Assessment of the heavy metal - levels in the incinerators bottom-ash from different hospitals in Dares Salaam

摘要

Understanding content of bottom ashes from incinerator especially toxic heavy metals is an important step towards ash utilization. The aim of this paper was to evaluate heavy metals levels of in bottom-ash from hospital waste incinerators in four different hospitals in Dar es Salaam city (Muhimbili National Hospital and three regional referral hospitals Mwananyamala Ilala and Temeke) in Dar es Salaam city, Tanzania. It has been estimated that Tanzania has an average annual generation of healthcare waste of 6,745 tons per year with a generation rate of about 0.41 kg/occupied bed/day of healthcare waste. Burning of hospital waste releases toxic metals in the bottom ash which can pollute the environment if not well managed. The samples were collected from a pile of bottom ash, according to Standard Guide for sampling waste piles ASTM D6009-96, digested with a 3:1 of concentrated acids HNO3 and HClO4. The concentration of heavy metal were determined using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). The maximum concentration of other metals were 0.348 0.161 Cr (Ilala Regional Hospital), 0.019 0.012 Cd (MNH) and 0.677 0.499 Pb (Ilala Regional Hospital). The level of metals determined exceeded the US-EPA regulation maximum permissible limit in good soil quality and therefore classified as harmful and toxic. There is a need to explore environmentally friendly techniques for proper disposal of ash generated by incinerators, to minimize heavy metals in products ending up in the healthcare waste.