Experiences with on-line measurements at a wastewater treatment plant for extended nitrogen removal

On-line sensors have been used at the Klagshamn treatment plant to measure the concentration of suspended solids in the raw wastewater, in the primary effluent and in the secondary effluent. By means of the sensors the short-term performance of the primary and the secondary treatment have been evaluated. The sensors are important when the total discharges of pollutants from the plant are to be considered during storm water events. Parallel on-line measurements and laboratory analyses of grab samples have shown that the used sensor type, based on NIR technique, reflects the concentrations rather well. The on-line measurement in the raw wastewater is rather unreliable due to clogging which means that using this application for control can be questioned.