Data play an important role in water-related research. In the field of limnology, monitoring data are needed to assess the ecological status of water bodies and understand the bio-geochemical processes that affect this status. In wastewater management, measured or simulated data are the basis for planning and control of sewer networks. Given the importance of data in water-related research makes them a valuable resource, which should be handled in an adequate way. Based on experiences in data collection and data processing in water-related research this paper proposes – both from a computer scientist’s and an environmental engineer’s point of view – a set of rules for data handling: Rule 1: Protect raw data. Rule 2: Save metadata. Rule 3: Use databases. Rule 4: Separate data from processing. Rule 5: Use programming. Rule 6: Avoid redundancy. Rule 7: Be transparent. Rule 8: Use standards and naming conventions. Applying these rules (i) increases the quality of data and results, (ii) allows to prepare data for long-term usage and make data accessible to different people, (iii) makes data processing transparent and results reproducible, and (iv) saves – at least in the long run – time and effort. With this contribution the authors would like to start a discussion about best data handling practices and present a first checklist of data handling and data processing for practitioners and researchers working in the water sector.

This study exemplifies the use of Life Cycle Assessment (LCA) as a tool to quantify the environmental impacts of processes for wastewater treatment. In a case study, the sludge treatment line of a large wastewater treatment plant (WWTP) is analysed in terms of cumulative energy demand and the emission of greenhouse gases (carbon footprint). Sludge treatment consists of anaerobic digestion, dewatering, drying, and disposal of stabilized sludge in mono- or co-incineration in power plants or cement kilns. All relevant forms of energy demand (electricity, heat, chemicals, fossil fuels, transport) and greenhouse gas emissions (fossil CO2,CH4,N2O) are accounted in the assessment, including the treatment of return liquor from dewatering in the WWTP. Results show that the existing process is positive in energy balance (–162 MJ/PECOD * a) and carbon footprint (–11.6 kg CO2-eq/PECOD *a) by supplying secondary products such as electricity from biogas production or mono-incineration and substituting fossil fuels in co-incineration. However, disposal routes for stabilized sludge differ considerably in their energy and greenhouse gas profiles. In total, LCA proves to be a suitable tool to support future investment decisions with information of environmental relevance on the impact of wastewater treatment, but also urban water systems in general.

The surplus of nutrients in surface waters due to anthropogenic influences makes eutrophication an important issue in water quality in Europe. According to the Water Framework Directive of the European Union (EU-WFD) an improvement of all water bodies to a “good ecological status” is aimed. One aspect for achieving the goal is an additional reduction of nutrient immissions. In particular, the study has a focus on advanced nitrogen removal at large scale wastewater treatment plants (WWTP) in the area of Berlin and Brandenburg, Germany. A comprehensive life cycle assessment (LCA) of a generic WWTP with 1.47 million population equivalent (pe) is carried out. The WWTP includes a secondary treatment with upstream denitrification. Sludge treatment is realized by anaerobic digestion with biogas utilization and sludge disposal in a mono-incineration plant. On basis of the generic WWTP, five scenarios for an advanced nitrogen removal are analyzed and compared within the LCA: an expansion of the denitrification reactor (ExpDeni), a retrofit to a step-feed nitrogen removal (SFNR), a biologically active filtration (BAF) as post-treatment step as well as two processes for sludge liquor treatment by deammonification (Anammox) and by an SBR-reactor (SBR). Data for energy and chemical demand, effluent quality and infrastructure are based on an existing plant from Berlin and data of nitrogen removal processes on simulations and planning data for this particular WWTP. For the life cycle impact assessment, the following categories are considered: global warming potential (GWP), acidification potential (AP), marine (MEP) and freshwater eutrophication (FEP) as well as human (HTP) and freshwater ecotoxicity (FETP). Additional, the cumulative energy demand (CED) of fossil and nuclear energy resources is taken into account. For the generic WWTP two results have to be emphasized: the influence of high energy demand on potential environmental impacts and the relevance of the primary function of nutrient removal due to a high influence in eutrophication impact categories MEP and FEP. Hence, reducing electricity demand and an increased use of renewable energy resources will lead to reduced impacts. Comparing the nitrogen removal processes, SFNR is preferable to ExpDeni because of reduced energy demand (SFNR: -6%, ExpDeni: +9%) which leads to an improved environmental profile throughout all categories. Focusing on sludge liquor processes, Anammox may be recommended due to mainly lower additional impacts to SBR-process. Main issues at SBR are the high energy consumption (almost twice as high as energy demand of Anammox) and addition of methanol as carbon source. The BAF has the highest impacts in CED (+33%) and GWP (+14%) due to high energy demand for pumping and backwashing (+5%) and methanol dosing. However, favorable side-effects such as a reduction of phosphorus and heavy metal loads lead to a significant reduction in FEP (-18%) and FETP (-9%). All in all, SFNR is recommended in an overall comparison, Anammox has the second best environmental profile. BAF can be recommended if other effects in wastewater treatment are aimed at. Due to lack of data concerning trace organics, uncertainties in toxicity potential are still apparent. Besides, uncertainties in estimating N2O-emission factors have a high effect on the result of GWP. Further investigations on N2O emissions from biological treatment steps should be done to reduce the uncertainties. Finally, LCA is a powerful tool for revealing potential environmental impacts for supporting a sustainable way of decision making process.

To sustain good harvests, about 975,000 tons of mineral phosphorus need to be imported to Europe every year, while the potentials to recover and recycle this essential resource remain untapped or are just inefficiently used as in the case of sewage sludge. In the recent years various technical alternatives to the traditional but disputed application of sludge in agriculture have been developed to recover the nutrient. Especially user friendly solutions have already made their way to full-scale or at least pilot-scale application. National and international initiatives are dedicated to foster the implementation of new solutions, to bridge the gaps between the relevant sectors of science, policy and industry to finally increase the overall anthropogenic phosphorus efficiency according to the motto of the recent First European Sustainable Phosphorus Conference: use less, recycle more and cooperate smart. (www.phosphorusplatform.eu)

Combined sewer overflows (CSO) after heavy rainfall can cause acute depletions of dissolved oxygen (DO) in the Berlin River Spree. Further aggravation of ecological deficits can be expected from global climate change. A planning instrument for CSO impact assessment under different sewer management and climate conditions has been developed at Kompetenzzentrum Wasser Berlin. It couples the sewer model InfoWorks CS, the river water quality model Hydrax/QSim and an impact assessment tool. The planning instrument was validated for the years 2010 and 2011. Simulation results for the critical parameters discharge and DO concentrations in the Berlin River Spree agree well with measurements. Although not all observed DO deficits can be simulated accurately, the very good representation of processes related to the oxygen budget allows assessing relative changes in boundary conditions, e.g. from climate change or different CSO control strategies. The conducted scenario analysis indicates that the coupled sewer-rivermodel reacts sensitively to changes in boundary conditions (temperature, rainfall, storage volume and other CSO control strategies, etc.). Based on the simulation year 2007 – representing an extreme year with regards to CSO volume and critical conditions in the river – sewer rehabilitation measures planned to be implemented until 2020 are predicted to reduce total CSO volumes by 17% and discharged pollutant loads by 21 - 31%. The frequency of critical DO conditions for the most sensitive local fish species will decrease by one third. For a further improvement of water quality after the year 2020, the reduction of impervious surfaces emerges as a very effective management strategy where feasible. A reduction of the impervious connected area by 20% results in a decrease in the frequency of critical DO conditions by another third. The studied increase in surface air and water temperature as part of the climate change scenarios leads to a significant aggravation of DO stress due to background pollution in the Berlin River Spree, while acute DO depletions after CSO are barely affected. However, changes in rain intensity have a considerable effect on CSO volumes, pollutant loads and the frequency of critical DO concentrations. A general reduction of discharged pollutant loads by 60% based on the sewer status 2020 can prevent critical DO conditions in the Berlin River Spree, even for the exceptionally rain intense year 2007. A detailed analysis of river processes after CSO, has shown that the biodegradation of organic carbon compounds is the most important contributor to acute DO depletions in the Berlin River Spree. An additional impairment of DO conditions is caused by the inflow of oxygen free CSO spill water and suspended solids into the Berlin River Spree. In this report, CSO impacts under different management strategies or climate change conditions are assessed only for a part of the Berlin combined sewer system (although the main part) and for one exemplary year. An extension of the planning instrument to the entire combined sewer system would enable to evaluate the full impact of measures. For a robust prediction of future CSO impacts it is also recommended to test different simulation periods or conduct long-term simulations.

A MBBR before an advanced sedimentation step was operated as new wastewater process scheme for maximum COD extraction. The objective of this biological reactor was to modify the soluble COD ratio in primary wastewater. At high loads, the MBBR is able to consume the soluble COD for bacteria activity with very little oxidation. This process changes the soluble COD into particulate COD which is better separate from the wastewater during the following step with coagulation, flocculation and micro sieve filtration. Goals were 95% removal of suspended solids and 80% of COD extracted through separation. To check these new scheme performances, a pilot plant (0.5 to 3 m³/h) was operated at the Stahnsdorf WWTP in the south of Berlin. First results showed that a HRT of 20-30 min and a load 40-60 g CODf /(m2*d) can be recommended for maximum accumulation and minimum oxidation and that the 80% of COD extraction can be achieved (at low oxygen concentration below 1 mg/L). However the performance difference between the scheme with or without MBBR did not exceed 8 %