Theoretical methane production generated by the co-digestion of organic fraction municipal solid waste and biological sludge

The co-digestion of two problematic and available wastes, namely Organic Fraction Municipal Solid Waste (OFMSW) and biological sludge, was carried out in this work. Biochemical Methane Potential (BMP) tests are a useful tool for determining the best substrate and co-digestion configurations, however there are some methodologies destined to save costs and time from this process by using the theoretical final methane potential of a substrate from its organic composition. Besides there are some models capable not only of reproducing the methane curve behavior, but also of predicting final methane productions from the first days of experimentation. Methodologies based in the elemental composition for the determination of theoretical production fit better with the experimental results and behavior, nevertheless the Gompertz model was capable of predicting the final productivity within the 7th day of experiment, selecting at the same time the co-digestion of 80% OFMSW and 20% Biological sludge as the optimum

Molecular analysis of the biomass of a fluidized bed reactor treating synthetic vinasse at anaerobic and micro-aerobic conditions

The microbial communities (Bacteria and Archaea) established in an anaerobic fluidized bed reactor used to treat synthetic vinasse (betaine, glucose, acetate, propionate, and butyrate) were characterized by denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis. This study was focused on the competitive and syntrophic interactions between the different microbial groups at varying influent substrate to sulfate ratios of 8, 4, and 2 and anaerobic or micro-aerobic conditions. Acetogens detected along the anaerobic phases at substrate to sulfate ratios of 8 and 4 seemed to be mainly involved in the fermentation of glucose and betaine, but they were substituted by other sugar or betaine degraders after oxygen application. Typical fatty acid degraders that grow in syntrophy with methanogens were not detected during the entire reactor run. Likely, sugar and betaine degraders outnumbered them in the DGGE analysis. The detected sulfate-reducing bacteria (SRB) belonged to the hydrogen-utilizing Desulfovibrio. The introduction of oxygen led to the formation of elemental sulfur (S(0)) and probably other sulfur compounds by sulfide-oxidizing bacteria (¿-Proteobacteria). It is likely that the sulfur intermediates produced from sulfide oxidation were used by SRB and other microorganisms as electron acceptors, as was supported by the detection of the sulfur respiring Wolinella succinogenes. Within the Archaea population, members of Methanomethylovorans and Methanosaeta were detected throughout the entire reactor operation. Hydrogenotrophic methanogens mainly belonging to the genus Methanobacterium were detected at the highest substrate to sulfate ratio but rapidly disappeared by increasing the sulfate concentratio

A new device to select microcarriers for biomass immobilization : application to an anaerobic consortium

A new device was designed to compare the biomass retention capacity of different microcarriers. Microcarriers were placed in as many as 28 independent, parallel minibioreactors under selected and identical flow conditions. Sepiolite pozzolana, clay, and foam glass (Poraver™) were examined for biomass retention capacity, characterized in terms of attached volatile solids and specific methanogenic activity, and examined with scanning electron microscopy. Sepiolite had the greatest biomass retention capacity and better internal porous volume for biomass immobilization. The specific methanogenic activity of the immobilized biomass in different materials was found to be inversely correlated to the amount of attached biomass. A maximum difference of 19% overall activity of the colonized material was observed between foam glass and pozzolana. Compared with the suspended biomass, a clear enhancement of syntrophic activity (up to 110%) and reduction of acetoclastic activity (up to 73%) was observed in the biofilm. This system of examination provides information useful for preselecting microcarriers for biomass colonization