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Demonstration Bulletin. Membrane Microfiltration. E. I. DuPont de Nemours and Company, Inc. Oberlin Filter Company
Citation:
PRC Environmental Management. Demonstration Bulletin. Membrane Microfiltration. E. I. DuPont de Nemours and Company, Inc. Oberlin Filter Company. EPA/540/M5-90/007, 1991.
Impact/Purpose:
publish information
Description:
The DuPont/Oberlin microfiltration technology is a physical separation process that removes solid particles from liquid wastes. The process can filter particles that are submicron or larger in diameter. Pretreatment, such as chemical additions, will be required if dissolved contaminants are present in the liquid waste. The end microfiltration products are filtered solids, called filter cake, and filtered liquids, called filtrate. The DuPont/Oberlin microfiltration system is transportable and requires little or no attention during operation. The system uses Oberlin's automatic pressure filter and DuPont's special spunbonded olefin style filter material called Tyvek® T-980. The automatic pressure filter has two chambers—an upper chamber that feeds liquid waste under pressure through the Tyvek® and a lower chamber that collects the filtrate (Figure 1). A typical microfiltration cycle consists of four steps: (1) initial filtration, (2) main filtration and cake forming, (3) cake drying, and (4) cake discharge. The process begins with liquid waste being pumped usually from a waste feed tank into the upper chamber. During the first minute of filtration, or the initial filtration step, the filtrate is usually recycled to the waste feed tank. During the main filtration step, solids accumulate on the Tyvek® and form a filter cake, while filtrate drains from the lower chamber to a filtrate collection tank. When the pressure in the upper chamber reaches a preset value (blowdown pressure), the waste feed valve closes and the cake drying step begins. Pressurized air (typically, 35 psig) is fed into the upper chamber to further dry the cake. After air breaks through the cake, drying continues for a preset time (blowdown time). During this step, any remaining liquids are forced through the Tyvek® and are recycled to the waste feed tank. Immediately following the cake drying step, the upper chamber is lifted, clean Tyvek® is drawn from a roll into the unit for the next cycle, and the filter cake is discharged.