Role of nickel in high rate methanol degradation in anaerobic granular sludge bioreactors

The effect of nickel deprivation from the influent of a mesophilic (30°C) methanol fed upflow anaerobic sludge bed (UASB) reactor was investigated by coupling the reactor performance to the evolution of the Methanosarcina population of the bioreactor sludge. The reactor was operated at pH 7.0 and an organic loading rate (OLR) of 5–15 g COD l−1 day−1 for 191 days. A clear limitation of the specific methanogenic activity (SMA) on methanol due to the absence of nickel was observed after 129 days of bioreactor operation: the SMA of the sludge in medium with the complete trace metal solution except nickel amounted to 1.164 (±0.167) g CH4-COD g VSS−1 day−1 compared to 2.027 (±0.111) g CH4-COD g VSS−1 day−1 in a medium with the complete (including nickel) trace metal solution. The methanol removal efficiency during these 129 days was 99%, no volatile fatty acid (VFA) accumulation was observed and the size of the Methanosarcina population increased compared to the seed sludge. Continuation of the UASB reactor operation with the nickel limited sludge lead to incomplete methanol removal, and thus methanol accumulation in the reactor effluent from day 142 onwards. This methanol accumulation subsequently induced an increase of the acetogenic activity in the UASB reactor on day 160. On day 165, 77% of the methanol fed to the system was converted to acetate and the Methanosarcina population size had substantially decreased. Inclusion of 0.5 μM Ni (dosed as NiCl2) to the influent from day 165 onwards lead to the recovery of the methanol removal efficiency to 99% without VFA accumulation within 2 days of bioreactor operation

Hydrodynamic Mathematical Modelling of Aerobic Plug Flow and Non ideal Flow Reactors: A Critical and Historical Review

Existing mathematical models of wastewater treatment plants focus primarily on the bioconversion processes and often do not cope with the reactor hydrodynamics. However, in the literature several aerobic plug flow bioreactors with both kinetics modelling and hydrodynamics description are reported. The authors review mathematical models of aerobic plug flow reactors, such as activated sludge reactors, fluidized bed reactors, biofilters, and trickling filters focusing on their hydrodynamic approach and on the role of the reactor configuration on the process performance. For each reactor type the following modelling approach is compared: (a) ideal model, such as plug flow or complete mixed, (b) tank in series model, (c) dispersion model and (d) computational fluid dynamic model

Effect of temperature on selenium removal from wastewater by UASB reactors

The effect of temperature on selenium (Se) removal by upflow anaerobic sludge blanket (UASB) reactors treating selenate and nitrate containing wastewater was investigated by comparing the performance of a thermophilic (55 °C) versus a mesophilic (30 °C) UASB reactor. When only selenate (50 μM) was fed to the UASB reactors (pH 7.3; hydraulic retention time 8 h) with excess electron donor (lactate at 1.38 mM corresponding to an organic loading rate of 0.5 g COD L-1 d-1), the thermophilic UASB reactor achieved a higher total Se removal efficiency (94.4 ± 2.4%) than the mesophilic UASB reactor (82.0 ± 3.8%). When 5000 μM nitrate was further added to the influent, total Se removal was again better under thermophilic (70.1 ± 6.6%) when compared to mesophilic (43.6 ± 8.8%) conditions. The higher total effluent Se concentration in the mesophilic UASB reactor was due to the higher concentrations of biogenic elemental Se nanoparticles (BioSeNPs). The shape of the BioSeNPs observed in both UASB reactors was different: nanospheres and nanorods, respectively, in the mesophilic and thermophilic UASB reactors. Microbial community analysis showed the presence of selenate respirers as well as denitrifying microorganisms

Fate of trace metals in anaerobic digestion

© Springer International Publishing Switzerland 2015. A challenging, and largely uncharted, area of research in the field of anaerobic digestion science and technology is in understanding the roles of trace metals in enabling biogas production. This is a major knowledge gap and a multifaceted problem involving metal chemistry; physical interactions of metal and solids; microbiology; and technology optimization. Moreover, the fate of trace metals, and the chemical speciation and transport of trace metals in environments— often agricultural lands receiving discharge waters from anaerobic digestion processes— simultaneously represents challenges for environmental protection and opportunities to close process loops in anaerobic digestion.The authors acknowledge funding within the framework of the COST Action 1302 (‘European Network on Ecological Roles of Trace Metals in Anaerobic Biotechnologies’). GC is supported by a European Research Council Starting Grant (‘3C-BIOTECH; No. 261330).Peer Reviewe

Synergistic Effect of Sulfide and Ammonia on Anaerobic Digestion of Chicken Manure

The effect of the sulfur load on anaerobic digestion of chicken manure (CM) was investigated in a laboratory scale anaerobic mono-digester at high total ammonia nitrogen (TAN) concentrations. The digester was operated for 268 days by increasing the organic loading rate from 0.5 to 2.5kg-VS/m(3)/day and the total Kjeldahl nitrogen up to 5050mg/l. The CH4 yield of 0.36 +/- 0.02m(3)/kg-VS was achieved at 2.5kg-VS/m(3)/day of loading rate without any inhibition. The results showed that, anaerobic mono-digestion of chicken manure was applicable with the acclimation of microbial consortium to high TAN concentrations. However, when the sulfur content of the CM fed to the digester increased suddenly by coincidence, the CH4 yield decreased about 25\% from 0.36 +/- 0.02 to 0.27 +/- 0.03m(3)/kg-VS. As a result, the acetic acid concentration increased from 130 to 1700mg/l showing that the acetate consuming methanogens were detrimentally affected from TAN and total sulfide concentrations above 4000 and 100mg/l, respectively