Process Water Treatment
Process water is water that is used for a variety of manufacturing processes, including: boiler make-up water; cooling tower make-up water; coating and plating; rinsing and spraying; washing and many others. Municipal or ground water supplies often contain dissolved minerals which can cause a multitude of problems than can affect product quality and manufacturing costs.
Some of the problems caused by dissolved minerals in process water include: streaking, fouling, spotting and adherence interference. Higher energy costs may also result from poor quality process water. For example, demineralized process water will result in a notable reduction in boiler fuel consumption over untreated process water, allowing the boiler to operate at much higher concentration cycles, and greatly reducing the blowdown of extremely hot water into the drain.
The WaterProfessionals® have helped solve hundreds of process-related problems related to water using a wide variety of treatment technologies. We will work with you in developing a custom water treatment solution to meet your needs and an on-going service plan to totally or partially maintain your system. Please review our case studies which illustrate our experience in meeting your process water treatment needs.
Process Water Treatment Technologies
Process Water Treatment Services
Typical Process Water Problems Solved
• Dissolved Gases
• Dissolved Solids
• Hydrogen Sulfide
• Total Organic Carbon
Activated Carbon Filters
Activated carbon filters are used to remove free chlorine and organic compounds in water supplies. This method of filtration uses a bed of activated carbon to remove contaminants and impurities through chemical adsorption. Activated carbon is made from raw organic materials, such as coconut shells or coal, which are high in carbon. This carbonaceous material must be further treated or “activated” before it is useful in water treatment.
Carbon filters are typically activated in one of two ways, either by steam activation or chemical activation. Activated carbons produced by steam generally exhibit a fine pore structure and are ideal for absorbing both liquid and vaporous compounds. Activated carbons produced by a chemical reaction generally exhibit an open pore structure and are ideal for absorbing large molecules.
Aeration is the introduction of dissolved oxygen into water. Aeration is often used in the decarbonation or degasification of water to remove hydrogen sulfide and carbon dioxide gasses. Aeration is also used to filter oxidized contaminants in water, such as dissolved iron, by converting them into solid particles that can be more easily filtered out.
Aeration is typically performed through the use of diffusers, towers containing media (or fill) the water trickles over while large fan(s) blow air up through the fill with “bubblers” (or venturi devices), which introduce very small air bubbles into the water. The latter process works similar to the aeration process of a home aquarium.
Chlorination is the process of adding chlorine to water to kill viruses, bacteria and cysts. The pH level of the water, water temperature and length of time the chlorine is left in the water will all impact the effectiveness of chlorination. While chlorine is effective at killing water-borne diseases such as dysentery, it can also produce undesired byproducts as a reaction to organic compounds in water. Reactions between chlorine and organic compounds often result in trihalomethanes.
Exposures to high levels of Trihalomethanes (THM) are thought by some researchers to pose an increased risk of cancer, reproductive problems, and nervous system damage. The EPA regulates the amount of trihalomethanes allowed to be present in public drinking water. Enhanced filtration for better organic removal and the use of chloramines (ammonia combined with chlorine) to decontaminate drinking water help to reduce levels of trihalomethanes.
Increasing concern about this class of compounds will likely lead public water plants to utilize membrane technologies such as ultrafiltration or nanofiltration, which are capable of removing the organic precursors, and thereby prevent them reacting with chlorine. For high purity water, ultraviolet disinfection is often used as an alternative to chlorination to prevent changes in the chemical makeup of the end use water.
Dealkalization is the reduction of alkalinity in water. There are three types of alkalinity, depending on the pH value of the water: 1) carbonate, 2) bicarbonate, and 3) hydroxide. Dealkalization is commonly used to pre-treat boiler feedwater. As a general rule of thumb, dealkalization works best on boilers operating below 700 psi, with feed water containing 50 ppm alkalinity or greater, and make-up water of 1000 gallons or more per day. There are 4 different methods of dealkalization, which can be used to reduce raw water alkalinity: 1) chloride anion dealkalizers, 2) split stream dealkalization, 3) weak acid dealkalization, and 4) reverse osmosis. Each method of dealkalization has significant advantages and disadvantages.
Decarbonation, Degasification & Air Stripping
Decarbonation, degasification and air stripping are used in high purity water treatment to remove carbon dioxide from water. Decarbonation through air stripping is only effective in water with a low pH level, where the carbon dioxide is present as a gas. Air stripping is often used downstream of deionizers, after the cation exchanger, to remove up to 90% of carbon dioxide gas in water with a pH level of 4.5 or lower. This markedly reduces the ionic loading on the anion deionizer, leading to much longer run times between regeneration. Membrane degasification is widely used due to its much smaller size and ability to reach much lower levels of carbon dioxide.
Dechlorination is the removal of chlorine or chloramines (ammonia combined with chlorine) from water. Chlorine and chloramines can be removed from water in several ways, including: absorption through activated carbon, chlorine reducing chemical agents, and ultraviolet dechlorination.
Deionization & Demineralization
Demineralization is often referred to as deionization. Demineralization is the process of removing salts, minerals and nitrates from water through an ion exchange process. Demineralized water is high purity water that is generally similar to distilled water. The demineralization process is frequently accomplished by in-plant or exchange service deionizers, reverse osmosis or electro-deionization. There are several advantages to demineralizing water via membrane technologies or electrodeionization. These include: eliminating the need for chemicals, reducing hazardous waste, and lowering maintenance costs.
Distillation in water treatment is capable of separating out virtually all suspended and dissolved contaminants from water. The process of distillation requires water to be heated to a high enough temperature to convert into steam. The steam must then be captured and cooled to produce distilled water. Because of the high temperatures required for distillation, bacteria, viruses and spores are killed, and volatile organic compounds (VOCs) will vaporize. Distillation is typically the treatment method of choice for producing water for injection (WFI) in pharmaceutical or medical use.
Electrodeionization, or continuous electro deionization (EDI, CEDI or CDI) utilizes ion exchange resins and semi-permeable membranes to reduce ions in water. An electrical current continuously regenerates the ion exchange resins, which capture dissolved ions. The dissolved ions are continuously flushed out of the system during regeneration. Electrodeionization is environmentally friendly, but requires feedwater to be pre-treated upstream, typically with reverse osmosis, for the most economically efficient operation.
Greensand is the name commonly applied to glauconite, a sandy rock or sediment that is greenish-black to blue-green in color. When coated with manganese dioxide, glauconite can be used as an excellent filtration media. It is capable of removing iron, manganese and hydrogen sulfide from water. Prior to filtration with greensand, water must often be treated with an oxidizing agent, such as chlorine and/or potassium permanganate. A new generation of greensand has been developed that utilizes silica sand instead of glauconite. This new generation of greensand filtration is able to better withstand waters with higher operating temperatures and higher differential pressures.
Deionization and demineralization are often used interchangeably for ion exchange. Ion exchange is the process of exchanging ions between two electrolytes, or between an electrolyte solution and a complex. Ion exchange is used extensively in nuclear facilities and industrial processes to control the purity and pH level of water. The ion exchange process takes advantage of the fact that all ions have either a positive or negative charge. There are two types of ion exchange resins: cation exchange resins and anion exchange resins. Cation exchange resins exchange positive ions for negative ions. Anion exchange resins exchange negative ions with positive ions. When both cation and anion resins are used together, they form what is known as a mixed bed resin. Depending on the identity of the ions that a resin releases into the water, ion exchange may be used for water purification and/or the control of a particular ion concentration in a solution.
Microfiltration is a physical filtration process that removes suspended solids from water. Microfiltration is capable of removing particles in the 0.1 to 10 micron range. This filtration process is capable of removing bacteria, but does not remove dissolved contaminants. Microfiltration is carried out by a cross-flow separation process, where water is passed over a membrane surface using pressure, in a controlled flow path. Microfiltration is commonly used in the sterilization and clarification of beverages, juices, wines and beer. Microfiltration is also used as a pretreatment to reverse osmosis (RO) for removing suspended solids, which can foul RO membranes.
Mobile demineralization is a temporary water treatment process that uses trailer mounted demineralizers, which are regenerated at the vendor’s site. Mobile demineralizers are typically employed during plant failures or for new start-ups where permanent deionization equipment has not yet arrived.
Multi-Media Filtration is effective in removing dirt, silt, rust, and other suspended particles from water. Multimedia filters typically have three layers, consisting of anthracite, sand and garnet. A well-operated multi-media filter may remove particles from 10-25 microns. Flocculants or coagulants may be used upstream of a multimedia filter to induce the agglomeration of particles smaller than 10 microns (causing them to bind together), allowing the filter to remove these particulates. Multimedia filters are capable of delivering high quality filtered water at much faster flow rates than conventional sand filters.
Nanofiltration is a pressure related process, which typically removes 50%-90% of monovalent ions. Nanofiltration is commonly used for the removal of pesticides or heavy materials from water, water softening, and nitrates removal. Nanofiltration is often employed in manufacturing processes for pharmaceuticals, dairy products, textiles and bakeries.
Ozone is one of the most powerful disinfectants in water treatment, and is even more effective than chlorine at killing cysts, bacteria and viruses. However, ozonation is significantly more expensive than chlorine and does not have the same residual disinfectant properties as chlorine. Because it has no residual effects, ozonation is often the disinfectant of choice for bottled water companies. Ozone is effective at removing organic chemicals, color, and odor-causing contaminants from water and wastewater.
Reverse osmosis uses man-induced pressure to force water through an extremely fine filtration membrane, removing up to 98% of dissolved ions. Reverse osmosis has become one of the most cost-efficient technologies to deionize water, and is capable of removing very small particulates down to 0.0001 micron in size, including most organic carbon or TOC (Total Oxidizable Carbon). Maintenance of a reverse osmosis system is typically minimal if feedwater is properly treated upstream.
As groundwater dissolves limestone over time, calcium and bicarbonate ions are released into water. The measurement of the amount of limestone dissolved in water is termed "hardness." Conventional water softening uses a synthetic polymeric (plastic) material in the form of very small beads called an ion exchange resin to remove hardness from water. Water softening equipment typically comes with two tanks. A larger tank is used to hold the rock or pellet salt needed for regeneration, and a smaller tank contains the ion exchange resin through which the hard water passes.
Ultrafiltration involves the filtration of water through a semi-permeable membrane to remove suspended particles. Ultrafiltration is a physical filtration process typically used as a pretreatment method to separate solids from water used for industrial processes, such as food and beverage processing, semiconductor manufacturing, pharmaceutical production and power generation. Ultrafiltration is very effective at removing membrane fouling sedimentation and is typically utilized upstream of reverse osmosis systems to reduce the silt density index of water.
Ultraviolet disinfection (UV disinfection) is a physical filtration process that neutralizes microorganisms. The adoption of UV disinfection has grown significantly in the past few decades. This filtration process has no impact on the chemical composition or the dissolved oxygen content of the water, and ensures compliance with ever-tightening wastewater effluent discharge regulations. UV disinfection works by transferring ultraviolet radiation into an organism's genetic material (DNA and RNA). When UV radiation penetrates the cell wall of an organism, it destroys the cell's ability to reproduce. The effectiveness of an ultraviolet disinfection system depends on the characteristics of the wastewater, the intensity of UV radiation, and the amount of time the microorganisms are exposed to the radiation. Water treated with ultraviolet disinfection must be sufficiently free of sediment, manganese, iron and any colorant that could affect transmission of the UV light.
Ultraviolet Total Oxidizable Carbon (TOC) Destruction
Ultraviolet TOC destruction systems are utilized for the effective reduction of total oxidizable carbon compounds in water. Ultraviolet TOC destruction systems are typically placed in the recirculation loop, downstream of deionizers. A final “polishing” deionizer is typically placed downstream of the TOC unit to removed ionized carbonic acid.