Innovative Water Management Solutions
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Innovative Water Management Solutions
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| Questions and AnswersEvaluating various water management techniques often leads to many questions. Below you will find many of the common ones along with answers that we hope you'll find helpful. Click on a question to see the answer.
Answers What is DI water? DI (deionized) water is water in its purest form, H20. The process of deionization removes all ionizable particles, both organic and inorganic, from water by a two-phase ion exchange process. Cation and anion resins are used to remove the positive and negative ions. The cation resins remove the positive ions and replaces them with H+ ions. The anion resins remove the negative ions and replaces them with hydroxyls, OH-. When the H+ and OH- are combined, they form pure water. The quality of DI water is typically expressed in terms of resistivity. Resistivity is the measure of how difficult it is for a solution to carry an electrical charge. This is a function of how much ionic material is in the water. The more ionic material, the lower the resistivity. <return to questions> Why is DI water recommended for cleaning circuit assemblies? Ion free water absorbs ions aggressively and, therefore, is effective in removing ionic contamination from assemblies. In addition, a certain amount of evaporation is going to occur in the (drying) process, so the less ionic content in process water, the less ionic material will be evaporated on to the board. <return to questions> What quality DI water is required for cleaning circuit assemblies? Typically, DI water above 200 kohm (2.5 parts per million) will be sufficient to supply the final rinse of a cleaner, however, the cleaning application and cleanliness requirement will dictate the actual level of deionization. The more stringent the cleanliness specification, the more likely the need for greater resistivity (higher levels of deionization). Examples of resistivity and parts per million of contamination are: Resistivity PPM 18,000,000 ohm (18 megohm) 0.03 2,000,000 (2 megohm) 0.25 200,000 ohm (200 kohm) 2.50 1,000 to 5,000 ohm (tap water) 500 to 100 Two megohm water is significantly less conductive than typical tap water. There is a relatively small difference in parts per million contamination between 2 megohm and 18 megohm water. There is an exponential relationship that has a significant cost impact as well. Operating a system at 18 megohm will be substantially more costly than operating one at 2 megohm, yet the benefits in cleanliness will be minimal. <return to questions> Why close loop process water used in an in-line cleaning operation? Closed-looping the process offers cost savings, is environmentally responsible, and facilitates process control. Cost savings:
Environmental impact:
Process Control:
What technologies are available for filtering water? Particle filtration: Contamination of 1 micron or larger in size can be removed effectively by this process. Particulate filters are typically used as a pre-filter for water prior to entering ion exchange tanks. Typically, either a cartridge or bag filter is used with a rating of 5 microns. Microfiltration: Microfiltration will remove particles in the .1 micron range. In order to use this type of filtration, an additional waste stream is created with a portion of the water diverted from the effluent stream to purge the microfilters. This process is not well-suited to in-line aqueous cleaning because it does not sufficiently purify water and it produces the additional waste stream. Ultrafiltration: This process can filter down to the molecular level (.01 micron). As with microfiltration, this will not produce water quality suitable for the process and it, too, produces an additional waste stream. Reverse osmosis: RO will filter to the ionic level (.001 micron). Membranes used in the RO process are temperature sensitive, so they are not usually well-suited to recycling of cleaner effluent. This process also produces an additional waste stream of water used to purge the membranes. RO, however, is useful and often cost-effective in purifying incoming facilities water used in the process. By filtering incoming make-up water, ion exchange resin life is prolonged. Carbon/Ion exchange: This process uses granular activated carbon (GAC), cation and anion tanks (and possibly mixed cation and anion tanks) to filter down to the ionic level. The carbon tank removes organics and the ion exchange tanks produce water in the 1 to 18 megohm range, depending on configuration. Periodically, the carbon is replaced and the ion exchange media regenerated. There is no additional waste stream produced by this process making it ideal for recycling processer. <return to questions> What does REsys recommend for filtering and recycling cleaner effluent? REsys recycle systems typically use a combination of particulate filtration, proprietary heavy metals removal, and the carbon/ion exchange process. The cleaner's waste stream is directed to a 5 micron particulate filter to remove gross contamination. Heavy metal removal (HMR) tanks begin the ion exchange process by trapping heavy metals (lead, copper, etc.) that are in the wastewater. Granular activated carbon removes organics, and then cation and anion tanks deionize the water. A mixed bed tank can be added to achieve resistivity as high as 18 megohms. In areas with particularly poor quality tap water (high total dissolved solids (TDS) content), it may be cost effective to pre-filter incoming water with the reverse osmosis (RO) process. The cost of RO is outweighed by the savings of prolonged media tank life. REsys offers a comprehensive program for media replacement and regeneration that is cost effective and facilitates environmental regulatory compliance. <return to questions> How can I be sure my cleaning application is suitable for closed loop recycling? Closed loop recycling is a robust and proven process that easily removes water soluble fluxes and pastes commonly found in electronics cleaning. Likewise, it is suitable for other cleaning applications where contaminants can be removed by carbon/ion exchange. There are, however, a number of process additives that will inhibit the process and/or may require additional filtration or equipment. Water soluble masks, tapes and stand-offs are high in ionic content and will greatly reduce resin life. Chemical additives, such as saponifiers, used for rosin-based fluxes will also decrease media life. Isolating wash chemistry from the recyclable rinse stream will enable the process to be used. Contact REsys for specific application requirements. <return to questions> How long does filtration media last? It is difficult to estimate media life without knowing the process parameters. Simply put, everything introduced to the system as ionic contamination will reduce the life of resin media. The more contamination, the shorter the media life. Experience has shown that a typical, water soluble cleaning process running 40 hours per week will result in media life of approximately 6 to 8 weeks. The HMR tank is replaced at the time of the eighth media regeneration. <return to questions>What programs are in place for replacement and regeneration of media? REsys offers a comprehensive program to support the recycling process. Media tanks can be either purchased or leased from REsys, and all replacement and regeneration handled by us. REsys provides specially-designed shipping pallets, arranges for all environmental compliance testing and disposes of heavy metal removal tanks appropriately as hazardous waste. The goal of this program is to provide a one-stop resource for REsys recycle system users. Contact REsys for more information on the Media Program. <return to questions> |
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REsys, Inc.
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