Using Reporting Bacteria in a Combined Photocatalytic-Biological Wastewater Treatment

Zach Shidlovsky, Department of Chemical Engineering, Technion, Haifa, Israel
Sima Yaron, Dapartment Of Biotechnology And Food Engineering, Technion, Haifa, Israel
Yaron Paz, Department Of Chemical Engineering, Technion, Haifa, Israel


Water purification is often challenged by the co-presence of a large number of organic and inorganic industrial contaminants, some of which are too toxic for bacteria or too opaque for photocatalytic processes. A combination of Advanced Oxidation Processes (AOPs) and biological treatment is often presented as an integrated process that can overcome the difficulties of each method. For example, bacterial treatment can decrease the turbidity of the water stream, which reduces the efficiency of UV-illuminated based AOPs, such as photocatalysis. On the other hand, photocatalysis can degrade compounds that are too toxic for bacterial-based treatment. A combined photocatalytic-biological treatment approach requires optimizing the design of the system in terms of retention time of each reactor and their sequence in real conditions, where the toxicity and turbidity might vary over time.

This research explores the configuration of a combined process of photocatalysis and biological treatment. An optimized process, in terms of sequence, recycling and retention time, can be designed based on complete data of the effluent composition, kinetics and the required level of purification.

In this research a novel approach for a combined treatment, based on a control loop that responds to the bacteria well-being, is presented. The control unit is operated by on-line measurements of turbidity and bacterial-stress response that automatically control the process configuration. The bacterial-stress control is performed by bioluminescence, emitted from genetically modified Escherichia coli, proportional to biological-stress. The measurements are performed by a sequential-batch sample compartment, and are detected by a photomultiplier tube. The development of this toxicity-sensor can reduce the sampling interval of to a few minutes scale. Thus, automatizing the integrated process becomes feasible.