Germany’s municipal sewage treatment plants generate some two million tons of dry sewage sludge annually, with the proportion of thermally treated sewage sludge increasing from 31.5 per cent in 2004 to more than 54 % in 2011. Sludge, which is usually incinerated or used as agricultural fertilizer, contains a whole series of harmful substances that complicate the task of sludge management. But sludge also contains a number of nutrients such as phosphorus, nitrogen and potassium. Hence the goal of sewage sludge management is to remove sludge pollutants while retaining sludge nutrients. Sewage sludge undergoes thermal recycling at facilities such as sewage sludge mono-incineration plants, cement plants and coal fired power plants. Sewage sludge utilization for farming purposes has plateaued of late (2006 to 2011) at around 29 %, an evolution attributable to more stringent quality standards for sewage sludge. However, sewage sludge is set to take on greater importance as a raw material, mainly due to the increased concentrations of phosphorous it contains. This pamphlet discusses the potential offered by sewage sludge and the ways it can be used sustainably. The pamphlet also describes the current status of sewage sludge management in Germany, with particular emphasis on the extent to which sludge use as a fertilizer can be reduced without foregoing phosphorous and other sludge nutrients. Over the next one to two decades, Germany needs to wean itself away from using sewage sludge for farming and at the same time efficiently leveraging the potential for using sewage sludge as a low cost fertilizer.

Cylindrospermopsis raciborskii, a cyanobacterium of tropical origin, can produce the toxin cylindrospermopsin (CYN). This originally tropical cyanobacterium (bluegreen algae) has now spread to the distant waters of the Berlin area. Cylindrospermopsin has been detected in two lakes in the area, but none of the C. raciborskii strains isolated here so far were found to produce the toxin. The main objectives of the CYLIN project were therefore to analyze the distribution and regulation of C. raciborskii and cylindrospermopsin and to determine which cyanobacteria are producing this toxin in order to establish a basis with which to predict the further course of development of this species and the related health hazards for humans. The CYLIN project was implemented as a three-part program. A screening program was first conducted in 2004 to test regional water bodies for the presence of cylindrospermopsin and potential CYN-producing cyanobacteria in order to obtain an overview of their distribution in the study region. A total of 142 regional water bodies were sampled once each in this qualitative analysis cylindrospermopsin and cyanobacteria. The screening program was followed by a monitoring program designed to generate quantitative data on the concentrations of dissolved CYN, particulate CYN, cyanobacteria and target environmental parameters at 20 selected lakes, which were sampled 3 times each. Last but not least, we investigated the seasonal dynamics of these parameters at two selected lakes in 2004 and 2005. Apart from this we isolated different cyanobacterial strains and conducted chemical and molecular biological analyses of CYN and CYNcoding genes, in order to identify CYN-producing cyanobacteria. The results show that C. raciborskii and CYN are much more widespread than was previously assumed. C. raciborskii was detected in 22 % of the investigated water bodies, and cylindrospermopsin in 52 %. Additionally, two other toxic cyanobacteria of tropical origin were found for the first time in the BerlinBrandenburg region, Anabaena bergii and Aphanizomenon aphanizomenoides. The mean and maximum CYN concentrations were 1 µg L-1 and 12 µg L-1, respectively. Since the particulate CYN fraction did not exceed 0.5 µg L-1, the dissolved CYN fraction was found to be responsible for the high CYN concentrations. The proposed guideline safety value for cylindrospermopsin in drinking water (1 µg L-1) was exceeded 18 times at 8 different lakes. Although Aphanizomenon flos-aquae (Nostocales) has been unequivocally identified as a producer of cylindrospermopsin, the observed cylindrospermopsin concentrations cannot be attributed to this cyanobacterial species alone. Aphanizomenon gracile was also identified as a potential CYN-producing cyanobacterium. Based on the findings of the CYLIN project, we recommend that cylindrospermopsin be included as a risk factor in drinking and bathing water quality assessments. To identify hazard conditions associated with this cyanotoxin, further investigations are needed to identify all cyanobacteria that produce cylindrospermopsin and to elucidate the mechanisms regulating the occurrence of CYN-producing cyanobacteria, CYN synthesis by these organisms, and CYN decomposition in aquatic ecosystems. Our analysis of C. raciborskii population dynamics showed that its germination is temperature-dependent and its population growth light-dependent. Population size was determined by the time of germination, that is, the earlier the time of germination, the bigger the population. Based on these findings, it appears highly likely that the climate-related early rise in water temperatures over the course of the years has promoted the spread of this species to temperate regions. Our hypothesis for the future course of cyanobacterial and cyanotoxin development in German waters is as follows: The combination of trophic decline and global warming works to the general benefit of cyanobacteria of the order Nostocales and leads to a shift in cyanobacterial species and toxin composition. This may ultimately lead to an increase in the incidence of neurotoxins as well as cylindrospermopsin.

With the application of advanced treated wastewater to the ancient wastewater irrigation field Karolinenhöhe, the Berlin Water Company (Berliner Wasserbetriebe) started in 1990 an ecological passable and water economical reasonable cultivation of an old wastewater irrigation field. After a period of 10 years of operation the functional capability and the efficiency is assed. In the first aquifer a hydrodynamic impact by the trickled water could be proved in the measuring facilities and certified by modelling. Altogether the application of the advanced treated wastewater stabilized the water balance and therefore the basis flow of the river Havel. Especially admissions during the low water periods (summer and autumn) counteract the low water level in the surface water by a raised basis discharge. Since 1990 the ecological status of the first aquifer of the wastewater irrigation field is clearly improved. The concentration of the relevant parameters of eutrophication NO3, NH4 und PO4 regressed significantly. In the second aquifer the parameter boron and phosphate improved from 1990 to April 2002. For the other parameters a diffuse basis load remained. The admission of the advanced treated water has a positive effect to the quality of the groundwater compared to the initial situation. The concentration of most of the parameters regressed. Just the concentration of potassium (in the first and second aquifer) and of AOX (in the first aquifer) stayed almost constant because of the input. There are no risks by continuing applications. There is a degradation of the nitrogen compounds due of the soil passage of the water and a dilution by the natural groundwater recharge. Therefore the receiving water bodies are less polluted compared to a direct discharge (exception potassium). A clear improvement is reached for the river Havel. The retention time of the water in the underground passage is very long because of the great depth of the groundwater level. Therefore a degradation of germs is assured. More detailed studies and analyses must follow this primal estimation.

The Berlin Centre of Competence for Water organised, together with the International Water Association, the 2nd National Young Water Professionals Conference in Germany. This event was held on 4-5 June 2007 in Berlin and was following up on the first NYWP conference organised in Aachen in October 2005. It provided a forum for young researchers and professionals working in the membrane sector of the wastewater industry to present their work and meet their peers. The conference consisted on formal presentation of papers and posters, and an exchange with water industry professionals providing information on water career opportunities in Germany. This event was an initiative of “MBR-Network”, the European cluster on the membrane bioreactor technology, gathering about 50 European and international companies and institutions within the four FP6 projects Amedeus, Eurombra, MBR-Train and Puratreat (more info at www.mbrnetwork.eu). The technical program of the conference consisted mainly of contributions from German and international young water professionals including students, recent graduates and other professionals under the age of 35. This book contains most of the papers and posters which were presented at the Conference.

Two major points of view prevail in modelling aquatic ecosystems. For practitioners, the key question in modelling aquatic ecosystems is how well models describe system reactions to changes – particularly trophic change and climate change – and in consequence, how useful models are for predicting system responses and for informing water-body management. For researchers, the modelling objective is to investigate functional interactions between ecosystem components, to understand complex causalities and to identify knowledge gaps to close with further lab and field work. Ideally, successful modelling should address both purposes. A need for more intensive communication between modellers of both groups, as well as other model users, was identified at a modellers’ workshop organised by the project “OLIGO” in autumn 2005. OLIGO (2003-2007) was a project of the Berlin Centre of Competence for Water (KWB), executed by researchers of the Federal Environmental Agency (UBA) and the Berliner Wasserbetriebe (BWB) and funded by Veolia Water. Following up on the recommendation of this workshop and in the context of finalising this project, UBA together with KWB organised a 2-day workshop in Berlin, 8-9 November 2007. The workshop was hosted by the Berliner Wasserbetriebe and brought together 60 modellers and model users from 6 countries. The workshop aimed to consolidate and document the state of the art in modelling water quality in reaction to nutrient load or climate change, to discuss how well current lake and reservoir models can support and inform decision-makers, including dealing with the uncertainty of model predictions, and to explore future perspectives and needs for the development of models.