No abstract

Constructed wetlands in many different forms have been used in the rural regions of Bavaria for sewage treatment for several years. In 1998 the Abwassertechnische Vereinigung (ATV) published unique design and treatment guidelines with the aim to operate reed bed plants up to a size of 1000 p.e. according to technical standards concerning the oxidation of BOD and COD which will be presented. The treatment capacities of two reed bed plants in Bavaria which were constructed in accordance with these technical standards have been characterised by a high quality effluent during the first ten years of performance. This was especially the case during summer. After more than ten years the plant of See showed a reduced treatment quality. Practical results of investigations on the absorption of heavy metals and other hazardous organic compounds in the substrate of the two reed bed plants will demonstrate that only copper and zinc are significantly stored in the material after more than ten years of performance. The possibility of advanced sewage treatment in constructed wetlands will be discussed.

UV-irradiation as an effective method of diminishing germs in the outlet of wastewater treatment plants was studied in a half-scale pilot-project sponsored by the State of Bavaria/BRD for a period of 3 years. Technical, physical and biological parameters capable of influencing this process were examined. The possibility to improve the hygienic and also the ecological structure of receiving waters was put to discussion. Possible effects of formed bypproducts upon the water biocoenosis of rivers were pointed out. The results demonstrated that UV-irradiation can diminish the number of germs in the outlet of a treatment plant to an extent which is sufficient to guarantee the maintenance of the bacteriological and presumably also the virological values set by the EC Bathing Water Directive. Nevertheless the UV-treatment process requires further technological development and research work concerning i.e. the improvement of hydraulic conditions, coat-forming on the quartz sleeves of the lamps, photochemical forming of by-products, after-growth and effects upon the localised benthic flora and fauna of the receiving water. It has to be stressed that a significant improvement of the bacteriological structure of flowing waters is only attainable, if the influx from non-point sources can be reduced simultaneously.

No abstract

In biological wastewater treatment inorganic and organic substances are fixed and metabolized by mixed populations of microorganisms forming either activated sludge flocs or biofilms. Not only the type of wastewater but also the operational conditions promote the development of an adapted biocenosis of microorganisms with specialized enzymatic functions. Understanding the biological properties of the microorganisms, it is possible to assess the prevailing conditions in their natural environment. Regular microscopic and enzymatic investigations of activated sludge and biofilms thus improve the assessment of the stability of the processes and support troubleshooting in wastewater treatment plants. While the role of bacteria is often discussed, the importance of ciliated protozoes and metazoes for the maintenance of the stability of biofilm systems is rarely mentioned. In this paper we intend to show some new results of direct microscopic observations in different sorts of biofilm systems focussing upon ciliated protozoes and metazoes. Practical results will demonstrate the relation between enzymatic analysis, microscopic investigations and performance of biofilm systems.