Removal of inorganic pollutants in rainwater by a peat-derived porous material

Although roof-top runoff water has been considered as an alternative water resource, the harvested rainwater needs to be treated for further use because it usually contains various contaminants such as heavy metals and microbes. The degree of the harvested rainwater quality depends upon its end use such as drinking water and irrigation. Especially, when harvested rainwater is to be used as gray water, a cost effective treatment system is required. Accordingly, the main purpose of this study was to examine the adsorption characteristics of peat, cost-effective biosorbent, for various inorganic pollutants such as ammonium, copper, cadmium and lead from roof-top runoff water. As part of efforts to investigate the sorption properties of peat, batch isotherm tests were carried out under various pH conditions. The characterization of peat was carried out with powder X-ray diffraction, Brunauer-Emmett-Teller, and scanning electron microscope measurements. Both heat-treated peat and non-treated peat appeared to have high sorption capacity for all inorganic contaminants (NH ₄ ⁺, Cu²⁺, Cd²⁺, and Pb ²⁺). An interesting finding is that the amount of NH₄ ⁺ sorbed on the sorbents was slightly higher compared to the other cations. Also, the sorption capacity of the peat sorbents increased with an increase of pH. On the other hand, kinetic data were well described by pseudo-second kinetic model, indicating that removal mechanism of cations by peat-derived sorbents is likely due to chemisorptions. The results of this study suggested that peat-derived porous materials can be used as effective sorbents for removal of cationic inorganic contaminants from harvested rainwater.