexity of the current water quality and the likelihood that water quality would continue to degrade, additional treatability study goals were to:

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Establish future concentrations for contaminants that could be used as part of planning for additional treatment so that the treatment system could be efficiently modified in the future to address additional treatment requirements.

Establish design criteria for the 1,4-dioxane treatment system. Identify possible water quality parameters that could be causing the GAC life to have

decreased by greater than a factor of four in recent years and identify potential solutions.

Removal of 1,4-dioxane is accomplished using an advance chemical oxidation process (AOP). The two AOP treatment technologies that have been most commonly used for this contaminant are UV-Hydrogen Peroxide (UV-H2O2), using either low pressure high output or medium pressure UV lamps, and Ozone-Hydrogen Peroxide (Ozone-H2O2). The leading suppliers of the UV-H2O2 technology for 1,4-dioxane are Trojan Technologies (Trojan) and Calgon Carbon (Calgon). The leading supplier of the Ozone-H2O2 technology is Applied Process Technology (APT). These suppliers have extensive experience with AOP processes and were contacted to provide equipment sizing and costs based on the design criteria established in the treatability study. The following three treatment options were evaluated:

Treatment Option 1 – UV-H2O2 using low pressure high output UV lampsTreatment Option 2 – UV-H2O2 using medium pressure UV lampsTreatment Option 3 – Ozone-H2O2

In order to compare each of the AOP treatment options, conceptual designs, layouts and costs were prepared for each of the treatment options. In addition, non-economic factors were considered. A ranking system weighing both cost and non-economic factors was employed to identify the recommended treatment option for the Llangollen facility.

Regulatory Requirements

There is currently no federal Maximum Contaminant Level (MCL) or Maximum Contaminant Level Goal (MCLG) for 1,4-dioxane in drinking water. Several of the USEPA regional offices use an advisory guidance level of 6.1 µg/L. According the EPA’s Technology Transfer Network, “EPA estimates that, if an individual were to continuously drink water containing 1,4-dioxane at an average of 3.0 µg/L (3 x 10-3 milligrams per liter (mg/L)) over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of drinking water containing this chemical.” Prior to issuing a proposed regulation, EPA must list the contaminant on the Contaminant Candidate List (CCL), and 1,4-dioxane was listed in 2008. For a contaminant listed on the CCL, occurrence, concentration and exposure information is assembled to conduct a preliminary risk assessment. Once this information is obtained, the EPA then decides whether to regulate the contaminant. This regulatory decision process is currently ongoing at the EPA. Additionally, Delaware Office of Drinking Water has issued a requirement to report any 1,4-dioxane concentration levels greater than 3.5 µg/L.

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Design Scenarios

To determine the most cost-effective and feasible option, and to account for the potential increase in the concentration of 1,4-dioxane, each of the three AOP treatment options were evaluated based on treating a total flow of 1,500 gpm with two trains, each treating 50% of the flow. The systems were sized to provide initially up to 1.2-log removal, which would remove the 1,4-dioxane to less than 3 µg/L at the current concentrations in the wells. The systems were also sized to achieve a maximum of 2.0-log removal in the future should the concentration reach 300 µg/L, which is the maximum concentration found at the nearby Superfund sites. Annual costs used for the comparison of alternatives were based on providing 1.2-log removal, and the sizing was performed using two reactors each capable of treating 50% of the flow. The building was sized to accommodate a third reactor in the future.

Evaluation Methodology

Conceptual level capital cost estimates were prepared for each treatment alternative. A contingency of 40% was included in the estimates, since the designs were at the conceptual stage. The contingency is consistent with the standard AACE International Recommended Practice No. 18R-97. The capital and operation and maintenance (O&M) costs were converted to a life-cycle cost for comparison purposes.

Capital Costs

The capital cost consisted of the total cost of constructing the alternative and included equipment, site/civil, structural, architectural, instrumentation and control, mechanical and electrical work. Costs associated with project implementation such as legal, permitting, and engineering were not included, as these costs were considered comparable for all options.

O&M Costs

The operating and maintenance costs consisted of energy, chemical, equipment replacement, carbon replacement, and manpower. The operating costs used in the treatment option comparison were based on continuous operation, 24 hours/day for 365 days per year, at an average flow rate of 1,500 gpm.

Energy unit costs, carbon replacement costs, and manpower costs were based on Artesian’s current rates. Chemical costs and equipment replacements costs were obtained from chemical suppliers and equipment manufacturers.

Life-Cycle Costs

The capital and O&M costs for each treatment option were converted to a present worth life-cycle cost using an interest rate of 8% and a period of 20 years.

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Non-Economic Considerations

The selection of the optimum treatment system was not only based on cost, but also on non-economic factors such as system reliability, complexity, ease of maintenance and the experience of the equipment supplier. A weighted point system was developed during a workshop by the project team to identify and prioritize specific non-economic factors.

Treatment Options 1 and 2: UV-Hydrogen Peroxide

The UV-Hydrogen Peroxide technology involves the formation of a hydroxyl radical that will break apart the bonds of the 1,4-dioxane molecule. This technology also provides some BCEE removal, depending on the sizing of the system. The hydroxyl radical is created by adding hydrogen peroxide to UV light in a reactor. As part of the reaction, a portion of the hydrogen peroxide is not consumed and must be quenched. Quenching can be performed using chlorine or granular activated carbon (GAC). Chlorine is generally used where GAC is not feasible due to economics or system hydraulics. Unlike most conventional water treatment applications of GAC where 15 to 20 minutes of Empty Bed Contact Time (EBCT) is required, the quenching of hydrogen peroxide requires only 4 to 5 minutes of EBCT. The selection of the GAC for quenching is generally based on site specific test data. The optimization of the UV-H2O2 system involves balancing the UV dose, hydrogen peroxide dose and quenching requirements, along with integrating the system into the existing unit processes.

Treatment Option 1: Low Pressure High Output UV-Hydrogen Peroxide

Trojan manufactures both low pressure high output (LPHO) and medium pressure UV systems. LPHO systems use more lamps, but consume much less power and operate at much lower temperatures. Medium pressure systems use significantly less lamps, but operate at much higher power and temperatures. Trojan can provide both lamp types, but their experience in groundwater applications in the United States has shown the LPHO lamp is much more efficient and has a lower net present value over 20 years. Therefore, Trojan provided a quote based on LPHO lamps.

The Trojan system would consist of two reactors, each with 144 lamps. Each reactor uses 36 kW of power. The sizing is based on initially providing 1.2-log reduction of 1,4-dioxane at a flowrate of 1,500 gpm with each reactor treating 750 gpm. This flow allows for 50% of the plant’s capacity to be treated in each of the two reactors. The UV and hydrogen peroxide doses were based on bench testing of the raw water from samples (Wells 2, 7 and G-3R) that were provided to Trojan by Artesian and analyzed on March 8, 2013. If the raw water concentration were to increase to a level where1.5 or 2.0-log reduction was required, additional hydrogen peroxide would be added. The estimated hydrogen peroxide dose for 1.2-log reduction was 7.5 mg/L, for 1.5-log reduction was 10.5 mg/L, and for 2.0-log reduction was 17.7 mg/L.

The conceptual layout of the Trojan equipment required a 1,400 ft2 building that was 15 ft. high. The facility size was large enough to accommodate a third reactor in the future. Flow meters would be provided for each reactor and automatic valves would be provided on the inlet and

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outlet of each reactor, which would close in the event of the detection of a lamp break. The hydrogen peroxide tank and metering pumps would be located outside in an enclosure. The motor control center (MCC) in the existing high lift pumping station would be modified and would provide power to the ballasts in the new UV building. The use of LPHO lamps would result in low heat generation, and therefore air conditioning of the space would not be required. The estimated construction cost of the facility was $3,100,000, and the estimated annual O&M cost was $121,000. The present worth of the Trojan LPHO lamp UV-H2O2 option was $4,290,000.

Treatment Option 2: Medium Pressure UV-Hydrogen Peroxide System

Calgon’s UV division manufactures medium pressure UV reactors. Calgon has extensive experience with UV-AOP for industrial water treatment, and they have applied this experience to the treatment of drinking water. Conceptually, the Calgon process would function in a similar manner to the Trojan system. The Calgon system would consist of two reactors each with 9 medium pressure lamps. Each lamp uses 10 kW of power and therefore each reactor would use approximately 90 kW of power. The hydrogen peroxide dose for 1.2-log reduction was approximately 10.0 mg/L.

The conceptual layout of the Calgon equipment required a 1,050 ft2 building that was 15 ft. high. The footprint of the Calgon facility was smaller than the Trojan facility since the medium pressure reactors are smaller than the LPHO reactors. Like the Trojan facility, there would be sufficient space for a future third reactor, and the layout would include a flowmeter and automatic isolation valves on each train. The hydrogen peroxide tank and metering pumps would be located outside in an enclosure. The MCC in the existing high lift pumping station would be modified and would provide power to the ballasts in the new UV building. The use of medium pressure lamps would result in high heat generation, and therefore air conditioning of the space would be provided. The estimated construction cost of the facility was $2,901,000 and the estimated annual O&M cost was $224,000. The present worth of the Calgon medium pressure lamp option was $5,100,000.

Treatment Option 3: Ozone-Hydrogen Peroxide

The Ozone-H2O2 process is an advanced oxidation process that utilizes ozone and hydrogen peroxide to form hydroxyl radicals. This process is also known as Peroxone. APT’s Ozone-H2O2 system is called HiPOx. The HiPOx system adds ozone and hydrogen peroxide into a customized piping reactor. The system involves generation of ozone and adding the ozone and hydrogen peroxide into a reactor where the hydroxyl radicals are formed and combined with the raw water. Significant advantages of this system include the ability to provide up to 80% removal of the BCEE and the generation of much less residual hydrogen peroxide. The system will generate ozone gas and off gas treatment of ozone is required. The optimum location for the HiPOx system would be upstream of the aerator since the system is under much lower pressure.

The conceptual layout of the HiPOx system equipment requires a 2,230 ft2 building that was 15 ft. high. The floor plan was based on the use of liquid oxygen (LOX), which would be stored

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outside. The estimated construction cost of the facility was $3,787,000 and the estimated annual O&M cost was $77,000. The present worth of the HiPOx option was $4,540,000.

Comparison of Treatment Options

A workshop was held with the project team to evaluate the three treatment alternatives. During the workshop, a ranking system was used to prioritize the options. The summary of the rankings developed during the workshop are outlined in Table 1.

Table 1 – Ranking of 1,4-Dioxane Treatment Options

CriteriaTrojanLPHO

UV-H2O2

CalgonMedium Pressure

UV-H2O2

APTOzone H2O2

HiPOxEconomic

Construction Cost $3,100,000 $2,901,000 $3,787,000O&M Cost – Annual $121,000 $224,000 $77,000Lifecycle Cost (Present Worth) $4,290,000 $5,100,000 $4,540,000

Total Economic Score 60 50 57Total Non-Economic Score 38 32 19Total Score 98 82 76Note: Maximum possible economic score is 60, maximum possible non-economic score is 40, and maximum total score is 100.

The scoring system for the evaluation had a maximum total score of 100 broken down by a maximum economic score of 60 and maximum non-economic score of 40. The economic score was derived by the lowest lifecycle costs divided by the lifecycle cost of the option times 60. The non-economic score was based on a weighted points system developed by the project team for non-economic factors as follows:

Experience of the supplier (10 points) Equipment complexity (10 points) Level of permitting (5 points) Impact on BCEE removal (5 points) Ease of integration into the existing facilities (5 points) Operator training requirements (5 points)

The system with the highest evaluation score was the Trojan LPHO UV-Hydrogen Peroxide System followed by Calgon’s Medium Pressure UV-Hydrogen Peroxide System, and finally, Applied Process Technologies’ Ozone-Hydrogen Peroxide HiPOx System. Based on these results, the project team selected Trojan’s LPHO UV System for treatment of the Llangollen Wellfield.

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Quenching of Hydrogen Peroxide

As with all the AOP processes options evaluated, the hydrogen peroxide is not completely consumed in the selected Trojan LPHO UV-H2O2 system and requires subsequent quenching. The two most common forms of hydrogen peroxide quenching are chlorine and GAC. While chlorine can be used for quenching, approximately 1.8 mg/L of chlorine is required for each 1 mg/L of residual hydrogen peroxide. A residual hydrogen peroxide dose of approximately 8 mg/L was estimated to occur from the effluent of the UV-AOP process and therefore, would require the addition of approximately 14 mg/L of chlorine for quenching. Due to the high chlorine dosage and the potential for the formation of additional chlorinated by-products, GAC was recommended for quenching of hydrogen peroxide. The EBCT required for hydrogen peroxide quenching is reportedly approximately 4 to 5 minutes. The GAC system at the Llangollen Treatment Facility had sufficient EBCT, and the Facility’s existing F-300 carbon had reportedly been used successfully for hydrogen peroxide quenching in conjunction with BCEE removal. Bench testing involving both the recommended Trojan LPHO UV-H2O2 process and GAC system was undertaken to evaluate the impacts of the UV-H2O2 process on the GAC system, as well as to confirm the UV-H2O2 system design criteria.

Bench Testing

Overview

The purpose of the bench testing was to evaluate the effectiveness of UV-H2O2 treatment on the water currently being pumped from the Llangollen wells. Additional goals of the study were to:

Confirm the design UV and hydrogen peroxide dosages for 1,4-dioxane removal; Evaluate the extent of BCEE removal that could be obtained from the UV-H2O2 process; Evaluate the carbon consumption due to quenching of hydrogen peroxide; Evaluate the amount of BCEE removal from the GAC and the carbon usage rate post

UV-H2O2; Quantify the concentrations of by-products formed by the UV-H2O2 process; Quantify the amount of removal of UV-H2O2 byproducts post GAC; Evaluate the impact of the UV-H2O2 process on carbon life as compared to current

operations.

The bench testing was performed on a batch basis since BCEE and 1,4-dioxane do not readily volatilize. All of the water used for the bench testing was collected from Artesian Water Company’s Well G-3R during a single sampling event to minimize variability in the raw water quality used for each of the bench testing phases. The testing was performed on a batch basis using rapid small scale columns for carbon testing and a batch UV-H2O2 reactor. The testing was performed in two phases as follows:

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Phase I – Rapid Small Scale Column Test (RSSCT) Control for BCEE The purpose of the Phase I testing was to confirm that the batch RSSCT columns simulate the performance of the existing GAC system at the Llangollen Treatment Facility.

Phase II – UV-H2O2 and RSSCTThe purpose of the Phase II testing was to achieve 2-log reduction of 1,4-dioxane using the UV-H2O2 advanced oxidation process and to verify that the F-300 carbon would provide BCEE removal at least equal to the performance of the existing GAC system in terms of carbon usage rate.

Phase 1 – RSSCT Control for BCEE

Figure 1 presents a schematic of the Phase I testing.

Figure 1 – Phase I Testing Schematic

The purpose of the Phase I testing was to confirm that the columns used in the batch RSSCT replicated the performance of the existing GAC system at the Llangollen Treatment Facility. The existing GAC system consists of three pairs of GAC vessels. Each pair is operated in series with a lead and a lag vessel. The GAC system at the Llangollen Treatment Facility provides a total EBCT of approximately 20 minutes at a maximum plant flow rate of 2.2 MGD. The lead vessels provide approximately 10 minutes of EBCT, and the lag vessels provide an additional 10 minutes of EBCT. The carbon in the lead vessels was being replaced as frequently as every 4 – 6 months. Between December 2007 and March 2013, the plant’s average flow was 1.5 MGD and the carbon replacement in the lead vessels occurred at an average of 15,000 lead vessel bed volumes and at as little as 8,000 lead vessel bed volumes.

EPS Labs performed the RSSCTs for Phase I. Since the GAC vessels are located downstream of the aerators, EPS Labs initially performed a series of short duration (less than 1 hour) experiments with several aeration alternatives to determine the amount of aeration needed to raise the pH by approximately 1 unit to simulate the existing aeration system. Two RSSCT columns were then operated using the aerated water. One column simulated 10 minutes of EBCT, and one simulated 20 minutes of EBCT. Figure 2 presents the results of the RSSCTs

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with respect to BCEE removal. The Phase I 10 minute EBCT RSSCT began to experience BCEE breakthrough at approximately 15,000 bed volumes. The 20 minute EBCT RSSCT began to experience BCEE breakthrough at approximately 25,000 bed volumes. These breakthrough bed volumes are similar to the existing plant, confirming that the RSSCT columns replicated the performance of the existing GAC vessels and therefore the RSSCT columns were considered suitable for use with the UV-H2O2 testing performed in Phase II.

Figure 2 – Phase I BCEE Removal

Phase II – UV-AOP and RSSCT

Figure 3 presents a schematic of the Phase II testing.

Figure 3 - Phase II Testing Schematic

The goal of the Phase II testing was to achieve 2-log reduction of 1,4-dioxane using the UV-H2O2 advanced oxidation process and to verify that the F-300 carbon would provide BCEE

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removal at least equal to the performance of the existing GAC system in terms of carbon usage rate.

In Phase II, water from well G-3R was treated using Trojan’s batch UV-AOP reactor followed by aeration and then the Rapid Small Scale GAC columns. Table 2 presents the raw water quality of the Well G-3R sample that was used for Phase II testing.

Table 2 – Well G-3R Raw Water Quality

pH 5.7Alkalinity (mg/L as CaCO3) 29.0UVT (% transmission) 97.7DOC (mg/L) 1.2Nitrate (mg/L as NO3-) 4.31,4-Dioxane (µg/L) 55.2BCEE (µg/L) 8.7

Prior to initiating the Phase II testing, Trojan first operated the batch UV-AOP reactor at three combinations of UV and hydrogen peroxide and then selected an optimum combination of UV and hydrogen peroxide dose for the batch testing to achieve 2-log reduction of 1,4-dioxane. As a result of this preliminary testing, a hydrogen peroxide dose of 9 mg/L for the Phase II testing was selected along with a bench scale reactor electrical energy dose (EED) of approximately 7.5 kWh/kgal.

The Phase II UV-H2O2 bench testing results showed greater than 99% removal (2-log) of 1,4-dioxane by the UV-H2O2 process and greater than 98% removal of BCEE. Table 3 presents a summary of the UV-H2O2 process 1,4-dioxane and BCEE removal data.

Table 3 – UV-AOP 1,4-Dioxane and BCEE Removal

Sample Location 1,4-Dioxane(µg/L)

BCEE(µg/L)

Before UV Treatment 55.2 8.7After UV Treatment <0.41 0.14Percent Removal >99.2% 98.4%

After the bench UV-H2O2 process testing, the UV-H2O2 treated water was collected and aerated to raise the pH by one pH unit to simulate the existing plant’s aeration process. It was noted that hydrogen peroxide residual in the UV-H2O2 treated water was approximately 7.6 mg/L and that the aeration process had minimal effect on the hydrogen peroxide concentration in the water. Once the water was conditioned with the aeration process, two RSSCTs were performed. As in Phase I testing, one column simulated 10 minutes of EBCT, and one column simulated 20 minutes of EBCT. Both column tests were run to approximately 25,000 bed volumes. There was no breakthrough of either 1,4-dioxane or BCEE for the duration of either test.

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Summary of Findings

The following is a review of the bench testing objectives in conjunction with a summary of the findings.

1. Bench testing showed that a hydrogen peroxide dose of 9 mg/L and an electrical energy dose (EED) in the bench scale reactor of approximately 7.5 kWh/kgal would achieve 2-log reduction of 1,4-dioxane. Trojan’s full scale UVPhox reactor is approximately 9 times more efficient than the bench scale reactor, so at the full scale, the electrical energy dose (EED) would be 0.82 kWh/kgal.

2. Bench testing showed that BCEE removal of as much as 98% could be achieved through the UV-H2O2 advanced oxidation process.

3. No breakthrough of BCEE was observed in either the 10 min EBCT or the 20 min EBCT

columns for the duration of the post UV-H2O2 RSSCTs conducted in the Phase II testing. The bench testing results suggested that the UV-H2O2 process would decrease the carbon usage rate related to BCEE removal.

Design, Construction, Start-up and Testing

Overview

Based on the Treatment Evaluation findings and the bench testing results, Artesian authorized Hatch Mott MacDonald to undertake the detailed design of a new 1,4-dioxane treatment facility based on the UVPhox low pressure high output UV-H2O2 treatment system manufactured by Trojan. In order to expedite the return of the contaminated sources of supply to service, Artesian elected to pursue measures that would expedite the project delivery process, including:

Concurrent detailed design and equipment procurement. Procurement of the UV-H2O2 system equipment directly from Trojan. Separate contract for underground piping and buried infrastructure relocation. General construction contract for the new treatment facility.

Basis of Design

The UV-H2O2 system was designed in accordance with the design parameters outlined in Table 4.

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Table 4 – UV-H2O2 System Design Criteria

No. of Reactor Trains: 2 (with provisions for a third future train)Peak (Design) Flow: 2.2 MGD with one reactor out of serviceAverage Flow per Reactor: 1.1 MGDDesign UVT (minimum): 95% (at 254 nm, 1 cm path length)Primary Contaminant Influent Concentration: 1,4-Dioxane at 300 µg/LPrimary Contaminant Effluent Concentration: 1,4-Dioxane at 3 µg/L (2-log removal)Secondary Contaminant Influent Concentration: BCEE 8 µg/LSecondary Contaminant Effluent Concentration: BCEE 0.4 µg/LMaximum Hydrogen Peroxide Dose: 18.0 mg/L

The following treatment system equipment was selected based on the design criteria in Table 4:

Two (2) TrojanUVPhox™ D72AL75LPHO UV reactors, each equipped with 144 lamps (36 kW per reactor).

Two (2) Power Distribution Centers, which house the electronic ballasts and distribute power to each UV reactor.

One (1) System Control Center to monitor and control the UV system. One (1) UV transmittance analyzer panel to monitor the water quality of the UV-H2O2

system influent. One (1) 7,800 gallon double walled HDPE hydrogen peroxide storage tank and

appurtenances. One (1) hydrogen peroxide dosing pump system equipped with two dosing pumps and

appurtenances. Each dosing pump is dedicated to a UV reactor train, and space is provided for a third dosing pump for the third future reactor.

The UV treatment facility was designed with two structures. The first structure is the treatment building that houses the UV reactor trains and the electrical equipment. The UV building layout includes a separate electrical room to house the electrical equipment and a main process room with two UV reactor trains and space for a third future train. A monorail was provided in the main process room over each reactor train to facilitate reactor maintenance, as well as equipment installation and removal. In accordance with local building code requirements, the treatment building was designed to have a residential appearance. The second structure at the facility is a hydrogen peroxide area enclosure that houses the 7,800 gallon hydrogen peroxide storage tank and provides 120% chemical containment. The hydrogen peroxide dosing system with the feed pumps is also housed in this area. The structure was designed as an open structure with a roof and panels on two sides to minimize the visibility of the hydrogen peroxide system from adjacent properties. The remaining two sides were designed to remain open to allow natural ventilation. Supply piping to the treatment facility was configured to enable the UV reactors to receive water either pre or post aeration, thus providing additional operating flexibility.

Equipment Procurement and Construction

Due to the expeditious nature of the project, Artesian elected to be proactive in the procurement of the UV and hydrogen peroxide equipment and the installation of underground pipework in

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order to minimize the risk of any unforeseen issues. Artesian, having evaluated the options presented by Hatch Mott MacDonald, decided to procure the UV equipment from Trojan Technologies well in advance of the construction contract award to ensure that the equipment would arrive with adequate time for installation, testing, and start up, as well as for Trojan to obtain NSF approval for the equipment prior to shipment. During the procurement process, Trojan worked closely with both Artesian and Hatch Mott MacDonald to coordinate the submittal reviews and to keep Artesian informed of the status of the pending NSF certification. NSF certification of the UV reactor was obtained June 12, 2014.

By being proactive in both the equipment procurement and construction bidding, Artesian was able to successfully complete the underground pipework in advance of the treatment building general contractor Michael F. Ronca & Sons’ mobilization, and the equipment was delivered with NSF certification in late June. Ultimately, through strong coordination efforts amongst many different parties, the project was delivered on time with commissioning taking place between September 9 and September 19 of 2014 and was put in service on September 30, 2014.

Start-up and Testing

Start-up and testing was conducted over a two week period. For the first week of startup, both Trojan and US Peroxide representatives were on site to inspect the contractor’s work, ensuring all equipment was installed properly and with compatible parts. By the end of the first week of startup, both the UV system and hydrogen peroxide feed system had been inspected, tested, and deemed ready for integration during week two.

During the second week of startup, Trojan was on site and conducted simulation testing of their system to ensure all functions were operating properly. By the end of the second day Trojan had their equipment tested and ready for startup. On day three, Arkema successfully delivered 4,000 gallons of NSF 60 certified 50% hydrogen peroxide without any issues. Once the chemical was successfully delivered, it was Artesian’s responsibility to supply water from the worst well, Well G-3R, to the UV reactors, the aerator, clearwell, GAC vessels, and flow the water overboard. In an effort to ensure the water was clear before sending the G-3R water to the UV reactors, Artesian personnel isolated Well G-3R and pumped overboard until Artesian personnel were satisfied with the water clarity. Well G-3R was then placed on-line for startup. The US Peroxide skid was put into operation and initially dosed hydrogen peroxide into the raw well water from G-3R at 9 mg/L. The water at a flowrate of 400 gpm was then treated through one Trojan UVPhox reactor, which was turned on at 100% power.

In order to verify the hydrogen peroxide residual, Artesian took a post UV reactor sample and performed a field titration test for hydrogen peroxide. The titration results showed that the peroxide leaving the reactors was very similar to the dose being injected.

Once Trojan and US Peroxide confirmed that the treatment system was operating at a 18mg/L dose of hydrogen peroxide and the lamps were operating at 100% power and Artesian felt confident that the treated water was exiting the lag GAC vessel, Artesian began to take water quality samples. Samples for 1,4-dioxane and BCEE were taken at the following locations: raw water from Well G-3R, post UV reactor, post lead GAC vessel, and post lag GAC vessel.

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The results of the sampling are in Table 5.

Table 5 – Start-up Testing Water Quality Results

Sample Location 1,4-Dioxane(µg/L)

BCEE(µg/L)

Well G-3R pending 23Post UV- reactor pending 0.074Post lead GAC vessel pending 0.063Post lag GAC vessel pending Non-Detect** The minimum detect level for the BCEE analysis was 0.0043 µg/L.

The results showed that the UV-H2O2 process had removed___% of the 1,4-dioxane and 99.7% of the BCEE from the Well G-3R raw water.

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