Technologies and Costs for Removal of Arsenic From Drinking Water

surface water treatment is typically not accomplished without extensive pretreatment for particleremoval and possibly pretreatment for dissolved constituents to prevent fouling.Several NF studies for have been undertaken, and the results show that NF processes areeffective for the removal of arsenic. Removal however depends on operating parameters, membraneproperties, and arsenic speciation. AWWARF (1998) performed NF bench-scale studies for arsenicremoval on spiked deionized water and on a lake water. Single element and flat sheet testing wereperformed on a negatively charged NF membrane for a lake water and a spiked, deionized water.Results are shown in Table 2-7.As seen in Table 2-7, As(III) removal was low at only 12 percent. However, As(V) rejectionfor the negatively charged membrane was high at 89 and 85 percent for the lake water and deionizedwater, respectively. Flat sheet testing produced a comparable As(V) rejection of 90 percent.TABLE 2-7As(V) and As(III) Removal by NF MembranesMembrane Type MWCO MembraneChargeSingle ElementWaterTypeSpecies pH Total ArsenicRejection(%)NF 45-2540 300 ( - ) DI V 6.7 85NF 45-2540 300 ( - ) Lake V 6.9 89NF 45-2540 300 ( - ) DI III 6.9 12Flat SheetNF 45-2540 300 ( - ) DI V NA 90NA: Not AvailableAWWARF also performed several single element and array NF pilot-scale tests. Two ofthese tests were conducted on groundwaters, one high in DOC (11 mg/L) and one low in DOC (1mg/L). Another test was performed on spiked, high-DOC groundwater. One other test was performedon spiked, finished surface water. These tests are summarized in Table 2-8.As shown in Table 2-8, during the single element tests on the groundwaters the membranesdemonstrated substantial arsenic removal. Removal in the low DOC water, however, was only 60percent compared to over 80 percent in the high DOC water. As discussed in Section 2.5.5, this was2-34