By Gary Battenberg

In Part 1 in the June issue detailed the site visit to collect water samples for testing and to confirm the hydraulic characteristics of the well water supply. Additionally, an evaluation of the original equipment installation, assessment of environmental conditions and electrical supply was noted for subsequent system design considerations. Part 2 details the interpretation of the water analysis and the sales proposal as well the technical synopsis of the system function and maintenance requirements.

Upon review of the water quality report, microbiological testing indicated a standard plate count (SPC) detected above the minimum detection level but not above the referenced standard or action level. The report also indicated that total coliform was absent in this sample, which meant that the water supply was safe relative to pathogens. The only inorganic metal that was detected above the national standard was iron and, while it was detected above the staining threshold, it is enforceable because it fell within the US EPA Secondary standard. Sodium was very high.

Issues were apparent upon review of the physical factors of the testing report (see Figure 1), beginning with high alkalinity, which typically contributes a bitter taste to the water and tends to cause drying of the skin. Hardness was slight at 52 mg/L (3.09 grains per gallon) and pH was elevated at 8.0 but within the secondary standards of 6.5 to 8.5. Total dissolved solids were extremely high, which placed this challenge water in the brackish range of 1,000 to 15,000 mg/L (parts per million). (Brackish water is unfit for drinking and food preparation and at higher levels, can retard the growth of plants.) Turbidity in potable water, which should not exceed 0.5, was extremely high at 12 NTU (nephelometric turbidity units).

Other inorganic analytes noted in the report were also at higher levels. Chloride was 360 mg/L (ppm), which tended toward a corrosive condition and could contribute to degradation of metallic surfaces within the service plumbing infrastructure. Fluoride was indicated above the US EPA primary standard of 4.0 mg/L and had to be reduced or removed from the water supply before it could be deemed potable. (Naturally occurring fluoride above that limit can cause mottling (discoloring) of the teeth and has been linked to skeletal fluorosis, a crippling bone disorder that mimics osteoporosis.) And finally, sulfate was detected at 780.0 mg/L (ppm), more than three times the US EPA secondary standard.

For those not accustomed to sulfate in water at or above 250 mg/L (ppm), diarrhea or similar symptoms are generally linked to elevated levels of sulfate. Additionally, elevated sulfate may impart a medicinal taste to the water.

No trihalomethanes or volatile organic compounds were detected and therefore, no special consideration was necessary for remediation in the equipment specification.

Proposing the right system

After entering the water chemistry and hydraulic characteristics into a system analysis database, the company was able to determine the size of RO system needed to provide high quality water for internal household usage. The chosen system was rated for a recommended daily output of 2,160 gallons based on a maximum of eight hours run time and taking into account the 300-gallon (1,135.5 liters) capacity RO storage tank.

Specific elements of the actual proposal follow herein, outlining the expected system function and technical synopsis as well as maintenance requirements:

  • Date: 20 April, 2010
  • Quotation No.  04- 0110 – NM

We are pleased to offer you the following info-quote for our Model MS-375 Commercial RO water treatment system for your consideration. This system represents a considerable component upgrade from a system that is field engineered. It will provide substantial savings in installation costs, as well as consistent operational benefits. Its purpose is to significantly reduce hydrogen sulfide, turbidity, total dissolved solids, alkalinity, sulfate, chloride and fluoride to comply with US EPA and WQCC standards. Additionally, the system will significantly reduce manganese, iron, and hardness to within US EPA primary drinking water standards.

MS medium pressure series Reverse Osmosis Systems function automatically and will require only routine filter, food grade antiscalant stabilizer and UV lamp replacement, as determined by your well water analysis. They are designed for durability while providing peak performance to yield the highest quality water. The entire system, including the specific location of piping connections and components, is carefully designed for easy service and maximum efficiency.  

System description

An automatic pretreatment system will be specified to remove the hydrogen sulfide, iron and manganese from the challenge water utilizing an Advanced Non-Chemical treatment process. This pretreatment system oxidizes the offending constituents and filters them out with the automatic particulate and ozone conversion filters to ensure clear feedstock to the RO system. The fully self- contained Reverse Osmosis system will be mounted on a powder-coated frame with features that make it extremely reliable and versatile. The UL508A labeled microprocessor controller features a backlit LED that displays product water quality (TDS), system status lights, system on, tank full, feed water temperature gauge, low feed pressure and a time delay on system start-up to prevent pump damage. A double-float tree will control high and low tank levels to stop and start the RO system. Commercial grade, five-micron, high capacity pre-filtration will provide protection to the RO membrane assemblies. System pressure will be provided via a High-Pressure Stainless Steel, Multi Stage Pump to ensure sufficient pressure to the membrane assemblies for high rejection of target contaminants. The RO system is specially prepared to convert 75 percent of the feed water to high quality water for domestic use. Only 25 of every 100 gallons of water are sent to drain. Durable glycerin filled inlet and system operating pressure gauges (4). Stainless steel concentrate and recycle pressure regulating valves to maintain consistent, reliable operating pressure. Thin film composite membranes have been specified to ensure highest quality product water. Automatic membranes flush at system shutdown will ensure long membrane life.

Pretreatment stage: ozone generator, air dryer and system control panel. A hyper-contact ozone tank ensures adequate mass transfer of ozone and is fitted with air relief and ozone destruct. An automatic particulate filter intercepts oxidized sulfur, iron and manganese.

RO system, antiscalant solution tank and ozone conversion filters are show to the right.

Installation consists of transitioning the copper inlet plumbing at the point of entry to corrosion resistant, NSF approved Schedule 80 PVC piping into the pretreatment array of the system to remove turbidity, hydrogen sulfide, iron and manganese. The conversion filters will include a clear water backwash manifold that will allow the offline filter to backwash with clean water from its twin to prevent cross contamination of the media beds. This exclusive configuration uses less backwash water than typical mono-tank filters. The turbidity free water will then enter the five-micron pre-filter to the RO system to protect the membranes. The RO system will be controlled by a twin float-level tree in the storage tank to initiate the RO for makeup to the storage tank when the water level drops to a predetermined level and defeats the RO system when the tank is full. A transfer pump float will function as a low water level switch/alarm to defeat the re-pressurization system should the storage tank water level become too low for the transfer pump to safely pump water. The re-pressurization pump will be capable of up to 10 gallons per minute with an average delivery pressure of 50 PSI.

The water from the RO will pass through an up flow neutralizer vessel prior to entering the storage tank. The purpose of the neutralizer is to lightly re-mineralize the water (using NSF-certified Calcium Carbonate – Georgia marble) to prevent corrosive attack of metallic components in the plumbing system. The upflow neutralizers are specially prepared and designed with blending valves to provide fine adjustment of the final pH in the RO water stream. The water from the storage tank will then pass through an Ultraviolet sterilizer to ensure complete disinfection of the water before it enters the service plumbing, and finally, an activated carbon filter to remove any taste and odor from the tank and piping for delivery to the service plumbing. A small diameter return line from the UV will provide a continuous recirculation of the water in the storage tank at 2.5 gallons per hour (.04 gpm) or 64 gallons per day. This feature will ensure no heat build-up inside the UV system while maintaining bacteriologically safe water at all times. 

Connection form UV: a stainless steel light trap prevents UV degradation of PVC piping components. The lower valve is the cooling circuit for the UV that maintains continuous recirculation of the RO water in the storage tank.

Transfer pump constructed of corrosion-resistant plastic with service valves.

The system maintenance requirements are critical to the long-term reliability of this system. We will provide quarterly maintenance for the antiscalant blend level in the solution tank, and perform a system diagnostic to ensure that the ozonation system, automatic filters and mechanical filters are operating within specified operating parameters. Mechanical filters will be replaced as required when the pressure drop is at 10 percent of the system feed pressure. A service invoice will be forwarded to you for payment upon receipt after each quarterly visit. We will provide routine maintenance as required by company policy for the first year. After that, should you or your assignee desire to be cross-trained in the full maintenance of this system, we will be happy to perform the training at your request. An operating manual will be provided for those details that may be attended by you during the service intervals. We provide 24/7/365 service should a problem occur and you need to reach technical support.

Final results

The client accepted the proposal, based on the test results and recommended treatment options. The selected system was installed and fully operational as of June of 2010. 

Some additional specifics of the system included advanced non-chemical process is ozone injection into the challenge water, which eliminated problems associated with a chemical batch tank for hydrogen peroxide or chlorine. (A properly designed ozone system with an air dryer and off-gas destruct has been a part of my ground water remediation system design for over 25 years. It requires virtually no attendance by the homeowner other than a cursory check as instructed by the service policy.)

Turbidity was addressed in the first phase of the treatment process with an automatic particulate filter followed by ozone conversion filters. Additionally, the design of this hyper-contact ozone system featured a manual blow-down valve, which will be purged every quarter as an additional maintenance step to check the tank ‘sweep’ feature of the design.

Silica, with levels up to and exceeding 100 mg/L and lead, both prevalent issues for virtually all of northern New Mexico’s ground water have successfully been treated by this company for over 25 years. Reverse osmosis technology, long an extremely effective methodology for reducing and removing lead and silica, were used to resolve the levels as noted in the testing report. Food-grade antiscalant sequestered these constituents and rejected them at very high percentages. Follow-up testing showed no detectable lead and 0.12 mg/L of silica in the final product water.

Final water quality, relative to the parameters indicated previously, have been calculated to be as follows:

  • Hydrogen Sulfide: 0.0mg/L (See system description in proposal.)
  • Iron: 0.0 mg/L
  • Sodium: 20.6 mg/L
  • Alkalinity: 27.0 mg/L
  • Hardness: 0.13 mg/L
  • Total Dissolved Solids: 68 mg/L
  • Chloride: 7.9 mg/L
  • Fluoride: 0.12 mg/L
  • Sulfate: 11.4 mg/L
  • Turbidity: 0.0 NTU
  • pH: 7.1-7.3 after remineralization

The system has proven to be highly reliable and routine maintenance has been typical with no unscheduled calls. One exception was for a failed ozone chamber that failed at six months. The manufacturer was quick to remedy the warranty repair; after reinstallation, no additional problems have occurred.

About the author

Gary Battenberg is Managing Director of Santa Fe, NM-based Good Water Company, Inc. He has 29 years experience in the field of water treatment processes, including equipment design and manufacturing utilizing filtration, ion exchange, UV disinfection, RO and ozone technologies. Battenberg is also a member of the WC&P Technical Review Committee. Contact him at [email protected] or at (505) 471-9036.

 

About the company

Good Water Company serves Santa Fe and northern New Mexico residential, commercial, farm and ranch customers with remediation for severe groundwater problems, specifically arsenic, fluoride, nitrate, uranium, silica and high TDS. The locally owned water treatment business, founded in 1988 and purchased by geologist Stephen Wiman, Ph.D. in 2004, is committed to pursuing the most efficient use of precious water resources. Its goal is to minimize the use of chemicals and reduce wastewater in the treatment process. Wiman applies scientific principles and fundamental water chemistry for each individual application and offers state-of-the-art equipment from a variety of manufacturers to solve complex water problems.

 

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