THE EFFICIENCY OF REMOVAL OF LEAD AND OTHER ELEMENTS FROM DOMESTIC DRINKING WATERS USING A BENCH-TOP WATER FILTER SYSTEM

The efficiency of removal of lead (Pb) and other elements from natural drinking waters using a bench-top water filter system was evaluated i n three recently-built houses in Sydney, Australia, and two from rural centres. In addition, one filter system was tested for copper (Cu), P b and cadmium (Cd) under rigorously-controlled laboratory conditions u sing Sydney water. For two Sydney houses, the efficiency was evaluated using special filter cartridges concomitant with the ordinary filters . Waters after passing through the filter, was sampled when the filter had been exposed to '0', 50, 100, 150, 200, and 250 1 respectively an d were analysed for lead isotopes and lead concentrations by high prec ision isotope dilution mass spectrometry. Samples that passed through the filter after '0', 50, 150 and 250 1 collections were analysed for four anions and 39 cations by various methods. Sydney water was fairly uniform in its anion and cation composition, whereas water from the t wo rural areas contained higher concentrations of Ca, Mg and HCO,. Eff ects of the filter on the water compositions can be summarised into th ree groups: (1) elements removed during filtration-Ca, Mg, Sr, Ba, Cu, Pb, Zn and Ni. With 'age' of the filter, the efficiency of removal fo r Pb was maintained in the two houses with Pb concentrations greater t han 10 mu g/1 in the first flush water and was maintained for Cu throu gh all concentrations. Ca, Mg, Sr and Ba were largely removed in the f irst 50 1 of usage. (2) Elements added during filtration-K, Rb, Ag and P. Except for Ag, which was present throughout the testing period, th ese elements were added only in the first filtration. (3) Elements una ffected by filtration-Al, Si, Na, Fe, Cl and F. Efficiency of Pb remov al from tap water by this system depends generally on the initial Pb c ontent in the water. However, it also seems to depend, to some extent, on Pb speciation and water composition, as found in earlier studies o f natural waters. The control in filtering efficiency as a function of Pb speciation and chemical composition becomes more important at low initial Pb concentrations in the water. However, the Pb concentrations at which speciation and water composition appear to play a role in fi lter efficiency are so low that these factors, though scientifically i nteresting, have no relevance from a practical point of view, especial ly the impact on human health. acidification of six sets of duplicate water samples, one sample immediately after collection and the other a cidified after more than 2 weeks, showed negligible changes in Pb or C u concentrations between duplicates. (C) 1997 Elsevier Science B.V.