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Abstract

Hydrogen sulfide removal from biogas was studied under anoxic conditions in a pilot-scale biotrickling filter operated under counter- and co-current gas-liquid flow patterns. The best performance was found under counter-current conditions (maximum elimination capacity of 140 gS m−3h−1). Nevertheless, switching conditions between co- and counter-current flow lead to a favorable redistribution of biomass and elemental sulfur along the bed height. Moreover, elemental sulfur was oxidized to sulfate when the feeding biogas was disconnected and the supply of nitrate (electron acceptor) was maintained. Removal of elemental sulfur was important to prevent clogging in the packed bed and, thereby, to increase the lifespan of the packed bed between maintenance episodes. The larger elemental sulfur removal rate during shutdowns was 59.1 gS m−3h−1. Tag-encoded FLX amplicon pyrosequencing was used to study the diversity of bacteria under co-current flow pattern with liquid recirculation and counter-current mode with a single-pass flow of the liquid phase. The main desulfurizing bacteria were Sedimenticola while significant role of heterotrophic, opportunistic species was envisaged. Remarkable differences between communities were found when a single-pass flow of industrial water was fed to the biotrickling filter.
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... However, all had H 2 S removal efficiencies over 80% for inlet concentrations ranging from 1200 to 6000 ppm. The duration of the experiments (indicated by the size of the circles in Fig. 5) was higher, from 576 h [39] to 200 days [40]. That is, the tests were performed and the data were collected in higher periods, but the removal of hydrogen sulfide was observed in the first stages, as will be discussed further. ...
... Especially the latter has tested a two-stage system, the first aerobic to treat landfill leachate and the second an anoxic bioreactor to treat biogas [43]. Fig. 5 has four studies with full-scale biogas wastewater treatment plants [39,40,44,45]. The paper from Pirolli et al. [40] reports a 43 L prototype installed in the field to treat the biogas from a UASB reactor from a swine farm. ...
... Almenglo and others [39] tested a pilot-scale anoxic BTF with biogas from the anaerobic digestion of wastewater (4000-4800 ppm v H 2 S) with polyurethane foam cubes as packing material. They assessed the counter-current and co-current modes and different times of experimentation. ...
Article
Desulfurization is a critical process for biogas upgrading to biomethane, because hydrogen sulfide is toxic and corrosive. In this paper, we conduct a systematic review to check the most recent studies on desulfurization technologies and find trends, potentials, and limitations of each technique. The information of 51 articles published since 2015 was extracted, highlighting the maximum H2S removal efficiency, the highest inlet H2S concentration studied, and the duration of the experiment. Only 23 papers studied raw biogas, and just 10 reported full-scale tests. Other researchers performed their studies with commercial gases and laboratory or bench scales. In addition, it became clear that tests were performed in different conditions, which was an obstacle to comparing them in the same data visualization. However, it was still possible to get insights, and overall the highest efficiencies were observed in experiments with lower H2S concentrations. About 92% of the articles of this set report H2S removal efficiencies over 80%. The following tests stand out: a trickling filter system, biodesulfurization and bioscrubbing processes, a photocatalytic desulfurizer, and micro-aeration tests. Therefore, the present study has an overview of the most recent studies. After this process, it seems relevant to sort the papers by test scale and gas type in future studies.
... Among the research mentioned (Table 2) are those describing biogas anoxic desulphurisation (Table 2), in which parameters of BTF efficiency have been widely described, but their microbiological study is scarce [18]. Anoxic H 2 S biofiltration studies are very recent and most refer to the analysis of the gene encoding 16S rRNA from samples of packing material taken at different heights of the BTF [32,35,42,44]. However, there are two types of samples to be considered in the study of microbiological changes occurring in a BTF: (1) the support material that is inside the BTF bed, where the bacterial biofilms to be used in the bioremediation are formed, as previously described ( Figure 1B); and (2) the bacterial culture contained in the bioreactor of the BTF, the analysis of which we also propose, since it influences changes in the BTF ( Figure 1A). ...
... Regarding this last point, there are disadvantages in laboratory-scale experimentation as when taking samples from the support material it is necessary to open the sample ports ( Figure 1C) interrupting the anaerobiosis affecting the BTF's performance and requiring a re-acclimatization that must be standardized for each experiment, according to the AD biogas composition. Most of the studies described (Table 2) have analysed changes in the BTF microbial community through the DNA extraction from the bacterial resuspension obtained from the packing material, the subsequent amplification of the gene encoding 16S rRNA, and later analysis by denaturing gradient gel electrophoresis (DGGE) [32,42,44] or by amplifying sequences and making phylogenetic analysis [35]. ...
... This technique was the first of the so-called next-generation sequencing, implemented in 2005 [65]. This technique allows parallel sequencing of many different fragments at the same time and is ideal for obtaining DNA sequences of all the microorganisms in a biomass sample from a BTF, without the need for a previous separation in a gel or the requirement to isolate the strains [35]. ...
Article
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The agriculture and livestock industry generate waste used in anaerobic digestion to produce biogas containing methane (CH4), useful in the generation of electricity and heat. However, although biogas is mainly composed of CH4 (~65%) and CO2 (~34%), among the 1% of other compounds present is hydrogen sulphide (H2S) which deteriorates engines and power generation fuel cells that use biogas, generating a foul smell and contaminating the environment. As a solution to this, anoxic biofiltration, specifically with biotrickling filters (BTFs), stands out in terms of the elimination of H2S as it is cost-effective, efficient, and more environmentally friendly than chemical solutions. Research on the topic is uneven in terms of presenting performance markers, underestimating many microbiological indicators. Research from the last decade was analyzed (2010–2020), demonstrating that only 56% of the reviewed publications did not report microbiological analysis related to sulphur oxidising bacteria (SOB), the most important microbial group in desulphurisation BTFs. This exposes fundamental deficiencies within this type of research and difficulties in comparing performance between research works. In this review, traditional and microbiological performance markers of anoxic biofiltration to remove H2S are described. Additionally, an analysis to assess the efficiency of anoxic BTFs for biogas desulphurisation is proposed in order to have a complete and uniform assessment for research in this field.
... The anoxic desulfurization of biogas has commonly been carried out in biotrickling filters (BTFs) and this approach is robust and provides high removal efficiencies Cano et al., 2019). BTFs have mainly been operated at high N/S molar ratios to produce sulfate as the main oxidation product to avoid the problems caused by the accumulation of elemental sulfur on the packing bed, which forces periodical maintenance to be carried out (Almenglo et al., 2016a;Qiu and Deshusses, 2017). Despite the fact that sulfur accumulation can be slowed by working at high N/S molar ratios (Almenglo et al., 2016b), sulfate generation is undesirable because it can be reduced again to H 2 S under anaerobic conditions (Celis-García et al., 2008). ...
... Moreover, the nitrification of landfill leachates has been widely reported (Capodici et al., 2019;Kim et al., 2006;Vilar et al., 2010). Despite the fact that the microbial communities of the biofilm present in anoxic BTFs have been widely reported in the literature (Almenglo et al., 2016a;Brito et al., 2018;Valle et al., 2018), their composition has never been reported in SBBs. In contrast to BTFs, the characteristics of these bioreactors, in which biomass is suspended, are believed to favor the predominance of very few species and it may be of interest to characterize these further (Davey and O'toole, 2000). ...
... Anoxic BTFs are capable of working at N/S molar ratios as low as 0.4 on using NO 3 − as the main electron acceptor without affecting the RE (Cano et al., 2019;Fernández et al., 2014). However, the system cannot be operated for prolonged periods due to clogging caused by the generation of elemental sulfur in the packed bed (Almenglo et al., 2016a). The elemental sulfur production was also measured during the experiment. ...
Article
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%).
... However, the performance of other anoxic BTFs was affected at higher EBRTs than those tested in the present study, probably due to the lower height/diameter ratios compared to Cano et al. (2019). For example, Almenglo et al. (2016b) obtained a RE drop from 99 % to 80 % when the EBRT was decreased from 601 to 137 s. Also, the H 2 S RE was greatly affected by EBRT in another anoxic BTF when EBRT was diminished from 121 s (RE = 98 %) to 30 s (RE = 47 %) (Montebello et al., 2012). ...
... Similar or better results were obtained in aerobic or anoxic bioreactors removing sulfide from wastewaters (Krishnakumar et al., 2005;Mahmood et al., 2007;Fajardo et al., 2012;Jing et al., 2010). Also, the EC values obtained in the present study exceed the performance of several BTFs at comparable EBRTs (Brito et al., 2017;Almenglo et al., 2016b;Fernández et al., 2013;Zeng et al., 2018). Despite there being some BTFs that have higher ECs (Merchuk, 1991;Manconi et al., 2007), the accumulation of elemental sulfur in the packing material would limit its application. ...
Article
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.
... Qiu and Deshusses (2017) tried to set the H 2 S/O 2 ratio to no smaller than 1:2, which avoided biogas dilution. In recent years, there have been many studies that have utilized nitrate (NO 3 − ) as an electron acceptor to replace O 2 , because nitrate causes no biogas dilution and the risk of explosion is reduced (Almenglo et al., 2016a). In some cases, the anoxic BTFs system does have some advantages compared to aerobic process. ...
... The N:S ratio fed ranged from 0.96 to 1.25 mol-N mol-S −1 . Under this conditions, the sulfate selectivity, which is defined as the percentage of sulfate produced with respect to the H 2 S removed, ranged from 47 ± 0.05-57 ± 0.06 %, respectively (Almenglo et al., 2016a). Hence, low N/S ratios in the anoxic process, which are similar to the O 2 /H 2 S ratios in the aerobic process, resulted in increased sulfur production rates, while high N/S ratios led to high sulfate production. ...
Article
The presence of hydrogen sulfide (H2S) in biogas negatively affects human health and corrodes metal. Therefore, the removal of H2S from biogas before using is an essential requirement in many cases. Recently, biotrickling filters (BTFs) have been widely applied to the treatment of H2S on both laboratory and industrial scales. However, BTFs method also has some drawbacks such as low mass transfer efficiency, clogging the bed filter due to further elemental sulfur (S) excess accumulation, and biogas dilution. This paper reviews the recent development of aerobic BTF systems and solutions for those limitations during the H2S oxidation process in biogas. In addition, the factors affecting H2S removal efficiency, including sulfur-oxidizing bacteria, biofilm, packing material, pH, dissolved oxygen (DO), empty bed retention time (EBRT), ingredients of nutrients for the growth of bacteria, trickling liquid and gas velocity, are also discussed. Finally, the current strength of research in the field of H2S removal in biogas using BTF and its future prospects are also suggested. Some of highest elimination capacity (EC) of 78.57 g H2S/m³h, 144 g H2S/m³h, 228.6 g H2S/m³h were obtained from previous experiments.
... Surprisingly, putative strains of sulfur oxidizers were significantly associated with non-filamentous Beggiatoaceae. The sulfur-oxidizers were three ASVs of Omnitrophia (Verrucomicrobiota), members of which are thought to oxidize sulfur with iron as an electron acceptor [137], one low abundance ASV of the SAR 324 clade [138], two unclassified Gammaproteobacteria, two Thiotrichaceae Gammaproteobacteria [139] and one highly enriched ASV of an unknown family of the Gammaproteobacteria Incertae Sedis [140], which was also very abundant in the Station 23002 sample (1200 vs. <10). In addition, two ASVs of the Alphaproteobacteria clades Rhizobiales [141] and Rhodobacterales could represent organoheterotrophic sulfur-oxidizers [142]. ...
Article
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Due to their lithotrophic metabolisms, morphological complexity and conspicuous appearance, members of the Beggiatoaceae have been extensively studied for more than 100 years. These bacteria are known to be primarily sulfur-oxidizing autotrophs that commonly occur in dense mats at redox interfaces. Their large size and the presence of a mucous sheath allows these cells to serve as sites of attachment for communities of other microorganisms. But little is known about their individual niche preferences and attached microbiomes, particularly in marine environments, due to a paucity of cultivars and their prevalence in habitats that are difficult to access and study. Therefore, in this study, we compare Beggiatoaceae strain composition, community composition, and geochemical profiles collected from sulfidic sediments at four marine stations off the coast of Namibia. To elucidate community members that were directly attached and enriched in both filamentous Beggiatoaceae, namely Ca . Marithioploca spp. and Ca . Maribeggiatoa spp., as well as non-filamentous Beggiatoaceae, Ca . Thiomargarita spp., the Beggiatoaceae were pooled by morphotype for community analysis. The Beggiatoaceae samples collected from a highly sulfidic site were enriched in strains of sulfur-oxidizing Campylobacterota, that may promote a more hospitable setting for the Beggiatoaceae, which are known to have a lower tolerance for high sulfide to oxygen ratios. We found just a few host-specific associations with the motile filamentous morphotypes. Conversely, we detected 123 host specific enrichments with non-motile chain forming Beggiatoaceae. Potential metabolisms of the enriched strains include fermentation of host sheath material, syntrophic exchange of H 2 and acetate, inorganic sulfur metabolism, and nitrite oxidation. Surprisingly, we did not detect any enrichments of anaerobic ammonium oxidizing bacteria as previously suggested and postulate that less well-studied anaerobic ammonium oxidation pathways may be occurring instead.
... Vienas iš būdų pašalinti H2S iš biodujų -valymas anoksinėmis sąlygomis naudojant nuotekas (Zeng et al., 2018). Anoksinis metodas naudoja NOx, kurie yra nuotekose, kaip elektronų akceptorių, o H2S oksiduojamas į elementinę sierą arba sulfatus (Almenglo et al., 2016). Reakcijos sąlygos reikalauja nedaug energijos ir tuo pačiu galima išvalyti biodujas ir denitrifikuoti nuotekas, panaudojant "atliekų tvarkymo atliekomis" principą (Li et al., 2009): (2019) teigia, kad jeigu biodujos yra išvalomos ir konvertuojamos į biometaną (CH4 koncentracija -98 %), tai biometanas turi tas pačias savybes kaip ir gamtinės dujos. ...
Article
Hydrogen sulphide (H2S) in biogas is a problematic impurity that can inhibit methanogenesis and induce equipment corrosion. This review discusses technologies to remove H2S during anaerobic digestion (AD) via: input control, process regulation, and post-treatment. Post-treatment technologies (e.g. biotrickling filters and scrubbers) are mature with >95% removal efficiency but they do not mitigate H2S toxicity to methanogens within the AD. Substrate pretreatment (i.e. chemical addition) reduces sulphur input into AD via sulphur precipitation. However, available results showed <75% of H2S removal efficiency. Microaeration to regulate the digester condition is a promising alternative for controlling H2S formation. Microaeration, or the use of oxygen to regulate the redox potential at around −250 mV, has been demonstrated at pilot and full scale with >95% H2S reduction, stable methane production, and low operational cost. Further adaptation of microaeration relies on a comprehensive design framework and exchange operational experience for eliminating the risk of over-aeration.
Article
This study showed the impact of an anoxic desulfurization process on the CH4 and CO2 content of the purified biogas. The desulfurization system was implemented in an anoxic bioscrubber, which supported H2S removal efficiencies ranging from 92 ± 8 to 97 ± 6% for H2S loading rates between 28.3 and 37.8 g S mliquid⁻³h⁻¹. CO2 absorption during the desulfurization process mediated a slight reduction in the CO2 concentration from 39.5% in the raw biogas to 36.5–38.2% in the purified biogas. Such reduction in the CO2 concentration was proportional to the increase of CH4 concentration recorded, passing from 60.0% in the raw biogas to 61.7–63.5% in the purified biogas. Bacterial community characterization by means of 16S rRNA high-throughput sequencing revealed the consistent presence of both methanotrophs (Methylibium, Methylomonas and Methylosinus genera) and methanol-oxidizing denitrifiers (Simplicispira and Methyloversatilis genera), which suggested that methane oxidation indeed occurred. The quantification of a potential CH4 uptake in the desulfurization process was hindered by the CO2 absorption observed, however, strategies for quantifying biological CH4 consumption in anoxic desulfurization systems are proposed and discussed, based on the results herein obtained.
Article
A two-stage bioreactor operated under anoxic denitrifying conditions was evaluated for desulfurization of synthetic biogas laden with H2S concentrations between 2500 and 10,000 ppmv. H2S removal efficiencies higher than 95% were achieved for H2S loads ranging from 16.2 to 51.9 gS mliquid⁻³h⁻¹. Average H2S oxidation performance (fraction of S-SO4²⁻ produced per gram of S-H2S absorbed) ranged between 8.2 ± 1.2 and 18.7 ± 5.3% under continuous liquid operation. Nitrogen mass balance showed that only 2–6% of the N-NO3⁻ consumed was directed to biomass growth and the rest was directed to denitrification. Significant changes in the bacterial community composition did not hinder the H2S removal efficiency. The bioreactor configuration proposed avoided clogging issues due to elemental sulfur accumulation as commonly occurs in packed bed bioreactors devoted to H2S-rich biogas desulfurization.
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The lack of tax incentives for biomethane use requires the optimization of both biogas production and upgrading in order to allow the full exploitation of this renewable energy source. The large number of biomethane contaminants present in biogas (CO2, H2S, H2O, N2, O2, methyl siloxanes, halocarbons) has resulted in complex sequences of upgrading processes based on conventional physical/chemical technologies capable of providing CH4 purities of 88–98 % and H2S, halocarbons and methyl siloxane removals >99 %. Unfortunately, the high consumption of energy and chemicals limits nowadays the environmental and economic sustainability of conventional biogas upgrading technologies. In this context, biotechnologies can offer a low cost and environmentally friendly alternative to physical/chemical biogas upgrading. Thus, biotechnologies such as H2-based chemoautrophic CO2 bioconversion to CH4, microalgae-based CO2 fixation, enzymatic CO2 dissolution, fermentative CO2 reduction and digestion with in situ CO2 desorption have consistently shown CO2 removals of 80–100 % and CH4 purities of 88–100 %, while allowing the conversion of CO2 into valuable bio-products and even a simultaneous H2S removal. Likewise, H2S removals >99 % are typically reported in aerobic and anoxic biotrickling filters, algal-bacterial photobioreactors and digesters under microaerophilic conditions. Even, methyl siloxanes and halocarbons are potentially subject to aerobic and anaerobic biodegradation. However, despite these promising results, most biotechnologies still require further optimization and scale-up in order to compete with their physical/chemical counterparts. This review critically presents and discusses the state of the art of biogas upgrading technologies with special emphasis on biotechnologies for CO2, H2S, siloxane and halocarbon removal.
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We report the closed genome sequence of Sedimenticola thiotaurini strain SIP-G1 and an unnamed plasmid obtained through PacBio sequencing with 100% consensus concordance. The genome contained several distinctive features not found in other published Sedimenticola genomes, including a complete nitrogen fixation pathway, a complete ethanolamine degradation pathway, and an alkane-1-monooxygenase. FOOTNOTES Address correspondence to Beverly E. Flood, beflood{at}umn.edu. ↵* Present address: Daniel S. Jones, University of Minnesota, BioTechnology Institute, St. Paul, Minnesota, USA. Citation Flood BE, Jones DS, Bailey JV. 2015. Complete genome sequence of Sedimenticola thiotaurini strain SIP-G1, a polyphosphate- and polyhydroxyalkanoate-accumulating sulfur-oxidizing gammaproteobacterium isolated from salt marsh sediments. Genome Announc 3(3):e00671-15. doi:10.1128/genomeA.00671-15. Received 18 May 2015. Accepted 19 May 2015. Published 18 June 2015. Copyright © 2015 Flood et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported license.
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A marine facultative anaerobe, strain SIP-G1T, was isolated from salt marsh sediments, Falmouth, MA, USA. Phylogenic analyses of its 16S rRNA gene indicated that it belongs to an unclassified clade of Gammaproteobacteria that includes numerous sulfide-oxidizing bacteria that are endosymbionts of marine invertebrates endemic to sulfidic habitats. SIP-G1T is a member of the genus Sedimenticola, of which there is one previously-described isolate, Sedimenticola selenatireducens AK4OH1T. S. selenatireducens AK4OH1T was obtained for further characterization and comparison with SIP-G1T. Our study found that both strains are capable of coupling the oxidation of thiosulfate and sulfide with autotrophic growth and they produce sulfur granules as metabolic intermediates. They have varying degrees of O2 sensitivity, but when provided amino acids or peptides as a source of carbon, they appear more tolerant of O2 and exhibit concomitant production of intracellular elemental sulfur granules. The organic substrate preferences and limitations of these two organisms suggest that they possess an oxygen-sensitive carbon fixation pathway(s). Organic acids may be used to produce NADPH through the TCA cycle and are used in the formation of polyhydroxyalkanoates. Cell wall-deficient morphotypes appeared when organics (esp. acetate) are present in excess and reduced sulfur is absent. DNA-DNA hybridization (~47%) and phenotypic characterization indicate that the strain SIP-G1 is a separate species within the Sedimenticola, for which the name Sedimenticola thiotaurini sp. nov. is proposed. The type strain is SIP-G1T (ATCC = BAA-2640T; DSMZ = 28581T). Our results also justify an emended description of the genus Sedimenticola and of S. selenatireducens.
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Globally, denitrification is commonly employed in biological nitrogen removal processes to enhance water quality. However, substantial knowledge gaps remain concerning the overall community structure, population dynamics and metabolism of different organic carbon sources. This systematic review provides a summary of current findings pertaining to the microbial ecology of denitrification in biological wastewater treatment processes. DNA fingerprinting-based analysis has revealed a high level of microbial diversity in denitrification reactors and highlighted the impacts of carbon sources in determining overall denitrifying community composition. Stable isotope probing, fluorescence in situ hybridization, microarrays and meta-omics further link community structure with function by identifying the functional populations and their gene regulatory patterns at the transcriptional and translational levels. This review stresses the need to integrate microbial ecology information into conventional denitrification design and operation at full-scale. Some emerging questions, from physiological mechanisms to practical solutions, for example, eliminating nitrous oxide emissions and supplementing more sustainable carbon sources than methanol, are also discussed. A combination of high-throughput approaches is next in line for thorough assessment of wastewater denitrifying community structure and function. Though denitrification is used as an example here, this synergy between microbial ecology and process engineering is applicable to other biological wastewater treatment processes.