An experimental study on iron and manganese removal and optimum operating conditions for a small water treatment system

Xiao, Lin (2013) An experimental study on iron and manganese removal and optimum operating conditions for a small water treatment system. Masters thesis, Memorial University of Newfoundland.

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Abstract

In sparse rural communities, it is often not cost-efficient to construct large or medium-scale water treatment plants or to connect to existing municipal facilities. In Newfoundland, many rural communities are facing similar situations in terms of drinking water supply, and a potable water dispensing unit (PWDU) was previously developed in order to supply reliable and safe drinking water to these communities. While the initial testing of this treatment system demonstrated its reliability in meeting drinking water standards, the insufficient removal of colour present in treated water occurred in some cases, which is often caused by high levels of iron and/or manganese. Aimed to improve the performance of the PWDU in removing iron and manganese, this study used a combination of central composite design and response surface model approaches to evaluate iron and manganese removal efficiencies under varying operational (e.g. ozone doze and flow rate) and environmental conditions (i.e., concentration of iron and manganese). In terms of iron removal efficiency, the initial iron concentration in the influent had the strongest effect followed by influent manganese concentration, while flow rate and ozone dose had no significant effect on iron removal efficiency. In terms of manganese removal efficiency, all 4 factors analyzed had significant effects but the flow rate had the weakest effect when compared to the effects of initial iron (strongest) and manganese (second strongest) concentrations. The results also indicated that an ozone dose of 8.5 g/hr was optimal for iron and manganese removal in most cases tested. While higher flow rate was preferred for raw water with lower iron and manganese concentrations, lower flow rate was better for raw water with higher iron and manganese concentrations. This study greatly improved our knowledge in system performance as well as iron and manganese removal by the PWDU, which would benefit the water treatment industry as well as the rural communities across NL by improving the quality and capacity of drinking water supply. In addition, the experimental approaches used by this study also provided a useful reference and tool for further studies aimed to improve the performance of small-scale water treatment systems.

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