Coagulation-microfiltration

Clifford, D.A. and Ghurye, G.L. (2002) Metal-oxide adsorption, ion exchange, and coagulation-microfiltration for arsenic removal from water, in Environmental Chemistry of Arsenic (ed. W.T. Frankenberger Jr.), Marcel Dekker, New York, pp. 217-45. 

Chwirka, J.D., Colvin, C., Gomez, J.D. and Mueller, P.A. (2004) Arsenic removal from drinking water using the coagulation/microfiltration process. Journal of American Water Works Association, 96(3), 106-14. 

Metal-Oxide Adsorption, Ion Exchange, and Coagulation-Microfiltration for Arsenic Removal from Water... 

Arsenic in drinking water supplies can be removed by a variety of treatment processes including those cited in Table 1, which also lists the typical applications of each process. All these processes do a much better job of removing As(V) compared with As(III). Thus, before using these processes, it will often be necessary to oxidize As(in) to As(V) using chlorine or an alternative oxidant. This chapter focuses arsenic treatment by metal-oxide adsorption (MOA), ion exchange (IX), and iron (III) coagulation-microfiltration (C-MF), because these processes have proven to be the most efficient and cost effective in bench- and pilot-scale studies, especially for point-of-use (POU), point-of-entry (POE), wellhead, and small community treatment systems. 

Ion exchange using packed beds of chloride-form anion-exchange resins Iron(n) coagulation-microfiltration without flocculation and presedimentation Lime softening... 

Figure 13 Results of extended iron coagulation-microfiltration tests on a groundwater in Albuquerque, NM. (From Ref. 3.)...

J Tong. Development of an iron (Ill)-coagulation-microfiltration process for arsenic... 

Mo, L., and Huanga, X. (2003). Fouling characteristics and cleaning strategies in a coagulation-microfiltration combination process for water purification. Desalination 159, 1-9. 

Microfiltration (MF) and ultrafiltration (UF) membranes can be used as forms of pretreatment for nanofiltration (ISIF) or reverse osmosis (RO) desalination processes. Membrane pretreatment reduces the amount of chemicals that are required and hence reduces the environmental impact of the final discharge. MF membranes can be used to filter particles with diameters of 0.1-10 pmm and typically remove bacteria, viruses, precipitates, coagulates and large colloidal particles. UF can remove particles with diameters as small as 0.002 pm, and... 

Colloidal materials present in surface waters can also plug RO membranes, causing a decrease in permeate flux. Colloidal plugging can be avoided by using one of several possible pretreatment steps. Ultrafiltration (qv) (UF) or microfiltration (MF), depending on the size of the colloid, can be used to filter out the colloidal material. Alternatively, a coagulant such as alum can be added to the water to form aggregates of the colloid, which can then be filtered in a similar manner as suspended solids. 

Among the numerous approaches studied so far to minimize such phenomena in ED, it is worth citing pretreatment of the feed solution by coagulation (De Korosy et al., 1970) or microfiltration (MF) or ultrafiltration membrane processing (Ferrarini, 2001 Lewandowski et al., 1999 Pinacci et al., 2004), turbulence in the compartments, optimization of the process conditions, as well as modification of the membrane properties (Grebenyuk et al., 1998). However, all these methods are partially effective and hydraulic or chemical cleaning-in-place (CIP) is still needed today, thus... 

Zhu, B.T., Cliford, D.A., Chellam, S. (2005). Comparison of electrocoagulation and chemical coagulation pretreatment for enhanced virus removal using microfiltration membranes. Water Res. 39, 3098-3108. 

Heidenreich S and Scheibner B. Hot gas filtration with ceramic filters Experiences and new developments. Filtr. Sep. 2002 May 22-25. Heidenreich S and Wolters C. Hot gas filter contributes to IGCC power plant s reliable operation. Filtr. Sep. 2004 June 22-25. Larbot A, Bertrand M, Marre S, and Prouzet E. Performances of ceramic filters for air purification. Sep. Purif. Technol. 2003 32 81-85. DeFriend KA and Barron AR. A simple approach to hierarchical ceramic ultrafiltration membranes. J. Membr. Sci. 2003 212 29-38. Endo Y, Chen D-R, and Pui DYH. Collection efficiency of sintered ceramic filters made of submicron spheres. Filtr. Sep. 2002 March 43-47. Sakol D and Konieczny K. Application of coagulation and conventional filtration in raw water pre-treatment before microfiltration membranes. Desalination 2004 162 61-73. 

The combination of electro-coagulation, flotation and microfiltration is applied by Pouet et al. [60]. In this case Membralox 1P19-40 membranes are used a zircortia/alumina composite membrane of 50 or 100 nm pore size. With 100 nm and the use of electro-coagulation fluxes stabilise on 250-3501/m h. 

C. Moulin, M.M. Bourbigot and M. Faivre, Interest of the ozone/coagulant combination for the potabilization of surface waters by crossflow microfiltration on mineral membranes, in Ref. [2], pp. 229-236. 

Hillis P., Padley M., Le M.S. (1996), Removal of natural organic matter by coagulation and microfiltration... 

Membranes used in microfiltration, reverse osmosis, dialysis, and gas separation are usually prepared by the wet-extrusion process, since it can be used to produce almost every membrane morphology. In the process, homogeneous solutions of the polymers are made in solvent and nonsolvent mixtures, while phase inversion is achieved by any of the several processes, such as solvent evaporation, exposure to excess nonsolvent, and thermal gelation. In most formulations, polymer solutions of 15-40 wt% concentration are cast or spun and subsequently coagulated in a bath containing a nonsolvent (usually water). 

Sakol D and Konieczny K. Application of coagulation and conventional filtration in raw water pre-treatment before microfiltration membranes. Desalination 2004 162 61-73. 

Various techniques can be used to reduce the loading of suspended solids, organics and microbes in feed water. These include physical processes such as media filtration, cartridge microfiltration and chemical treatments. Chemical addition enhances the filter-ability of the solids such as the addition of coagulants (Table 2.2). Foulants and their control strategies are addressed in Table 2.8. Since any traces of soHds and organics get removed in the first membrane modules in RO and NF systems, these materials typically foul the first stages of an RO/NF system (Table 2.9). Once deposited on the membranes. 

Huang, C.P., Lin, J.L., Lee, W.S., Pan, J.R., Zhao, B.Q., 2011a. Effect of coagulation mechanism on membrane permeability in coagulation-assisted microfiltration for spent filter backwash water recychng. Colloid Surf. A 378, 72—78. 

Operational costs are primarily associated with power and vary from 50 to 120 hp/mgd. Pretreatment chemicals include coagulants, and when biofonhng is a problem, hypochlorite solution can be used on some membranes for cleaning. Citric acid can also be used for membranes that do not tolerate chlorine. Microfiltration membranes are typically not compatible with polymer addition, which is not reqnired, since even small pin floes cannot permeate the membranes. 

Ghurye, G., Clifford, D. Tripp, A. (2004) Iron coagulation and direct microfiltration to remove arsenic from groundwater. Journal American Water Works Association, 96 (4), 143-152. 

---