Biotechnology based processes for arsenic removal

The regulations for arsenic control have become strict. Therefore, better technologies to remove arsenic from bleeds and effluents are desired. In addition, no single solution is suitable for all cases. The properties of the process streams and the storage facilities are major factors determining the selection of a certain technology. In this paper, two technologies are described. What these technologies have in common is that they are based on high-rate engineered bioreactors that allow optimal control, efficient resource use, and predictable and reliable process performance. One technology (Arsenoteq) converts arsenic to corodite, which is most suitable for storage under oxidising conditions. The other technology (Thioteq) operates under reducing conditions and produces arsenic sulphide (As2S3, orpiment) with 61 mass% arsenic. The first technology is suitable for medium to high (> 1000 mg/L) concentrations of arsenic in acidic process streams, whereas the latter is ideal for effluent treatment up to <5000 mg/L of arsenic. The residual arsenic concentration that can be obtained with the latter method is <0.1 mg/L