Biosensor for Toxic Detection and Process Control in Nitrification Plants

This paper presents the design and possible applications of a nitrification biosensor suitable for continuous monitoring of the potential toxicity of incoming wastewater at a treatment plant. The measurement principle of the biosensor is based on the on-line determination of the alkaline (Na2CO3) consumption required for the neutralization of protons produced during nitrification. Toxicity is detected by a rapid decrease in the consumption of Na2CO3. Based on early diagnosis of incoming toxicity, a process control concept for flow pattern manipulation is proposed and tested in a pilot plant, where programmed toxic substances were added. The pilot plant behavior with and without flow pattern control was compared. The control system was capable of diverting most of a toxic load to a buffer tank at the head of the plant, from which it can be released it later in a safer way. A significant process improvement is demonstrated in the case of flow pattern control. The experimental results show that the biosensor is a useful diagnostic tool for continuous monitoring of the nitrification activity and potential toxicity of incoming wastewater to the treatment plant.