Eaux usées

Investigations involving human faeces and faecal sludge are of great importance for urban sanitation,such as operation and maintenance of sewer systems, or implementation of faecal sludge management.However, working with real faecal matter is difficult as it not only involves working with a pathogenic,malodorous material but also individual faeces and faecal sludge samples are highly variable, making itdifficult to execute repeatable experiments. Synthetic faeces and faecal sludge can provide consistentlyreproducible substrate and alleviate these challenges. A critical literature review of simulants developedfor various wastewater and faecal sludge related research is provided. Most individual studies sought todevelop a simulant representative of specific physical, chemical, or thermal properties depending ontheir research objectives. Based on the review, a suitable simulant can be chosen and used or furtherdeveloped according to the research needs. As an example, the authors present such a modification forthe development of a simulant that can be used for investigating the motion (movement, settling andsedimentation) of faeces and their physical and biological disintegration in sewers and in on-site sanitationsystems.

Ozonation can be applied to mitigate the discharge of organic micropollutants from municipal wastewater treatment plants (WWTPs) to the aquatic environment. The toxicity of metals also present in WWTP effluents strongly depends on their speciation. Therefore, knowledge on the change of the metal speciation during ozonation of a WWTP effluent is essential to assess possible negative impacts. The kinetics and the stoichiometries of the reactions of ozone with three metal sulfides (ZnS, CuS and CdS) and metal-ethylenediaminetetraacetate (EDTA)/nitriloriacetic acid (NTA) complexes of Cu(II), Cd(II), Ni(II), Zn(II), Mg(II) and Pb(II) were investigated. With a stoichiometric factor of 2.6–3.9 moles of ozone per mole of sulfide and apparent second-order rate constants at pH 8 > 10⁴ M⁻¹ s⁻¹, a complete oxidation of the sulfides and a concomitant release of the respective metals is expected during ozonation of a WWTP effluent for enhanced micropollutant abatement. The apparent second-order rate constants at pH 8 for the reactions of metal-EDTA complexes with ozone ranged from 42 M⁻¹s⁻¹ to 2.0 × 10⁴ M⁻¹s⁻¹ and increased in the order Cd(II) < Cu(II) < Mg(II) < Ni(II) < Zn(II). Approximately 40% of Cd(II)-EDTA spiked to a WWTP effluent was oxidized at typical specific ozone doses of 0.5–0.7 g_O3/g_DOC. For the other metal-EDTA complexes a significantly higher fraction was oxidized. The bioavailable fraction determined by the diffusive-gradient thin films (DGT) method in the WWTP effluent increased during ozonation, due to the oxidative release of the metal ions. Algal toxicity (chlamynomodas reinhardtii) tests with CuS/CdS spiked WWTP effluent revealed a high tolerance toward Cu and Cd in the respective media. A toxic response was only observed at Cu concentrations above 10 μM, which is above typical WWTP effluent concentrations. Biological post-treatment after ozonation generally reduced the bioavailability of the metals, which resulted in a lower toxicity. Therefore, the biological post-treatment serves as an additional barrier to protect the downstream ecology of receiving waters.

Noch liegen in der Schweiz erst wenige grosstechnische Erfahrungen mit den Technologien zur Elimination organischer Spurenstoffe auf Abwasserreinigungsanlagen vor. Deswegen wurde 2012 die Plattform «Verfahrenstechnik Mikroverunreinigungen» gegründet und innerhalb des Verbands der Schweizer Abwasser- und Gewässerschutzfachleute (VSA) angesiedelt. Sie soll helfen, Wissen aufzubauen, den Austausch unter den Akteuren zu fördern sowie offene Fragen zu bearbeiten.

Auf einer durchschnittlichen Kläranlage werden Tausende Signale aufgezeichnet. Ihr Potenzial für einen besseren Anlagebetrieb ist beachtlich. Dennoch werden sie selten systematisch genutzt und ausgewertet. Dank einer spezialisierten Software ist es jetzt möglich, eine Anlage und ihre Prozesse schneller und besser zu verstehen, zu überwachen und zu optimieren.

Ist eine ressourcenschonende Abwasserreinigung durch Abwassertrennung und Dezentralisierung realistisch? Rund 40 international bekannte Wissenschafter und Wissenschafterinnen behandeln auf 520 Seiten in einem 2013 erschienenen Buch nuanciert diese Fragestellung. Die Editoren der Eawag diskutieren das Thema des Buches im Schweizer Kontext.

Anaerobic digestion (AD) reduces the amount of waste and generates products of value, such as biogas and nutrient-rich digestate. Contrary to the wide dissemination of digesters in rural areas where animal manure is used as feedstock and despite its apparent potential, AD still plays a negligible role as a treatment option for organic kitchen and market waste in cities of low-and middle-income countries.
This book compiles existing and recently generated knowledge on AD of urban biowaste at small and medium scale with special consideration given to the conditions prevailing in developing countries. Written for actors working in the waste and renewable energy sector, the book is divided into two parts: Part 1 focuses on practical information related to the AD supply chain (substrate-, process-, and product chain), and Part 2 presents selected case studies from around the world.