Monitoring of the inlet of the biology in a wastewater treatment plant

GO Systemelektronik supplied the measurement technology for a municipal wastewater treatment plant to implement the monitoring of the inlet of the biology and a separate monitoring of a direct industrial discharge.

To monitor the influent and optimise the biology of a wastewater treatment plant, it makes sense to continuously measure the expected loads of the wastewater.
For this purpose, the Chemical Oxygen Demand (COD) and Ammonium (NH4) are measured simultaneously in the general inlet of the biology. For the direct discharge of an industrial plant into the biological phosphate stage, the COD content is also determined. The measurement data collected can thus be used as a basis for determining wastewater charges. Furthermore, the data can provide an early warning when limit values are exceeded and therefore ensure the operational safety of the wastewater treatment plant.
Particularly for these tasks, high-resolution measurements with short measurement intervals are indispensable and make it possible to derive optimal decisions for optimising the control processes of the wastewater treatment plant.

The BlueBox controller is at the heart of the measuring system configuration. The controller collects all measurement data and transmits them simultaneously via 4-20 mA, as well as via an integrated UMTS modem.
The two ISA measuring heads are each connected to the corresponding UV/Vis spectrometer module via an optical fibre. The modules are in turn connected to the BlueBox controller via CAN bus. The two spectrometers were calibrated specifically to the characteristics of the local water matrix. The spectrometer for monitoring the general inlet of the biology is calibrated for the simultaneous determination of the parameters COD and NH4. The spectrometer for monitoring the industrial wastewater has a specific calibration for COD.

The BlueBox controller and the two spectrometer modules are mounted in the analysis house directly next to the biology inlet. The modules are connected to the BlueBox via CAN bus lines, which are used for both power supply and data transmission. In the analysis house, the wastewater from the general influent and the industrial discharge is pumped into separate measuring pots with sample overflow. The ISA sensor heads are inserted into the measuring pots via a chain, which ensures the optimal insertion angle. The modules are also connected to a compressor for automated compressed air cleaning of the sensor optics.

All parameters are measured every 30 seconds and automatically transmitted to the BlueGate data service via UMTS modem; at the same time, the measured values are also transmitted directly to the control room via 4-20 mA. The measured data is thus accessible to the operator at any time. In addition to providing the data, the connection also allows remote maintenance to make changes to the settings if necessary. Thanks to the availability of the data and the possibility of remote maintenance, the ideal time for on-site maintenance operations can be determined. With this information it is possible to ensure, that the system is always in perfect working order.