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Pollution Prevention and Control Technologies for Plating Operations
Section 4 - Chemical Solution Maintenance
4.3 MICROFILTRATON
4.3.6 Performance Experience and O&M Problems
Only one respondent to the Users Survey has employed microfiltration as a bath maintenance technology (PS 199). This unit was purchased from Prosys in 1992 to maintain a 600 gallon alkaline soak cleaner on a barrel line. The unit was purchased because the cleaner builds up an oil concentration of 5% (50 g/l) and requires disposal (on-site treatment) every two weeks. At the higher oil content, the bath begins to impact work quality. Their cleaner is formulated with sodium hydroxide, sodium metasilicate, sodium tripolyphosphate and mixed surfactants. This bath is used to clean approximately 10 million fasteners per year prior to zinc plating. The equipment cost of the microfiltration unit was $50,000. PS 199 estimated that non-labor operating costs were $500/yr and they projected an O&M labor requirement of 1,000 hrs/yr (plumber/pipe fitter, electrician, trained technician, and common labor).
PS 199 used the microfiltration unit for a period of only five months and then returned it to the manufacturer because of problems with membrane fouling. However, PS 199 indicated that they have considered trying a second unit from the same manufacturer that has a different back-pulse (self-cleaning) design that may eliminate the membrane fouling problem and thereby reduce labor requirements.