Use of bone char as an adsorbent in preparation of water for dialysis

Currently, deionizers (DI) and reverse osmosis (RO) are used to prepare water for dialysis. When water metal levels increase, for example, with the use of alum, the variation in metal content can reduce RO performance. Pretreatment of water with ethylenediaminetetraacetic acid or alkali can be used to reduce Al fouling. The authors examined adsorption of metal water contaminants with bone char (BRIMAC, Biolab, Oakville, Canada) as a cheaper alternative. Water treatment for the unit consists of a blend valve, 30 mu filter, 2 X 3 cu ft adsorption tanks, 5 mu filter, 30,000 grain automatic water softener, 5 mu filter, Millipore RO 1,000, 2 X 7" mixed bed DI in series, and a polysulfone ultrafilter. During 29 weeks of continuous bone char adsorption, raw water Al ranged from 0.022 to 0.298 ppm (mean, 0.097 +/- 0.075 ppm; cf. the Environmental Protection Agency's proposed drinking water standard of < 0.05 ppm). Postadsorption Al ranged from 0.002 to 0.076 ppm (0.041 +/- 0.04), a decrease of 55-91% (83.0 +/- 8.5%). Final water Al was < 0.001 at all times. No fouling of the RO membrane occurred. Residual chlorine after the first adsorption was < 0.02 to 0.09 ppm. Significant reductions in other metals, notably Pb, Cu, and Zn were noted. Bone char is a cheap, effective, and simple alternative for removing excess trace elements from water for hemodialysis. Further study to evaluate the efficacy of bone char in removing other organic and inorganic water contaminants is needed.