This paper presents the results of an evaluation of the environmental footprint of the Braunschweig wastewater scheme with Life Cycle Assessment. All relevant inputs and outputs of the system are quantified in a substance flow model and evaluated with a set of environmental indicators for cumulative energy demand, carbon footprint, acidification, eutrophication, and human and ecotoxicity. The analysis shows that energy demand and carbon footprint of the Braunschweig system are to a large extent offset by credits accounted for valuable products such as electricity from biogas production, nutrients and irrigation water. The eutrophication of surface waters via nutrient emissions is reduced in comparison to a conventional system discharging all effluent directly into the river, because some nutrients are diverted to agriculture. For human and ecotoxicity, a close monitoring of pollutant concentrations in soil is recommended to prevent negative effects on human health and ecosystems. Normalised indicators indicate the importance of the primary function of the wastewater system (= protection of surface waters) before optimisation of secondary environmental impacts such as energy demand and carbon footprint. A further decrease of the energy-related environmentalfootprint can be reached by applying optimisation measures such as the addition of grass as co-substrate into the digestor, thermal hydrolysis of excess sludge, or nutrient recovery from sludge liquors.

In this study the applicability of the microsieve technology together with coagulation and flocculation for advanced phosphorus removal was investigated. A pilot unit including a microsieve with 10 µm mesh size is operated continuously with secondary effluent. By applying a pretreatment of 0.036 – 0.179 mmol/L coagulant and 2 mg/L cationic polymer total phosphorus values below 100 µg/L were easily achieved. Values below 50 µg/L were possible at high metal dosing, but the higher suspended solid load reduced the capacity of the pilot unit. Coagulation with polyalumium chloride (PACl) produced better effluent quality compared to FeCl3 as less suspended solids and less residual coagulant were found in the microsieve effluent. Also the transmission of UV radiation through the water is improved by using PACl. The amount of backwash water was very low (< 3 %). In total, if combined with UV disinfection, microsieving with chemical pretreatment is a viable option for high quality effluent polishing.

In this study the applicability of the microsieve technology together with coagulation and flocculation for advanced phosphorus removal was investigated. A pilot unit including a microsieve with 10 µm mesh size is operated continuously with secondary effluent. By applying a pretreatment of 0.036 – 0.179 mmol/L coagulant and 2 mg/L cationic polymer total phosphorus values below 100 µg/L were easily achieved. Values below 50 µg/L were possible at high metal dosing, but the higher suspended solid load reduced the capacity of the pilot unit. Coagulation with polyalumium chloride (PACl) produced better effluent quality compared to FeCl3 as less suspended solids and less residual coagulant were found in the microsieve effluent. Also the transmission of UV radiation through the water is improved by using PACl. The amount of backwash water was very low (< 3 %). In total, if combined with UV disinfection, microsieving with chemical pretreatment is a viable option for high quality effluent polishing.

Bisherige Analysen des Energieverbrauchs in der Abwasserreinigung beschränken sich oft auf die naheliegende Erfassung des Stromverbrauchs. Im Sinne einer ganzheitlichen Betrachtung sollten aber auch andere Formen der Energie erfasst werden, wie zum Beispiel für die Herstellung von benötigten Chemikalien wie Flockungs- und Flockungshilfsmittel, beim Transport des zu entsorgenden Schlamms oder für zusätzliche Brennstoffe bei der Klärschlammtrocknung. Dafür ist die Erweiterung der Grenzen des zu betrachtenden Systems auf vor- und nachgelagerte Prozesse notwendig, um alle relevanten Beiträge zum Energieverbrauch zu berücksichtigen. Zudem können so auch die verschiedenen Sekundärprodukte der Abwasserreinigung erfasst werden: die Stromproduktion aus Faulgas, die Rückführung von Nährstoffen und Wasser in die Landwirtschaft oder die Substitution von fossilen Brennstoffen in der thermischen Klärschlammentsorgung. Ein geeignetes Instrument für diese Betrachtungsweise ist die Methodik der Ökobilanz nach ISO 14040/44. Mit dieser Methodik lassen sich alle unterschiedlichen Energieformen und Sekundärfunktionen abbilden und in einheitlichen Indikatoren darstellen, ergänzt durch weitere Umweltwirkungen wie den Treibhauseffekt.

This study presents the use of Life Cycle Assessment as a tool to quantify the environmental impacts of processes for wastewater treatment. In a case study, the sludge treatment line of a large sewage treatment plant is analysed in energy demand and the emission of greenhouse gases. Results show that the existing process is positive in energy balance (+166 MJ/PECOD*a) and GHG emissions (+19 kg CO2-eq/PECOD*a) by supplying secondary products such as electricity from biogas production and substituting fossil fuels in incineration. However, disposal routes for stabilised sludge differ considerably in their environmental impacts. In total, LCA proves to be a suitable tool to support future investment decisions with information of environmental relevance on the impact of WWTPs, but also larger urban water systems.

Triggered by climate change, local freshwater scarcity and rising public awareness towards ecological issues, environmental aspects are becoming key decision criteria for planning of urban water management infrastructure. Simultaneously, the implementation of measures according to the EU Water Framework Directive requires huge investments in the coming years for both upgrading of existing infrastructure and the construction of sewer networks or treatment plants. Among existing tools for environmental impact assessment, LCA offers the most accepted and comprehensive method to support decision makers with information on the environmental profile of new investments or upgrading of existing infrastructure. This paper describes on-going case studies using LCA for systems of urban water management and raises potential difficulties while applying LCA in the water sector.

This paper deals with the performance and the optimisation of the hydraulic operating conditions of the A3 Water Solutions flat sheet membrane technology in a MBR pilot-plant to achieve a satisfying fouling control and also a reduction in the required aeration. Two vertically stacked modules were tested at pilot-scale at Anjou Recherche under typical biological operating conditions (mixed liquor suspended solids concentration (MLSS) = 10 g/l; sludge retention time (SRT) = 28 days; food to microorganism ratio (F/M) = 0.12 kg COD/kg MLSS/d). The use of a double-deck and of specific backwashes for this membrane technology enabled to achieve satisfying membrane performances for a net flux of 25 L h-1m-2, 20°C at a low specific aeration demand per membrane surface (SADm = 0.2Nm3 h-1m-2) which corresponds to a specific aeration demand per permeate volume unit (SADp) of 8Nm3 air/m3 permeate, which is lower than reported for many commercial membrane systems. The mixed liquor characteristics (foaming, MLSS concentration) appeared to influence the fouling behaviour of the membranes but no correlation was found with the fouling rate. However, with the new operating conditions, the system is robust and can cope with fouling resulting from biological stress and daily peak flows for MLSS concentrations in the membrane tank up to 18 g/l.

Membrane bioreactors (MBRs) have been increasingly employed for municipal and industrial wastewater treatment in the last decade. The efforts for modelling of such wastewater treatment systems have always targeted either the biological processes (treatment quality target) as well as the various aspects of engineering (cost effective design and operation). The development of Activated Sludge Models (ASM) was an important evolution in the modelling of Conventional Activated Sludge (CAS) processes and their use is now very well established. However, although they were initially developed to describe CAS processes, they have simply been transferred and applied to MBR processes. Recent studies on MBR biological processes have reported several crucial specificities: medium to very high sludge retention times, high mixed liquor concentration, accumulation of soluble microbial products (SMP) rejected by the membrane filtration step, and high aeration rates for scouring purposes. These aspects raise the question as to what extent the ASM framework is applicable to MBR processes. Several studies highlighting some of the aforementioned issues are scattered through the literature. Hence, through a concise and structured overview of the past developments and current state-of-the-art in biological modelling of MBR, this review explores ASMebased modelling applied to MBR processes. The work aims to synthesize previous studies and differentiates between unmodified and modified applications of ASM to MBR. Particular emphasis is placed on influent fractionation, biokinetics, and soluble microbial products (SMPs)/exo-polymeric substances (EPS) modelling

Over the past decade, membrane bioreactors have been increasingly implemented to purify municipal wastewater. However, even with submerged modules which offer the lowest costs, the membrane bioreactor (MBR) technology remains in most cases more expensive than conventional activated sludge processes. In addition, the European municipal MBR market is to date a duopoly of two non-European producers, despite many initiatives to develop local MBR filtration systems. In 2005, the European Commission decided to finance four projects dedicated to further technological development of MBR process: the four projects AMEDEUS, EUROMBRA, MBR-TRAIN and PURATREAT were implemented from October 2005 up to December 2009 and joined their efforts within the coalition “MBR-Network” (www.mbr-network.eu). The present report synthesises the major outcomes of the project AMEDEUS, conducted from October 2005 up to May 2009. The AMEDEUS research project aimed at tackling both issues of accelerating the development of competitive European MBR filtration technologies, as well as increasing acceptance of the MBR process through decreased capital and operation costs. The project targets the two market segments for MBR technology in Europe: the construction of small plants (semi-central, 50 to 2,000 population equivalent or p.e., standardized and autonomous), and the medium-size plants (central, up to 100.000 p.e.) for plant upgrade.