Diversity and dynamics of bacterial communities in the drinking water distribution network of a mid-sized city in Brazil.

This study assessed the bacterial community composition of a drinking water system (DWS) serving a mid-sized city (120,000 inhabitants) in Brazil. Water samples, including raw and treated water, were collected at seven points throughout the DWS. DNA was extracted and analysed using high-throughput sequencing (Ion Torrent). Free chlorine and turbidity were measured in situ. Results showed that the highest relative abundance of 16S rRNA genes was from phyla Proteobacteria, followed by Bacteroidetes and Actinobacteria. The next most abundant phylum was Cyanobacteria, represented by Arthronema, Calothrix, and Synechococcus. An interesting observation was that the DNA-based analysis suggested a bacterial community change in the distribution network, with treated reservoir water being very different from the network samples. This suggests active microbiology within the distribution network and a tendency for bacterial diversity to decrease after chlorine disinfection but increase after pipeline distribution. In raw water, a predominance of Proteobacteria was observed with reduced Cyanobacteria, showing a negative correlation. In treated water, Proteobacteria were negatively correlated with Bacteroidetes. Finally, 16S rRNA genes from Firmicutes (especially Staphylococcus) had a high abundance in the chlorinated water, which may indicate the phylum's resistance to chlorine residuals. Opportunistic pathogens, e.g., Mycobacteria, Legionella, and Staphylococcus, were also observed.

Nitrogen removal from food waste digestate using partial nitritation-anammox process: Effect of different aeration strategies on performance and microbial community dynamics.

The feasibility of employing anammox and partial nitritation-anammox (PN/A) processes for nitrogen removal from food waste (FW) digestate was investigated in this study. The effects of different aeration strategies on the microbial community were also investigated. To achieve this, after anammox enrichment (Phase 1), the reactor was fed with digestate supplemented with nitrite (Phase 2), and subsequently different aeration strategies were evaluated to establish PN/A. Aeration strategies with high anoxic periods (30 and 45 min) in relation to aerobic periods (15 min) coupled with low air flow rates (0.026 L  min-1. Lreator-1) were found to be better for establishing PN/A, as coefficients of produced nitrate/removed ammonium were closer to those reported previously (0.17 and 0.21). Aeration conditions considerably altered the microbial community. Candidatus Brocadia was replaced by Candidatus Jettenia, after the first aeration strategies. These results support the feasibility of FW digestate treatment using anammox and PN/A processes and provide a better understanding of the effect of aeration on microbial dynamics in PN/A reactors.

Impact of inocula and operating conditions on the microbial community structure of two anammox reactors.

The microbial community structure of the biomass selected in two distinctly inoculated anaerobic oxidation of ammonium (anammox) reactors was investigated and compared with the help of data obtained from 454-pyrosequencing analyses. The anammox reactors were operated for 550 days and seeded with different sludges: sediment from a constructed wetland (reactor I) and biomass from an aerated lagoon part of the oil-refinery wastewater treatment plant (reactor II). The anammox diversity in the inocula was evaluated by 16S rRNA gene-cloning analysis. The diversity of anammox bacteria was greater in the sludge from the oil-refinery (three of the five known genera of anammox were detected) than in the wetland sludge, in which only Candidatus Brocadia was observed. Pyrosequencing analysis demonstrated that the community enriched in both reactors had differing compositions despite the nearly similar operational conditions applied. The dominant phyla detected in both reactors were Proteobacteria, Chloroflexi, Planctomycetes, and Acidobacteria. The phylum Bacteroidetes, which is frequently observed in anammox reactors, was not detected. However, Acidobacteria and GN04 phyla were observed for the first time, suggesting their importance for this process. Our results suggest that, under similar operational conditions, anammox populations (Ca. Brocadia sinica and Ca. Brocadia sp. 40) were selected in both reactors despite the differences between the two initial inocula. Taken together, these results indicated that the type of inoculum and the culture conditions are key determinants of the general microbial composition of the biomass produced in the reactors. Operational conditions alone might play an important role in anammox selection.

Antibiotic resistance profile of wastewater treatment plants in Brazil reveals different patterns of resistance and multi resistant bacteria in final effluents.

Wastewater treatment plants (WWTPs) are recognized as important sources of Antibiotic Resistant Bacteria (ARBs) and Antibiotic Resistant Genes (ARGs), and might play a role in the removal and dissemination of antimicrobial resistance (AMR) in the environment. Detailed information about AMR removal by the different treatment technologies commonly applied in urban WWTPs is needed. This study investigated the occurrence, removal and characterization of ARBs in WWTPs employing different technologies: WWTP-A (conventional activated sludge-CAS), WWTP-B (UASB reactor followed by biological trickling filter) and WWTP-C (modified activated sludge followed by UV disinfection-MAS/UV). Samples of raw sewage (RI) and treated effluent (TE) were collected and, through the cultivation-based method using 11 antibiotics, the antibiotic resistance profiles were characterized in a one-year period. MAS was effective in reducing ARB counts (2 to 3 log units), compared to CAS (1 log unit) and UASB/BTF (0.5 log unit). The composition of cultivable ARB differed between RI and TE samples. Escherichia was predominant in RI (56/118); whilst in TE Escherichia (31/118) was followed by Bacillus (22/118), Shigella (14/118) and Enterococcus (14/118). Most of the isolates identified (370/394) harboured at least two ARGs and in over 80 % of the isolates, 4 or more ARG (int1, blaTEM, TetA, sul1 and qnrB) were detected. A reduction in the resistance prevalence was observed in effluents after CAS and MAS processes; whilst a slight increase was observed in treated effluents from UASB/BTF and after UV disinfection stage. The multi-drug resistance (MDR) phenotype was attributed to 84.3 % of the isolates from RI (27/32) and 63.6 % from TE (21/33) samples and 52.3 % of the isolates (34/65) were resistant to carbapenems (imipenem, meropenem, ertapenem). The results indicate that treated effluents are still a source for MDR bacteria and ARGs dissemination to aquatic environments. The importance of biological sewage treatment was reinforced by the significant reductions in ARB counts observed. However, implementation of additional treatments is needed to mitigate MDR bacteria release into the environment.

Quantification of SARS-CoV-2 in wastewater samples from hospitals treating COVID-19 patients during the first wave of the pandemic in Brazil.

The COVID-19 pandemic has caused a global health crisis, and wastewater-based epidemiology (WBE) has emerged as an important tool to assist public health decision-making. Recent studies have shown that the SARS-CoV-2 RNA concentration in wastewater samples is a reliable indicator of the severity of the pandemic for large populations. However, few studies have established a strong correlation between the number of infected people and the viral concentration in wastewater due to variations in viral shedding over time, viral decay, infiltration, and inflow. Herein we present the relationship between the number of COVID-19-positive patients and the viral concentration in wastewater samples from three different hospitals (A, B, and C) in the city of Belo Horizonte, Minas Gerais, Brazil. A positive and strong correlation between wastewater SARS-CoV-2 concentration and the number of confirmed cases was observed for Hospital B for both regions of the N gene (R = 0.89 and 0.77 for N1 and N2, respectively), while samples from Hospitals A and C showed low and moderate correlations, respectively. Even though the effects of viral decay and infiltration were minimized in our study, the variability of viral shedding throughout the infection period and feces dilution due to water usage for different activities in the hospitals could have affected the viral concentrations. These effects were prominent in Hospital A, which had the smallest sewershed population size, and where no correlation between the number of defecations from COVID-19 patients and viral concentration in wastewater was observed. Although we could not determine trends in the number of infected patients through SARS-CoV-2 concentrations in hospitals' wastewater samples, our results suggest that wastewater monitoring can be efficient for the detection of infected individuals at a local level, complementing clinical data.

Aeration strategies and temperature effects on the partial nitritation/anammox process for nitrogen removal: performance and bacterial community assessment.

The partial nitritation/anammox process (PN/A) could be a promising alternative for nitrogen removal from high-strength wastewater. There is, however, a lack of information about suitable aeration and temperature for PN/A in single-stage reactors for high-strength wastewater, such as food waste (FW) digestate treatment. To this end, a laboratory-scale (10 L) partial nitritation/anammox sequencing batch reactor was operated for more than 230 days under four different intermittent aeration strategies and temperature variations (35°C and ambient temperature - 26-29°C) to investigate the feasibility of nitrogen removal from real FW digestate. High ammonium (NH4+-N) and total nitrogen (TN) removal median efficiencies of 81 and 63%, respectively (corresponding to median NH4+-N and TN loads removed of 76 and 67 g.m-3.d-1), were achieved when the aeration strategy comprised by 7 min/14 min off and an airflow rate of 0.050 L.min-1.Lreactor-1 was applied. Nitrogen removal efficiencies were not affected by temperature variations in southeastern Brazil. COD, chloride and organic nitrogen (520, 239 and 102.8 mg.L-1, respectively) did not prevent PN/A. Changes of the bacterial community in response to aeration strategies were observed. Candidatus Brocadia dominated most of the time being more resistant to aeration and temperature changes than Candidatus Jettenia. This study demonstrated that optimizations of anoxic periods and airflow rate support PN/A with high nitrogen removal from FW digestate.

Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant.

Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and genes (ARB and ARGs) in wastewaters. The present work aimed to build on the current knowledge about the effects of activated sludge and UV irradiation on antibiotic resistance determinants in biologically treated wastewaters. For that, the microbial community and ARGs' composition of samples collected after preliminary (APT), secondary (AST), and tertiary (ATT) treatments in a full-scale wastewater treatment plant using a modified activated sludge (MAS) system followed by an UV stage (16 mJ/cm2) were investigated through culture-dependent and independent approaches (including metagenomics). A total of 24 phyla and 460 genera were identified, with predominance of Gammaproteobacteria in all samples. Pathogenic genera corresponded to 8.6% of all sequences on average, mainly Acinetobacter and Streptococcus. Significant differences (p < 0.05) in the proportion of pathogens were observed between APT and the other samples, suggesting that the secondary treatment reduced its abundance. The MAS achieved 64.0-99.7% average removal efficiency for total (THB) and resistant heterotrophic bacteria, although the proportions of ARB/THB have increased for sulfamethoxazole, cephalexin, ciprofloxacin, and tetracycline. A total of 107 copies/mL of intI1 gene remained in the final effluent, suggesting that the treatment did not significantly remove this gene and possibly other ARGs. In accordance, metagenomic results suggested that number of reads recruited to plasmid-associated ARGs became more abundant in the pool throughout the treatment, suggesting that it affected more the bacteria without these ARGs than those with it. In conclusion, disinfected effluents are still a potential source for ARB and ARGs, which highlights the importance to investigate ways to mitigate their release into the environment.

Long-term monitoring of SARS-CoV-2 RNA in sewage samples from specific public places and STPs to track COVID-19 spread and identify potential hotspots.

Coronavirus pandemic started in March 2020 and since then has caused millions of deaths worldwide. Wastewater-based epidemiology (WBE) can be used as an epidemiological surveillance tool to track SARS-CoV-2 dissemination and provide warning of COVID-19 outbreaks. Considering that there are public places that could be potential hotspots of infected people that may reflect the local epidemiological situation, the presence of SARS-CoV-2 RNA was analyzed by RT-qPCR for approximately 16 months in sewage samples from five public places located in the metropolitan area of Belo Horizonte, MG, Brazil: the sewage treatment plant of Confins International Airport (AIR), the main interstate bus terminal (BUS), an upscale shopping centre (SHC1), a popular shopping centre (SHC2) and a university institute (UNI). The results were compared to those of the influent sewage of the two main sewage treatment plants of Belo Horizonte (STP1 and STP2). Viral monitoring in the STPs proved to be an useful regional surveillance tool, reflecting the trends of COVID-19 cases. However, the viral concentrations in the samples from the selected public places were generally much lower than those of the municipal STPs, which may be due to the behaviour of the non-infected or asymptomatic people, who are likely to visit these places relatively more than the symptomatic infected ones. Among these places, the AIR samples presented the highest viral concentrations and concentration peaks were observed previously to local outbreaks. Therefore, airport sewage monitoring can provide an indication of the regional epidemiological situation. For the other places, particularly the UNI, the results suggested a greater potential to detect the infection and trace cases especially among employees and regular attendees. Taken together, the results indicate that for a regular and permanent sentinel sewage surveillance the sewage from STPs, AIR and UNI could be monitored.

Inhibition of anammox activity by municipal and industrial wastewater pollutants: A review.

The use of the anammox process for nitrogen removal has gained popularity across the world due to its low energy consumption and waste generation. Anammox reactors have been used to treat ammonium-rich effluents such as chemical, pharmaceutical, semiconductor, livestock, and coke oven wastewater. Recently, full-scale installations have been implemented for municipal wastewater treatment. The efficiency of biological processes is susceptible to inhibitory effects of pollutants present in wastewater. Considering the increasing number of emerging contaminants detected in wastewater, the impacts of the different types of pollutants on anammox bacteria must be understood. This review presents a compilation of the studies assessing the inhibitory effects of different wastewater pollutants towards anammox activity. The pollutants were classified as antibiotics, aromatics, azoles, surfactants, microplastics, organic solvents, humic substances, biodegradable organic matter, or metals and metallic nanoparticles. The interactions between the pollutants and anammox bacteria have been described, as well as the interactions between different pollutants leading to synergistic effects. We also reviewed the effects of pollutants on distinct species of anammox bacteria, and the main toxicity mechanisms leading to irreversible loss of anammox activity have been identified. Finally, we provided an analysis of strategies to overcome the inhibitory effects of wastewater pollutants on the nitrogen removal performance. We believe this review will contribute with essential information to assist the operation and design of anammox reactors treating different types of wastewaters.

Persulfate mediated solar photo-Fenton aiming at wastewater treatment plant effluent improvement at neutral PH: emerging contaminant removal, disinfection, and elimination of antibiotic-resistant bacteria.

This work investigated an innovative alternative to improve municipal wastewater treatment plant effluent (MWWTP effluent) quality aiming at the removal of contaminants of emerging concern (caffeine, carbendazim, and losartan potassium), and antibiotic-resistant bacteria (ARB), as well as disinfection (E. coli). Persulfate was used as an alternative oxidant in the solar photo-Fenton process (solar/Fe/S2O82-) due to its greater stability in the presence of matrix components. The efficiency of solar/Fe/S2O82- at neutral pH using intermittent iron additions is unprecedented in the literature. At first, solar/Fe/S2O82- was performed in a solar simulator (30 W m-2) leading to more than 60% removal of CECs, and the intermittent iron addition strategy was proved effective. Then, solar/Fe/S2O82- and solar/Fe/H2O2 were compared in semi-pilot scale in a raceway pond reactor (RPR) and a cost analysis was performed. Solar/Fe/S2O82- showed higher efficiencies of removal of target CECs (55%), E. coli (3 log units), and ARB (3 to 4 log units) within 1.9 kJ L-1 of accumulated irradiation compared to solar/Fe/H2O2 (CECs, 49%; E. coli, 2 log units; ARB, 1 to 3 log units in 2.5 kJ L-1). None of the treatments generated acute toxicity upon Allivibrio fischeri. Lower total cost was obtained using S2O82- (0.6 € m-3) compared to H2O2 (1.2 € m-3). Therefore, the iron intermittent addition aligned to the use of persulfate is suitable for MWWTP effluent quality improvement at neutral pH.

Nitratation in pilot-scale bioreactors fed with effluent from a submerged biological aerated filter used in the treatment of dog wastewater.

Nitrification is a biochemical process that allows oxidation of ammonium ion to nitrite, and nitrite to nitrate in a system. Aerobic processes, such as use of submerged biological aerated filter (SBAF), enable nitrification. However, some variables that are entirely unavailable or not available at the required concentration range may hamper the process. In this study, nitratation under high dissolved oxygen (DO) concentrations was evaluated in laboratory-scale bioreactors containing 10% inoculum (0.5 kg kg-1) fed with affluent from a SBAF that receive the sewage generated from washing the bays of a dog kennel. The following variables were monitored over time: ammoniacal nitrogen (12.44-29.62 mg L-1), nitrite (0.28-0.54 mg L-1), nitrate (1.75-3.55 mg L-1), pH (8.11 ± 0.62), temperature (21.61 ± 1.24°C) and DO (9.69 ± 0.36 mg L-1). Quantification of nitrifying bacteria by the multiple tube technique showed the value of 1.4 × 1012 MPN mL-1for ammonia-oxidizing bacteria (AOB) and 9.2 × 1014 MPN mL-1 for nitrite-oxidizing bacteria. These values were higher than those found in a synthetic medium, which can be explained by the greater availability of ammonium and nitrite in the effluent. By the extraction of genomic DNA, and PCR, with specific primers, the presence of the AmoA (Ammonia monooxygenase) gene for AOB and of the Nitrobacter was detected in the bioreactor samples. By PCR-DGGE, the sequenced bands showed high similarity with denitrifying bacteria, such as Pseudomonas, Limnobacter, Thauera, Rhodococcus, and Thiobacillus. Thus, the saturation of dissolved oxygen in the system resulted in improvement in the nitratation step and allowed detection of bacterial genera involved in the process.

Effect of alkaline treatment on pathogens, bacterial community and antibiotic resistance genes in different sewage sludges for potential agriculture use.

Alkaline treatment is widely used to reduce pathogens in sewage sludge in developing countries and guarantee that it is safe for use in agriculture. The aim of this study was to investigate the effect of alkaline treatment applied to waste-activated (WAS) and Upflow Anaerobic Sludge Blanket (UASB)-sludge on the bacterial community, pathogens (viable helminths eggs and Salmonella spp), and antibiotic resistance genes (ARG). The bacterial community structure was examined through denaturing gel gradient electrophoresis (DGGE), targeting 16S rRNA genes. Polymerase chain reaction (PCR) was applied to evaluate the presence of several ARGs. The conducted alkaline experiment consisted of adding hydrated lime (Ca(OH)2) to sewage sludges. Samples were taken before and after 2, 24, 48, and 72 hours of treatment. Alkaline treatment changed considerably the bacterial community structure and after 24 hours, shifts in bacterial profiles were more pronounced in the UASB sludge sample than in WAS. Some bacteria remained under extreme pH conditions (pH > 12), such as Azospira oryzae and Dechloromonas denitrificans in the WAS samples, and Geothrix and Geobacter in the UASB sludge samples. The values of pathogens and indicators in the sludge after 24 hours of alkaline treatment meet sanitary law regulations and thus the sludges could have the potential to agricultural distribution. It is important to highlight that ARG, which are not currently present in sanitary regulations, were detected in the sludge samples after the alkaline treatment, which could be a concern for human health.

Evaluation of nitrogen removal and the microbial community in a submerged aerated biological filter (SABF), secondary decanters (SD), and horizontal subsurface flow constructed wetlands (HSSF-CW) for the treatment of kennel effluent.

To ensure microbial activity and a reaction equilibrium with efficiency and energy saving, it is important to know the factors that influence microbiological nitrogen removal in wastewater. Thus, it was investigated the microorganisms and their products involved in the treatment of kennel effluents operated with different aeration times, phase 1 (7 h of continuous daily aeration), phase 2 (5 h of continuous daily aeration), and phase 3 (intermittent aeration every 2 h), monitoring chemical and physical parameters weekly, monthly microbiological, and qualitative and quantitative microbiological analyzes at the end of each applied aeration phase. The results showed a higher mean growth of nitrifying bacteria (NB) (106) and denitrifying bacteria (DB) (1022) in phase with intermittent aeration, in which better total nitrogen (TN) removal performance, with 33%, was achieved, against 21% in phase 1 and 17% in phase 2, due to the longer aeration time and lower carbon/nitrogen ratio (15.7), compared with the other phases. The presence of ammonia-oxidizing bacteria (AOB), the genus Nitrobacter nitrite-oxidizing bacteria (NOB), and DB were detected by PCR with specific primers at all phases. The analysis performed by 16S-rRNA DGGE revealed the genres Thauera at all phases; Betaproteobacteria and Acidovorax in phase 3; Azoarcus in phases 2 and 3; Clostridium, Bacillus, Lactobacillus, Turicibacter, Rhodopseudomonas, and Saccharibacteria in phase 1, which are related to the nitrogen removal, most of them by denitrifying. It is concluded that, with the characterization of the microbial community and the analysis of nitrogen compounds, it was determined, consistently, that the studied treatment system has microbiological capacity to remove TN, with the phase 3 aeration strategy, by simultaneous nitrification and denitrification (SND). Due to the high density of DB, most of the nitrification occurred by heterotrophic nitrification-aerobic. And denitrification occurred by heterotrophic and autotrophic forms, since the higher rate of oxygen application did not harm the DB. Therefore, the aeration and carbon conditions in phase 3 favored the activity of the microorganisms involved in these different routes. It is considered that, in order to increase autotrophic nitrification-aerobic, it is necessary to exhaust the volume of sludge in the secondary settlers (SD), further reducing the carbon/nitrogen ratio, through more frequent cleaning, whose periodicity should be the object of further studies. Graphical abstract.

Enhanced biodiesel industry wastewater treatment via a hybrid MBBR combined with advanced oxidation processes: analysis of active microbiota and toxicity removal.

In the present study, a multistage route is proposed for the treatment of biodiesel industry wastewater (BWW) containing around 1000 mg L-1 of total organic carbon (TOC), 3500 mg L-1 of chemical oxygen demand (COD), and 1325 mg L-1 of oil and grease. Initially, BWW aerobic biodegradability was assessed via Zhan-Wellens biodegradability test to confirm the appropriate treatment route. Then, a hybrid moving bed bioreactor (MBBR) system was chosen as the first treatment stage. The hybrid MBBR achieved 69 and 68% removal of COD and TOC removals, respectively, and provided great conditions for biomass growth. The bacterial community present in the hybrid MBBR was investigated by PCR-DGGE and potential biodegraders were identified such as: members of Desulfuromonadales, Nocardioidaceae and Pseudomonadaceae. Since biodegradation in the hybrid MBBR alone was unable to meet quality requirements, advanced oxidation processes, such as Fenton and photo-Fenton, were optimized for application as additional treatment stages. Physicochemical properties and acute toxicity of BWW were analyzed after the multistage routes: hybrid MBBR + Fenton, hybrid MBBR + photo-Fenton and hybrid MBBR + UV-C254nm/H2O2. Hybrid MBBR + Fenton or photo-Fenton showed overall COD removal efficiencies greater than 95% and removed acute toxicity, thus being appropriate integrated routes for the treatment of real BWW. Graphical abstract ᅟ.

DGGE with genomic DNA: suitable for detection of numerically important organisms but not for identification of the most abundant organisms.

Identification of all important community members as well as of the numerically dominant members of a community are key aspects of microbial community analysis of bioreactor samples. A systematic study was conducted with artificial consortia to test whether denaturing gradient gel electrophoresis (DGGE) is a reliable technique to obtain such community data under conditions where results would not be affected by differences in DNA extraction efficiency from cells. A total of 27 consortia were established by mixing DNA extracted from Escherichia coli K12, Burkholderia cepacia and Stenotrophomonas maltophilia in different proportions. Concentrations of DNA of single organisms in the consortia were either 0.04, 0.4 or 4ng/microl. DGGE-PCR of genomic DNA with primer sets targeted at the V3 and V6-V8 regions of the 16S rDNA failed to detect the three community members in only 7% of consortia, but provided incorrect information about dominance or co-dominance for 85% and 89% of consortia with the primer sets for the V6-V8 and V3 regions, respectively. The high failure rate in detection of dominant B. cepacia with the primers for the V6-V8 region was attributable to a single nucleotide primer mismatch in the target sequences of both, the forward and reverse primer. Amplification bias in PCR of E. coli and S. maltophilia for the V6-V8 region and for all three organisms for the V3 region occurred due to interference of genomic DNA in PCR-DGGE, since a nested PCR approach, where PCR-DGGE was started from mixtures of 16S rRNA genes of the organisms, provided correct information about the relative abundance of original DNA in the sample. Multiple bands were not observed in pure culture amplicons produced with the V6-V8 primer pair, but pure culture V3 DGGE profiles of E. coli, S. maltophilia and B. cepacia contained 5, 3 and 3 bands, respectively. These results demonstrate DGGE was suitable for identification of all important community members in the three-membered artificial consortium, but not for identification of the dominant organisms in this small community. Multiple DGGE bands obtained for single organisms with the V3 primer pair could greatly confound interpretation of DGGE profiles.

Effect of temperature on microbial diversity and nitrogen removal performance of an anammox reactor treating anaerobically pretreated municipal wastewater.

The effects of temperature reduction (from 35 °C to 20 °C) on nitrogen removal performance and microbial diversity of an anammox sequencing batch reactor were evaluated. The reactor was fed for 148 days with anaerobically pretreated municipal wastewater amended with nitrite. On average, removal efficiencies of ammonium and nitrite were high (96%) during the enrichment period and phases 1 (at 35 °C) and 2 (at 25 °C), and slightly decreased (to 90%) when the reactor was operated at 20 °C. Deep sequencing analysis revealed that microbial community structure changed with temperature decrease. Anammox bacteria (Ca. Brocadia and Ca. Anammoximicrobium) and denitrifiers (Burkholderiales, Myxococcales, Rhodocyclales, Xanthomonadales, and Pseudomonadales) were favoured when the temperature was lowered from 35 °C to 25 °C, while Anaerolineales and Clostridiales were negatively affected. The results support the feasibility of using the anammox process for mainstream nitrogen removal from anaerobically pretreated municipal wastewater at typical tropical temperatures.

Illumina sequencing-based analysis of a microbial community enriched under anaerobic methane oxidation condition coupled to denitrification revealed coexistence of aerobic and anaerobic methanotrophs.

Methane is produced in anaerobic environments, such as reactors used to treat wastewaters, and can be consumed by methanotrophs. The composition and structure of a microbial community enriched from anaerobic sewage sludge under methane-oxidation condition coupled to denitrification were investigated. Denaturing gradient gel electrophoresis (DGGE) analysis retrieved sequences of Methylocaldum and Chloroflexi. Deep sequencing analysis revealed a complex community that changed over time and was affected by methane concentration. Methylocaldum (8.2%), Methylosinus (2.3%), Methylomonas (0.02%), Methylacidiphilales (0.45%), Nitrospirales (0.18%), and Methanosarcinales (0.3%) were detected. Despite denitrifying conditions provided, Nitrospirales and Methanosarcinales, known to perform anaerobic methane oxidation coupled to denitrification (DAMO) process, were in very low abundance. Results demonstrated that aerobic and anaerobic methanotrophs coexisted in the reactor together with heterotrophic microorganisms, suggesting that a diverse microbial community was important to sustain methanotrophic activity. The methanogenic sludge was a good inoculum to enrich methanotrophs, and cultivation conditions play a selective role in determining community composition.

Studies of filter media for zero-discharge systems collecting light greywater.

Zero-discharge constructed wetland environments are more prone to the accumulation of pollutants. The relationship between filter media and microbial communities in this type of environment is still poorly known. We conducted bench-scale studies of different filter media (polyurethane foam, blast-furnace slag, and loofah) in these systems by simulating the batch operation with light greywater for 433 days. Physicochemical and microbiological analyses (scanning electron microscopy and polymerase chain reaction electrophoresis denaturing gradient gel) were used. In all systems, anoxic environments prevailed. These environments were crucial for methanogenesis and sulfidogenesis processes, which are primarily responsible for organic material conversion. The chemical oxygen demand/sulfate (COD/SO42-) ratio was the limiting factor in the competition of microorganisms involved in these processes. This condition, combined with the neutral-alkaline pH, also allowed Chloroflexi phylum bacteria to oxidize sulfide to sulfate and elemental sulfur in all studied media. The results showed strong evidence supporting that the microbial community formed in the present study is more related to operational/environmental conditions than to the different tested filter media. Thus, this demonstrates that the control of interactive effects between pH, redox potential, and the COD/SO42- ratio can prevent the accumulation and/or release of sulfide in anoxic environments.

Metagenomic analysis and performance of a mesophilic anaerobic reactor treating food waste at various load rates.

The performance of a demonstration-scale anaerobic reactor treating food waste was evaluated with an emphasis on microbial response to increasing organic loading rates (OLRs). The reactor exhibited a stable performance in terms of methane yield at OLR ranging from 1.0 to 2.4 kg VS L-1 day-1 (phases I and II), compared to that at phase III (OLR: 1.0-1.5 kg VS L-1 day-1) when the food waste exhibited greater acidity. Deep sequencing analysis revealed shifts in the microbial composition at each operational phase. The phyla Firmicutes and Bacteroidetes were favoured, whereas the abundance of Proteobacteria and Chloroflexi decreased at higher OLRs, indicating that fermenting-, hydrolytic- (and acidogenic) bacteria were selected under this condition. Changes were observed in the composition of methanogens, and not the abundance, in response to a shift in OLR. Methanosaeta and Methanospirillum dominated at low OLRs, indicating the importance of both acetoclastic and hydrogenotrophic methanogens for methane production during this condition. Methanosaeta almost disappeared at high OLRs, whereas Methanoculleus was favoured. Syntrophic prokaryotes were in high abundance (>9%), indicating that syntrophic methane production was important in this reactor. Syntrophic interactions between hydrogen-producer (Syntrophomonas and Desulfosporosinus) and hydrogenotrophic methanogens were more evident at high OLR. These results indicate that hydrogenotrophic methanogenesis contributed significantly to methane production at higher OLRs than when the reactor was operated at low OLR.

Uma revisão sobre: tratamento biológico de drenagem de mina — cenário atualizado, perspectivas e recomendações de futuros trabalhos / Biological treatment of mine drainage — scenario updated, perspectives, and recommendations for future works

RESUMO Rochas contendo sulfetos metálicos podem ser oxidadas em um processo catalisado por procariotos quimiolitoautotróficos ou Fe3+. A atividade mineradora acelera esse processo ao gerar resíduos contendo sulfetos metálicos com grande superfície de contato. O lixiviado resultante, conhecido como drenagem de mina (DM), é rico em sulfato, íons hidrogênio e contaminantes químicos inorgânicos como ferro (Fe), zinco (Zn), cádmio (Cd), manganês (Mn), níquel (Ni), arsênio (As) e alumínio (Al). Para remover tais poluentes, atualmente, o principal tratamento utilizado é a adição de reagentes alcalinos. Entretanto, esse método tem limitada eficiência, alto custo e gera grandes volumes de resíduos sólidos tóxicos de relativa solubilidade. Bactérias redutoras de sulfato (BRS) podem oxidar matéria orgânica com geração de sulfeto. Algumas vias metabólicas do processo consomem H+neutralizando o pH. O sulfeto produzido pode reagir com contaminantes inorgânicos e precipitá-los, permitindo sua recuperação da fase líquida. O uso de subprodutos industriais e urbanos contendo diferentes fontes de carbono como doadores de elétrons no tratamento de DM tem sido investigado. Este artigo sumariza dados sobre as variáveis relevantes para a atividade microbiana durante o tratamento biológico de DM, analisando o atual cenário de pesquisas com fontes alternativas de carbono. Discute-se ainda novas fontes de matéria orgânica ainda não aplicadas para tratamento biológico de efluentes e que, sob aspectos de sustentabilidade, dos pontos de vista sustentável e econômico, podem ser usadas no tratamento de resíduos.

ABSTRACT Rocks containing metal sulfides be can oxidized biologically or chemically. Chemolithoautotrophics prokaryotes and Fe3+ catalyze this process. The mining activities also accelerate the process for creates metal sulphides tailings with a big contact surface. The leached formed is called Mine Drainage (MD) whose composition is rich in sulphate, hydrogen ions and inorganic chemical contaminants such as Fe, Zn, Mn, Cd, Ni, As e Al. Currently, in order to remove these pollutants, the main treatment used is the addition of alkaline reagents. However, the method has limited efficiency, high cost with input reagents and generates wide amounts of toxic solid residues with high solubility. The sulphide reducing bacterias (RSB) can oxidize organic matter generating sulphide. Some metabolic pathways consume H+ neutralizing the pH. The sulphide formed can react and precipitate inorganic pollutants, allowing their recuperation from the liquid phase. The use of industrial and urban by-products containing different carbon sources have been investigated as an electron donor in the MD treatment. The diverse microbial consortia synergic acting can present bigger efficiency in the presence of mixed carbon sources, besides lower cost in relation to the pure matter. Here will be detailed the biological treatment about which and how the variables of the system can influence the microbial activity and relevant molecules to the treatment. After is described the current situation of the research about alternative carbon sources. New carbon sources whose are a by-product of the expanding industry presenting good feature to anaerobic degrading are suggested. The by-product potential is described from the point of view of sustainability, and waste management.