Potential biosorbents for treatment of chromium(VI)-contaminated water discharged into Asopos River

The present study reports on the preliminary investigation of three low-cost natural materials with respect to their chromium(VI) removal efficiency from contaminated water. The tested materials were reed, in milled and chopped form, compost, and dewatered sludge from a municipal wastewater treatment plant. The chromium(VI) removal capacity of the aforementioned materials was investigated by simulating the physicochemical conditions prevailing in a stormwater outfall flowing into the Asopos River in Inofyta, Central Greece. Thus, batch and column experiments were carried out using solutions of 3-5 mg/L chromium(VI) and pH value 8.5 +/- 0.5. The results showed that the tested materials were capable of removing 3 mg/L chromium(VI), however by allowing different contact times for each material. The chromium(VI) removal kinetics were studied through batch experiments, and reed was found to be the most efficient material. Therefore, at a second series of batch and up-flow column experiments, the effect of the liquid-to-solid ratio, pH, and contact time on chromium(VI) removal using chopped reed was investigated. Chromium(VI) removal took place through both reduction and adsorption mechanisms, while the released soluble organic matter from reed seemed to favor the reduction mechanism. As a result, reed is a potential biosorbent capable of treating heavily chromium(VI)-contaminated water flows, although a high mass of reed is required for a treatment process, such in the case of the stormwater discharged into Asopos River.