MEASUREMENT OF AMMONIUM CONCENTRATION AND NITRIFICATION RATE BY A NEWTITRIMETRIC BIOSENSOR

Nitrifiers are more sensitive than heterotrophic bacteria to environme ntal changes (such as temperature, pH, shock loads as biological oxyge n demand or nitrogen, and toxic/inhibiting loads). Moreover, they are slow-growing bacteria. Thus, a careful control of their activity is ne eded to achieve continuous good effluent quality. To maintain an activ ely nitrifying population, efficient process control requires monitori ng of the toxicity and the ammonium concentration. The latter is commo nly measured by on-line ammonium analyzers. A new sensor has been deve loped to measure both the ammonia nitrogen (NH4+-N) content in the mix ed liquor and the activity of the nitrifiers. The operating principle of the biosensor is based on a titration method, which measures the pr otons produced during nitrification. This paper describes the biosenso r and the experimental results (estimation of NH4+-N concentration and nitrification rate) obtained using activated sludge from wastewater t reatment plants receiving hospital and food industry effluents. The in fluence of changes in operational factors such as pH, temperature, and bicarbonate alkalinity on the measurements has been examined. The pot ential applications of the system as an on-line biosensor are outlined .