Screening of trace metal supplementation for black water anaerobic digestion

Abstract

Community on-site separation of wastewater is a treatment approach that leads to more efficient processes, with former pollutants considered resources to be recycled.Black water has high organic matter content and can be a suitable feedstock for anaerobic treatment systems. Biological methane production (BMP) tests were conducted using Plackett-Burman design to screen the effects of adding Fe, Ni, Cu, Co, Mn, Ba and Se, with simulated black water (SBW) as the substrate. In the inoculum, most metals were found mainly in the organic matter/sulfide and residual fractions except for Mn, which was present at 12.3% in the bioavailable fractions (exchangeable and carbonates), and Ba, which was evenly distributed among all the fractions. Under the studied ranges of added metals, Fe, Ni, and Co did not show a clear effect on the anaerobic digestion of the black water. Ba had a significant negative effect on methane production and Mn addition enhanced the toxic effect. A specific methanogenic activity (SMA) between 18 and 27% lower than the control, 11.17 mLCH4.gCOD-1.d , respectively.

Biological treatment of organic sulfate-rich wastewaters

“…(1) a drop in methane yield (2) volatile fatty acid (VFA) accumulation (3) a decrease in the chemical oxygen demand (COD) removal efficiency Biogas or methane production can be monitored by water displacement (Veiga et al, 1990;Walker et al, 2009), by the displacement of a plunger of glass syringes (Owen et al, 1979) or by electronic pressure transducers (Braga et al, 2018;Colleran & Pistilli, 1994;Souto et al, 2010). The methane percentage of the biogas produced and the VFA levels are usually monitored by gas chromatography (GC).…”

“…Specific sludge activities are typically analysed using batch experiments. Sludge samples are placed in glass serum bottles in the presence of a basal medium which may or may not contain nutrients and a buffering agent (Braga et al, 2018;Kiyuna et al, 2017;O'Flaherty et al, 1998a). Substrates of interest are added in appropriate concentrations to control vials, whereas an inhibitor (sulfide) is included at various concentrations in parallel tests for an assessment of activity as a function of the sulfide concentration.…”

“…The methanogenic activity can be determined by measuring the methane concentration in the headspace of the serum vials over time (Visser, 1995). Alternatively, the gas pressure increase (or decrease in the case of H 2 /CO 2 ) in the headspace can be measured with a pressure transducer device and the concentration of methane can then be determined by GC (Braga et al, 2018;O'Flaherty et al, 1998a). In both cases, the activity is calculated from the slope of the progress line, either relative methane concentration or millilitres of methane.…”

“…Furthermore, addition of transition metals could alleviate sulfide toxicity by precipitating metal sulfides, similar to iron addition (Godoi et al, 2017). Transition metals can also enhance methanogenesis, since some of them are micronutrients for MA (Braga et al, 2018;Fermoso et al, 2008). It is, however, not clear whether supplementation with these transition metals could favour methanogens to an extent that MA can outcompete SRB.…”

Derivation of volatile fatty acids concentration-independent optimum trace elements configuration and elucidation of optimization kinetics of biomethanization processes

“…It is also possible that due to differences in the enzymology of the phases of biomethanization, the different dominant metallo-enzymes (MEs) of the phases may require specific TEs for activation and activity enhancement (Ingram-Smith et al, 2005;Ragsdale and Pierce, 2008). While there is justification for the differences in TEs requirements for different levels of VFA, in practical operation of a biogas digester, a single dose of TEs mixture is often administered (Braga et al, 2018;Mancini et al, 2018). Single dose application of TEs formulations remains the most feasible and practical approach.…”