1. The DTW Systems filtration system operates at low pressures, typically less than 15 psi. The separation is accomplished in a dead-head mode of operation.
2. Due to the low pressure operation and the dead-head filtration, a sludge buildup on the surface of the membrane is achieved during separation. Without affecting the filtrate through-put of the filter vessel, the sludge typically achieves a thickness of over 1/4". As the maximum operating pressure of the filter vessel is reached, the sludge cake on the membrane surface partially de-waters, increasing its percent weight by volume of liquid. The forward pressure gradient maintains the sludge in contact with the membrane.
3. All contaminates or product particles which are larger than the pore size of the membrane are rejected from passage through the membrane.
There is a positive barrier as defined by the physical pore size of the membrane. Membrane selection, coupled with molecular engineering of the effluent, allows larger pore sizes to be implemented while achieving consistent discharge parameters at higher flow rates.
4. The filtrate passes through the membrane tubes and is discharged from the top of the filter vessel by gravity. When system reaches the maximum operating pressure, the feed flow to the filter vessel is interrupted. The filtrate valve closes and the vessel pressure is relieved. Air is applied to the filtrate side of the membrane, creating a force that drives the clean water back through the membrane. This breaks the sludge cake buildup on the membranes. The sludge quickly settles to the bottom of the filter vessel due to its relative weight. After a few seconds, the filtration vessel is restored to operation at the rated flow and a lower operating pressure.
5. Gravity compacts the sludge held in the cone section of the filter vessel. Periodically, the sludge is isolated from the vessel and removed for further dewatering. The sludge content is typically between 5%w solids to greater than 30%w solids.
6. Installation involves connecting the feed, filtrate, relief, sludge withdrawal and air supply headers. Multiple units are available in a skid configuration. Vessels vary in diameter from 12" to 36", with flows between 20 GPM and 125 GPM per vessel.