In recent years the Chemical Park Bitterfeld-Wolfen has planned and realized a large-area wastewater monitoring. One hundred and twenty sampling stations and six complete container monitoring stations have been installed allowing to assess the responsible discharger if monitoring limits are exceeded at the treated water effluent.
Dipl.-Ing. (FH) Stephan Schaum, Horst Heilemann
The Chemical Park Bitterfeld-Wolfen is located in the middle German chemical triangle between Magdeburg, Halle and Leipzig. With an area of about 1200 ha it is one of Europe’s largest chemical sites that can look back on a history of more than 100 years. Tasks of P-D ChemiePark Bitterfeld Wolfen GmbH are cleaning former waste sites, creating areas for new companies and organizing water supply and disposal. They are in charge of a treated water net of approximately 130 km, seven rain water catchments and one wastewater collection container, which have a total volume of 35 000 m³. With this the design rain water can be managed and contaminated treated waters like cooling water or non-loaded ground water can be stored in case of an incident.
In addition, there is a wastewater network of approximately 40 km that collects the production wastewaters, sanitary effluent and contaminated groundwater of the Chemical Park. These waters are routed to the joint wastewater treatment plant on site.
Polluter pays principle
The wastewater monitoring of the Chemical Park pursues two main objectives: On the one hand, the wastewater quality has to meet the authority’s regulations and the wastewater quality contractually demanded by the wastewater treatment plant in order to guarantee a smooth treatment at any time. On the other hand, the wastewater monitoring allows to track the origin for the exceeding of limit values. The sampling and analysis of wastewater provide the basis for a polluter pays principle.
In order to reach these two main aims the installation of samplers at the wastewater and treated water manholes started at the beginning of the 1990s in order to monitor the indirect dischargers (Fig. 1). About one half of the samplers are equipped with an additional multiparameter sensor made by YSI in order to monitor wastewater relevant parameters like temperature, pH-value and conductivity. The data can be transmitted via modem. Because of the positive experience in the past the decision was made to generally apply analyzers made by Stip for wastewater monitoring. Based on this, the first on-line analyzer came into operation at the treated water effluent into the receiving water (river Mulde) in 1996. The Stip analyzer Stip-toc measured the TOC content on-line and the Stiptox-norm analyzer was installed for a continuous toxicity monitoring. This was the starting point of a comprehensive and efficient monitoring network.
To ensure that no chemically contaminated water was charged into the receiving water it was necessary amongst others to extend the continuous wastewater monitoring. For this reason five more monitoring stations at net junctions in the Chemical Park were defined and six container monitoring stations were planned. The sixth container monitoring station was designed as a twin container and replaced the above mentioned effluent monitoring at the treated water effluent of the Chemical Park (Fig. 2). Stip was awarded with engi-neering and manufactoring of the containers.
Measuring in the monitoring station
In contrast to cabinet style analyzers the ammonium buoy PBS1 and the multi-parameter probe Stip-scan are in-situ analyzers, which normally measure directly in the wastewater. Therefore, the two in-situ systems are installed in a collection container within the monitoring station. The waters to be monitored are continuously pumped to the monitoring stations by submersible pumps and forwarded via different bypass systems directly to the analyzers and the collecting containers of the in-situ systems. The flow volume is set at a high level of approximately 5 m³/h in order to allow a real-time measurement and to prevent further contamination of the piping system. In case of sedimentation of the piping system easy cleaning is possible due to the screw fittings which make dismantling a simple task. Only a small part of the wastewater is taken out of the bypasses for analysis. The largest part is discharged back to the sewer. As the on-line analyzers are especially designed for wastewater there is no need for an additional filtration or sample preparation (e.g. ultra-filtration).
Thus all important nutrient and global carbon parameters are permanently and real-time monitored and transmitted together with possible failure and alarm signals via the analog outputs and digital relays to the control system of the Chemical Park. On customer’s request the data transmission can be connected to an existing bus system.
In combination with the on-line analyzers the samplers automatically take samples when a pre-set limit value is exceeded. These samples are used for further labo- ratory analysis, documentation and proof of evidence. In addition to the event-controlled sampling, samples can be taken flow-proportionally and time-proportionally.
The multi-parameter probe Stip-scan is most applicable for the required event control. It measures several parameters as COD, TOC, NO3-N, SAC and the sludge parameters total solids (TS), sludge volume (SV) and sludge index (SI). The analyzer is a spectroscopic probe, which measures the wastewater within the light spectrum of 190 to 720 nm. The settling process within the probe allows to use the Stip-scan for inlet and outlet measurement and for measurement directly in the aeration basin. The probe sucks the non-treated wastewater sample into a cylindrical quartz cell (Fig. 3).When installed in the aeration basin the probe determines the dry substance of the activated sludge and displays it as TS in mg/l in a first step. In a second step the time dependent course of the settling behavior is recorded and calculated as sludge volume SV in ml/l. The controller calculates the sludge index SI based on dry substance and sludge volume and displays it in ml/g.
Parallel to the settling process the directly measurable parameters nitrate (NO3-N), spectral absorption coefficient (SAC), COD and TOC are measured. When reaching the clear water zone in the light beam of the quartz cell NO3-N, SAC, COD and TOC as well as turbidity are available as multiply confirmed measured values (Fig. 4).
The complete measuring process takes between 1 to 10 minutes depending on the sludge index. Stip-scan operates nearly maintenance free and without reagents. On the Bitterfeld-Wolfen site the analyzer is used for the measurement of COD, nitrate and SAC.
The concept of wastewater monitoring of the Chemical Park Bitterfeld-Wolfen shows that the right measuring instrumentation at the right place delivers the right results. A complete monitoring network and compliance with the discharge limit values, the most significant objectives, are thus being reached.
Having taken the six monitoring stations into operation new projects are already being planned. One project within the creation of a water information system is to connect the samplers installed at the transfer junctions to the control system of the Chemical Park Bitterfeld-Wolfen GmbH via the already installed Siemens M 20 and Ubicom radio modems.
Chemical Park Bitterfeld-Wolfen
More about Stip-scan
Endress+Hauser Conducta takes over Stip Isco
Endress+Hauser Conducta GmbH+Co.KG, Germany, part of the world-wide operating En-dress+Hauser group, acquired Stip Isco GmbH (Groß-Umstadt, Germany). This completes the product range of the company specialised in liquid analysis for the environmental and process industry in an ideal fashion. Stip products are predominantly used in water and waste water treatment. The acquisition fully corresponds to the Endress+Hauser strategy of providing customers with a comprehensive program from one source and adapting fast to the needs of the market.
Stip develops, produces and maintains analysers for the environmental industry. These instruments measure the quality of water and waste water and help, for example, to operate municipal and industrial sewage treatment plants in an economically efficient and environment-compatible manner. The product range includes online process analysers for TOC-UV and high temperature, COD, BOD and toxicity as well as a multiparameter probe for turbidity, SAC, COD, sludge volume and sludge index.
Stip previously belonged to the American Teledyne Isco group. The company operates predominantly in Germany, Great Britain, USA, China, Spain and Eastern Europe. It was agreed not to disclose the purchase price. The company will be carried on as a profit centre by Endress+Hauser Conducta. The Groß-Umstadt site as well as about 50 jobs will continue. In the medium term, Stip products are supposed to be integrated in view of a uniform operating philosophy and a common Endress+Hauser product design.