Filtration technology

Most continuous pressure filters available (ca 1993) have their roots in vacuum filtration technology. A rotary dmm or rotary disk vacuum filter can be adapted to pressure by enclosing it in a pressure cover however, the disadvantages of this measure are evident. The enclosure is a pressure vessel which is heavy and expensive, the progress of filtration cannot be watched, and the removal of the cake from the vessel is difficult. Other complications of this method are caused by the necessity of arranging for two or more differential pressures between the inside and outside of the filter, which requires a troublesome system of pressure regulating valves. 

Vourch et al49 studied the applicability of the RO process for the dairy industry wastewater. The treated wastewater total organic carbon (TOC) was <7 mg/L. It was found that in order to treat a flow of 100 m3/d, 540 m2 of the RO unit is required with 95% water recovery. Dead-end NF and RO were studied for the treatment of dairy wastewater.50 Permeate COD, monovalent ion rejection, and multivalent ion rejection for the dead-end NF were reported as 173-1095 mg/L, 50-84%, and 92.4-99.9%, respectively. When it comes to the dead-end RO membranes, the values for permeate COD, monovalent ion removal, and multivalent ion removal were 45-120 mg/L, >93.8%, and 99.6%, respectively. Membrane filtration technology can be better utilized as a tertiary treatment technology and the resultant effluent quality will be high. There can be situations where the treated effluents can be reused (especially if RO is used for the treatment). 

All experimental setups described in the literature for the separation of homogeneous catalysts by membrane filtration technology can be divided into two general classes Dead-end filtration and cross-flow filtration. The first type of unit is characterized by a product flow perpendicular to the surface of the membrane, while the flow in the case of cross-flow filtration is parallel to the membrane surface (see Figure 4.1). 

When Bayer started the planning phase for its new membrane cell chlorine plant the company also evaluated new filtration technologies to eliminate costs for the use and disposal of filter aid and to reduce the cost of filter operation significantly. 

Membrane absorbers are continuous chromatographic supports, which circumvent some of the above-mentioned problems of particulate stationary phases. They were originally derived from membrane (filtration) technology. The immobilization of interactive (ionic, hydrophobic, or biospecific) groups on the surface of microfiltration membranes was found to increase the selectivity of certain separation procedure. Ideally such activated membranes, or membrane adsorbers, allow the selective adsorption of certain substances and substance classes, which may subsequently be eluted by means of a stepwise change of the mobile phase (elution buffer). More complete information on the various types of modern membrane technology can be found in some recent reviews [e.g., 31-33]. 

Tobacco industry scientists studied filtration technology and indicated that then-results showed that this too can have a major influence on smoke pH and free-base nicotine (Chen 1976). They presented results indicating that carbon in filters can increase the pH of the smoke (Creighton 1988). By increasing air dilution of... 

Source-, compiled based on Wagner (2001) and Membrane filtration Technology for Sustainable Water Management (American Water). 

The plating bath can also contain impurities which cannot be removed by ordinary filtration, such as solubilized metals dragged in from a previous etching bath (Foecke 1989). Ion exchange (IE) treatment can often be used for removing solubilized metals, although IE systems are fairly expensive compared to standard filtration technologies. 

Membrane filtration technology has not yet proven economically feasible in the industry,... 

Steindl, R.J., Membrane Filtration Technology in the Cane Sugar Industry, Proc. Internat. Society Sugar Cane Technologists, 24, 3-10 (2001). 

Singh RK, Patel C, Conner G, Yang HJ, Towle T. Advances in CMP filtration technology. Proceedings of the Semicon China 2004 SEMI Technology Symposia (CMP) 2004 Mar 17-19 Shanghai. 

For all the aforementioned liquid filtration technologies, membrane selectivity is most often expressed as the membrane retention, R, toward the species to be separated. 

Microfiltration is a technique that allows the differential concentration in the retentate of the feed components that are larger than the average pore diameter of the membrane [8]. Developed as early as 1929 by Sartorius-Werke, in Germany, microfiltration is one of the oldest filtration technologies whose main use was for water and beverage sterilization [9,10]. MF membranes have pore diameter ranging 0.1-10 p.m, which can selectively separate particles with molecular weights >200 kDa based on sieve effect [8,11,12]. 

Cross-flow MF Pall PSS (2.5 pm limit of separation), Fairey Microfilfrex FM4 (1 pm) and APV Ceraver (1.4 pm) ceramic and stainless steel membranes SpinTek ST IIL centrifugal membrane filtration technology... 

Typical Influent Raw Water Characteristics and Capacities of Seven Filtration Technologies for Water Treatment... 

There are several filtration technologies that can be utilized to meet the US EPA requirements outlined in the lESWTR and what is anticipated to be finalized for small systems. However, DE filtration should be at the top of the list when considering microbial removal, capital costs, operating cost, and ease of operation. DE is a proven and approved technology for the filtration of potable water. 

In the US EPA publication Small System Compliance Technology List for the Surface Water Treatment Rule (SWTR) and Total Coliform Rule (ICR) (September 1998), DE is a specifically approved filtration technology for compliance with the SWIR. In its comments the US EPA notes that DE is very effective for the removal of Giardia and Cryptosporidium" (23). 

---