TW_AWP_Conceptual_Design_for_Review_v4.pdf

Technical Memorandum

Jacobs Engineering Group Inc.

250812143438_4bbc5ac9

Tucson Water Demonstration Advanced Water Purification Facility Conceptual Design

Date: September 17, 2025 1501 West Fountainhead Parkway Suite 401 Tempe, AZ 85282 United States

T +1 480 966 8188

F +1 480 966 9450 www.jacobs.com

Project Name: Tucson Water Demonstration AWP Facility Conceptual Design

Attention: Kristen Amante

Client: Tucson Water

Prepared By: Katie Vanyo, Joseph Chang, Talitha Dryer, Eric Zenoni

Reviewed By: Mike Hwang, Larry Schimmoller, Jodi Hoskinson

1. Introduction In 2024, Tucson Water (TW) received notification of funding from the United States Bureau of Reclamation (Reclamation) to build a 2.5-million gallon per day (MGD) advanced water purification facility (AWPF) by September 2031. The AWPF will treat secondary effluent from the Pima County Tres Ríos Water Reclamation Facility (WRF) to potable water standards. Implementing this facility will increase TW’s resiliency in the northwestern part of their distribution system in addition to diversifying their water resources portfolio. Public education and engagement are key to implementing AWPFs given that these facilities treat WRF effluent to potable water standards. Additionally, pilot operations are used to prove out the treatment train’s efficacy and train operations staff in handling advanced water purification (AWP) technologies.

To prepare for the implementation of the full-scale 2.5 MGD AWPF, TW retained Jacobs in January 2025 to prepare a Conceptual Design of a pilot-scale Demonstration AWPF at TW’s reclaimed water treatment plant (WTP). The Demonstration AWPF’s source water will be the tertiary effluent from Pima County’s Agua Nueva WRF because the Agua Nueva WRF is adjacent to TW’s reclaimed WTP. The facility will accomplish the following objectives.

Verify that the treatment processes succeed in producing finished water that complies with Arizona Department of Environmental Quality (ADEQ) AWP requirements and meets TW’s treated water quality goals.

- It should be noted that the Tres Ríos WRF, which is the source for the future full-scale AWPF, and Agua Nueva WRF, which is the source for the Demonstration AWPF, are different facilities, but they treat wastewater from the same sewershed. However, the treated water quality varies in that Agua Nueva WRF produces Class A+ tertiary effluent, and Pima County Produces Class A+ secondary effluent. ADEQ requires a pilot study for full-scale AWPF implementation and may not accept the Demonstration AWPF results as fulfillment of the pilot study requirement because of the treated wastewater effluent quality differences. Further discussions with ADEQ will be needed to confirm whether the Demonstration AWPF results will fulfill the pilot study requirement.

Establish preliminary design criteria for full-scale treatment processes.

Serve as a public engagement center with educational tours, water tasting, and other public outreach activities.

Provide TW operators with the necessary experience to become AWP certified as part of ADEQ’s AWP certification program required for operating AWP facilities.

2. Regulatory Requirements In March 2025, the State of Arizona published rules for AWP, which are nested in Arizona Administrative Code Title 18, Chapter 9, Article 8. The rules include requirements for both full-scale AWPF permits for distribution as well as demonstration testing permits for the purpose of showcasing an AWPF for public engagement and finished water tasting. This facility will require permitting as a Demonstration AWPF intended to serve water for tasting. The regulatory pathway for a demonstration permit includes the following elements to be completed and submitted to ADEQ for approval:

Initial Source Water Characterization Plan and Report Enhanced Source Control Plan Demonstration of Technical, Managerial, and Financial Capability Pilot Study Plan and Report Design Report Draft Operations Plan Construction Documents Draft Communications Plan Tier 2 analysis, Tier 3 chemical list, and critical control points development and explanation Pathogen and chemical action levels identification for ongoing monitoring

An initial pre-application meeting with ADEQ will need to be conducted to establish the regulatory roadmap for this demonstration project. A preliminary regulatory roadmap is provided on Figure 1.

Figure 1. Preliminary Regulatory Roadmap for Demonstration AWPF Permitting

Additionally, ADEQ requires modification to a discharging facility’s Aquifer Protection Permit (APP) if the facility changes treatment technology before discharge. This includes a technical document describing the new demonstration treatment technologies and expected water quality produced, demonstrating it meets regulatory requirements outlined in the existing permit. This existing APP includes all regulated discharges, including Class A+ reclaimed water uses, general APP, and Arizona Discharge Pollutant Elimination System. Because the Demonstration AWPF will discharge all tank overflows, waste streams, and unused purified water back into the reclaimed water system, an APP modification may be required.

3. Treatment Train Selection

3.1 Source Water Quality

As mentioned previously, the source water for the Demonstration AWPF is Agua Nueva WRF tertiary effluent. A summary of the historical water quality data from 2019 to 2024 for Agua Nueva WRF tertiary effluent is provided in Table 1 along with AWP finished water limits and guidelines (or targets). Data sources are the TW sample location 510 and Agua Nueva WRF effluent water quality. Parameters such as 1,4-Dioxane, total nitrogen, N-nitrosodimethylamine (NDMA), and per- and polyfluoroalkyl substances (PFAS)—represented by perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—are commonly assessed in AWP applications because of their prevalence in wastewater and known adverse health effects. The NDMA concentrations were unusually high, so additional sampling is being conducted to confirm the NDMA levels. This affects the design ultraviolet (UV) dose and subsequent energy demand of the UV treatment system. Ammonia and bromide were of interest because they affect bromate formation potential during ozonation, a common AWP treatment unit process. Calcium, magnesium, pH, alkalinity, and orthophosphate were of interest because they affect scaling on reverse osmosis (RO) membranes, another common AWP unit process. Strontium and silica also affect scaling on RO membranes, so sampling is being conducted to confirm the levels for those constituents. Total organic carbon (TOC) levels were evaluated because TOC is a precursor to disinfection byproducts like total trihalomethanes, which form in the distribution system after chlorination and are also a regulated contaminant. All other parameters were of interest for blending modeling with TW’s existing distribution system water quality.

Table 1. Agua Nueva WRF Tertiary Effluent Historical Water Quality (2019–2024) Summary and AWP Purified Water Limits

Parameter Units Average Maximum Purified Water Limit/Guideline

Basis Value

1,4-Dioxane[a] µg/L 0.61 0.70 TW OG[b] ND

Alkalinity[a] mg/L as CaCO3 166 216 - -

Ammonia[c] mg/L as N 1.2 3.0[d] - -

Bromide[a] mg/L 0.23 1.84 - -

Calcium[a] mg/L 78.5 85.5 - -

Chloride[a] mg/L 146 166 - -

Hardness[e] mg/L as CaCO3 285 348 - -

Magnesium[a] mg/L 14.1 24.6 - -

Nitrogen, Total[e] mg/L as N 6.47 13.8 Nitrate MCL[f] 10

Nitrate[a] mg/L as N 2.3 8.9 MCL[f] 10

NDMA[e] µg/L 0.44 0.50 CA NL[g] 0.01

Orthophosphate as P[a] mg/L as P 1.3 5.2 - -

PFOA[e] ng/L 5.9 13 TW OG[b] ND

PFOS[e] ng/L 2.0 4.0 TW OG[b] ND

Parameter Units Average Maximum Purified Water Limit/Guideline

Basis Value pH[e] SU 7.3 7.9 - -

Sodium[a] mg/L 130 144 - -

Temperature[a] °C 27.9 33.7 - -

TDS[a] mg/L 707 774 SMCL[h] 500

TOC[a] mg/L 7.7 9.6 ADEQ AWP Rule 2

TTHM[a] µg/L 6.6 11.6 MCL[f] 80

Turbidity[a] NTU 2.1 5.3 SMCL[h] 5 [a] Data source is TW sample location 510

[b] TW Operational Guideline (OG) [c] Data source is TW sample location 510 and Pima County Agua Nueva WRF effluent water quality [d] Used 95th percentile instead of maximum to omit outliers

[e] Data source is Pima County Agua Nueva WRF effluent water quality [f] Environmental Protection Agency (EPA) Maximum Contaminant Level (MCL) [g] California (CA) Notification Level (NL). Though this is not a contaminant regulated under the Safe Drinking Water Act, it is listed on the fourth EPA Contaminant Candidate List and is likely to be a regulated contaminant. Applying strict limits to chemicals of concern regulated in other states, including California, aligns with best practices for potable reuse and TW's goal of serving water better than what is currently served.

[h] EPA Secondary Maximum Contaminant Level (SMCL)

°C = degree(s) Celsius µg/L = microgram(s) per liter CaCO3 = calcium carbonate mg/L = milligram(s) per liter N = nitrogen ng/L = nanogram(s) per liter NTU = nephelometric turbidity unit OG = Operational Guideline P = phosphorus TDS = total dissolved solids

3.2 Treatment Goals

TW’s treatment goal for the full-scale AWPF, which translates to the demonstration facility, is to serve purified water that is “better than currently served.” Table 2 presents TW’s distribution system water quality data collected near the Tres Ríos WRF, where the full-scale AWPF finished water will enter into the distribution system in the future. The water quality data were retrieved from TW’s Water Quality Dashboard.

Further discussion with TW resulted in additional guidance on treatment goals, which are also summarized in Table 2. The nitrate treatment goal of 5 mg/L as N was selected while considering the high prevalence of nitrate in WRF effluent and targeting 50% of the nitrate MCL, which is 10 mg/L as N.

Table 2. Tucson Water Existing Distribution System Water Quality and AWP Treatment Goals

Parameter Units Existing Water Quality Treatment Goal

Alkalinity mg/L as CaCO3 100-150[a] 100-150

Calcium Carbonate Precipitation Potential (CCPP) mg/L as CaCO3 - 4–10

Free Chlorine Residual mg/L 1.5[b] 0.8–1.3

Hardness mg/L as CaCO3 253[b] <254

Langelier Saturation Index - - 0–0.5

Nitrate mg/L as N 0.48[b] 5 pH SU 7.8[b] 7.9

TDS mg/L 526[b] <500[c] a Alkalinity range for zone A1 provided by HDR. Dataset representative of distribution system water quality near Agua Nueva WRF. Range assumed to be representative of distribution water quality near Tres Ríos entry point to distribution system.

b Water quality data retrieved from TW Quality Dashboard in water service area ZA, 4505 W INA RD TUCSON AZ 85741 closest to sample point SP-030, representative of distribution system water quality near the entry point to the distribution system.

c Water quality in the zone receiving water from the AWP varies seasonally, with primarily recharged Central Arizona Project water with TDS>500 mg/L most of the year and native groundwater in during other parts of the year; native groundwater TDS is typically <500 mg/L. The blended water quality goal is to improve water quality, primarily TDS.

3.3 Treatment Options

Figure 2 through Figure 4 present the three main treatment options typical for potable reuse and acceptable in Arizona AWP regulations. All three options meet the ADEQ AWP Rule chemical removal requirements and pathogen removal requirements, including achieving cumulative validated treatment values from raw waste water to finished water, which are 13-log removal for viruses, 10-log removal for Cryptosporidium, and 10-log removal for Giardia (13-10-10). Jacobs’ validated treatment process starts from treated wastewater effluent, establishing the basis of water quality. The log removal values (LRVs) achieved by each unit process in each treatment option are presented along with each respective figure in Table 3 through Table 5.

The primary advantages of RO-based treatment are that it removes TDS and is typically not as affected by variable source water quality compared with carbon-based treatment. The primary disadvantages of RO-based treatment are high energy consumption and that it produces a reverse osmosis concentrate (ROC) waste stream, which may be difficult to dispose. In addition, carbon-based treatment typically has lower operating costs than RO-based treatment. The carbon-based treatment with a side-stream RO option has the same advantages of carbon-based treatment while partially removing TDS; however, it may be more complicated to operate, higher cost, and more energy intensive because it has more unit processes.

Ultraviolet advanced oxidation process (UVAOP) is used in potable reuse applications as a chemical and pathogen barrier. Advanced oxidation is achieved by creating hydroxyl radicals using UV light and a chemical oxidant, which could include chlorine, hydrogen peroxide, or ozone. Most UVAOP applications in potable reuse use chlorine or peroxide. UV/chlorine is most effective in low pH, typically 5.5–6.0 which is common for RO permeate. Carbon-based treatment trains will have much higher pH (higher than 7) and are therefore more conducive to hydrogen peroxide application. The side-stream RO option may use either depending on the amount of RO treatment and pH of the blended water.

Figure 2. RO-based Treatment

Table 3. RO-based Treatment LRV Summary

Treatment Process Virus Cryptosporidium Giardia

Membrane filtration (MF/UF)[a] 0 4 4

RO 1–2[b] 1–2[b] 1–2[b] UV Advanced Oxidation Process (UVAOP) 6 6 6 Chlorination 6 0 0

Total LRVs 13–14 12–13 11–12 [a] Membrane filtration which may include either microfiltration (MF) or ultrafiltration (UF) membranes.

[b] RO LRVs based on selected critical control point monitor and demonstration of removal of selected surrogate.

Figure 3. Carbon-based Treatment

Table 4. Carbon-based Treatment LRV Summary

Flocculation/ Sedimentation

2 4 2.5

Ozone 6 2a 6

BAC 0 0 0

GAC 0 0 0

UVAOP 6 6 6

Chlorination 6 0 0 Total LRVs 20 12 14.5 [a] 2-LRV credit for Cryptosporidium based on Concentration × Contact Time (CT) of 8 mg-L/min, which may be difficult to achieve for tertiary effluent because of high ozone demand.

BAC = biological activated carbon GAC = granular activated carbon

Figure 4. Carbon-based Treatment with Side-stream RO

Table 5. Carbon-based Treatment with Side-stream RO LRV Summary

Ozone 6 2[a] 6

BAC 0 0 0

MF/UF 0 4 4

GAC 0 0 0

RO[b] 0 0 0

UVAOP 6 6 6

Chlorination 6 0 0

Total LRVs 18 12 16 [a] 2-LRV credit for Cryptosporidium based on CT of 8 mg-L/min, which may be difficult to achieve for tertiary effluent because of high ozone demand.

[b] RO does not provide LRV credits in this option because it is a side stream and is only for TDS removal

One of TW’s treatment goals is that full-scale AWPF finished water TDS match or be lower than distribution system TDS. Consequently, Jacobs conducted a preliminary blending evaluation of the purified water produced with the potable water in the distribution system. The evaluation compared the projected TDS levels of the three treatment options while assuming that the ROC waste produced from RO treatment would be discharged to the sewer to Agua Nueva WRF. Table 6 summarizes the results of this study. Currently, the distribution system TDS near the Tres Ríos WRF is 533 mg/L, and the Agua Nueva WRF influent TDS is 707 mg/L.

Table 6. Treatment Options TDS

Treatment Option Estimated AWPF Finished Water TDS (mg/L)

Blended Potable Water TDS (mg/L)

Estimated Agua Nueva TDS (mg/L) and TDS Increase (%) from ROC Sewer Discharge

RO-based AWPF 20 300

(10% increase)

Ozone BAC GAC

Agua Nueva WRF Final

Effluent

UV AOP

H2O2

Microfiltration

Reverse Osmosis RO Brine Disposal

Treatment Option Estimated AWPF Finished Water TDS (mg/L)

Blended Potable Water TDS (mg/L)

Estimated Agua Nueva TDS (mg/L) and TDS Increase (%) from ROC Sewer Discharge

Carbon-based AWPF 798 650

(no change)

Carbon-based with RO Side-stream AWPF[a]

500 520

(4% increase)

[a] 40% of the flow was sent to the RO side stream for this evaluation

TW may select the RO-based treatment option for Tres Ríos WRF effluent at the full-scale AWPF, based on the water quality evaluation and treatment option comparison; however, this will be confirmed during full-scale facility design. Therefore, the Demonstration AWPF treating Agua Nueva WRF effluent will be designed as an RO-based treatment train. The facility will include designated space to conduct additional research using alternate treatment processes.

4. Conceptual Design The Demonstration AWPF will be installed inside TW’s reclaimed WTP Filter Building. The Filter Building previously housed vertical pressure vessels that treated secondary effluent from the decommissioned Roger Road WRF followed by chlorination at the reclaimed WTP’s chlorine contact basin (CCB) to tertiary levels. The equipment in the Filter Building was demolished in 2024. Tertiary effluent is currently received from the Agua Nueva WRF at TW’s tertiary effluent pump station before being pumped through piping near the Filter Building toward the reclaimed WTP’s CCB. The Demonstration AWPF will receive its influent flow from the existing piping adjacent to the Filter Building. The Conceptual Design drawings are shown in Attachment A.

The Demonstration AWPF will consist of the following process components:

MF/UF skid

RO skid

UVAOP skid

Chlorine contact pipe

GAC skid (optional)

- GAC was considered in the RO-based train for the Demonstration AWPF because it can serve as an additional chemical barrier for low molecular weight organic compounds that are not removed by

RO.

The Demonstration AWPF Conceptual Design will also include site and Filter Building architectural improvements.

4.1 Site Layout

TW’s reclaimed WTP is west of Interstate 10 and north of Sweetwater Drive. It is adjacent to TW’s Sweetwater Wetlands Park, TW’s reclaimed water recharge basins, Pima County’s abandoned Roger Road WRF, and the Agua Nueva WRF. Figure 5. shows the general location of the facility.

Figure 5. Site Location

Image Source: Pima County GIS 2022

The reclaimed WTP site includes the Administration, Control and Filter Building, Ammonia Building, CCB, reclaimed water reservoir, and reclaimed water pump station. Figure 6 shows the project site layout at the northern end of the reclaimed WTP with planned improvements as part of the Demonstration AWPF Conceptual Design. A new parking lot will be added on the northern side of the Filter Building, and pavement will be added to the western side of the Filter Building. A new entrance will be provided at the southwestern corner of the Filter Building for public tours.

Figure 6. Demonstration AWPF Site Layout

4.1.1 Existing Piping and Hydraulics

As previously noted, the Demonstration AWPF will receive influent flow through an existing 16-inch pipeline on the western side of the Filter Building. Aboveground piping conveys tertiary effluent south through the 16-inch filter influent header and splits between three 12-inch filter influent laterals that head east toward the Filter Building. Each lateral splits into two branches that head below ground. For each lateral, one branch connects to the 36-inch filter effluent header that heads south and the other branch continues east before elbowing up above ground, ending at a 10-inch closed valve and blind flange inside the Filter Building. Jacobs proposes to tie into the southernmost blind flange to supply the Demonstration AWPF. Additional piping modifications are proposed, including removing the existing isolation valve upstream of the 90-degree bend outside of the building as reflected in Attachment A Conceptual Design Drawings.

The 36-inch filter effluent header continues south toward the CCB. North of the CCB, the 36-inch header elbows up to an air gap having an elevation of 2279.23 feet, as shown on Figure 7. Initial hydraulic conditions of the Demonstration AWPF are the maximum water level at the MF/UF feed tank, estimated to be at elevation 2,271.50 feet. Therefore, the secondary effluent pump station is expected to provide sufficient head to pump water through existing piping and fill the MF/UF feed tank.

Figure 7. 36-inch Filter Effluent Header Air Gap at the CCB1

1 The source of Figure 7 is the Reclaimed Water Treatment Plant Chloramination Project design drawings, which were completed by

Jacobs and delivered to TW in 2013.

4.2 Process Definition

The Demonstration AWPF process flow diagram (PFD) is presented on Figure 8. Each of the treatment processes (MF/UF, RO, UVAOP, and GAC) will be vendor-supplied as independent pilot skids. As shown on Figure 8, equipment and instrumentation within the yellow boxes are inclusive with that particular skid.

Items outside of the yellow boxes are not included with the vendor-skids and will need to be procured separately.

Figure 8. Demonstration AWPF Process Flow Diagram

Estimated flows are provided in the PFD at each step of the treatment process. Each pilot skid is designed to have an overflow so that adequate flow is provided to the next skid. This results in a Demonstration AWPF feed flow of 62 gallons per minute (gpm) and a finished water flow of 2.6 gpm. Overflows and backwash waste streams will be directed to a sump that will be pumped to the to the existing Agua Nueva final effluent piping downstream of the pilot intake.

Table 7 details how the treatment train meets the 13-10-10 LRV requirements.

Table 7. Demonstration AWPF LRV Summary

Treatment Process Virus Cryptosporidium Giardia

MF/UF 0 4 4

RO 1-2[a] 1-2[a] 1-2[a]

UVAOP 6 6 6

Chlorination 6 0 0

GAC 0 0 0

Total LRVs 13-14 12-13 11-12 [a] RO LRVs based on selected critical control point monitor and demonstration of removal of selected surrogate

The Demonstration AWPF process layout is presented on Figure 9. Agua Nueva tertiary effluent flows through an existing aboveground header to the west of the Filter Building before flowing through laterals that elbow below ground. These laterals enter the building from the west and come aboveground where they are capped with a closed valve and blind flange. The Demonstration AWPF feed line will tap into the existing lateral in the southwestern corner of the Filter Building as shown in the layout. This line will be connected to the MF/UF skid feed tank in the southeastern corner of the building. Filtrate from the MF/UF skid will then be pumped north to the RO skid where it will be pressurized through the RO membranes, all the way through the UVAOP skids before the product water is discharged into the UVAOP product water tank. The UVAOP product water then flows south by gravity through the serpentine chlorine contact pipe before being pumped through the GAC skid. From there, finished water fills the purified water tank before being dispensed for tasting. The sump that collects overflows and waste streams will be on the northern end of the site. It will be outdoors and built in the existing sodium hypochlorite containment area, which is under a canopy. From the sump, submersible pumps will return the overflows and waste streams to the existing pressurized filter effluent header.

Figure 9. Treatment Process Layout

The treatment processes were arranged to facilitate tours in order of process treatment and immerse visitors in the process space. From the welcome center and visitor space, tours will start at MF/UF and flow in a counter-clockwise direction to each unit process, with signs that describe the treatment process and objectives. A large space was provided in the center of the processes for the tour group to gather, discuss, and ask questions. The group is then directed to the tasting station to facilitate water taste tests and revisit process areas as needed. From there the group has access to the welcome center and patio to enjoy the surrounding landscape. Chemicals, future research processes, and purified water storage are located away from public tour access, adjacent to the existing roll-up door for operations access.

Treatment process equipment will be supplied by various vendors as independent and fully functional pilot skids. Vendor provided information is provided in Appendix B. Each skid includes the mechanical equipment required for pilot operation. Online analyzers and transmitters communicate to programmable logic controllers (PLCs) independent to the pilot skid to allow for pilot operation according to the desired design criteria.

4.2.1 Preformed Monochloramine

Preformed monochloramine will be added upstream of the MF/UF to help control biological fouling of the strainers, MF/UF, and RO processes. Currently, Agua Nueva WRF uses chloramination post filtration before conveyance into the reclaimed water system. The reclaimed water typically carries a chloramine residual of 0.5 to 1 mg/L. The preformed monochloramine system will be designed to boost the monochloramine to 3 mg/L chlorine. This will be further defined during the design effort. The goal will be to maintain as low of a residual in the RO permeate as possible to maximize UV transmittance for the benefit of the downstream UVAOP process while simultaneously providing adequate biofouling protection to the RO membranes. A residual in the range of 0.5 to 1.0 mg/L in the RO permeate is anticipated based on operation of other potable reuse systems.

UVAOP product water will be used as the carrier water for the preformed monochloramine system. The carrier water will be pumped from the UVAOP product water tank to a chemical injection location upstream of the MF/UF feed tank. Sodium hydroxide will first be added to the carrier water to increase the pH to 8.0 or above, then sodium hypochlorite will be added to the carrier water, followed by liquid ammonium sulfate. A static mixer will be installed after each chemical injection into the carrier water to properly mix the chemicals. All chemicals will be fed from the chemical skid discussed further in the next sections.

4.2.2 MF/UF and RO Systems

The preliminary MF/UF and RO skid designs were based on information provided by H2O Innovation, an integrated membrane system supplier that has standard pre-engineering pilot systems for both MF/UF and RO.

4.2.2.1 MF/UF System

The standard H2O Innovation MF/UF skid is equipped with a feed tank and feed pump that will receive chloraminated effluent. The feed pump will pressurize the strainer and the MF/UF membrane modules.

The H2O Innovation MF/UF skid allows for parallel testing using up to three membrane modules that can be the same or a different manufacturer model. The MF/UF filtrate is collected in a filtrate tank that will feed the downstream RO skid and also provide backwash water for the MF/UF system. The skid is equipped with a backwash pump and air compressor used to backwash the membrane modules. Backwash wastewater will be directed to the sump. The air system will also be used for pneumatic valve operation and to perform membrane integrity testing. MF/UF will be periodically cleaned through a clean-in-place (CIP) system. CIP waste will be neutralized in the CIP skid and drain to sewer.

Figure 10 shows a photo of the MF/UF skid, and Table 8 presents the MF/UF system design criteria. The values are based on the Toray HFU-2020AN membrane, though alternate membrane suppliers may be selected.

Figure 10. H2O Innovation MF/UF Skid

Image Source: H2O Innovation

Table 8. MF/UF System Design Criteria

Parameter Units Criteria

Module Supplier and Model - Toray HFU-2020AN[a]

Number of Modules - 3

Module Area, each ft2 775

Flux gfd 36

Feed Flowrate gpm 60

Recovery % 95.5

Monochloramine Dose[b] mg/L 1.0–3.0 [a] Alternate membranes may be tested [b] To be confirmed with further water quality analysis gfd = gallon(s) per square foot per day

A separate chemical storage and feed skid will be used to perform the routine chemical cleaning of the UF and RO membranes required by each supplier for sustained operation. The chemical skid is equipped with dosing pumps to inject cleaning agents—sodium hypochlorite, sodium hydroxide, citric acid, and sulfuric acid—into the CIP tank. The MF/UF system is programmed to automatically initiate maintenance cleaning or enhanced backwash cycles at required intervals—typically every 1 to 7 days—depending on the feed water quality. More extensive CIP cycles will be manually initiated if needed and will be conducted with onsite assistance from H2O Innovation.

The MF/UF skid will include a PLC and human-machine interface (HMI) with data logging capabilities. The PLC will be programmed to execute all modes of operation specific to each module installed, including backwashing and membrane cleaning regimes. The UF skid will include online analyzers for feed tank level and pH as well as UF influent flow, turbidity, pressure, and pH. The skid will also include online analyzers for individual membrane filtrate pressure, backpulse supply flow, and filtrate tank level. The UF skid PLC and HMI are on the skid, and the operator can locally monitor system performance at the HMI. The PLC is capable of connecting to an external network (direct or wireless) to allow for remote monitoring.

4.2.2.2 RO System

The H2O Innovation RO skid is equipped with chemical feed, including sulfuric acid and antiscalant to adjust the feed pH to prevent membrane scaling, and a transfer pump that will pump MF/UF filtrate from the filtrate tank through a cartridge filter to the high-pressure pump, which pressurizes the water through the RO membranes. The RO system includes seven pressure vessels arranged in a 4:2:1 three-stage vessel array that will house 4-inch RO elements. For flux balancing, the RO system will include valving to allow for permeate throttling and an interstage booster pump to boost the flow and pressure between the second and third stages. The RO process will produce RO permeate and RO concentrate waste. The permeate will be collected in a permeate tank not included with the skid and feed the downstream UVAOP system. A CIP/flush tank will collect RO permeate to perform CIP and flush. A CIP/flush pump will use the permeate collected in the CIP/flush tank to perform system flushes after chemical cleaning or before the system shuts down. RO concentrate will be directed to the sump. CIP waste will be neutralized in the CIP skid and drain to sewer.

The RO skid is equipped with a PLC and HMI with data logging capabilities. The RO skid includes online analyzers for feed flow, conductivity, turbidity, and TOC as well as post-cartridge filter pressure, pH, temperature, and oxidation-reduction potential furthermore, the skid will include online analyzers for permeate flow, pressure, temperature, conductivity, and TOC as well as concentrate flow, pressure, and conductivity. Similar to the UF skid, the RO skid PLC and HMI are on the skid, and the PLC is capable of connecting to an external network (direct or wireless) to allow for remote monitoring.

Figure 11 provides a photo of the RO skid, and

Table 9 presents the RO system design criteria. The membrane design summarized later in this section is based on Hydranautics membranes, though alternate membrane suppliers may be selected.

Figure 11. H2O Innovation RO Skid

Image Source: H2O Innovation

Table 9. RO System Design Criteria

Parameter Units Criteria

Element Supplier and Model - Hydranautics ESPA2-LD-4040[a]

Module Area, each ft2 80

Membrane System Array 4:2:1

Design Flux gfd 12

Permeate Flowrate gpm 28

Recovery % 80-85

Design Feed Pressure psi 200

Antiscalant Dose[b] mg/L 2–4

Sulfuric Acid Dose[b], [c] mg/L 25–40 [a]Alternate membranes may be tested [b]Antiscalant and acid dose to be refined during detailed design [c]Dose presented as 100% chemical

4.2.2.3 MF/UF and RO Chemical Systems

The aforementioned chemical skid, based on the offering provided by H2O Innovation, will provide antiscalant, sulfuric acid, citric acid, ammonium sulfate, sodium hydroxide, and sodium bisulfite. Similar to the UF system, the RO system will require routine chemical cleaning. The RO skid includes a CIP/flush tank that will be used to batch cleaning chemicals to perform a manual CIP using the included CIP/flush pump as needed

4.2.3 UVAOP System

The UVAOP concept design is based on Trojan Technologies UVAOP skid, which includes a chemical feed pump for oxidant injection and a 4-lamp UV reactor. The oxidant will be sodium hypochlorite or hydrogen peroxide, and the skid includes an HMI with data logging capabilities. Figure 12 is a picture of the UVAOP skid, and Table 10 presents the UVAOP system design criteria.

Figure 12. Trojan Technologies UVAOP Skid

Image Source: Trojan Technologies, Inc.

Table 10. UVAOP Design Criteria

NDMA Target = CA NL[a] NDMA Target = 50% of CA NL[a]

Reactor Supplier and Model

TrojanUV AOP

Demonstration Pilot

Flowrate gpm 26

Number of Lamps # 4

Lamp Wattage W 150–500

NDMA Target µg/L 0.010 0.005

NaOCl Dose mg/L 3.4 2.8

H2O2 Dose mg/L 6.6 5.9

NaOCl UV Dose mJ/cm2 1,792 2,145

H2O2 UV Dose mJ/cm2 1,826 2,148 [a] NDMA CA NL is 0.010 µg/L

# = number H2O2 = hydrogen peroxide mJ/cm2 = millijoule(s) per square centimeter NaOCl = sodium hypochlorite W = watt(s)

The high-pressure feed pump and interstage booster pump on the RO skid will be designed provide sufficient head to pump water through the UVAOP skid to the UVAOP product water tank. The UVAOP skid includes a peristaltic pump that pumps oxidant from the chemical skid to the injection point on the UVAOP skid. An in-line static mixer then mixes the oxidant into the permeate before flowing through an adjustable serpentine pipe to achieve sufficient oxidant CT. The oxidant-laden permeate then enters the 4-lamp UV reactor where the advanced oxidation process takes place. Either two or four lamps can be turned on, and the output of the lamps can be adjusted from 150 to 500 W. UV reactor effluent then flows through a modulating butterfly valve that maintains constant flow before filling a permeate tank downstream.

The UVAOP skid will include online analyzers for feed flow, UV transmittance, free chlorine, and pH as well as reactor effluent UV transmittance. The UVAOP skid HMI is on the skid where the operator can locally monitor system performance.

4.2.4 Chlorine Contact Pipe

As presented in Table 11, 6-log removal by chlorination will be needed to meet the required 13-log removal for viruses. Jacobs performed CT calculations to size the chlorine contact pipe based on the water quality constraints presented in Table 11 for minimum temperature. Jacobs assumed a maximum pH of 6 for RO permeate and a baffling factor of 0.9 for plug flow through the pipe. The calculation results indicated that a free chlorine residual of 1.90 mg/L is required in a 3-inch pipe that is 16 feet long to achieve at least 6-log reduction across the whole year.

Table 11. Agua Nueva WRF Effluent Maximum pH and Minimum Temperature

Month Minimum Temperature (°C)

January 22.3

February 20.6

March 22.2

April 23.4

May 22.7

June 20.4

July 28.7

August 30.3

September 30.4

October 26.8

November 24.2

December 22.2[a]

[a] Outlier temperature of 7.15 °C in December was not considered

Following UVAOP, sodium hypochlorite will be injected, and the UVAOP effluent pipe will be upsized from a 2-inch to 3-inch pipe and will be routed in a serpentine fashion to increase CT. The sodium hypochlorite will be stored and fed from the H2O Innovation chemical skid, and the free chlorine in the chlorine contact pipe will be quenched by GAC downstream. A free chlorine online analyzer will be added at the end of the serpentine pipe to achieve the required 1.90 mg/L of free chlorine.

4.2.5 GAC System

The GAC skid concept design was based on Intuitech Inc.’s GAC skid, which will include four granular media filtration columns and an HMI with data logging capabilities. Figure 13 is a picture of the GAC skid, and Table 12 presents the GAC system design criteria.

Figure 13. Intuitech Inc. GAC Skid

Image Source: Intuitech, Inc.

Table 12. GAC Design Criteria

Parameter Units Criteria

Total Flowrate gpm 2.6

Number of Columns # 4

Flowrate per Column gpm 10-min EBCT: 0.875 20-min EBCT: 0.425

Column Diameter in 6

Column Surface Area ft2 0.20

Media Depth ft 6

EBCT min 10, 20

Loading Rate gpm/ft2 2.93

Media - Media #1: Calgon F400

Media #2: TBD

Media Effective Size mm 0.55–0.75

Media Uniformity Coefficient - 1.9

EBCT = Empty Bed Contact Time in = inch(es) mm = millimeter(s)

Each column has its own feed pump, so the flow rate can be specified for each column. The columns are 6 inches in diameter and are designed to hold up to 6 feet of media. Two of the columns will be loaded with the Calgon F400, the other two will be loaded with another medium to be determined during detailed design. Both media will be evaluated at two EBCTs: 10 minutes and 20 minutes. All columns will be run in parallel. GAC effluent will be collected in a separate purified water tank and a backwash supply tank included with the skid. Water from the purified water tank will supply the purified water tap and purified water tasting station. The backwash supply pump will pump water from the backwash supply tank to backwash the columns in conjunction with air from the included air compressor.

The GAC skid will include online analyzers for individual column influent flow, differential pressure, and effluent turbidity. The skid also includes online analyzers for the backwash supply tank level and backwash supply flowrate. The GAC skid HMI is on the skid where the operator can locally monitor system performance.

4.3 Future Research Functions

TW expressed interest in investigating ozone and BAC as potential treatment options in the future, as the carbon-based option and side-stream RO option both include ozone-BAC in their treatment trains.

Ozone-BAC would precede MF/UF and could be located as displayed on Figure 14. The preliminary design is based on an Intuitech-provided ozone skid, and BAC skid footprints are based on a design flowrate of 45 gpm, to ensure adequate flow to the RO system.

Figure 14. Ozone-BAC Layout Option

4.4 Potable Water Feed

Periodically, Agua Nueva WRF will need to shut down or divert flow from the Demonstration AWP facility.

Though this is only expected to happen 1 to 2 times per year, unexpected water quality changes or events can result in an immediate diversion of plant effluent and therefore a loss of pilot feed. Coordination with Agua Nueva WRF operations staff is recommended to avoid or minimize shutdown events to maintain constant feed flow to the pilot process. However, to reduce the operational burden of preparing the pilot plant for shut down, a backup potable water feed will be provided. This alternate feed option will need to be further evaluated during detail design as the potable water source contains a chlorine residual that will need to be accounted for in the monochloramine dosing strategy.

4.5 Electrical

4.5.1 Electrical Supply and System Configuration

The existing electrical equipment room is in the Blower/Control Room in the southwestern corner of the building. The Control Room houses a 400A-rated motor control center (MCC) alongside other equipment, including a wireway, disconnect switches, an automatic transfer switch (ATS), and blowers. The MCC is part of the reclaimed WTP’s larger power distribution system and is served by a Tucson Electric Power Company utility transformer on the western side of the building. The transformer is a 500-kilovolt ampere (kVA), 13.8kV-480Y/277V step-down transformer with the neutral bonded at the transformer and supplies different areas of the site via separate disconnect switches. The Control Room MCC is served by the 400A “FILTER BLDG DSW” main fused disconnect on the southern wall of the Control Room. The Control Room wireway is served by the ATS by a 90kW generator, or by the “Control Room ATS DSW.”

An electrical load analysis is to be undertaken separately to identify equipment that can be replaced, consolidated, or removed. Several potential options will be considered for supplying electrical power to the Demonstration AWPF. For all options, an electrical load analysis must be undertaken separately to determine the demand load already existing on the electrical equipment at the site. Billing history from the utility can be used to determine the existing demand load at the main service. Existing 480V electrical panels BL and EH and existing 208Y/120V panels BP and EL are in the existing filter room space. As part of the electrical load analysis, equipment will be identified for replacement, consolidation, or removal.

After this is performed, the existing panelboards can be relocated if needed and their loads reconnected.

Existing space in the panels can be used to supply the new Demonstration AWPF loads, depending on the results of the load study. Alternatively, existing space in the 400A MCC can be used to provide a 175A branch feeder to a 480V, 3-phase panelboard and to provide a separate 40A branch feeder to a 480V-120/240V single-phase step-down transformer that will supply a 120/240V panelboard on its secondary. The new panelboards will be provided with surge protection equipment to current standards.

Loads requiring uninterruptible power supply are not anticipated. There will be no need to provide standby generator power for the equipment installed in this scope.

Interior luminaires will be selected based on the use-case of the spaces in the Demonstration AWPF.

Exterior luminaires will be provided above entry doors with photocell control. Interior ground fault circuit interrupter receptacles will be replaced to meet current standards.

4.5.2 Applicable Codes and Standards

The design will be based on the following codes and standards:

2023 National Fire Protection Association 70 – National Electrical Code 2023 Institute of Electrical and Electronic Engineers C2 – National Electrical Safety Code American National Standards Association National Electrical Manufacturers Association Institute of Electrical and Electronic Engineers Instrument Society of America Insulated Cable Engineers Association Occupational Safety and Health Administration ASTM International Underwriters Laboratory (UL) Illuminating Engineering Society National Fire Protection Association

4.5.3 Listed and Labeled Equipment

Electrical equipment, materials, or services to be provided will have an attached label, symbol, or other identifying mark of an organization concerned with product evaluation, compliance with appropriate standards, and equipment performance. Typically, this is the UL Label or Listing. In situations where a UL Label or Listing cannot be provided for equipment because of a lack of UL standards, then testing will be performed by an organization that is acceptable to the authority having jurisdiction (AHJ).

4.5.4 Conduit and Wiring

General guidelines for raceway sizing, selection, and installation are given as follows:

Conduit sizing will be based on thermoplastic, heat- and water-resistant insulation. Conduit sizes will be 3/4-inch minimum diameter.

Rigid galvanized steel conduit and fittings will be used when exposed in interior noncorrosive areas and in noncorrosive areas outdoors. Polyvinyl chloride-coated rigid galvanized steel conduit and fittings will be used in exposed corrosive interior and exterior areas.

Flexible, metallic, liquid-tight conduit will be used for connections to equipment as required.

General guidelines for wire and cable sizing, selection, and installation are given as follows:

Stranded copper conductors will be used for all low-voltage applications except lighting and receptacle wiring. Solid conductors Number (No.) 10 American Wire Gauge (AWG) and smaller will be used for lighting and receptacle wiring.

Minimum conductor size of No. 12 AWG will be used for power and lighting branch circuits. Type THHN/THWN-2 insulation will be used for No. 10 AWG and smaller conductors. Type XHHW-2 insulation will be used for No. 8 AWG and larger conductors. For sizing conductors No. 1 AWG and smaller, 60°C conductor ampacity ratings will be used. For sizing conductors larger than No. 1 AWG, 75°C ratings will be used.

Low-voltage status/control (less than 100 volts) and analog signal circuits will be routed in 600-volt, single-twisted, shielded-pair instrumentation control cables.

Shields of shielded instrumentation cables will be grounded to the ground bus at the power supply for the analog or low-voltage discrete signal circuit. Shielded instrumentation cables will not be grounded at more than one point.

4.6 Architectural Design Approach

The architectural design approach focuses on maximizing patron experience while minimizing impact and costs to the existing facility. The approach identifies the experience beginning at the arrival in the parking facility and completing as one returns back to their vehicle. Thus, the experience is both interior, exterior, and transitive in nature. It also happens in real time at the site, as well as after one’s visit to the facility is complete. It is an educational journey through water, the impact of which is intended to last beyond just this visit. The full experience and the facility itself are intended to inspire and educate visitors on the impacts of water and what the facility as a whole provides. Attachment A includes interior and exterior renderings of the AWPF facility.

The approach begins with reanalyzing the parking and proving a better layout for visitors. Parking is strategically located and laid out to take advantage of existing site conditions that benefit the patron experience. Shade trees on site are left in place, and parking is laid out to focus the entry path to a walk that is shaded. Added landscaping will be provided to contrast the surrounding landscape, highlighting the power of water and its impact. It will be noted (as all parts of the educational journey will be) via strategic signage, that the water is cast water from the process equipment inside and is not inappropriate water usage. This entry path will take advantage of the existing water piping on site that will act as a guide leading to the entry, but it will also work to build intrigue of what is to come on this journey of water education. The pipe will be cleaned up, painted to TW branding, and slightly altered to create an entry portal, all of which is low cost with big impact.

The exterior of the building will largely be left alone, with the exception of two large openings that will be cut into the existing façade: one to create an entry, the other to access outdoor educational and social patio space. The openings are strategically located to minimize structural impact to the building, while taking advantage of shading provided by existing trees. This lessens the impact of the new glazed openings on the building’s conditioning. The modern materials and transparency will stand in contrast to the more simple and muted existing masonry, creating large impact with minimal material and cost.

Once inside, the design team has conceptualized the space split between three key functional zones:

Public/Entry/Educational Public/Process/Educational, and Private/Storage/Functional. The location of each zone is specifically chosen to minimize impact to the facility, lessening the cost of implementing each zone’s requirements into the design.

The educational zone provides for a more sound controlled environment appropriate for educational and social interactions. It provides flexible space that can be tailored to many functions supported by new public restrooms and a kitchen and bar. These elements are located strategically to access existing infrastructure lessening the cost and impact to the existing facility. The zone takes advantage of the most exterior wall space of any of the zones for entry, exiting, sound control, and educational wall space. These walls are also most easily converted to new International Energy Conservation Code (IECC) appropriate walls to support the conditioning of this space. The layout also takes advantage of an existing alternate exit that will be required by code. Many of the finishes in the space are simple but impactful, with color being an important factor. As noted, this zone would be conditioned to provide comfort that educational and social spaces require.

This first educational zone is separated from the second process education space by glass partition, allowing a direct connection to what is being learned to the actual equipment doing the work. It also creates a large sense of each space, making them almost feel as one. This second zone is more industrial and durable in its finishes, matching the equipment and function inside. A path of educational travel is laid out within this zone, terminating in tasting stations that adjoin the second exterior exit (a glass rolling door) that provides access to the outdoor patio––a place to relax and enjoy the experience just had. This second zone (along with the third) are idealized as nonconditioned or semi-conditioned, but this will have to be negotiated with the AHJ as outlined in the code section in the next section.

A third zone is separated from this space by a durable, solid partition that provides private, access-controlled space for support storage, chemicals, and loading. The space again takes advantage of existing elements such as the existing overhead door and secondary human exit already provided. Simple floor leveling is all that is required to round out this space. Fork lift access and travel path are accounted for, as well as access to the process space for such vehicles and support.

4.6.1 Code Review

A critical first step in any design process is to review the Conceptual Design against all applicable codes and standards. Architectural code review focuses on the life and safety of building occupants based on the building layout and building classification. A full code analysis will be performed by the design team focusing on building occupancy, separation requirements, and proper exiting sequences and paths based on egress requirements for both individual spaces and the building as a whole. Any passive fire suppression and control elements are identified via proper building classification and the material parameters set forth in code, along with separations and division of space based on risk analysis of each space.

A wholistic code analysis is done internally while a key path of compliance is…