Removal of ferrous and arsenic from contaminated groundwater by co-precipitation coupling with membrane separation process

Abstract

This work aimed to​ treat contaminated groundwater with arsenic and ferrous iron pollutants to be drinking water standard following by WHO by co-precipitation process and membrane separation process. The relative effect of different solid media types (scouring sponge, scouring pad, plastic ring, and activated carbon foam) and operating conditions on oxygen mass transfer coefficient (KLa) and hydrodynamic bubble parameters was studied. The optimization process of ferrous oxidation and arsenic removal was observed by Design of Experiment (DOE) with Central Composition Design of Response Surface Methodology (CCD-RSM). Lastly, separation process was experimented with conventional process and membrane technology, i.e., settling process, different effect of scouring sponge loading on turbidity removal, and impact of settling process on ultra-filtration membrane fouling. The result showed that scouring sponge was the most effective solid media to enhance volumetric oxygen transfer coefficient around 9-80% by impact of bubble rising velocity not breaking up bubble mechanism. The maximum removal of ferrous by optimization process was Qg =14 LPM, initial pH=8, initial [Fe2+]=5mg/L, adding [Fe3+]=25mg/L and operating time 25 min. However, for arsenic removal with co-precipitation process, the optimization process found under condition Qg=8, initial pH=8, initial [Fe2+]=36mg/L, adding [Fe3+]=25mg/L and operating time 33 min. Furthermore, initial pH and ferrous initial concentration was defined as the most significant factor. In separation process, the removal of turbidity by settling process was remaining around 60NTU while the highest scouring sponge loading (10%) was able to remove turbidity around 15% (not pass WHO standard). Finally, ultra-filtration was used to get complete clear and clean drinking water. The result showed that the performance of settling process before membrane filtration could reduce the membrane fouling mechanism. Thus, the combination of settling process and membrane technology could provide more benefits.