Ultrafiltration water treatment process flow

Mobile units for photocatalytic treatment have been constructed (126,127). The European Joint Research Center laboratory pilot plant, placed on a truck, includes Ti02 loaded on membranes in UV-irradiated tubular reactors behind microfiltration and ultrafiltration modules. The waste water flow rate for this unit was typically 40 L hr-1, and hydrogen peroxide was added to the photocatalytic process (134). 

The individual membrane filtration processes are defined chiefly by pore size although there is some ovedap. The smallest membrane pore size is used in reverse osmosis (0.0005—0.002 microns), followed by nanofiltration (0.001—0.01 microns), ultrafiltration (0.002—0.1 microns), and micro filtration (0.1—1.0 microns). Klectrodialysis uses dectric current to transport ionic species across a membrane. Micro- and ultrafiltration rely on pore size for material separation, reverse osmosis on pore size and diffusion, and dectrodialysis on diffusion. Separation efficiency does not reach 100% for any of these membrane processes. For example, when used to desalinate—soften water for industrial processes, the concentrated salt stream (reject) from reverse osmosis can be 20% of the total flow. These concentrated, yet stiU dilute streams, may require additional treatment or special disposal methods. 

The recovery of caustic from the mercerization process is a common practice in the textile industry. Mercerizer rinse water is normally recovered when its concentration is above 2-3% and below this concentration it is discharged to waste treatment. An alternative to this procedure is to use an ultrafiltration membrane to filter caustic rinse water before the solution goes to the evaporator. A flow sheet diagram of caustic recovery solution is shown in Fig. 13-12. The clarified and concentrated solution is then ready for re-use and consumption of caustic is significantly decreased [59],... 

A membrane filtration plant suitable for process water from reactive dyeing and printing of cotton is a two step plant Pre-filtration by ultrafiltration and a final treatment by reverse osmosis. Pre-treatment technologies for RO spiral wound membrane filtration have focused on flat sheet polymer UF membranes in a high cross-flow filter. The quality of water produced by this plant will go beyond what most dyehouses use today and will be well suited for all processing, including reactive dyeing of cotton." ... 

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