German Waste Processor uses turbidity measurements |

German Waste Processor uses turbidity measurements

German Waste Processor uses turbidity measurements
September 25, 2008 - AVG, a waste processing company in Hamburg. Germany, disposes of huge amounts of different types of waste every year in an environmentally responsible way. The company’s activities are centered around a high-temperature incineration plant, one of the largest and most modern of its kind in the world. Moreover, apart from various storage facilities as well as a separator unit, AVG also maintains a chemical-physical treatment plant (CPA). In this plant, inorganic wastes that can be pumped are treated in chemical-physical processes in such way that the resulting effluent can be discharged safely into the public sewer system in compliance with official regulations.

Conserving natural resources
The energy produced by the waste incinerator is supplied to the Hamburg district heating network via a neighboring cogeneration power plant. In this way, some 30’000 households are supplied with waste heat from the incineration plant, thereby saving expensive conventional fuels and contributing towards conservation of natural resources. AVG’s high-temperature incineration plant is the focal point of an efficient disposal center. Besides the incineration process, large amounts of inorganic liquids, oil-water mixtures as well as wastewater from the stack gas scrubber of the incinerator are treated in the CPA.

Chemical-physical plant (CPA)
By means of chemical reactions in the aqueous phase, harmful substances present in the wastes are either oxidized and / or reduced, neutralized, precipitated out, as the case may be. For this, four stirred reactors are available, connected to the various storage tanks for the treatment chemicals. Following treatment, the neutralized waste mixture is discharged to a sedimentation basin and finally the precipitated sludge dewatered by a chamber press. The effluent is subsequently passed through a gravel / active carbon filter and before final discharge to the public sewer system is subjected to analysis in accordance with official regulations covering the discharge of wastewater.

InPro 8200 protects and monitors the gravel filter
For control of the effluent stream, the AVG in Hamburg relies, among other factors, on backscattered light turbidity measurements using equipment supplied by METTLER TOLEDO. To prevent clogging of the gravel filter and the downstream active carbon filter, solid matter concentration may not exceed a limit value of 25 g/l; since this would mean having to carry out time-consuming and costly back flushing of the gravel filter and regeneration of the active carbon. The limit value is monitored by the turbidity sensor InPro 8200 in conjunction with the turbidity transmitter Trb 8300. Ease of handling and the rugged design of the sensor are particular advantages offered by this combination. Previously, the turbidity value was determined using 90° scattered light measurement. However, with this technology it was not possible to achieve reproducible measurement values. Only after installation of the InPro 8200 turbidity sensor was online measurement truly feasible. Measurement is done in the bypass of the main feed pipe to the gravel filter, and the sensor installed in such way that air bubbles are unable to interfere with the actual measurement. The second turbidity measurement system is positioned at the point of effluent discharge into the public sewer system. The limit value for solid particles in this case is 15 g/l. The InPro 8200 turbidity sensor together with transmitter Trb 8300 are used as the preferred measurement system in this application. Measurement here takes on particular importance; as it is used to monitor compliance with official discharge regulations.

Particular benefits of the InPro 8200
The dual optical fiber sensors InPro 8200 offer high resolution in the low-temperature turbidity range and high linearity in the mid turbidity range.
  • High resolution
  • Reliable measurements in the range 5...4000 FTU and 0...30 g/l suspended solids
  • Wide scope of application
  • Versatile, compact 12 mm design
  • Robust, with low maintenance requirement
  • Sapphire windows protect the optical fibers against abrasion and fouling