The combination of advanced oxidation (e.g. ozonation) and subsurface passage could overcome known limitations of MAR techniques with respect to dissolved organic carbon (DOC) and trace organics removal. The objective of the OXIRED project is to assess possibilities and limitations as well as practicability and technical feasibility of different combinations of advanced oxidation and subsurface passage with respect to this topic. As part of the first project phase, existing data on subsurface removal of organic trace substances was evaluated in order to identify substances that should be targeted in laboratory and technical scale experiments. This report summarizes the outcomes of this evaluation.

The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions. The present report deals with (iii) and has the purpose to provide a brief overview of the current state of knowledge related to the role of riparian zones as best management practices for water quality improvement at the watershed scale. Research indicates that landscape hydrogeological characteristics such as topography and surficial geology influence both riparian zone hydrology and biogeochemistry. Topography, depth to a confining layer and soil hydraulic conductivity all affect groundwater input to riparian zones and the water table fluctuation regime throughout the year. Research also indicates that although most biologically mediated reactions in soil are redox dependant, landscape hydrogeology, by affecting riparian hydrology, affects the redox conditions in the soil profile. In turn, microbial processes and changes in element concentrations are predictable as a function of the redox state of the soil.Variations in biogeochemical conditions directly affect the fate of multiple contaminants in riparian systems. In particular, variations in soil redox potential in riparian zones can affect the evolution of numerous contaminants and solutes within riparian zones like pesticides, phosphorus, NO3-, N2O, NH4+, SO42-, CH4, Fe2+/Fe3+ or Dissolved Organic Carbon (DOC). Of all the solutes/contaminants mentioned above, nitrate is one of the most important concerning water quality in many areas of the US and Western Europe. Consequently, many studies have investigated nitrate removal in riparian systems. Depending on site conditions, nitrate retention generally varies between 60 and 90 %; however, there are situations where nitrate removal is less or even where a riparian zone becomes a source of N to the stream. Although the riparian literature is clearly dominated by nitrate removal studies, many studies also focus on phosphorus, sediments, pesticides, chloride, bromide and bacteria. Although there are situations where riparian zones have been shown to be sources of P, Atrazine, bromide, E. coli or E. streptococci bacteria, riparian zones generally contribute to the reduction of most contaminants in subsurface flow and overland flow. Nevertheless, although conditions favorable to the reduction or oxidation of a given contaminant at the microbial level are often known, more research needs to be conducted to determine the variables controlling the fate of contaminants other than nitrate in soil at the riparian zone scale.Finally, although many studies have investigated the hydrological and biogeochemical functioning of riparian zones in the past few decades, much research remains to be conducted in order to quantify and predict the impact of riparian zones on water quality at the watershed scale in a variety of climatic and hydrogeological settings. In particular, better strategies and/or tools to generalize riparian function at the watershed scale need to be developed. Particular areas where research is needed to achieve this goal include: 1) the development of strategies to quantify and model the cumulative impact of individual riparian zones on water quality at the watershed scale; 2) a better quantification of the importance of spatial and temporal variability in hydrologic and biogeochemical riparian functioning relative to annual nutrient transport; 3) a better understanding of the role of vegetation in terms of its impact on riparian biogeochemical processes and the response of these processes to manipulations of vegetative cover; 4) a better understanding of the impact of human activities and infrastructure on riparian zone function in both urban and rural landscapes; 5) a better understanding of the fate of emerging contaminants in riparian systems.

In rural areas, small wastewater treatment plants (SWWTP) are a cost-efficient solution to sewage disposal issues. In Europe, small WWTPs are defined as plants for treating domes- tic wastewater up 50 PE. In Germany, about 2.2 million SWWTPs are in operation or are being installed. In France about 10 to 12 million people are served by decentralised sys- tems. There are many different technical solutions on the market, ranging from artificial wetlands, reed bed filters to activated sludge systems. All systems available on the European market have to meet the EU-Certification EN 12566-3, which regulates a minimum standard of op- eration reliability and purification limits. Furthermore, additional guidelines have to be con- sidered, depending on national and regional specifications. There is still a lack of information about performance, operation reliability and maintainability of the different types of SWWTP under real operating conditions. These parameters are however, of particular importance to both customers and service providers. To fill this gap, during a duration time of 14 month in this study 12 different treatment systems were simultaneously compared and evaluated un- der real operating conditions. The study delivers now detailed information about the perfor- mances of different plant models with regard to purification capacity, effluent values, operat- ing expenditures, sludge treatment etc. The results will be published in a user guide. The study was performed at the Training and Demonstration Centre for Decentralised Sew- age Treatment (BDZ) in Leipzig with a special range of small wastewater treatment plant, already installed at BDZ for training purposes as well as two additional plants, which has been installed there especially for the compass study.

WELLMA-1, WP 1.2 includes a statistical analysis of Berlin and French well data. The aim is to identify parameters by which the extent of iron related clogging can be assessed and which can be used for grouping the wells for further investigations. The data analysis is based on data on well construction, water chemistry and well operation for about 615 wells in Berlin and 47 in France. The approach is first to do a descriptive analysis of the datasets. It shows amongst others that the French data are not extensive enough to be included in further statistical analysis. They were therefore interpreted individually and added as annex to the report. In the second step, a reliable indicator for iron related clogging in the Berlin wells is identified. This is done by testing the significance of differences in parameters recommended by BWB (Qs, number of H2O2-treatments and results of TV-camera inspections) that indicate either intense clogging or no clogging. The analysis of the reduced dataset reveals that TV-camera inspections are the most reliable cloggingindicator for the Berlin wells for statistical analysis with the current database. Thirdly, the relation of all available constructional, hydro-chemical and operational parameters is checked for four different stages of clogging indicated by the TV-camera inspections. It can be stated that most wells reveal increasing clogging with increasing well age and decreasing depth of the first filter. Clogged wells are characterized often by lower iron and higher manganese and nitrate concentrations, a higher mean total discharge and more operating hours than wells without clogging indication. Finally, the clogging indicator is evaluated by a multiple linear regression. For this, the dependent variable clogging is linked to the ten variables, which are obviously related to clogging processes. Although all comprised parameters are partly related to the clogging intensity of the wells, only well age, depth of the first filter, iron and manganese concentrations as well as operating hours and total discharge have an explanatory value for clogging. However, their total explanatory value of 20% of the variance in clogging is low. Either the most relevant parameters to identify clogging are missing or the selected parameters reveal too much data variability. This can be due to temporal and depth oriented variations what could not be included in the recent analysis. Measurements in mixed raw water cannot characterize all processes involved in iron related clogging. Therefore, several recommendations of well operation and monitoring are given to improve the explanatory power of the data. The most important ones are the development of a more detailed matrix for the evaluation of well condition by TV-camera inspections and an improvement of measurements of specific capacity Qs by constant discharge rates and fully documented initial step pumping tests. Groups of wells that would be useful for more detailed field investigations and further data analysis are: (i) wells with different depth of the first filter, (ii) wells with significant differences in mean discharges (and similar construction and number of switchings), (iii) wells with different amounts of switchings, (iv) wells with similar number of switchings but different filter lengths or pump capacities and (v) wells of different age, but otherwise same construction and operational characteristics.

Combined sewer overflows (CSO) can have a strong impact on the quality of surface waters. A common measure to reduce CSO is the construction of storage tanks. The objective of this study was to determine the required volume of a storage tank by means of a numerical long-term simulation and to assess uncertain input data. Particularly, the influence of the considered rain series’ length on the calculated storage volume was investigated. Engineering standards usually recommend the use of at least 10 to 15 years of rain series. Here, the hydraulic behaviour of the studied sewer system was simulated in a 30 year hydrodynamic simulation. Special effort was made to calibrate an available model by use of currently measured data. The quality of calibration was evaluated by means of the Nash-Sutcliffe model efficiency coefficient. The analysis of input data uncertainty revealed that applying a 10 year series results in tank volumes that differ between -12 % and +19 %, respectively from the dimensioning result achieved by applying the 30 year rain series.

Management models for aquatic systems can be used to determine which measures in the watershed or in the water body have been effective and/or which one should be used in future. The newly developed management models presented in the following for Lake Tegel and Schlachtensee are empirical and lake specific. The values for the unknown factors are estimated by an iterative process using optimisation routines and sensitivity analysis methods. The resulting models describe the water and phosphorus balance of each lake. The Lake Tegel water balance model calculates the unknown water inflow from the River Havel depending on the other main in- and outflows with very good validation results. The phosphorus models of both lakes quantify mixing of the upper and lower water body as well as sedimentation and release from the sediment as functions of measured variables. For Lake Tegel, management scenarios were run indicating effective management interventions. For Lake Schlachtensee, the phosphorus model captured the variations in the hypolimnion well but produced poorer results for the epilimnion because of unknown external phosphorus loads. For these the model indicated possible sources and magnitudes.