Work package WP 5.2 “Combination of Managed Aquifer Recharge (MAR) and adjusted conventional treatment processes for an Integrated Water Resources Management“ within the European Project TECHNEAU (“Technology enabled universal access to safe water”) investigates bank filtration (BF) + post-treatment as a MAR technique to provide sustainable and safe drinking water supply to developing and newly industrialised countries. One of the tasks within the project was the identification of state-of-the-art tools in the field of well field optimization modelling. Most of the currently used tools are process-driven simulation models like MODFLOW or FEFLOW. These are sometimes also combined with optimization models to reduce the computational demand and are utilized as strategic planning tools for water supply managers. However, in case of optimizing well field operation (i) under relatively constant boundary conditions and (ii) enough field data (temporal and spatial resolution dependent of the dynamics of the state parameter of interest, e.g. groundwater table, contaminant concentrations) data-driven approaches like support vector machines (SVM) can be used instead. If the water manager’s key interest is only a good predictive capability in combination with low computational demand, the application of this approach is more goal-orientated to simulate the dynamics of well field performance indicators efficiently. The contents of this report were presented to possible end-users, experts from Berliner Wasserbetriebe and Veolia. In agreement with their recommendations it was decided to focus further research within TECHNEAU on the empirical, data driven modelling approach. The selected approach is currently tested in the framework of a diploma thesis for a Berlin waterworks with the objective to analyse available production and observation well hydrographs by using modern statistical methods like principal component analysis and SVM (www.support-vector-machines.org).

This report presented recent developments in the field on the UV-LED disinfection. This technological field is very recent and further interests - along with rapid and continuing improvements in performance (especially in terms of emission power) - are expected within the next years. After the physical characterisation of the few UV-LEDs - at 269 and 282 nm - that are currently available on the market, their disinfecting action was to be measured via biodosimetric tests. They show an increase of the inactivationwith an increasing fluence using different types of raw water, although some early static tests tend to highlight potential recontamination and inhomogeneous distribution of UV-light - which may be explained by the module configuration. Main other results indicate that UV-absorbing compounds in the various waters reduce the disinfection capacity. Morevoer, a more effective disinfection is observed at 269 nm than at 282 nm for a similar fluence. However, the emission output is better with 282 nm - UV-LEDs. Therefore, an interesting aspect, worth being investigated in the future is to ensure an optimized configuration, which balances the input power, which is necessay to run the UV-LED module, and its disinfecting action. With potential enhanced emission powers, new developments for UV-LED water purification applications would enable to perform larger-scale tests and shorten UV exposure times.

The study aims at assessing in long-term trials a gravity-driven ultrafiltration pilot plant designed for a capacity of 5 m3/d. The unit was operated in South Africa with Ogunjini surface water and was run with restricted chemical intervention or maintenance (no backflush, no aeration, no crossflow and no chemical). Under South African environmental conditions and with direct filtration of the river water and only one manual drainage of the membrane reactor every weekday, the unit could fulfil the design specification in terms of water production (5 m3/d) as long as the turbidity of the raw water remained in a reasonable level (up to 160 NTU), with a filtration flux typically 4 to 6 L/h.m² (corrected at 20°C). This value was in the same range as the lab results and was consistent with the first phase results (around 5-7 L/h.m² after biosand filtration). However, the flux dropped significantly to a range of 2 to 4 L/h.m² after a rain event resulting in a turbidity peak over several days up to > 600 NTU. This demonstrated that for variable raw water types with expected turbidity peaks above 100 NTU, a pre-treatment would be required for the system (biosand filter or other). The performance of microbiological tests confirmed the integrity of the membrane and the ability of the system to achieve complete disinfection.

The study aims at validating the point-of-use investigations on long-term gravity-driven ultrafiltration for a scaled-up system, which could produce drinking water for a community of 100-200 inhabitants using natural surface water. Eawag, KWB and Opalium conceived a membrane-based small-scale system (SSS) which can operate without crossflow, backflush, aeration or chemical cleaning. Equipped with a biosand filter as pre-treatment (not used in South Africa), it is designed to be robust, energy-sufficient (gravity-driven) and run with restricted chemical intervention (only residual chlorine). The containerised unit (10’) requires to be fed with raw water at a 2 m-height (energy-equivalent to <8 Wh/m3). As sole operational requirement, the membrane reactor is to be drained (i.e. emptied) on daily to weekly basis to superficially remove the material retained by the membrane and accumulated in the module. Otherwise, the system, which is only driven by a 40 cm differential pressure head (i.e. 40 mbar), is totally self-determined and autonomous. This report details the validation tests performed at Ogunjini in the region of Durban (South Africa) from February to April 2010: the gravity-driven UF compact unit showed promising results in regards to flux stabilization and flow capacity. The unit was operated in South Africa with Ogunjini surface water and was run with restricted chemical intervention or maintenance (no backflush, no aeration, no crossflow and no chemical). Under South African environmental conditions and with direct filtration of the river water and only one manual drainage of the membrane reactor every weekday, the unit could fulfill the design specification in terms of water production (5 m3/d) as long as the turbidity of the raw water remained in a reasonable level (up to 160 NTU), with a filtration flux typically around 4 to 6 L/h.m² (corrected to 20°C). This value was in the same range as the lab results and was consistent with the first phase results (around 5-7 L/h.m² after biosand filtration). However, the flux dropped significantly to a range of 2 to 4 L/h.m² after a rain event resulting in a turbidity peak over several days up to > 600 NTU. This demonstrated that for variable raw water types with expected turbidity peaks above 100 NTU, a pre-treatment would be required for the system (biosand filter or other). The performance of microbiological tests confirmed the integrity of the membrane and the ability of the system to achieve complete disinfection.

Bank filtration (BF) is a well established and proven natural water treatment technology, where surface water is infiltrated to an aquifer through river or lake banks. Improvement of water quality is achieved by a series of chemical, biological and physical processes during subsurface passage. This paper aims at identifying climate sensitive factors affecting bank filtration performance and assesses their relevance based on hypothetical 'drought' and 'flood' climate scenarios. The climate sensitive factors influencing water quantity and quality also have influence on substance removal parameters such as redox conditions and travel time. Droughts are found to promote anaerobic conditions during bank filtration passage, while flood events can drastically shorten travel time and cause breakthrough of pathogens, metals, suspended solids, DOC and organic micropollutants. The study revealed that only BF systems comprising an oxic to anoxic redox sequence ensure maximum removal efficiency. The storage capacity of the banks and availability of two source waters renders BF for drinking water supply less vulnerable than surface water or groundwater abstraction alone. Overall, BF is vulnerable to climate change although anthropogenic impacts are at least as important.

In the densely populated semi-arid territory around Delhi, the water demand is rising continuously, while the surface- and groundwater resources are threatened by contamination and overexploitation. This is a typical scenario in many newly industrialising and developing countries, where new approaches for a responsible resources management have to be found. Bank filtration holds a great potential, thus being a low tech method and benefiting from the storage and contaminant attenuation capacity of the natural soil/rock. For this study, three field sites have been constructed to investigate bank filtration in different environments in and around the megacity with a main focus on inorganic contaminants. Hydraulic heads, temperature gradients and hydrochemistry of surface water and groundwater were analysed in three different seasons. Depending on sitespecific conditions, distinct hydrogeological conditions were observed and both positive and negative effects on water quality were identified. Most concerning issues are the impact of anthropogenic ammonia, the mixing with ambient saline groundwater and the mobilisation of arsenic during the reductive dissolution of manganese- and iron(hydr)oxides. Positive aspects are the dilution of contaminants during the mixing of waters from different sources, the sorption of arsenic, denitrification, and the precipitation of fluoride under favourable conditions.

Submersible data loggers are widely used for groundwater monitoring, but their application often runs the risk of hardware and data loss through vandalism or theft. During a field study in India, the authors of this article experienced that well locks attract the attention of unauthorized persons and do not provide secure protection in unattended areas. To minimize the risk of losing data loggers, a cheap and simple solution has been invented to hide the instruments and associated attachments below the ground surface, inside observation wells. It relies on attaching the logger to a length of small-diameter pipe that is submerged at the bottom of the well, instead of attaching it to the top of the well. The small-diameter pipe with the logger is connected to a small bottle containing a magnet that floats on the water surface of the well and can be recovered using another bottle also with a magnet. A logger that is concealed in this way is difficult to detect and access without knowledge of the method and adequate removal tools. The system was tested and successfully applied for monitoring shallow

Rver Bank Filtration (RBF) is a drinking water (pre-)treatment that can remove a wide variety of surface water contaminants . However, the efficiency of this natural treatment process depends on hydrochemical, aquifer- and operational characteristics. Therefore, complementary treatment options may be required in order to build up a multiple-barrier-system and obtain drinking water quality. As a follow-up to the TECHNEAU WP5.2 field investigations, this report aims at identifying potential post-treatment schemes for drinking water production at three river bank filtration sites in New Delhi - Palla, Nizamuddin and Najarfgarh – for which physicochemical parameters as well as levels of inorganic and trace organic substances and microbial contamination have been measured during field campaigns in 2007 and 2008 (see deliverables D5.2.2 and D5.2.6). The three investigated RBF sites in Delhi have distinctive geographical locations and contamination exposures. For each of them, critical water parameters were identified that present a challenge with regards to drinking water production, for which different treatment technologies are envisaged (see table below). For Palla and Najafgarh, one specific water component (fluoride and salinity, respectively) requires targeted treatment. For Nizamuddinm, however, where surface water is highly exposed to contamination from poorly treated waste water, theoretical post-treatment options are no longer efficient and extensive conventional wastewater treatment is recommended. One other possible option for Nizamuddin is the Oxidation / Biofiltration / Membrane technology (OBM process) developed by NTNU and SINTEF within the TECHNEAU project and a specific report on its application to Delhi is planned within TECHNEAU WP7.9. This report shows the theoretical post-treatment options for river bank filtration sites in Delhi. The strong technological requirements for Nizamuddin and Najafgarh seem inadequate to be currently implemented. The priority in Delhi would be to develop an integrated water and wastewater management, in order to reduce contamination in the surface water and thereby lower the technological requirements for drinking water production.

The study aims at validating the point-of-use investigations on long-term gravity-driven ultrafiltration for a scaled-up system, which could produce drinking water for a community of 100-200 inhabitants using natural surface water. Eawag, KWB and Opalium conceived a membrane-based small-scale system (SSS) which can operate without crossflow, backflush, aeration or chemical cleaning. Equipped with a biosand filter as pretreatment, it is designed to be robust, energy-sufficient (gravity-driven) and run with restricted chemical intervention (only residual chlorine). The containerised unit (10’) requires to be fed with raw water at a 2 m-height (energy-equivalent to ~8Wh/m3). As sole operational requirement, the membrane reactor is simply to be drained (i.e. emptied) on daily to weekly basis to superficially remove the material retained by the membrane and accumulated in the module. Otherwise, the system, which is only driven by a 40 cm differential pressure head (i.e. 40 mbar), is totally self-determined and autonomous. This report details the validation tests performed at Veolia Water Research Center in Annet-sur-Marne (France) from January to August 2009 : the gravity-driven UF compact unit showed promising results in regards to flux stabilization and flow capacity. Although early investigations take place in winter, an initial flux stabilization to 2.5 lmh is observed, which is below the reference results from the Eawag lab tests (i.e. 7-10 lmh, at 20 ± 2°C). However, the “scaled-up” system can benefit from a weekly drainage which seems to enhance the flux to 4-5 lmh, and thereby, the unit is to produce more than 4 m3/d, which is consistent with the design target of 5 m3/d. Moreover, the increase of the drainage frequency (to 3 times/week) along with warmer temperatures – leading to a better membrane permeability and biological activity - contribute to a further enhancement to 5-7 lmh. This is particularly relevant for South Africa, for which decentralized water supply is a burning issue and where the unit is to be further tested from November 2009. The investigations also highlighted the critical performance of the biosand filter as pretreatment. More than the UF step – whose membrane integrity was confirmed with bacterial analyses, the pretreatment step needed more frequent (i.e. monthly) O&M requirements. Therefore, the pretreatment necessity will be further assessed in South Africa where high turbidity peaks could represent an extra challenge for the unit.

The use of bank filtration for drinking water treatment in Europe dates back to the days of beginning industrialization in the 19th century. With regard to improved source water quality in Europe, the millennium development goals and global climate change, aquifer recharge (AR) and bank filtration (BF) need to be reassessed in terms of sustainability and their role within an integrated water resource management. Based on the IC-NASRI study comprising 194 drinking water facilities worldwide integrating aquifer recharge techniques in their treatment system, an average AR/BF site would be located in Central Europe alongside a river and is characterized by: a sandy gravel aquifer with a hydraulic conductivity of 2x10-3 m/s, a maximum aquifer thickness of 30 m, 175 m travel distance from bank to well, a travel time of 70 days and by vertical well operation with a daily capacity of 55.000 m³. A literature survey conducted within the TECHNEAU project demonstrated that for substances highly relevant to newly-industrialized or developing countries (e.g. pathogens) the removal efficiency is good. Hydro-chemical analyses from three study sites in Delhi support these results. However, it was also shown that poor surface water quality, saline groundwater or subsurface conditions leading to mobilization of trace metals like iron, manganese or arsenic may limit the applicability of AR / BF without further post-treatment. Climate change might affect the performance of AR / BF worldwide, impairing source water quality and influencing removal efficiency. However, other factors like changes in demography or land-use can impact the systems by far more severely.