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Page 30


www.us-tech.com


March, 2020


Achieving Water Authority Compliance for Wastewater Treatment in Semiconductor Manufacturing


By Del Williams O


ver 200 organic and inorganic chemicals and large amounts of water are used by manufac- turers to produce semiconductor chips. As a


result, wastewater from semiconductor manufac- ture usually contains a broad range of contami- nants, including acids, alkalis, a variety of metals, such as copper, lead, arsenic, and antimony, ammo- nium, and fine oxide particles, salts, and solvents. Nevertheless, semiconductor manufacturing


facilities must meet local, state, and EPA waste- water requirements for effluent discharge, includ- ing those under the Clean Water Act. Failing to do so can result in severe fines that quickly escalate. Under the Clean Water Act, the U.S. EPA


identified 65 elements and groups of compounds as “toxic pollutants.” The EPA has expanded this list to include 126 specific substances which have been designated “priority pollutants.” In order to meet discharge limitations for


these priority pollutants semiconductor manufac- turing facilities must either have their wastewater hauled to a liquid hazardous waste disposal site, which is extremely costly, or have a wastewater treatment system that effectively separates the contaminants from the water so it can be legally discharged into sewer systems or even reused.


Treating Waste at the Source Traditional wastewater treatment systems can


be complex, however, often requiring multiple steps, a variety of chemicals and a considerable amount of labor. Too often, technicians must still monitor the equipment in person, even when the process is auto-


agents produce very fragile chemical flocs that can release pollutants, when under pressure during dewatering. Chemical flocs also tend not to retain pollutants during EPA-mandated toxic character- istic leaching procedure (TCLP) testing, so the re- sulting sludge cannot be disposed of inexpensively as nonhazardous waste in a municipal landfill. In contrast, it is much more cost-effective to


treat the industrial wastewater at its source, so treated effluent can go into a sewer and treated sludge passes a TCLP test and can be disposed of as nonhazardous waste in a local landfill. Fortunately, complying with EPA and local


wastewater regulation has become much easier with more fully automated wastewater treatment sys- tems. Such systems not only reliably meet regulato- ry wastewater requirements, but also significantly reduce the cost of treatment, labor and disposal when the proper separating agents are also used.


Automated Wastewater Treatment An automated wastewater treatment system


EconoFlow series flow-through wastewater treatment system.


mated. This usually requires oversight of mixing and separation, adding of chemicals and other tasks re- quired to keep the process moving. Even then, the water produced can still fail to


meet mandated discharge limits, because the processes rely on polymer or inorganic chemical flocculants and coagulants. These separating


can eliminate the need to monitor equipment in person, while complying with EPA and locally mandated requirements. Such automated systems separate suspended solids, heavy metals, emulsi- fied oil and encapsulate the contaminants, produc- ing an easily de-waterable sludge in minutes. The water is typically then separated using a


de-watering table or bag filters before it is dis- charged into sewer systems or further filtered for reuse as process water. Other options for de-water-


Continued on page 32


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