Comparison of the Quaternary Treatment Technologies in Municipal Wastewater Purification

The removal of micropollutants during wastewater treatment is an essential element of pollution control due to the last amendment of the Directive 91/271/EEC. Reducing and control at the source is usually the most cost-effective measure for a given substance or group of substances, but wastewater treatment plants with load above 150.000 PE (and between 10.000 and 150.000 PE based on the recieving watercourse or environmental risk assessment) have to reduce and remove the micropollutant in the future. The treatment plants have to install technologies which are optimal to eliminate the micropollutant (fourth stage or quaternary treatment technologies). The main quaternary treatment technologies are the different form of activated carbon filtration, membrane technologies (e.g. nanofiltration or reverse osmosis) and Advanced Oxidation Processes, AOP (e.g. ozone treatment). Among the options available for the removal of micropollutants, the most cost-effective solutions are activated carbon processes, ozone treatment, and their combination in different process configurations. At present, the combination of ozone treatment and activated carbon filtration is an effective technology to degrade the micropollutants, also the antibiotic resistant genes, and also remove the harmful by-products from the AOP treatment. For each wastewater treatment plant, it is necessary to individually examine which technology will be the most optimal to accomplish the new requirements.