Dynamic Mathematical Modelling of the Removal of Hydrophilic VOCs by Biotrickling Filters

A mathematical model for the simulation of the removal of hydrophilic compounds using biotrickling filtration was developed. The model takes into account that biotrickling filters operate by using an intermittent spraying pattern. During spraying periods, a mobile liquid phase was considered, while during non-spraying periods, a stagnant liquid phase was considered. The model was calibrated and validated with data from laboratory- and industrial-scale biotrickling filters. The laboratory experiments exhibited peaks of pollutants in the outlet of the biotrickling filter during spraying periods, while during non-spraying periods, near complete removal of the pollutant was achieved. The gaseous outlet emissions in the industrial biotrickling filter showed a buffered pattern; no peaks associated with spraying or with instantaneous variations of the flow rate or inlet emissions were observed. The model, which includes the prediction of the dissolved carbon in the water tank, has been proven as a very useful tool in identifying the governing processes of biotrickling filtration

Simultaneous removal of ammonium from landfill leachate and hydrogen sulfide from biogas using a novel two-stage oxic-anoxic system

Anoxic biodesulfurization has been achieved in several bioreactor systems that have shown robustness and high elimination capacities (ECs). However, the high operating costs of this technology, which are mainly caused by the high requirements of nitrite or nitrate, make its full-scale application difficult. In the present study, the use of biologically produced nitrate/nitrite by nitrification of two different ammonium substrates, namely synthetic medium and landfill leachate, is proposed as a novel alternative. The results demonstrate the feasibility of using both ammonium substrates as nutrient solutions. A maximum elemental sulfur production of 95 +/- 1% and a maximum H2S EC of 141.18 g S-H2S m(-3) h(-1) (RE = 95.0%) was obtained using landfill leachate as the ammonium source. Next Generation Sequencing (NGS) analysis of the microbial community revealed that the most common genera present in the desulfurizing bioreactor were Sulfurimonas (91.8-50.9%) followed by Thauera (1.1-24.2%) and Lentimicrobium (2.0-9.7%). (C) 2020 Elsevier B.V. All rights reserved

Effect of two different intermediate landfill leachates on the ammonium oxidation rate of non-adapted and adapted nitrifying biomass

A widely employed approach to minimize the detrimental effect of landfill leachates (LL) on nitrifying biomass is to adapt it to these contaminated effluents prior to use. In the study reported here the impact of different intermediate landfill leachates (intermediate 1 (ILL1) and intermediate 2 (ILL2)) and synthetic medium (SM) on the nitritation rates of non-adapted and adapted nitrifying biomass were evaluated and modeled. The models, based on previously reported models (Haldane, Edwards and Aiba), considered the effect of three different heavy metals (Cu, Ni and Zn) present in both landfill leachates. The proposed models fitted well with the different biomasses. The highest specific substrate oxidation rate (q(s)) of the present study (41.85 +/- 1.09 mg N-NH4+ g TSS-1 h(-1)) was obtained by the non-adapted biomass using SM. The non-adapted biomass was characterized by similar to 5- and similar to 28-fold higher nitritation rates on using the different ammonium sources tested (SM, ILL1 and ILL2) when compared to the other biomasses adapted to ILL1 (similar to 9 mg N-NH4+ g TSS-1 h(-1)) and ILL2 (similar to 1.3 mg N-NH4+ g TSS-1 h(-1)), respectively. The calculated inhibition constants indicate that the inhibitory effect of the heavy metals followed the order Ni>Zn>Cu. The results reported here bring into question the commonly accepted idea that an adaptation period of the biomass is required to treat landfill leachate

Hydrogen sulfide removal from biogas and sulfur production by autotrophic denitrification in a gas-lift bioreactor

Biogas biodesulfurization has been successfully performed in biotrickling filters (BTFs). Nevertheless, elemental sulfur (S-0) generation and accumulation in the packed bed cause an increase in operating costs restricting its application. This drawback could be avoided using a gas-lift bioreactor as proposed in the present work, which allows recovery and reuse of the generated S-0. The effect of governing operational parameters [nitrite concentration, nitrogen/sulfur (N/S) molar ratio, hydraulic residence time (HRT), pH, inlet load (IL), and gas residence time (GRT)] was studied. Results showed that no inhibition by nitrite was found at concentrations up to 760 mg N-NO2- L-1. H2S removal efficiencies (REs) over 95% were obtained under ILs over 55 g S-H2S m(-3) h(-1) when N/S molar ratios of 1.1 mol mol(-1) or above were used. A HRT of 36 h and a pH of 7.8 +/- 0.05 were found to be optimal. The maximum S-0 production (99%) was obtained under an IL of 180 g S-H2S m(-3) h(-1) using a N/S molar ratio of 1.1 (RE = 98.1 +/- 0.5%). A maximum elimination capacity of 194.2 +/- 4.2 g S-H2S m(-3) h(-1) (RE = 83.9%) was obtained under a GRT of 41 s. Therefore, gas-lift biorcactors stand as a successful and feasible alternative to BTFs to accomplish the anoxic biodesulfurization

Anoxic biogas biodesulfurization promoting elemental sulfur production in a Continuous Stirred Tank Bioreactor

Biological desulfurization of biogas has been extensively studied using biotrickling filters (BTFs). However, the accumulation of elemental sulfur (S) on the packing material limits the use of this technology. To overcome this issue, the use of a continuous stirred tank bioreactor (CSTBR) under anoxic conditions for biogas desulfurization and S production is proposed in the present study. The effect of the main parameters (stirring speed, N/S molar ratio, hydraulic residence time (HRT) and gas residence time (GRT)) on the bioreactor performance was studied. Under an inlet load (IL) of 100 g S-H2S m(-3) h(-1) and a GRT of 119 s, the CSTBR optimal operating conditions were 60 rpm, N/S molar ratio of 1.1 and a HRT of 42 h, in which a removal efficiency (RE) and S production of 98.6 +/- 0.4 % and 88 % were obtained, respectively. Under a GRT of 41 s and an IL of 232 g S-H2S m(-3) h(-1) the maximum elimination capacity (EC) of 166.0 +/- 7.2 g S-H2S m(-3) h(-1) (RE = 71.7 +/- 3.1 %) was obtained. A proportional-integral feedback control strategy was successfully applied to the bioreactor operated under a stepped variable IL

Sand dune survey of Great Britain Site report no. 85; Dawlish Warren Dunes, 1990

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