Technologies and Costs for Removal of Arsenic From Drinking Water

arsenic size distribution to correlate with turbidity or organic content, indicating that arsenic sizedistribution was specific to individual waters.To increase removal efficiency in source waters with a low percentage of particulate arseniccontent, MF can be combined with coagulation processes. Coagulation assisted microfiltration forarsenic removal is discussed in Section 2.2.3. For utilities using MF alone for particulate arsenicremoval, removal would primarily depend on the influent arsenic concentration and percentage ofparticulate arsenic since the MF rejection mechanism is mechanical sieving. Therefore, theeffectiveness of MF arsenic rejection is a function of pore size. Variation in MF performance is dueto pore size distribution.2.5.5 UltrafiltrationUltrafiltration processes are generally capable of removing some colloidal and particulateconstituents, based on the above discussion on particulate arsenic occurrence. Considering this, UFalone, like MF, may not be a viable technique for arsenic removal for groundwaters, however, UF maybe appropriate for surface waters with high colloidal and particulate arsenic concentrations.Recent research has found that electric repulsion of UF may play an important role in arsenicrejection and increase rejection beyond that achievable with only pore size-dependent sieving.AWWARF (1998) performed bench-scale tests on two low-MWCO UF membranes. Single elementtesting was performed on Desal GM and FV UF membranes for a spiked, deionized water. Flat sheettesting was also performed on Desal GM, FV, and PM UF membranes for spiked, deionized water.Since the samples were spiked, no particulate or colloidal arsenic was present. Results of this studyare given in Table 2-5.2-31