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Abstract This study evaluates the main effects of including 'non-ideal' bio-physical-chemical corrections in high-solids anaerobic digestion (HS-AD) of the organic fraction of municipal solid waste (OFMSW), at total solid (TS) between 10 and 40%. As a novel approach, a simple 'non-ideal' module, accounting for the effects of ionic strength (I) on the main acid-base equilibriums, was coupled to a HS-AD model, to jointly evaluate the effects of 'non-ideality' and the TS content dynamics on the HS-AD bio-physical-chemistry. 'Non-ideality' influenced the pH, concentration of inhibitors (i.e. NH 3), and liquid-gas transfer (i.e. CO 2), particularly at higher TS (i.e. ≥ 20%). Meanwhile, fitting the experimental data for batch assays at 15% TS showed that HS-AD of OFMSW might be operated at I ≥ 0.5 M. Therefore, all HS-AD simulations should account for 'non-ideal' corrections, when assessing the main inhibitory mechanisms (i.e. NH 3 buildup and acidification) potentially occurring in HS-AD of OFMSW. Graphical abstract Image 1 Highlights • Ionic strength can be higher than 0.5 M in high-solids anaerobic digestion. • Non-ideality strongly affects NH 3 inhibition and CO 2 liquid-gas transfer. • Non-ideal effects on anaerobic digestion are exacerbated at total solids ≥20%. • High-solids simulations jointly require non-ideality and reactor mass/volume dynamics. • Non-ideality is interrelated to NH 3 inhibition parameters and the model structure. [ABSTRACT FROM AUTHOR]

Abstract In this study, mono-digestion of the organic fraction of municipal solid waste (OFMSW) and co-digestion of OFMSW with beech sawdust, simulating green waste, were used to investigate the maximum operational total solid (TS) content in semi-continuous high-solids anaerobic digestion (HS-AD). To alleviate substrate overloading in HS-AD, the effluent mass was relatively reduced compared to the influent mass, extending the mass retention time. To this aim, the reactor mass was daily evaluated, permitting to assess the reactor content removal by biogas production. During mono-digestion of OFMSW, the NH 3 inhibition and the rapid TS removal prevented to maintain HS-AD conditions (i.e. TS ≥ 10%), without exacerbating the risk of reactor acidification. In contrast, the inclusion of sawdust in OFMSW permitted to operate HS-AD up to 30% TS, before acidification occurred. Therefore, including a lignocellulosic substrate in OFMSW can prevent acidification and stabilize HS-AD at very high TS contents (i.e. 20–30%). Graphical abstract Image 1 Highlights • A reduced effluent compared to the influent extended the MRT in HS-AD of OFMSW. • Uncoupling was not sufficient to avoid overload/acidification in HS-AD of OFMSW. • Substrate overload in HS-AD of OFMSW was exacerbated by NH 3 inhibition. • HS-AD overload can be controlled by adding green waste to OFMSW. [ABSTRACT FROM AUTHOR]

Fe(II)-mediated autotrophic denitrification in the presence of copper (Cu), nickel (Ni) and zinc (Zn) with four different microbial cultures was investigated in batch bioassays. In the absence of metals, complete nitrate removal and Fe(II) oxidation were achieved with a Thiobacillus -dominated mixed culture and Pseudogulbenkiania sp. 2002 after 7 d. A nitrate removal of 96 and 91% was observed with a pure culture of T. denitrificans and an activated sludge enrichment, respectively, after 10 d of incubation. Cu, Ni and Zn were then supplemented at an initial concentration of 5, 10, 20 and 40 mg Me/L. A decrease of approximately 50% of the soluble metal concentrations occurred in the first 4 d of denitrification, due to metal precipitation, co-precipitation, sorption onto iron (hydr)oxides, and probably sorption onto biomass. A higher sensitivity to metal toxicity was observed for the microbial pure cultures. Pseudogulbenkiania sp. 2002 was the least tolerant among the biomasses tested, resulting in only 6, 8 and 6% nitrate removal for the highest Cu, Ni and Zn concentrations, respectively. In contrast, the highest nitrate removal efficiency and specific rates were achieved with the Thiobacillus -dominated mixed culture, which better tolerated the presence of metals. Averagely, Cu resulted in the highest inhibition of nitrate removal, followed by Zn and Ni. [ABSTRACT FROM AUTHOR]

The comparative performance of an inverse fluidized bed reactor (IFBR) having high density polyethylene beads as carrier materials for biofilm formation and a continuous stirred tank reactor (CSTR), both maintaining autotrophic denitrification using biogenic sulphur (ADBIOS) in the absence and presence of nickel (Ni2+), was studied. The reactors were compared in terms of NO 3 −-N and NO 2 −-N removal and SO 4 2--S production throughout the study. A simulated wastewater with an inlet NO 3 −-N concentration of 225 mg/L and a decreasing concentration of biogenic sulphur (bio-S) from 1.5 to 0.375 g/L was used. Both reactors were operated at a hydraulic retention time (HRT) of 48 h for 140 days and at an HRT of 42 h for the following 68 days. A more efficient ADBIOS was observed in the CSTR than IFBR throughout the study due to a better mixing of the feed wastewater in the bulk liquid and a higher availability of bio-S to the suspended cells. The NO 3 −-N removal efficiency in the IFBR decreased by approximately 41% when the feed bio-S was reduced to 0.375 g/L, while it remained unaffected in the CSTR. Conversely, the presence of Ni2+ did not significantly affect NO 3 −-N removal in both reactors even at a feed Ni2+ concentration of 120 mg/L. The highest NO 3 −-N removal rates achieved were 86 and 108 mg NO 3 −-N/(L·day) in the IFBR and CSTR, respectively, in the presence of 120 mg/L of feed Ni2+ at an HRT of 42 h. Batch studies conducted with acclimatized biomass showed that the continuous-flow operation mode in both reactors played a major role in helping the autotrophic denitrifiers to tolerate Ni2+ toxicity. Image 1 • Autotrophic denitrification with biogenic S (ADBIOS) was studied in IFBR and CSTR. • The highest removal rates were 86 and 108 mg NO 3 −-N/(L·day) in IFBR and CSTR. • Ni2+ was fed to both reactors on day 91 and gradually increased up to 120 mg/L. • Continuous-flow mode played a crucial role in the tolerance of denitrifiers to Ni2+. • The ADBIOS performance in IFBR was not affected even at 120 mg/L of Ni2+. [ABSTRACT FROM AUTHOR]

The hydrolysis of elemental sulfur (S 0 ) coupled to S 0 -based denitrification and denitritation was investigated in batch bioassays by microbiological and modeling approaches. In the denitrification experiments, the highest obtained NO 3 − -N removal rate was 20.9 mg/l·d. In the experiments with the biomass enriched on NO 2 − , a NO 2 − -N removal rate of 10.7 mg/l·d was achieved even at a NO 2 − -N concentration as high as 240 mg/l. The Helicobacteraceae family was only observed in the biofilm attached onto the chemically-synthesized S 0 particles with a relative abundance up to 37.1%, suggesting it was the hydrolytic biomass capable of S 0 solubilization in the novel surface-based model. S 0 -driven denitrification was modeled as a two-step process in order to explicitly account for the sequential reduction of NO 3 − to NO 2 − and then to N 2 by denitrifying bacteria. [ABSTRACT FROM AUTHOR]

The issue of polycyclic aromatic hydrocarbons (PAHs) is widespread in marine sediments involving ecological systems and human health. Sediment washing (SW) has proven to be the most effective remediation approach for sediments polluted by PAHs, such as phenanthrene (PHE). However, SW still raises waste handling concerns due to a considerable amount of effluents generated downstream. In this context, the biological treatment of a PHE- and ethanol-containing spent SW solution can represent a highly efficient and environmentally-friendly strategy, but its knowledge is still scarce in scientific literature and no studies have so far been conducted in continuous mode. Therefore, a synthetic PHE-polluted SW solution was biologically treated in a 1 L aerated continuous-flow stirred-tank reactor for 129 days by evaluating the effect of different pH values, aeration flowrates and hydraulic retention times as operating parameters over five successive phases. A PHE removal efficiency of up to 75–94% was achieved by an acclimated PHE-degrading consortium mainly composed of Proteobacteria , Bacteroidota and Firmicutes phyla through biodegradation following the adsorption mechanism. PHE biodegradation, mainly occurring via the benzoate route due to the presence of PAH-related-degrading functional genes and a phthalate accumulation up to 46 mg/L, was also accompanied by a reduction of dissolved organic carbon and ammonia nitrogen above 99% in the treated SW solution. [Display omitted] • Spent sediment washing solution was treated in a continuous-flow stirred-tank reactor. • Phenanthrene (PHE) removal was affected by aeration, pH and hydraulic retention time. • Biodegradation and adsorption mechanisms were mainly involved in the removal of PHE. • Proteobacteria , Bacteroidota and Firmicutes were the main PHE-degrading phyla present. • The mixed microbial consortium retained various PHE-related-degrading genes over time. [ABSTRACT FROM AUTHOR]

Soil contamination by pyrene has increased over the years due to human-related activities, urgently demanding for remediation approaches to ensure human and environment safety. Within this frame, phytoremediation has been successfully applied over the years due to its green and cost-effectiveness features. The scope of this review includes the main phytoremediation mechanisms correlated with the removal of pyrene from contaminated soils and sediments to highlight the impact of different parameters and the supplement of additives on the efficiency of the treatment. Soil organic matter (SOM), plant species, aging time, environmental parameters (pH, soil oxygenation, and temperature) and bioavailability are among the main parameters affecting pyrene removal through phytoremediation. Phytoextraction only accounts for a small part of the entire phytoremediation process, but the addition of surfactants and chelating agents in planted soils could increase pyrene accumulation in plant tissues by 20% as a consequence of the increased pyrene bioavailability. Rhizodegradation is the main phytoremediation mechanism involved due to the activity of bacteria capable of degrading pyrene in the root area. Inoculated-planted soil treatments have the potential to decrease pyrene accumulation in shoots and roots by approximately 30 and 40%, respectively, further stimulating the proliferation of pyrene-degrading bacteria in the rhizosphere. Plant-fungi symbiotic association results in an enhanced accumulation of pyrene in shoots and roots of plants as well as a higher biodegradation. Finally, pyrene removal from soil can be improved in the presence of amendments, such as natural non-ionic surfactants, biochar, and bacterial mixtures. [Display omitted] • The main parameters affecting pyrene removal through phytoremediation are reviewed. • Soil organic matter and pyrene bioavailability strongly govern pyrene fate in soils. • Higher aging times reduce pyrene bioavailability and hinder pyrene biodegradation. • Multiple plant species result in a higher number of pyrene degraders in rhizosphere. • Additives can affect pyrene uptake by plants as well as biodegradation. [ABSTRACT FROM AUTHOR]