pH and Phosphate Induced Shifts in Carbon Flow and Microbial Community during Thermophilic Anaerobic Digestion

pH is a central environmental factor influencing CH4 production from organic substrates, as every member of the complex microbial community has specific pH requirements. Here, we show how varying pH conditions (5.0–8.5, phosphate buffered) and the application of a phosphate buffer per se induce shifts in the microbial community composition and the carbon flow during nine weeks of thermophilic batch digestion. Beside monitoring the methane production as well as volatile fatty acid concentrations, amplicon sequencing of the 16S rRNA gene was conducted. The presence of 100 mM phosphate resulted in reduced CH4 production during the initial phase of the incubation, which was characterized by a shift in the dominant methanogenic genera from a mixed Methanosarcina and Methanoculleus to a pure Methanoculleus system. In buffered samples, acetate strongly accumulated in the beginning of the batch digestion and subsequently served as a substrate for methanogens. Methanogenesis was permanently inhibited at pH values ≤5.5, with the maximum CH4 production occurring at pH 7.5. Adaptations of the microbial community to the pH variations included shifts in the archaeal and bacterial composition, as less competitive organisms with a broad pH range were able to occupy metabolic niches at unfavorable pH conditions

Formation of phenylacetic acid and phenylpropionic acid under different overload conditions during mesophilic and thermophilic anaerobic digestion

Abstract Background Substrate spectra for anaerobic digestion have been broadened in the past decade, inter alia, due to the application of different pretreatment strategies and now include materials rich in lignocellulose, protein, and/or fat. The application of these substrates, however, also entails risks regarding the formation of undesired by-products, among which phenolic compounds are known to accumulate under unfavorable digestion conditions. Methods Different states of overload were simulated in batch experiments while reviewing the generation of phenyl acids out of different lab-use substrates in order to evaluate the impact on biogas and methane production as well as some additional process performance parameters under defined laboratory conditions. Investigations were conducted under both mesophilic and thermophilic conditions. Results It could be shown that the tested input materials led to the formation of phenyl acids in a substrate-dependent manner with the formation itself being less temperature driven. Once formed, the formation of phenyl acids turned out to be a reversible process. Conclusions Although a mandatory negative impact of phenyl acids per se on the anaerobic digestion process in general and the methanogenesis process in particular could not be proven, phenyl acids, however, seem to play an important role in the microbial response to overloaded biogas systems

Data filtering methods for SARS-CoV-2 wastewater surveillance

In the case of SARS-CoV-2 pandemic management, wastewater-based epidemiology aims to derive information on the infection dynamics by monitoring virus concentrations in the wastewater. However, due to the intrinsic random fluctuations of the viral signal in wastewater caused by several influencing factors that cannot be determined in detail (e.g. dilutions; number of people discharging; variations in virus excretion; water consumption per day; transport and fate processes in sewer system), the subsequent prevalence analysis may result in misleading conclusions. It is thus helpful to apply data filtering techniques to reduce the noise in the signal. In this paper we investigate 13 smoothing algorithms applied to the virus signals monitored in four wastewater treatment plants in Austria. The parameters of the algorithms have been defined by an optimization procedure aiming for performance metrics. The results are further investigated by means of a cluster analysis. While all algorithms are in principle applicable, SPLINE, Generalized Additive Model and Friedman's Super Smoother are recognized as superior methods in this context (with the latter two having a tendency to over-smoothing). A first analysis of the resulting datasets indicates the positive effect of filtering to the correlation of the viral signal to monitored incidence values.132413391

Kosten und Erlöse bei der Co-Vergärung von mechanisch aufbereitetem Bioabfall in Faultürmen kommunaler Kläranlagen

Die moderne Abwasserbehandlung weist ein großes Potenzial zur Bereitstellung erneuerbarer Energien auf. Auf Kläranlagen kann die chemische Energie im Abwasser genutzt werden, indem in den Faultürmen Biomethan produziert wird. Diese Biomethanproduktion kann durch die gezielte Zugabe organischer Abfälle in die Faultürme gesteigert werden (= Co-Vergärung). Abfälle, die in den Faulturm als Co-Substrate zugegeben werden, müssen pumpfähig und in den Faulschlamm einmischbar sein. Typische Abfallströme, die dafür in Frage kommen sind z. B. Speisereste aus Großküchen oder Molkereiabfälle. Derartige Abfälle können meist nach geringer mechanischer Aufbereitung dem Faulturm beigemischt werden. Diese Abfälle sind begehrte Reststoffe der Kläranlage, da sie im Allgemeinen weitgehend frei von Störstoffen wie Glas, Steinen oder Kunststoffen sind. Die begrenzte Verfügbarkeit von Speiseresten oder Molkereiabfällen führt zunehmend dazu, dass auch Bioabfälle aus der Getrenntsammlung oder überlagerte Lebensmittel mechanisch aufbereitet und in den Kläranlagen mitverarbeitet werden. Bei der Nutzung derartiger Substrate ist vermehrt mit Folgeproblemen auf der Kläranlage zu rechnen, da sie stärker mit Störstoffen belastet sind. Durch Abrasion an Aggregaten, verlegte Leitungen oder Sedimenten im Faulturm ergeben sich Mehrkosten für die Kläranlage. Bei der Betrachtung der Mehrkosten durch die Co-Vergärung von mechanisch aufbereitetem Bioabfall müssen neben den Aufwendungen, die auf Störstoffe zurückzuführen sind, auch Kosten für den Schlammanfall aus den Co-Substraten und der Rückbelastung, insbesondere von Stickstoff, in die Abwasserreinigung der Kläranlage berücksichtigt werden. In dieser Arbeit wird eine ökonomische Betrachtung aufgestellt, die die relevanten Kosten der Co-Vergärung erfasst und den Erlösen aus der Verwertung des zusätzlich produzierten Biomethans gegenüberstellt.The production of methane in wastewater treatment plants can be increased by applying co-digestion. Leftovers from canteens or waste from dairy production are frequently used for co-digestion in wastewater treatment plants. These substrates are free from impurities and pumpable and hence almost no further mechanical treatment is necessary before adding these wastes to the fermentation process. Due to the limited availability of suitable leftovers etc., also separately collected municipal biowastes or packed food wastes from supermarkets are used as co-substrates. These waste materials need to be milled or shredded before digestion. Although impurities like plastic films are separated, other impurities, such as stones and glass particles, can reach the digester. These impurities are a cause for extra costs for the wastewater treatment plant operators because they can provoke plant malfunctions, increased equipment wear, pipe clogging, or accumulation of sediments in the digester. These costs caused by impurities in the pretreated biowaste are investigated in this work. Furthermore, the costs for the ensuing additional sludge disposal and additionally required removal of nitrogen because of added co-substrates are considered. All additional costs caused by the co-digestion of biowaste in wastewater treatment plants are compiled and compared with the revenue generated by the additionally produced methane from biowaste (production of electrical power for use at the wastewater treatment plant, selling the produced energy or selling the methane).(VLID)459073

Quest for Optimal Regression Models in SARS-CoV-2 Wastewater Based Epidemiology

Wastewater-based epidemiology is a recognised source of information for pandemic management. In this study, we investigated the correlation between a SARS-CoV-2 signal derived from wastewater sampling and COVID-19 incidence values monitored by means of individual testing programs. The dataset used in the study is composed of timelines (duration approx. five months) of both signals at four wastewater treatment plants across Austria, two of which drain large communities and the other two drain smaller communities. Eight regression models were investigated to predict the viral incidence under varying data inputs and pre-processing methods. It was found that population-based normalisation and smoothing as a pre-processing of the viral load data significantly influence the fitness of the regression models. Moreover, the time latency lag between the wastewater data and the incidence derived from the testing program was found to vary between 2 and 7 days depending on the time period and site. It was found to be necessary to take such a time lag into account by means of multivariate modelling to boost the performance of the regression. Comparing the models, no outstanding one could be identified as all investigated models are revealing a sufficient correlation for the task. The pre-processing of data and a multivariate model formulation is more important than the model structure

Medium Preparation for the Cultivation of Microorganisms under Strictly Anaerobic/Anoxic Conditions

In contrast to aerobic organisms, strictly anaerobic microorganisms require the absence of oxygen and usually a low redox potential to initiate growth. As oxygen is ubiquitous in air, retaining O2-free conditions during all steps of cultivation is challenging but a prerequisite for anaerobic culturing. The protocol presented here demonstrates the successful cultivation of an anaerobic mixed culture derived from a biogas plant using a simple and inexpensive method. A precise description of the entire anoxic culturing process is given including media preparation, filling of cultivation flasks, supplementation with redox indicator and reducing agents to provide low redox potentials as well as exchanging the headspace to keep media free from oxygen. Furthermore, a detailed overview of aseptically inoculating gas tight serum flasks (by using sterile syringes and needles) and suitable incubation conditions is provided. The present protocol further deals with gas and liquid sampling for subsequent analyses regarding gas composition and volatile fatty acid concentrations using gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively, and the calculation of biogas and methane yield considering the ideal gas law.Video Article(VLID)4466098Version of recor

Standards zur Qualitaetssicherung in der Markt- und Sozialforschung

Die Verfasser legen einen den gesamten Forschungsprozess umfassenden Orientierungsrahmen vor, der Standards zur Qualitaetssicherung setzen und darueberhinaus eine Grundlage fuer die Zertifizierung von Markt- und Sozialforschungsinstituten nach ISO 9000 bilden soll. Neben allgemeinen Aspekten der Qualitaetssicherung wie Qualitaetsmanagement, Mitarbeiterschulung und Vertraulichkeit werden die Gestaltung der Zusammenarbeit mit dem Auftraggeber, die konzeptionelle Studienbegleitung, die Datenerhebung und Datenverarbeitung sowie die Beratung des Auftraggebers beruecksichtigt. Der gesamte Text liegt zweisprachig in deutsch und englisch vor. (ICE)SIGLEAvailable from UuStB Koeln(38)-20000106016 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman