Remediation and recycling of chromium from tannery wastewater using combined chemical–biological treatment system

Abstract

Tannery wastewater containing chromium (Cr) is one of the most serious problems in leather industry. In order to develop an effective and eco-friendly treatment technology, a combined chemical–biological treatment system was performed for Cr remediation and recycling. The aim of the present study is to design a laboratory scale system using chemical precipitation of Cr(III) combined with biological removal of Cr(VI) from tannery wastewater, and to investigate the possibility of recycling the recovered Cr(III) in the tanning industry.Chemical precipitation of Cr(III) was carried out using lime and cement dust. The actinomycete strain Kitasatosporia sp. was used in microcosm studies for Cr(VI) bioremoval. Moreover, parameters such as type of porous medium, inoculum size, flow rate and culture conditions were investigated. The precipitated Cr(III) that was recovered from the chemical precipitation stage was recycled in the leather tanning industry.Our findings indicate that the maximum Cr(III) precipitation (98%) was achieved using 2g/100mL of lime and 2h of settling rate. On the other hand, microcosm columns using sand that was inoculated with induced culture (OD600=2.43) and flow rate (2mL/min) gave the maximum recovery (99%) of Cr(VI). The experimental Cr(III) was successfully recycled in the tanning process and the experimental leathers showed comparable properties as same as the leathers tanned with commercial Cr(III). Thus, we concluded that using combined chemical–biological treatment system for Cr remediation from tanning wastewater together with recycling process for the recovered Cr(III) is a promising strategy for economic and environmental friendly tanning industry.