The Valmet TS device makes the reliable and accurate measurement of solids content in sewage sludge of different origin possible - and this at minimal maintenance efforts. Continuous measuring increases operational safety within the entire sewage treatment plant and facilitates the optimization of processes.
ProRheno AG is treating waste water of households, commercial enterprises and the industry within the region of Basel ever since 1982. ProRheno AG is made up of ARA Basel (municipal wastewater treatment), ARA Chemie Basel (purification of chemical wastewater) and the sludge treatment (incineration of accumulated sewage sludge). The entire land covers an area of 76,300 m2.
The advantages of the Valmet TS became quickly obvious in the particular processes: The accurate and continuous measurement of solids content ensures optimal control. The positive impact on downstream system components can only be quantitated after some time – but these effects are tremendous!
The continuous measurement of solids content (TS) in sewage sludge constitutes a huge challenge for online analytics. High viscosity, polluted sensors, the fluctuating consistency and different color shades of sludge are limiting the use of conventional online analytics to a few applications.
The sensor Valmet TS is similar to a flow meter: The sensor technology is built straight into the pipe wall. Such a design method will not alter the profile and the risk of blockage is almost ruled out. The device measures the duration needed to travel from the microwave all the way through the process line and by doing so, it calculates the content of TS. In combination with the Endress+Hauser flow meter Promag 53, the content of TS and the load can be measured continuously.
The ProRheno AG sewage treatment plant in Basel has six Valmet TS and Promag 53 in use (as of 2016) – the first device was introduced within preliminary treatment in 2010. “The very low maintenance needed for the Valmet TS sensor is impressive,” explains Jörg Gautschi. The measuring system delivers accurate results even with fluctuating sludge characteristics; thanks to the characteristics of the measuring principle a single point calibration is sufficient.
Industrial waste water is neutralized and freed of solids in a special section of the plant. To protect downstream processes and to economize on calcium hydroxide (milk of lime), sludge enriched with lime milk is fed back in parts into the neutralization process. The Ratio between sludge that is fed back and sludge to be siphoned is controlled with help of the Valmet TS.
Measuring the TS content online allows feeding the static thickener out of the communal and industrial part of the plant in a perfect way. The pumping-off cycles within the secondary treatment and the GUS flotation process can be adjusted to match the current load and phase separation is carried out reliably.
Water is still removed from the sewage sludge by means of the centrifuge after the process of static thickening. The operator is able to optimally control speed and chemical metering thanks to real-time data provided by the Valmet TS. The operator is also able to identify critical operating conditions early enough to take the appropriate corrective actions.
Endress+Hauser is the official dealer for the Finnish company Valmet in Switzerland’s wastewater sector – this includes sales and services related to the Valmet TS device.