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Background Intensive wastewater irrigated urban horticulture in sub-Saharan West Africa receives high nutrient inputs, which lead to large gaseous and leaching losses. The addition of biochar to the usually sandy soils may reduce these losses and improve the habitat conditions for soil microorganisms. Two similar experiments focused on crop yields and nutrient balances have been carried out over a 2-year period in semi-arid Ouagadougou, Burkina Faso, and in sub-humid Tamale, Ghana, representing to some extent different but typical locations in West Africa. Methods Biochar and N fertilization effects were measured on soil microbial biomass carbon (MBC), fungal ergosterol, and functional diversity, estimated by multi-substrate-induced respiration. It was additionally possible to study the effects of clean water irrigation on the respective microbial properties in Tamale soil. Results Sole biochar addition did not affect any soil chemical or soil biological properties analyzed. In contrast, biochar application with N fertilization increased the mean respiratory response of the 11 substrates added by 23% in the Ouagadougou soil and by 13% in the Tamale soil. N fertilization decreased soil pH in both cities by 1.1 units. However, a pH-H2O of 4.7 led to reduced MBC and ergosterol contents at Tamale. Also, the Shannon index of the respiratory response was positively correlated with the soil pH. Clean water irrigation decreased the ergosterol content and increased the respiratory response to organic acids. Conclusions Biochar addition with N fertilization improved habitat conditions for soil microorganisms. An N fertilizer-induced decline in soil pH Graphical Abstract

The benefit of biochar as a soil fertility enhancer is well known and has been broadly investigated. Equally, many tropical and subtropical countries use wastewater for irrigation in urban agriculture. To assess the related health risks, we determined pathogen and heavy metal fate associated with biochar application and wastewater irrigation in the urban agriculture of northern Ghana. Rice (Oryza L.) husk biochar (20 t ha−1), N–P–K 15–15–15 fertilizer (212.5 kg ha−1), and their combinations were evaluated in a field‐based experiment. Untreated wastewater and tap water served as irrigation water. Red amaranth (Amaranthus cruentus L.) was used as a test crop and was grown in wet (WS) and dry (DS) cropping seasons. Irrigation water, soil, and vegetables were analyzed for heavy metals, Escherichia coli, fecal coliform, helminth eggs, and Salmonella spp. Unlike the pathogens, analyzed heavy metals from irrigation water and soil were below the FAO/WHO permissible standard for agricultural activities. Wastewater irrigation caused E. coli concentrations ranging from 0.5 to 0.6 (WS) and from 0.7 to 0.8 (DS) log10 colony forming units per gram fresh weight (CFU gFW−1) on vegetables and from 1.7 to 2.1 (WS) and from 0.6 to 1.0 (DS) log10CFU per gram dry weight (gDW−1) in soil. Average log10CFU gFW−1 rates of 6.19 and 3.44 fecal coliform were found on vegetables, whereas in soil, 4.26 and 4.58 log10CFU gDW−1 were observed in WS and DS, respectively. Helminth egg populations were high in wastewater and were transferred to the crops and soil. Biochar did not affect bacteria contamination. Pathogen contamination on vegetables and in soil were directly linked to the irrigation water, with minimal or no difference observed from biochar application., Core Ideas: Soil and vegetable contamination were linked to irrigation water source. Rice husk–derived biochar did not affect bacteria contamination on vegetables. Wastewater and biochar application did not affect heavy metal contamination in soil. Helminth eggs and bacteria pathogens in soil were not significantly affected by biochar., Bundesministerium für Wirtschaftliche Zusammenarbeit und Entwicklung http://dx.doi.org/10.13039/501100006456, Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347

Frischwasser ist eine wertvolle Ressource. Bevölkerungswachstum als auch Auswirkungen des Klimawandels werden zu einer verringerten Verfügbarkeit sowie gesteigerten Nutzung von Frischwasser in der Mittelmeerregion und im Nahen Osten führen. Daher gewinnen Alternativen wie die Bewässerung mit geklärtem Abwasser an Bedeutung. Aufgrund der Anreicherung des Frischwassers mit Fremdstoffen im Zuge der Nutzung können Abwässer erhöhte Konzentrationen von Nährstoffen, aber auch von potentiell schädlichen Inhaltsstoffen für Boden und Nutzpflanzen beinhalten, wenn es für landwirtschaftliche Bewässerungszwecke verwendet wird. Diese Arbeit befasst sich neben einer allgemeinen Beschreibung der Bewässerungssituation mit Abwässern in Israel mit der Erläuterung eines räumlichen Bewertungsverfahrens der regionalen Bodeneignung für Abwasserbewässerung und Auswirkungen von Abwasserbewässerung auf ausgewählte Bodeneigenschaften wie Benetzungshemmung sowie hydraulische Leitfähigkeit und Aggregatstabilität. Freshwater is a valuable resource and population growth as well as global climate changes are expected to lead to a decreased availability and increased utilization of it in the Mediterranean region and Middle East. As a consequence, alternatives such as irrigation with treated wastewater gain in importance. Due to the enrichment of freshwater with impurities in the wake of use, treated wastewater carries higher loads of potential nutrients but also of potential harmful substances for the soil and crops when used in irrigation. In addition to the general description of the treated wastewater irrigation context with focus on Israel, this thesis deals with (1) the description on a spatial assessment, its methodology and results of soil suitability for treated wastewater irrigation, (2) the effects of irrigation with treated wastewater on specific soil properties like water repellency as well as (3) hydraulic conductivity and aggregate stability.

For better planning of a managed aquifer recharge (MAR) project, the most promising strategies should analyze the environmental impact, socio-economic efficiency, and their contribution to the existing or future water resource conditions in the region. The challenge of such studies is to combine and quantify a wide range of criteria from the environment and society. This necessity leads to an integrated concept and analysis. This paper outlines an integrated approach considering environmental, health, social and economic aspects to support in the decision-making process to implement a managed aquifer recharge project as a potential response to water resource problems. In order to demonstrate the approach in detail, this paper analysed several water resources management strategies based on MAR implementation, by using treated wastewater in the Northern Gaza Strip and the potential impacts of the strategies on groundwater resources, agriculture, environment, health, economy and society. Based on the Palestinian water policy (Year 2005–2025) on wastewater reuse, three MAR strategies were developed in close cooperation with the local decision makers. The strategies were compared with a base line strategy referred to as the so-called “Do Nothing Approach”. The results of the study show that MAR project implementation with treated wastewater at a maximum rate, considered together with sustainable development of groundwater, is the best and most robust strategy amongst those analyzed. The analysis shows the defined MAR strategies contribute to water resources development and environmental protection or improvement including an existing eutrophic lake. The integrated approach used in this paper may be applicable not only to MAR project implementation but also to other water resources and environmental development projects. EC/FP6/Groundwater Artificial recharge Based on Alternative sources of wateR: aDvanced INtegrated technologies and management” (GABARDINE)

Die vorliegende Arbeit leistet einen Beitrag zur Bewertung der Ressourceneffizienz städtischer Abwassersysteme unter Anwendung von kombinierten Kosten-, Energie- und Stoffstromanalysen (ceMFA). Für zwei Fallbeispiele, Hamburg in Deutschland und Arba Minch in Äthiopien, wurde eine Reihe von möglichen Systementwicklungen untersucht. Eine geeignete Umgestaltung der Abwassersysteme bietet die Möglichkeit zur Reduzierung des Wasserverbrauchs, zur Erhöhung der Energieeffizienz und zur Rückgewinnung von Nährstoffen für die Landwirtschaft. Das ceMFA Modell erlaubt die Identifikation solcher Möglichkeiten und verdeutlicht mögliche Zielkonflikte. Damit kann diese Arbeit als Basis für eine Entscheidungsunterstützung verwendet werden, um Strategien für die Einführung ressourceneffizienterer Systeme zu entwickeln., This study contributes to assessing the resource efficiency of urban sanitation systems using combined cost, energy and material flow analyses (ceMFA). For two case studies, Hamburg in Germany and Arba Minch in Ethiopia, a number of possible system developments were assessed. Introducing appropriate system transformations in sanitation can provide the opportunity to reduce water consumption, increase energy efficiency and recover nutrients for agriculture. The ceMFA model allows the identification of such opportunities and highlights possible trade-offs. Using this work as a basis for decision support, strategies for implementing more resource efficient systems can be developed.

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van Straaten, Jos Kibo Wien, Univ. für Bodenkultur, Masterarb., 2008