Sulfate-reducing bacteria (SRB) can beneficially be applied to domestic wastewater treatment. In general, formed sulfide will stay in liquid phase, resulting in an elevated sulfide content, which might have inhibiting effects on the SRB. To study effects of environmental conditions on the SRB resistance against sulfide, two sequencing batch reactors fed with artificial domestic wastewater were operated at sulfate-reducing conditions. Required sulfide concentration within the reactor was achieved by adding 400 or 800 mg COD/L (acetate and propionate), the latter resulting in proportionally more sulfide production. Batch tests revealed that sulfide inhibited the rate of sulfate reduction by 50% at a concentration of 200 mg/L sulfide for biomass from the reactor fed with 400 mg COD/L. After adaptation to a feed of 800 mg COD/L, resulting in higher sulfide exposures, sulfide was less inhibitive to SRB. Complete COD removal was achieved in the reactor fed with 800 mg COD/L, and the SRB population changed from one (Desulfotalea arctica) to two (Desulfobacter postgatei and Desulfocapsa sulfexigens) dominant species. Results indicate that SRB are capable of adapting to higher sulfide exposure. Therefore, the SRB can also be applied to treat wastewater with higher COD levels, blackwater for instance.

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Más de mil millones de personas en las áreas urbanas y peri-urbanas de África, Asia y América utilizan tecnologías descentralizadas de saneamiento. Hasta ahora se ha descuidado tremendamente el manejo de los lodos fecales producidos por estas tecnologías. Los recursos financieros son frecuentemente insuficientes y estos sistemas descentralizados suelen ser vistos como soluciones temporales, hasta poder implementar sistemas con alcantarillado. Sin embargo, la verdad es que el saneamiento descentralizado está aquí para quedarse, sea como soluciones independientes (temporales o permanentes) o en combinación con sistemas basados en el alcantarillado. El manejo adecuado y apropiado de los lodos fecales es primordial para la protección de la salud humana y ambiental. Este es el primer libro dedicado netamente al manejo de lodos fecales. Compila el estado actual de conocimiento en este campo que está evolucionando rápidamente y presenta un enfoque integrado que incluye la tecnología, la gestión y la planificación. Aborda la planificación y organización de toda la cadena de servicios de manejo de lodos fecales, desde su recolección y transporte hasta su tratamiento y uso o disposición final. Además de resumir los fundamentos y tecnologías, el libro también expone los detalles de los aspectos operativos, institucionales y financieros y las pautas para planificar un proyecto para el manejo de lodos fecales con la participación de todos los actores.@en

P-limitation in enhanced biological phosphorus removal (EBPR) systems fed with acetate, has generally been considered as a condition leading to enrichment of organisms of the genotype’ Candidatus Competibacter phosphatis’ expressing the glycogen-accumulating organisms (GAO) phenotype. Recent studies have demonstrated in short-term experiments that organisms of the genotype ‘Candidatus Accumulibacter phosphatis’ clade I and II, known to express the polyphosphate-accumulating organisms (PAO) phenotype can switch to the GAO phenotype when poly-P is absent, but are performing the HAc-uptake at lower kinetic rates, where clade I showed the lowest rates. The objective of this study was to verify whether organisms of the genotype ‘Candidatus Accumulibacter phosphatis’ can also be enriched under P-limiting conditions while expressing a GAO phenotype and more specifically to see which specific clade prevails. A sequencing batch reactor was inoculated with activated sludge to enrich an EBPR culture for a cultivation period of 128 days (16 times the solids retention time) under P-limiting conditions. A mixed culture was obtained comprising of 49 % ‘Candidatus Accumulibacter phosphatis’ clade II and 46 % ‘Candidatus Competibacter phosphatis’. The culture performed a full GAO metabolism for anaerobic HAc-uptake, but was still able to switch to a PAO metabolism, taking up excessive amounts of phosphate during the aerobic phase when it became available in the influent. These findings show that P-limitation, often used as strategy for enrichment of ‘Candidatus Competibacter phosphatis’, does not always lead to enrichment of only ‘Candidatus Competibacter phosphatis’. Furthermore, it demonstrates that ‘Candidatus Accumulibacter phosphatis’ are able to proliferate in activated sludge systems for periods of up to 128 days or longer when the influent phosphate concentrations are just enough for assimilation purposes and no poly-P is formed. The ‘Candidatus Accumulibacter phosphatis’ retain the ability to switch to the PAO phenotype, taking up phosphate from the influent as soon as it becomes available.

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It is estimated that literally billions of residents in urban and peri-urban areas of Africa, Asia, and Latin America are served by onsite sanitation systems (e.g. various types of latrines and septic tanks). Until recently, the management of faecal sludge from these onsite systems has been grossly neglected, partially as a result of them being considered temporary solutions until sewer-based systems could be implemented. However, the perception of onsite or decentralized sanitation technologies for urban areas is gradually changing, and is increasingly being considered as long-term, sustainable options in urban areas, especially in low- and middle-income countries that lack sewer infrastructures. This is the first book dedicated to faecal sludge management. It compiles the current state of knowledge of the rapidly evolving field of faecal sludge management, and presents an integrated approach that includes technology, management, and planning based on Sandecs 20 years of experience in the field. Faecal Sludge Management: Systems Approach for Implementation and Operation addresses the organization of the entire faecal sludge management service chain, from the collection and transport of sludge, and the current state of knowledge of treatment options, to the final end use or disposal of treated sludge. The book also presents important factors to consider when evaluating and upscaling new treatment technology options. The book is designed for undergraduate and graduate students, and engineers and practitioners in the field who have some basic knowledge of environmental and/or wastewater engineering.@en