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NITRATE REMOVAL FROM WATER SUPPLIES BY ION EXCHANGE
Citation:
Clifford, D. AND W. Weber. NITRATE REMOVAL FROM WATER SUPPLIES BY ION EXCHANGE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-78/052 (NTIS PB285275), 1978.
Description:
Anion exchange using synthetic organic resins is a proven and practical technology for the removal of nitrate from water supplies. However, disposal of the spent regenerant brine solution containing nitrate is a potential problem. Two processes were examined in detail in this report--single-bed strong-base anion exchange with NaCl regeneration and two-bed strong-acid, weak-base ion exchange with HCl and NH4OH regeneration. Both systems must be operated to nitrate breakthrough to minimize regeneration costs. The two-bed process is one and one-half to two times as expensive to build and operate as is the single-bed process, but produces softened low-TDS, low-nitrate water, and has a readily disposable, spent regenerant with fertilizer value. Important design considerations were found to include the nitrate and sulfate concentrations in the raw water, the service flow rate, the resin bed depth, and the nitrate/chloride selectivity of the resin. The sulfate, nitrate, chloride, and bicarbonate selectivities and multicomponent column behavior of the anion resins available from U.S. manufacturers were examined and are reported in detail. An important peripheral finding was that significant quantities of nonvolatile organics were leached from 'clean' resins into the treated water.