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Technology Evaluation for Zero Liquid Discharge at a Combined Cycle Power

Plant with an Air Cooled Condenser

Nicole Makela Project Engineer

Advanced Power (NA)

Michele Funk; P.E. Bechtel Infrastructure and Power

Frederick, MD

Joel Davie; P.E. Bechtel Infrastructure and Power

Frederick, MD

Ian Mitchell; P.E. Bechtel Infrastructure and Power

Frederick, MD

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Keywords: ZLD, Zero Liquid Discharge, Ion Exchange

ABSTRACT

To expedite the permitting process and reduce environmental impacts, combined cycle power plant developers are analyzing options for minimal wastewater discharge. Due to the interdependent relationship between plant water users and wastewater producers,

analyzing options for minimal wastewater discharge requires a holistic approach, in which technology options for water users and wastewater producers are evaluated

concurrently. Development of an approach that minimizes cost and risk, yet maintains flexibility to variable plant makeup water quality requires innovative applications of

treatment and reuse technologies.

This paper will analyze water and wastewater treatment options for a combined cycle power plant with an air-cooled condenser and no permit to discharge wastewater. The paper will also illustrate how ion-exchange technologies with off-site regeneration may be a favorable option for this application. Process schematics for alternate treatment technologies will be presented and compared, along with a qualitative discussion of

each technology’s ability to handle variable water quality. Additionally, operating considerations and risks associated with each design will be provided. Finally, order of magnitude rental and capital costs will be provided for ion exchange technologies with

off-site regeneration.

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INTRODUCTION

Power project siting in areas with limited water supply and discharge options is causing combined cycle power plant developers to consider options for minimizing system water demand and wastewater discharge streams. This paper considers water and wastewater treatment options for a combined cycle power plant with an air-cooled condenser (ACC) and no permit to discharge wastewater. Design, operating considerations and risks associated with potential solutions are provided with respect to factors such as cooling strategy, materials of construction, cycles of concentration, technology-specific sensitivities and water source quality. Order of magnitude rental and capital costs are also provided for ion exchange technologies with off-site regeneration.

DESIGN INPUTS

This study considers a combined cycle power plant using two combustion turbines (CTs), two heat recovery steam generators (HRSGs) and one steam turbine (ST) in a 2x2x1 configuration. The system must produce a minimal liquid discharge (<1 gpm) that can be hauled offsite or produce a dry salt product suitable for disposal in a commercial landfill.

The study criteria includes certain fixed plant arrangement inputs including the use of an ACC, evaporative coolers at CT inlets, oil-water separators downstream of all CT and ST building drain streams, condensate polishing within the steam cycle, and the use of a closed cooling system fin fan cooler for HRSG blowdown cooling in lieu of quenching with service water. In addition to the fixed plant arrangement criteria, certain operating strategies were also assumed for the purposes of this paper. Operating criteria include the use of an all volatile treatment (AVT) chemical treatment program in the steam cycle, off-site regeneration of the steam cycle condensate polisher resin, segregation of equipment off-line water wash to a dedicated holding tank, and the use of sump covers and normally plugged floor drains to control the risk of wastewater contamination.

The quality of water available to the facility is well water that does not require pretreatment prior to demineralization (see Appendix A).

Should pretreatment be required for alternate water sources, the pretreatment technology would consist of suspended solids reduction with clarification and/or media filtration, then sludge dewatering. Since backwash from the pretreatment and clarifier sludge can be treated in the thickener to produce a solid cake, addition of a pretreatment system will likely not have an impact on the wastewater treatment technology selected and has not been considered in this paper. Wastewater system design depends greatly on the quality of the water coming out of the demineralizer train and subsequently out of the steam cycle blowdown. Demineralizer train effluent is assumed to be within typical steam cycle water quality requirements for HRSG OEMs, as summarized in Table 1 (GE, 2012).

Table 1: Steam Cycle Water Quality Requirements

Parameter Normal

Operating Level

Sodium, ppbw, as Na ≤2

Cation Conductivity or Degassed Cation Conductivity, µS/cm (at 25˚C) ≤0.2

Silica, ppbw, as SiO2 ≤10

Chloride, ppbw, as Cl ≤2

Sulfate, ppbw, as SO4 ≤2

Total Organic Carbon, ppbw, as C ≤100

Specific Conductivity -

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For the purposes of this study, steam cycle blowdown is assumed to be 1 percent of the ST exhaust flow, an AVT chemical treatment program is implemented in the steam cycle and the condensate is polished using a deep bed polisher which is regenerated off-site. Evaporative cooler blowdown quality is based on an assumed 3 cycles of concentration in the evaporative cooler. Sample losses are assumed to be 0.5 percent of the ST exhaust flow and where ultrafiltration units are used, the backwash flowrate is assumed to be 10 percent of the unit influent. Plant service water usage is estimated to be five gallons per minute.

As discussed in the introduction, the plant scenario under analysis does not include a NPDES permit for disposal of waste water. Therefore, all possible solutions must allow for process water recycle and water discharge must be minimal or zero, where possible. Using the basis described within this section, three potential options were identified. Further, the following streams were not considered for this study: (i) potable water; (ii) sanitary wastes; (iii) storm water runoff; (iv) and CT wash water. It is assumed that potable and sanitary waste is taken to and from the local municipality and wash waters from the CT are disposed of off site since these flows are infrequent.

DESIGN CONSIDERATIONS

Reducing water use and preventing ingress of contamination from other plant processes is essential for zero or a near zero liquid discharge system design. The design should incorporate water usage reduction at the facility to the extent practical, in addition to design changes required for optimum system performance. This section provides discussion of the necessary system design considerations included in this paper. Additional design considerations include protection against water and wastewater treatment system fouling or outages, as well as each technology’s ability to handle variable water quality.

When considering HRSG blowdown quenching, water makeup may be reduced via transfer of HRSG blowdown heat to the closed cooling water system’s fin fan cooler (air cooled) in lieu of enthalpy transfer to quench water. Off-site regeneration of the condensate polisher eliminates regeneration waste waters. Protection against water and wastewater treatment system fouling is achieved via incorporation of sump covers and curbed areas with floor drain plugs to reduce potential ingress of suspended solids and organic material to the waste water collection tank, and incorporation of a special area to wash glycol contaminated closed cooling water pump strainers and other equipment with possible organic contamination.

Design considerations for protection against water and wastewater treatment system fouling or outages include tank sizing and bypass capability. Designing for a larger wastewater collection tank can serve to mitigate inadvertent system upsets due to issues such as contaminated floor drains. This allows for continued system operation while maintaining minimum liquid discharge for limited periods of time in the event of a waste water treatment system outage. Designing for a larger demineralized water storage tank such that additional capacity may be stored in addition to typical operational needs, serves to mitigate outages in the demineralizer train and allows continued operation with contingency water storage for limited periods of time.

Design considerations to account for each technology’s ability to handle variable water quality include additional upstream filtration methods to prevent system fouling and implementation of certain operations practices to avoid contamination. Such systems include oily water sumps leading to oil/water separators upstream of the wastewater collection tank, and activated carbon units upstream of ion–exchange resins. Although not considered in this study, clarifiers could also serve this purpose in systems that have detectable concentrations of oil and grease. For the purposes of this paper pretreatment filtration backwash TSS is reduced with disposable cartridge filters upstream of the waste water collection tank. This prevents buildup of contaminants in the system. Operational mitigation measures include segregation of off-line CT water wash to a separate holding tank, and operations and maintenance procedures stressing conservative water usage, curbed areas with floor drain plugs and sump covers.

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MATERIALS OF CONSTRUCTION. Materials of construction of system components can also affect the quality of plant waste water streams. Carbon steel pipe used in lower pressure sections of the steam cycle and the ACC may undergo internal pipe wall corrosion and the corrosion byproduct (containing iron) can dislodge from the pipe wall and enter the system. Iron from the corrosion byproduct enters the steam cycle blowdown and shows up in the HRSG blowdown predominantly during startup and commissioning; however, this may occur to some extent during steady state operations as well. The condensate polisher can filter out some of the iron and the polisher system equipment may include cartridge filters upstream of the resin vessels to reduce the particulate loading on the resin. Further, every time the ACC is opened, a large surface area is exposed to oxygen, which accelerates corrosion. It has been well documented that even a small amount iron (on the order of a few ppm) can adversely affect ST equipment. Since an ACC and steam cycle constructed with no carbon steel components is cost prohibitive, periodically blowing down the steam cycle and purging iron contaminate is a cost effective and proven resolution to iron buildup in the system.

Additionally, the wastewater treatment system materials of construction will be driven by the treatment system chosen. For example, forced circulation heat exchangers that produce a solid crystal handle concentrations of chlorides at their solubility point (~180,000 ppm Cl-) and this concentration of chlorides produces a highly corrosive environment. This would require selection of duplex and super duplex stainless steel alloys for piping and components and would contribute to the overall cost of the wastewater treatment system. When evaluating the wastewater treatment technologies holistically the materials of construction must be considered since this will impact the total capital cost of the equipment.

CYCLES OF CONCENTRATION. Cycles of concentration in the evaporative cooler at the inlet to the combustion turbine can also affect the quality of plant waste water streams. Cycles of concentration in evaporative coolers affect the quality of evaporative cooler blowdown and the design (flow and salt content) of waste water treatment units. The cycles of concentration in evaporative coolers should be optimized to reduce scaling and corrosion of the cycled water while minimizing blowdown flow. CT OEMs provide guidance on the circulating water quality in the evaporative cooler including limits on ionic constituents subject to scaling and increasing corrosion potential. Unlike establishing cycles of concentration for cooling towers, CT OEMs do not allow use of inhibitors in evaporative coolers. Evaporative makeup water quality serves as the basis for cycles of concentration optimization. For example, in some systems, a softener or other pretreatment system upstream of the evaporative cooler may need to be added in order to meet the CT OEM’s makeup or circulating water quality requirements for the evaporative cooler. In other cases, blending service water and demineralized water may be the best choice. After deciding how to meet the evaporative cooler water quality requirements, the impacts on the resulting plant wastewater stream(s) must be determined. For the purposes of this paper and based on the raw water quality in Appendix A), pretreatment for the evaporative cooler makeup is not considered and 3 cycles of concentration is assumed for the plant evaporative coolers.

STEAM CHEMISTRY PROGRAM. Chemical treatment programs can also affect the quality of plant waste water streams. Use of a Phosphate Continuum (PC) chemistry program in the HRSG drum includes dosing of a phosphate-based chemical into the HRSG drum(s). This phosphate will be removed from steam cycle by means of HRSG blowdown. For this paper, phosphate is assumed to be dosed to the HRSG drum since condenser cooling is by means of an ACC. Use of phosphate dosing to the HRSG drum will facilitate the HRSG producing steam at elevated pH to provide better protection of the ACC. Use of an All Volatile Treatment (AVT) chemistry program for the HRSG condensate/feedwater includes an amine-based pH adjustment chemical and may include an oxygen scavenger dosed to the condensate/feedwater. This paper does not consider oxygen scavenger dosing of the condensate/feedwater. Oxygen scavengers are typically organic or an amine. The organic can be removed by a wastewater carbon filter. Amines added to the steam cycle through the AVT treatment program will volatilize in the HRSG drum, but then be removed by ion exchange in the condensate polisher. Amines will also be present in HRSG blowdown. These amines must be accounted for when designing the waste water treatment system. Though HRSG blowdown from the steam cycle will also affect the quality of the plant waste water, it is only the constituents in the HRSG blowdown added through the chemistry program, as discussed above, that will affect the wastewater treatment system selection. All other constituents are makeup feedwater water quality (Table 1) cycled up in the steam

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cycle (1 – 3% blowdown). Since the makeup water quality to the steam cycle has such a low conductivity, other constituents in the HRSG blowdown have too low a concentration to have any effect on wastewater system selection, .

METHODOLOGY/ ALTERNATIVES

When designing a plant for minimal liquid discharge, it is essential to understand that there is an interdependent relationship between plant water users and wastewater producers. The design engineer must take a holistic approach when analyzing options for minimal wastewater discharge. Technology options for water users and wastewater producers must be evaluated concurrently since wastewater produced from the treatment equipment, and chemicals used in the treatment processes, must be considered in the overall plant design. Both volumetric flows and salts must be balanced. Close attention must be paid to the demineralized system and wastewater system technologies evaluated to avoid build up of constituents in the closed system, causing a negative effect on cycle chemistry.

The following alternate approaches are presented below along with a discussion of the importance of developing an approach that minimizes cost and risk, yet maintains flexibility to variable plant makeup water quality:

1. Mobile Ion Exchange Technology with Off-site Regeneration for Cycle Makeup and Wastewater Treatment Systems

2. Permanent RO/EDI Cycle Makeup with Specialty RO/Crystallizer Wastewater System

3. Mobile Ion Exchange Cycle Makeup Demineralizer with Specialty RO/Crystallizer Wastewater Treatment System

MOBILE ION EXCHANGE TECHNOLOGY WITH OFF-SITE REGENERATION FOR CYCLE MAKEUP AND WASTEWATER TREATMENT SYSTEMS. - A sketch for this alternative is presented in Figure 1.

This design features off-site regenerated ion exchange technology for both the cycle makeup demineralization and wastewater treatment systems. The advantages of off-site resin regeneration is that salts are removed from the facility without the additional treatment systems required to generate a dry salt product or highly concentrated liquid waste stream; and avoiding the need to bring chemicals (salts) onsite that the additional treatment systems require.

The risks associated with this system are:

a. Colloidal particles (silica and others) are not charged and therefore cannot be removed by ion exchange with a high degree of confidence. This would lead to the formation of deposits in the steam cycle. Colloidal silica historically has been shown to be present in water analysis from some surface water bodies, so the design engineer should ensure sufficient sampling and analysis of silica to determine whether there is a possibility that it will be present in the makeup water. This risk is mitigated by providing a permanent ultra-filtration (UF) system ahead of the mobile ion exchange trailers.

The colloidal particles rejected by the UF system (if required for silica removal) are directed to the wastewater system. UF backwash/reject is processed through a cartridge filter. This removes colloidal particles that agglomerate or flocculate during their journey through the cycle. This agglomeration occurs due to hypochlorite injection at the service/fire water storage tank and the pH swing while passing through the wastewater ion exchange trailers. Both processes destabilize the surface charges that prevent the colloids from naturally forming larger solids. The second mechanism for colloid removal is adsorption onto the resin in the wastewater ion exchange trailers. Although colloidal silica is not an ion, the resin beads are porous and testing has shown that some amount of colloidal material will be collected on the resin.

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b. Oil and grease, or other organics such as propylene glycol (used for closed cooling water system freeze protection) which make their way into floor/equipment drains will foul ion exchange resin or pass through and lead to total organic carbon (TOC) excursions in the steam cycle chemistry. Resin vendors recommend that oil and grease be less than 1 mg/l in the influent to the ion exchange system. To mitigate this risk to the wastewater ion exchange demineralizer, an activated carbon filter is used as pretreatment to ion exchange on the wastewater system. Since most ion exchange trailers come with 6 vessels, activated carbon can easily be placed in 2 of the vessels. Alternatively an additional trailer for the carbon filters could be added since adding the carbon filters to the trailer reduces the ion exchange capacity by 40%. Other measures include providing TOC meters in the wastewater collection tank and education of operators and maintenance personnel to prevent organics from entering the floor drain system. In addition, an oil water separator with enhanced polishing capabilities (e.g., polymer filter cartridge vessels) will be provided.

c. An extensive makeup water sampling program is imperative. There is always a risk that contaminants in the makeup water could foul the resin or cause the regeneration facility to refuse to accept plant wastewater ion exchange resin; therefore, sampling and analysis is essential. This might occur if the salts from the plant cause the regeneration facility to exceed its wastewater discharge permit limits. Alternatively, contaminants (e.g., oil and grease) could foul the resin exposing the mobile fleet of trailers to this contamination. Most mobile regeneration vendors are familiar with the characteristics of power plant waste water and would not anticipate any discharge permit related issues. Depending on the particular contaminant, loading on the wastewater resin, mobile regeneration vendors may require that trailers be serviced out of a special facility that can handle the contaminant of concern, which may be farther from the site than the closest regeneration facility to the plant. One vendor has indicated that they consider the risk of fouling wastewater resin with oil and grease significant enough that they would require permanent ion exchange vessels for the wastewater ion exchange system and sluice resin (like the condensate polishers) in lieu of exchanging mobile trailers. With this methodology, fouled plant resin can either be disposed of or sent to a facility that can handle contaminated resin. When the time comes to negotiate, an agreement would likely be reached to mitigate this concern in regard to contamination of the provider’s mobile fleet.

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The use of ion exchange technology makes the system flexible to handle changes/transients in makeup water chemistry. The mobile trailers are rated for a certain grains (mass) of dissolved ions. As the makeup water total dissolved solids (TDS) increases (or decreases) for seasonal or other reasons, the number of gallons the mobile trailer can process decreases (or increases) proportionately. Meanwhile, the permanent equipment is unaffected.

A comparison of Vendor A and Vendor B ion exchange trailer approximate days to exhaustion (run length), when using the water quality presented in Appendix A, is provided in Table 2 below:

Table 2: Expected Mobile Ion Exchange Trailer Run Time (Days) (1)

Case 1 3 4 5 6 7

Makeup Demineralizer Ion Exchange

Run Time (days)

Vendor A(2)

9.1 11.9 9.0 9.4 12.7 12.5

Vendor B 7.8 10.3 7.8 8.1 10.9 10.8

Wastewater Ion Exchange

Run Time (days)

Vendor A(2)

9.1 10.4 9.0 10.1 11.8 12.8

Vendor B 7.6 8.6 7.4 8.4 9.8 10.5

1. Run length based on the power plant operating 24 hour/day. Daily plant cycling would increase run length.

2. Vendor A trailer offered slightly greater capacity than Vendor B (Vendor A = 5,000 kgr and Vendor B = 4,500 kgr).

Ion exchange off-site regeneration technology minimizes the permanent equipment required and the amount of operator attention – no regenerations to monitor or chemicals to handle. The ultra-filtration system can be set up to operate in batch mode with the trailers. The UF system will require occasional cleanings, but these should be infrequent based on the relatively good quality of the makeup water.

The permanent equipment for the mobile ion exchange trailers consists of parking spaces for a minimum of 3 trailers (one for makeup demineralizer ion exchange, one for wastewater ion exchange and one for carbon filters), pumps to push the water through the trailers, and piping manifolds with hoses to connect the trailers to the permanent piping. The trailers require 120 V power for lights, space heaters, and instruments.

Mobile ion exchange trailers produce a small amount of wastewater. Prior to transport of an exhausted mobile ion exchange trailer, the vessel must be drained. Prior to placing a trailer in service, the vessels are rinsed to drain to confirm product water purity. These wastewaters, essentially demineralized water, are collected in a sump and directed to the wastewater collection tank.

Except in extremely cold climates, only the UF system requires a water treatment building, since the mobile systems are self-contained, heated and ventilated trailers.

The distance from the plant to the closest mobile ion exchange regeneration facility will impact the mobile ion-exchange vendor’s costs

PERMANENT RO/EDI CYCLE MAKEUP WITH SPECIALTY RO/CRYSTALLIZER WASTEWATER SYSTEM - A sketch for this alternative is presented in Figure 2.

This design features a reverse osmosis (RO) system followed by electrodeionization (EDI) for polishing for the cycle makeup demineralizer, and a specialty (high efficiency) RO followed by a crystallizer and filter press to produce a solid, land-fillable cake. This design recycles Specialty RO permeate to the

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Fire/Service Water Tank, along with crystallizer distillate. If there is a nearby wastewater disposal facility nearby that can accommodate high TDS wastewater, it may make economic sense to remove the crystallizer since the reject flow from the wastewater RO is likely to be on the order of a few trucks a week of wastewater hauled off-site. Based on the technologies chosen, an optimized water balance calculation should be conducted to determine the actual wastewater quantity that would need to be disposed of in order to confirm that off-site disposal is a viable option.

MOBILE ION EXCHANGE CYCLE MAKEUP DEMINERALIZER WITH SPECIALTY RO/CRYSTALLIZER WASTEWATER TREATMENT SYSTEM - This design is illustrated in Figure 3.

This design features an ultrafiltration system followed by a mobile cation, anion and mixed-bed ion exchange system with off-site regeneration for cycle makeup demineralization. The wastewater treatment is a specialty RO followed by a crystallizer and filter press to produce a solid, land-fillable cake. This design recycles specialty RO permeate to the Service Water /Fire Water Tank, along with crystallizer distillate. As with the previous alternative it may make economic sense to remove, the crystallizer since the concentrated wastewater flow is likely to be on the order of a few trucks a week of wastewater hauled off-site.

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ORDER OF MAGNITUDE SYSTEM COSTS

Since the alternatives include a mix of permanent equipment and/or use of rental trailers, it is appropriate to compare the economic aspects of the options over a 25 year life of the facility as shown in Table 3 below. Order-of-magnitude cost estimates were obtained for the three alternatives. Rental costs for ion-exchange and carbon filter trailers were obtained from two suppliers for a plant in the Midwest. The costs are based on equipment/material purchase and an installation factor of 2.6 for buildings, foundations, and installation of the systems. Escalation costs for rental ion-exchange trailers are assumed to be 2% per year. General maintenance costs for permanent plant equipment are assumed to be 2% of the equipment costs. Membrane replacements are assumed to occur at 5 year intervals with an allowance of $50,000. The alternatives with permanent RO/crystallizer equipment would also incur chemical costs, higher power usage, and a higher level of operator attention than the first alternative with all rental trailers – these operating costs have not been estimated. In Table 3 below for calculating a net present value, the interest rate is assumed to be 10% and duration is 25 years.

Table 3: Cost Summary

Mobile IX/ Mobile IX

RO & EDI/ Specialty RO & Crystallizer

Mobile IX/ Specialty RO & Crystallizer

First year costs

Trailer Rental $ 536,000 $ - $ 225,000

Equipment $ 600,000 $ 2,300,000 $ 2,250,000

Installation $ - $ 5,750,000 $ 5,625,000

Present Value

General Maintenance $ - $ 409,000 $ 400,000

Membrane Replacement $ - $ 63,000 $ 25,000

Trailer Rental $5,718,000 $ - $ 2,400,000

Total Present Value $6,854,000 $ 8,522,000 $ 10,925,000

For the this combined cycle plant with an ACC and low TDS makeup water, the life cycle evaluation shown in Table 3 indicates that ion exchange technologies with off-site regeneration may be a favorable option.

CONCLUSIONS

When evaluating water and wastewater treatment alternatives for a combined cycle power plant with an air-cooled condenser (ACC) and no permit to discharge wastewater, the interdependent relationship between plant water users and wastewater producers must be evaluated holistically. Though ion-exchange technologies with off-site regeneration may be a favorable technology option for demineralizer and wastewater treatment for a combined cycle plant with an ACC depending on the raw water quality, the success of the plant depends heavily on implementation of operations practices to avoid contamination of wastewater, and design for additional storage volume during system outages is essential.

References: General Electric Company (GE), Steam Purity Recommendations for Steam Turbines, GEK 72281f, Revised July 2012

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APPENDIX A

Raw Water Demineralizer Makeup Quality

Constituents Units Maximum

Calcium mg/l 25

Magnesium mg/l 5.3

Hardness, as CaCO3 mg/l 83

Sodium mg/l 14

Potassium mg/l 2.3

Iron, dissolved mg/l 0.03

Iron, total mg/l 0.03

Manganese, dissolved mg/l

Manganese, total mg/l 0.008

Barium mg/l 0.03

Strontium mg/l 0.1

Sulfates mg/l 46

Chlorides mg/l 29

Fluorides mg/l 2.8

Nitrates / Nitrites, as N mg/l 0.5

Phosphorus mg/l 0.1

Alkalinity, total as CaCO3 mg/l 40

Carbonate Alkalinity, as CO3 mg/l 20

BiCarbonate alkalinity, as HCO3 mg/l 20

Silica, dissolved, as Si mg/l 4.6

Silica, total, as SiO2 mg/l 4.6

pH standard units 6 - 9

Conductivity µmho/cm 260

Temperature °F 32 - 85

Total Dissolved Solids (TDS) mg/l 150

Total Suspended Solids (TSS) mg/l 5

Turbidity NTU 1.0

Silt Density Index (SDI) mg/l 5

Aluminum mg/l 0.2

Arsenic mg/l 0.01

Cadmium mg/l 0.005

Chromium mg/l 0.005

Copper mg/l 0.005

Lead mg/l 0.01

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Constituents Units Maximum

Mercury mg/l 0.0001

Nickel mg/l 0.005

Selenium mg/l 0.02

Strontium mg/l 0.1

Vanadium mg/l 0.001

Zinc mg/l 0.012

Total Organic Carbon (TOC) mg/l 4.2

Chemical Oxygen Demand (COD) mg/l 20

Ammonia as N mg/l 0.13

Total Residual Chlorine mg/l 2

Oil & grease (O&G) mg/l 0

Sulfides mg/l 0.002