Influence of Temperature, VFA and pH on the inactivation of pathogens in anaerobic digestion of faecel sludge

On-site sanitation technologies such as septic tanks are widely used in low- and middle-income countries. A comprehensive management of the accumulating faecal sludge (FS) is however missing in most contexts and uncontrolled disposal of FS results in serious public and environmental health risks. Given the high pathogen and organic matter content of FS it is urgent to find an appropriate method to treat FS. One promising, but little investigated technology to treat FS is anaerobic digestion (AD). The goal of the present thesis was to evaluate the influence of temperature, VFA and pH on the inactivation of pathogens in AD of synthetic FS. Ascaris suum eggs and bacteriophages MS2 and T4 were selected as model organisms for parasitic, respectively viral pathogens. At a temperature of 50°C, Ascaris suum eggs were inactivated after 6 h, independent of the pH and the VFA concentration. Bacteriophages MS2 and T4 were however not fully inactivated after 6 h at 50°C, their initial concentration was reduced by almost 99 % for T4 but only by 50 % for MS2. The pH had an effect on bacteriophages T4 but not on MS2. VFA concentration did not have an influence on the bacteriophages inactivation at the tested temperatures. Viruses and not parasites seem to be the critical organisms to consider in thermophilic AD (TAD) at 50°C of FS. Future research could therefore focus on the inactivation of human viruses in TAD as bacteriophages are conservative indicators for inactivation of human viruses.

Aerobic granular sludge formation and performance at 30 and 35°C in sequencing batch bubble-column reactors

Sirous Ebrahimi, Sébastien Gabus, Graciela Gonzalez Gil, Christof Holliger, Maryam Hosseini

Aerobic granular sludge-based reactors represent an attractive alternative to conventional activated sludge systems due to their small footprint and their low energy consumption and excess sludge production. The granules developed in such systems have high biomass concentration, good settling properties, high COD removal efficiencies and eventually high phosphorus removal capacity. In addition, and depending on bulk oxygen concentrations and granule size, both nitrification and denitrification can occur in the granules. Therefore sequencing batch reactors operated with granular sludge have the potential to achieve organic matter and nutrient removal in a single compact system. So far, aerobic granular sludge development has been studied at 20°C as well as at relatively low temperatures (e.g. 5 and 10°C). Compact wastewater treatment systems are especially interesting for industry. Since they often produce wastewaters with temperatures above 20°C, we investigated whether aerobic granular sludge could be developed at higher temperatures and if so, what the physical and metabolic properties of the sludge were. The formation and performance of aerobic granular sludge was studied in sequencing batch bubble-column reactors. Two start-up strategies were examined. Reactor 1 and 2 were inoculated with activated sludge from a municipal wastewater treatment plant and operated at 20°C and 30°C, respectively. After failure of Reactor 2, it was inoculated with aerobic granular sludge of Reactor 1 and operated with a stepwise temperature increase from 20 to 35°C. Granular sludge with good physical and metabolic properties was obtained in Reactor 1. Virtually all acetate was consumed during the anaerobic period with concomitant high phosphorus release suggesting the predominance of phosphate accumulating organisms (PAO). After the aerobic phase, an average of 63% of phosphate was removed. Nitrogen removal was not observed in this system, not even nitrification. In Reactor 2, a mixture of smooth granules and irregular structures was obtained. Complete COD removal was achieved, however, the sludge had low density (

2008

Selecting appropriate treatment technologies for faecal sludge (FS) from onsite sanitation systems

Magalie Diane Bassan, Christof Holliger, Viet Anh Nguyen, Linda Strande

Context Worldwide: FS production much larger than treated volumes In Vietnam: • Urban households required to own septic tanks • Combined onsite and centralized sanitation • FS emptying frequency up to 10 years or more Negligible FS volumes treated before discharge PURR: Partnership for Urban Resource Recovery • Developing knowledge for adequate FS treatment in urban Vietnam • Testing feasibility of anaerobic digestion for FS treatment Study goal To understand the local context and factors influencing the selection of appropriate FS treatment technologies in case study cities in Vietnam Methods Field visits in 5 cities Review of literature and legal documents Interviews with local authorities and stakeholders in charge of wastes and FS Household surveys in sewered / non-sewered, poor and rich areas (100 houses per city) Results • 73% septic tanks have less than 5 years and need to be emptied within 5 to 15 years (emptying frequency in 5 case study cities >10 years) ->FS will continue to be produced in urban Vietnam and strategies are required in short term • A variety of stakeholders and management systems exist between cities with a lack of willingness to manage FS ->Need for a coherent sanitation strategy at the national level, with geographical separation of areas with onsite/centralized systems • Different waste management infrastructures exist in each city ->Different technologies are required, even in the same country Conclusions and perspectives • Current engineering approaches and sectorial strategies are not adequate • Comprehensive context assessment is required • Possibilities for co-treatment of organic wastes with FS to optimize financial flows, public and environmental protection will be assessed

2014

Imaging the aerobic granular sludge microbial community using light-sheet fluorescence micros

Arnaud Michel Gelb, Karen Gemayel, Christof Holliger, Julien Maillard

One of the aims of wastewater treatment is the removal of phosphorus before the water is discharged into the environment. Since phosphorus concentrations in wastewater exceed the requirement of bacterial growth, biological phosphorus removal is based on the ability of a group of microorganisms, named “Polyphosphate Accumulating Organisms” (PAO), to store large quantities of intracellular phosphate in form of polyphosphate. In this study, we are focusing on the PAO actively involved in bioreactors operated with Aerobic Granular Sludge (AGS) technology. This process based on dense microbial biofilms is a cost-effective and landsaving alternative to the conventional biological wastewater treatment with activated sludge. This promising technology has received a significant commercial interest, but questions remain unanswered regarding the system performances in the context of full-scale applications. Like many natural microbial communities, the microbial structure of the AGS is complex. Its spatial organization is shaped by the diffusion of nutrients from the external environment and by the diffusion of microbial by-products formed in the biofilm. Understanding how the AGS microbial community works requires the elucidation of its spatial architecture and development. Light-sheet fluorescence microscopy is a powerful tool for examining microbial communities by overcoming the limitations of the classical three-dimensional confocal fluorescence microscopy. This technique shapes the excitation laser into a thin sheet providing an optical sectioning in order to illuminate the sample on a single plane. Then the emission signal is collected by a perpendicular lens. The large datasets generated are analyzed with a pipeline on the FIJI platform[1] to extract quantitative information. Preliminary results indicate that AGS are composed of heterogeneous biofilm aggregates. Interestingly, our observations are contrasting the AGS model structure previously described[2]. We would like to highlight the necessity of multiple observations when highly variable structures, like AGS, are analyzed in order to capture data which are representative of the studied system. [1] Schindelin et al. in Nat. Methods 28;9(7):676-82 (2012) [2] Winkler et al. in Water Res. 15;46(16):4973-80 (2012) Poster 3 Conférence: Swiss Microbial Ecology Meeting 2019 (Lausanne) Titre: Anaerobic Biodegradation of organohalide pollutants: a crucial step towards the elucidation of proteins involved Auteurs: Lorenzo Cimmino, Adrian Schmid, Christof Holliger, Julien Maillard Abstract: Halogenated organic compounds (so-called organohalides) represent one of the major class of groundwater pollutants. The exploration of how organohalides are used as energy source is important in terms of ecosystem remediation but is also essential for the complete understanding of microbial metabolic interactions in the environment. Organohalide respiration (OHR) is a bacterial anaerobic process in which chlorinated compound, e.g. tetrachloroethene (PCE), is used as terminal electron acceptor. In the present work, Desulfitobacterium hafniense TCE1 and Dehalobacter restrictus, our model organohalide-respiring bacteria (OHRB) harbouring the pceABCT gene cluster, will be considered for the study of PCE respiration. To date, the function of PceA, the key catalytic enzyme in the process, and PceT, the dedicated molecular chaperone for PceA maturation, are well defined. However, the roles of PceB and PceC are not yet elucidated and the biochemistry of OHR electron transfer is still relatively elusive. Based on the genetic composition of the pce gene cluster, the hypothesis of a possible PceABC respiratory complex is tempting but the question remains largely unanswered. The present work represents an evaluation of the stoichiometry of PceA, PceB and PceC proteins via quantitative proteomics applied to the membranes fractions of our model organisms. In a second phase, the use of Blue-Native electrophoresis technology will be considered to investigate whether PceC participates in a membrane-bound protein complex toge.