Wastewater analyser

Endress+Hauser have launched an inline analyser for municipal and industrial wastewater treatment plants. The new STIP-scan device overcomes the costly sampling and maintenance procedures required by historical 'cabinet analysers' since it operates directly in the process.

Endress+Hauser's STIP-scan inline analyser allows the measurement of multiple parameters simultaneously. Using a single probe, nitrate, chemical oxygen demand (COD) or total organic carbon (TOC), total solids (TS), sludge volume (SV), sludge index (SI) and spectral absorption coefficient (254 low) can be measured.

The core of STIP-scan technology is a miniaturised spectrometer. A xenon lamp sends light flashes through a measurement cell containing the sample. After being transmitted through the sample, the light is collected and recorded by a photo diode array spectrometer in the wavelength range between 190 and 720 nm. The quartz settling chamber also serves as the spectrometer cell. Immediately after sampling, the particles and sludge flocs start to settle.

During the settling process, continuous, rapid measurements are taken of the total solids (TS in g/l) using the absorption of visible light. From the results of the settling kinetics, a settling curve is recorded and the sludge volume (SV in ml/l) is calculated.

After approximately 30 s of settling, the sample is sufficiently clear for analysis, and nitrate, spectral absorption coefficient (254 low) and chemical oxygen demand (COD) or total organic carbon (TOC) are measured. The sample is expelled out of the measuring cell and a new measurement cycle is initiated. Depending on the settling characteristics of the wastewater, the complete measurement cycle takes between one and five minutes.

Endress+Hauser's STIP-scan inline analyser does not need any chemicals for calibration or operation and essentially operates with no maintenance. The system can be installed in the inlet, in the aeration basin and in the effluent.