D10: Impact of Contaminants - Hydromod

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Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas EUROLAKES D10: Impact of Contaminants FP5_Contract No.: EVK1-CT1999-00004 Version: 4.0 Date: 25/07/01 File: D10-vers.4.0.doc Page 98 of 136 The Council Directive 86/278/EEC of 12 th June 1986 on the protection of environment and in particular of soil, when sludge is used in agriculture; and most of all Council Directive 1999/31/EC of 26 th April 1999 on the landfill of waste, which makes disposal of surplus sludge on landfills practically only possible after sludge drying (which is very energy consuming) will favour the incineration and agricultural use of sewage sludge, and reduce disposal on landfills for the future. Other processes applied Besides these basic processes applied for treatment of sewage the following processes are applied for improving the effluent quality, in particular in order to meet the requirements for phosphorus removal according to Council Directive 91/271/EEC on urban waste water treatment. • Phosphorus removal: According to this directive urban wastewater discharged into sensitive areas must be subjected to further treatment in order to reduce phosphorus and nitrogen concentrations. In fact the most common way to reduce phosphorus is precipitation with metal salts which is added mostly the aeration tank and the precipitant being disposed with the surplus sludge. It is also possible to reach phosphorus concentrations in the effluent below 2mg/l by enhanced nutrient removal, say by biological phosphorus removal.The principle of biological phosphorus removal is based on providing the treatment plant with a supply of micro-organisms (or rather groups of micro-organisms) that are capable of enhanced phosphorus incorporation into their cells as a polyphosphate. These must Therefore be given a selection advantage over the other groups of micro-organisms. This can be done by setting the biocoenosis of the treatment plant, at least for a short period, under strong anaerobic conditions by connecting an anaerobic tank into the sludge cycle • Wastewater disinfection: Direct discharge into bathing waters requires the disinfection of wastewater. Whereas in the past chlorine has been used now UV radiation is mostly applied. The effect of these processes on Endocrine Substances Current knowledge about endocrine substances in wastewater and their elimination / breakdown in wastewater treatment plants in general Only a very few research works have been done on this matter, consequently only very little information is available. It must be noted that in wastewater technology an analytic accuracy of only 1/10 mg/l is usually applied, and that wastewater is characterised by sum parameters like BOD5 or COD. So it simply has never been possible to take care of these substances by operating entities of wastewater treatment plants. The few publications on this matter shall be summarised in the following. It must be outlined that the existing publications hardly contain any information about processes applied or process parameters which would be necessary to gain information about the effect of processes and operation modes on the substances considered. Obviously the involved scientists were not wastewater process engineers.
Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas EUROLAKES D10: Impact of Contaminants FP5_Contract No.: EVK1-CT1999-00004 Version: 4.0 Date: 25/07/01 File: D10-vers.4.0.doc Page 99 of 136 Another problem is that the standard of wastewater treatment has changed considerably the last 20 years what makes extrapolation or interpretation of data gained in the 80ies impossible. A research programme in these questions has started on June 2000 in Austria under the Title “Austrian Research Co-operation on Endocrine Modulators (ARCEM). The programme is scheduled up to mid 2003 and is initiated by Austrian Scientists from different universities together with the Austrian Federal Environment Agency and the Federal Ministry for Agriculture, Forestry, Environment and water management. One module under this programme will deal with the aspect of the reduction of endocrine modulators from the point of wastewater /drinking water process engineering. However results may not be expected before mid 2001. Currently the following can be stated regarding the effect of wastewater treatment processes on endocrine substances: • The elimination rate of the substances by mechanical treatment, particularly in the primary sedimentation is depending on the hydraulic retention time of the wastewater in the primary sedimentation tank. Since the substance in this treatment stage are sourced out with the primary sludge the physical chemical properties of these substances in relation to the primary sludge play an important role. Considering classical wastewater parameters as BOD5, max. 30 % of the waste load can be eliminated in this stage. Since many endocrine substances are lipophil the rate of reduction in this treatment process can even be higher if high amounts of fat are contained in the wastewater. [KREUZINGER, 1998] • However from the point of view of wastewater process engineering it has to be stated that a high reduction of waste by primary sedimentation is not always desired. There is even a recent trend to reduce the efficiency of primary sedimentation since too much reduction of carbonaceous compounds in the primary sedimentation can cause difficulties in Nitrogen reduction in the activated sludge process. (change of ratio C:N). And since more and more treatment plants are legally obliged to reduce nitrogen the efficiency of primary sedimentation is being reduced. • Difficult biodegradable substances are being adsorbed to activated sludge flocks due to their higher molecular weight (most of all steroid hormones are made up of large molecules), and are being soured out with the excess biological sludge for further treatment. [KREUZINGER, 1998] • During aerobic excess sludge stabilisation, in which course the sludge is aerated for days, even weeks, a further reduction of endocrine substances is assumed. Anaerobic stabilisation can also induce anaerobic degradation mechanisms which can complete aerobic processes, like it is the case with NPnEOs [KREUZINGER, 1998]). • If the final excess sludge is disposed in agriculture or if it is composted (what exposes the sludge to further intensive aerobic biological processes) also the ad-
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D10: Impact of Contaminants - Hydromod

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