PC Plants – Best Available Techniques (BAT) to Reduce the Input of Micropollutants from Wastewater from PC Treatment Plants for Hazardous Wastewater into Water Bodies

 

Physico-chemical treatment plants, PC plants for short, are used to treat liquid and water-containing waste containing organic substances that can be indirectly discharged into water bodies via wastewater. Although the wastewater is first fed into a treatment plant, the complete elimination of hardly degradable organic substances is often not possible.

The overarching goal of the project is to identify organizational and technical measures to minimize the input of micropollutants from PC plants. In order to address this issue, a project group consisting of the Research Institute for Water and Waste Management, FIW for short, various plant operators, and the Environmental Analysis Laboratory of the Institute for Environmental Engineering, ISA for short, has been established.

The ISA is responsible, among other responsibilities, for the identification of substances in the different partial streams and waste types of the PC plants, as well as for chemical-analytical consulting within the project. Organic trace substances are the main focus of the investigations and were selected according to the following criteria:

• Environmental impact, toxicity, environmental dose rate
• Volume of waste from PC plants
• Biodegradability in the sewage treatment plant
• Eliminability in the fourth treatment stage at municipal sewage treatment plants

An early detection of trace substances is to be ensured by implementing suitable analytical methods, such as sum parameters, individual substances, or toxicological parameters. In addition, a quantitative assessment, for example by means of input and output controls, offers the possibility of minimizing the input of organic micropollutants from PC plants into water bodies.

For the identification and quantification of trace substances, gas chromatographic, or GC, methods are used for the non-polar, volatile organic trace substances. Liquid chromatographic, or HPLC, methods are applied to polar compounds. In addition, wastewater substreams are also tested for toxicity or harmfulness to the biocoenosis in the wastewater treatment plant using the TTC test as well as for ecotoxicity using the luminescent bacteria test. Sample preparation methods such as solid phase extraction, derivatization and headspace techniques are used for matrix separation and enrichment.

The analysis of trace substances in the partial streams of the practice plants validates previous findings and helps to adapt the treatment concepts. The practice partners develop treatment concepts for various waste streams, which may contain trace substances, based on the findings of the preliminary investigations in order to achieve elimination or retention of the micropollutants before discharge into the wastewater network.

In addition to the classical processes of emulsion splitting, neutralization and precipitation, various treatment techniques, such as separation of the trace substances by distillation or membrane processes or activated carbon, can be used. A subsequent material flow analysis illustrates the change in trace substance elimination for the respective treatment steps of the concepts.

In summary, recommendations for best available techniques to minimize the input of trace substances from PC treatment plants are developed according to the European guidelines for the preparation of BAT reference documents.