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 online 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.