Pilot testing and cost calculation for centralized systems using IOC media

The presence of arsenic in water for drinking purposes is a threat to human health; therefore,the WHO guideline concerning its presence in water became stringent (from 50 to 10 ìg/L).To meet new guideline proposed by WHO efficient, effective and affordable technologies forarsenic removal are required.Arsenic adsorption on iron oxide coated sand (IOCS) is being studied at UNESCO-IHE byseveral researchers and it has proved to be efficient on a small and large scale. After somedays of filter run the media became exhausted and regeneration was performed. However,after several filter runs and regeneration cycles, the arsenic adsorption capacity of IOCSdecreased and the length of filter runs reduced from 7 to 3 days. In addition, the related costshave not been estimated for centralised systems.The goals set for the current research was to further optimise the arsenic adsorption anddeveloped regeneration procedures and to estimate the related costs. To meet the goal setsmaller grain size of IOCS compared with the one used by previous researchers at UNESCOIHEwas used for arsenic adsorption experiments in pilot columns. In addition, virgin pumicewas coated and also used for arsenic adsorption experiments in columns. The conditionsapplied for IOCS and IOCP experiments were the same. The experiments performed pilotcolumns provided input for calculation of investment, operation and maintenance costs.Better performance was obtained using smaller grain size of IOCS because under theconditions applied, 6 filter runs and 5 regeneration cycles were performed and the length offilter runs remained the same. For IOCP 8 filter runs and 7 regeneration cycles wereperformed and the length of filter runs decreased from 8 to 2 days.Treatment costs for plant capacities of 1,000 and 12,000 m3/d were calculated. The unit costof treated water was estimated to be 0.20 and 0.14 for 1,000 and 12,000 m3/d plant capacity,respectively