Assessment of Heavy Metal Concentrations and Water Quality Parameters in Hemodialysis Water in Kirkuk, Iraq

Objective: To assess physicochemical parameters and selected trace/heavy metals in water before and after the reverse osmosis (RO) treatment system at the main dialysis center in Kirkuk, Iraq, and to compare the results with WHO reference values and applicable AAMI/ANSI/ISO requirements. Methods: Water was sampled at the RO inlet (In) and outlet (Out) at two-week intervals from the beginning of April to mid-May 2024. Samples were collected in 0.5-L polyethylene bottles and stored at approximately 8 °C until analysis. pH, total dissolved solids (TDS), electrical conductivity (EC), Na, K, Ca, Mg, and selected trace metals were measured using pH/TDS/EC meters, flame photometry, flame atomic absorption spectrometry, and ICP-OES. Results: pH decreased from 7.60 ± 0.0493 to 6.50 ± 0.0950. TDS decreased from 688.3 ± 1.528 to 6.00 ± 0.800 mg/L, and EC from 1459 ± 2.646 to 13.00 ± 1.00 µS/cm (P < 0.0001). Na remained below its applicable limit. K decreased from 9.439 ± 0.1063 to 4.053 ± 0.02292 mg/L (P = 0.0002). Ca and Mg decreased to 39.08 ± 0.02235 and 21.70 ± 0.1865 mg/L, respectively, but remained above their applicable limits (P < 0.0001). Zn, Pb, and Cd decreased after RO but remained above their respective limits; Cr was 0.0200 ± 0.0006 mg/L at the inlet (P = 0.004) and was not detected after RO at the reported analytical level. Fe remained detectable at 0.1044 ± 0.0001 mg/L before RO and 0.09550 ± 0.0002 mg/L after RO. Al, Be, Ba, As, Ag, Sb, Se, Tl, Co, Ni, Mn, and Cu were not detected at the reported analytical level. Conclusion: RO treatment substantially reduced several measured parameters but did not achieve chemical compliance for Ca, Mg, Zn, Pb, and Cd. The findings support routine monitoring and systematic evaluation of pretreatment, membrane condition, storage, and distribution components.