Influence of heavy metal supplementation on specific methanogenic activity and microbial communities detected in batch anaerobic digesters

Abstract

Natural and modified zeolites (0.5-1.0 mm) from the Tasajera deposit in Cuba were used to enhance the anaerobic digestion process of synthetic substrates. Natural zeolites were modified by ionic exchange and by adsorption with nickel, cobalt and magnesium. The experiments were carried out by using an inoculum from a full-scale anaerobic reactor treating winery wastewater. Modified natural zeolites not only enhanced the anaerobic digestion process, but also increased the specific methanogenic activity (SMA) of the sludges. The textural and chemical surface characteristics of the modified zeolites were related to the process performance, volatile fatty acid (VFA) production and microbial communities found in the digesters. For the selected dose of modified zeolites [0.05 g/g of volatile suspended solids (VSS)], the lowest concentration was found for cobalt followed by nickel and magnesium. Based on the analyses of anaerobic biofilms, the heavy metal incorporated into the zeolite was shown to have a great influence on the predominance of species. For example, the presence of nickel and cobalt favoured Methanosaeta, while at the same dose magnesic zeolite stimulated the presence of Methanosarcina and sulfate-reducing bacteria (SRB). In digesters with modified zeolites and metal supplementations the values of SMA were higher than those obtained in the control and natural zeolite digesters.

Influence of the food to microorganisms (F/M) ratio and temperature on batch anaerobic digestion processes with and without zeolite addition

“…(2) Grau [35] : µ = µ max S/S 0 (3) Contois [36] : µ = µ max S/(BX + S) (4) where: µ and µ max are the specific microorganisms growth rate and maximum specific microorganisms growth rate (time −1 ), respectively; S is the substrate concentration or organic matter content in the medium (mass/volume); K s is the Monod saturation constant (mass/volume); K I is an inhibition constant (mass/volume); S 0 is the influent substrate concentration (mass/volume); B is a kinetic coefficient that represents the relationship between substrate and microorganism concentrations. Finally, the duplication time (t d ) was also determined in all cases studied.…”

“…To solve this problem, reactors have been designed with supports that fix the biomass and result in high loading densities and low hydraulic retention times. [1][2][3][4] With the increase of population density on the given support, there is a greater change in cross-feeding, co-metabolism and interspecies hydrogen and proton transfer, which may further stimulate the growth of microcolonies. The use of a porous support such as zeolite enables the anaerobic reactor to retain high biomass concentrations and thereby operate at significantly reduced hydraulic retention times.…”

“…The use of a porous support such as zeolite enables the anaerobic reactor to retain high biomass concentrations and thereby operate at significantly reduced hydraulic retention times. [1,2,4,5] The structure and physical properties of natural zeolite [channel and pore cavities, minimum diameter of pores in the range of 3 to 10 Angstroms, average surface area of 24.9 m 2 /g, low bulk density, high exchange (CEC) and adsorption capacities] make it ideal for use in anaerobic digestion processes for wastewater treatments. [6,7] Other researchers have demonstrated the suitability of the use of zeolite as microbial immobilization support in batch anaerobic processes operating at mesophilic temperatures.…”

Innovative application for bauxite residue: Red mud-based inorganic polymer spheres as pH regulators

“…These values are not expected to present any inhibitory effect in anaerobic digestion. In fact, the addition of trace elements (heavy metals), such as Fe, Ni, Cu, Zn and Co, among others, has been found to enhance methane production [27,28], while its absence is detrimental to anaerobic processes [29]. Recently, red mud was used to improve the methanogenesis during sludge anaerobic digestion [30].…”

Feasibility of sunflower oil cake degradation with three different anaerobic consortia

“…[8][9][10] The microbial community structure has been studied under low temperature conditions and under the influence of metal supplementation. [11][12][13] However, the transformations which occur in the microbial communities during the anaerobic digestion of organic wastes and methane production are still not fully understood.…”