RESUMO
The high content of nitrogen in wastewater brings some operational, technical, and economical issues in conventional technologies. The aim of this study was to evaluate the nitrogen removal by hybrid hydrogels containing consortium microalgae-nitrifying bacteria in the presence of activated carbon (AC) used as an adsorbent of inhibitory substances. Hybrid hydrogels were synthesized from polyvinyl alcohol (PVA), sodium alginate (SA), biomass (microalgae-nitrifying bacteria), and AC. The hybrid hydrogels were evaluated based on the change in ammonium (NH4), nitrate (NO3), and chemical demand of oxygen (COD) concentrations, nitrification rate, and other parameters during 72 h. Results indicated that NH4 removal was more effective for hydrogels without AC than with AC, without significant differences regarding consortium biomass concentration (5 or 16%), presenting final concentrations of 3.13 and 3.75 mg NH4/L for hydrogels with 5 and 16% of the biomass, respectively. Regarding NO3 production, hydrogels without AC reached concentrations of 25.9 and 39.77 mg NO3/L for 5 and 16% of the biomass, respectively, while treatments with AC ended with 2.17 and 1.37 mg NO3/L. This confirms that hydrogels can carry out the nitrification process and do not need AC to remove potential inhibitors. The best performance was observed for the hydrogel with 5% of biomass without AC with a nitrification rate of 0.43 mg N/g TSS·h.
Assuntos
Microalgas , Águas Residuárias , Desnitrificação , Nitrogênio/análise , Nitrificação , Bactérias , BiomassaRESUMO
The rapid growth of the use of nanomaterials in different modern industrial branches makes the study of the impact of nanoparticles on the human health and environment an urgent matter. For instance, it has been reported that titanium dioxide nanoparticles (TiO2 NPs) can be found in wastewater treatment plants. Previous studies have found contrasting effects of these nanoparticles over the activated sludge process, including negative effects on the oxygen uptake. The non-utilization of oxygen reflects that aerobic bacteria were inhibited or decayed. The aim of this work was to study how TiO2 NPs affect the bacterial diversity and metabolic processes on an activated sludge. First, respirometry assays of 8 h were carried out at different concentrations of TiO2 NPs (0.5-2.0 mg/mL) to measure the oxygen uptake by the activated sludge. The bacterial diversity of these assays was determined by sequencing the amplified V3-V4 region of the 16S rRNA gene using Illumina MiSeq. According to the respirometry assays, the aerobic processes were inhibited in a range from 18.5 ± 4.8% to 37.5 ± 2.0% for concentrations of 0.5-2.0 mg/mL TiO2 NPs. The oxygen uptake rate was affected mainly after 4.5 h for concentrations higher than 1.0 mg/mL of these nanoparticles. Results indicated that, in the presence of TiO2 NPs, the bacterial community of activated sludge was altered mainly in the genera related to nitrogen removal (nitrogen assimilation, nitrification and denitrification). The metabolic pathways prediction suggested that genes related to biofilm formation were more sensitive than genes directly related to nitrification-denitrification and N-assimilation processes. These results indicated that TiO2 NPs might modify the bacteria diversity in the activated sludge according to their concentration and time of exposition, which in turn impact in the performance of the wastewater treatment processes.
Assuntos
Nanopartículas , Esgotos , Bactérias/genética , Biodegradação Ambiental , Humanos , RNA Ribossômico 16S/genética , TitânioRESUMO
Titanium dioxide nanoparticles (TiO2 NPs) are widely used in consumer products and one of their major fate is the wastewater treatment plants. However, NPs eventually arrive to aquatic and terrestrial ecosystems via treated water and biosolids, respectively. Since low concentration of NPs is accumulating in the upflow anaerobic sludge blanket (UASB) reactors that treat wastewater and reclaim water quality, the accumulation of TiO2 NPs in these reactors may impact in their performance. In this work, the long-term effects of TiO2 NPs on the main benefits of treating wastewater by UASB reactors such as, biogas production, methane fraction in biogas and organic matter removal were evaluated. Evaluation consisted of monitoring such parameters in two identical UASB reactors, one UASB-Control (without NPs) and the experimental one (UASB-TiO2 NPs) that received wastewater with TiO2 NPs. The fate of NPs in the UASB reactor was also determined. Results indicated that biogas production increased by 8.8% due to the chronic exposure of UASB reactor to TiO2 NPs during the first 44 days of experiment. However, the methane content in the biogas had no significant differences between both UASB, ranging between 78% and 90% of methane during the experiment. The removal of organic matter in both UASB was similar and ranged 92-98% along the experimental time. This means that accumulation of TiO2 NPs did not altered the biogas production and organic matter removal. However, the content of total volatile solids (TVS) in UASB-TiO2 NPs dropped off from 137.8 g to 64.2 g in 84 days, while for control reactor that decreased from 141.6 g to 92.4 g in the same period. Hence, the increased biogas production in the UASB exposed to TiO2 was attributed to hydrolysis of the TVS in this reactor. The main fate of TiO2 NPs was the granular sludge, which accumulated up to 8.56 mg Ti/g, which represent around 99% of the Ti spiked to the reactor and the possible cause of the biomass hydrolyzation in the UASB. Disposal of UASB sludge containing NPs from may raise ecotoxicological concerns due to the use of biosolids in agricultural activities.
Assuntos
Nanopartículas , Águas Residuárias , Anaerobiose , Reatores Biológicos , Ecossistema , Metano , Esgotos , Titânio , Eliminação de Resíduos LíquidosRESUMO
Combining microalgae and nitrifiers in a single photobioreactor has attracted attention as an alternative approach for conventional nitrogen removal from wastewater. However, nitrifiers are known to be sensitive to light exposure. This study demonstrated the effectiveness of using fluidized carriers to mitigate light stress in nitrifiers. An outdoor raceway pond containing microalgae and nitrifiers with fluidized carriers was used to treat two-fold diluted anaerobic digestion effluent (785 mg-N L-1 as a form of dissolved total Kjeldahl nitrogen: TKN) over 50 days. The average daily sunlight intensity reached the inhibition level of nitrifiers (423 µmol photons m-2 s-1); however, stable nitrification with a specific ammonium oxidation rate of 55 mg-N g-total suspended solid-1 day-1 was observed. TKN was mostly removed via nitrifier metabolism (ammonium oxidation and uptake: 40.1%) and partially via microalgae uptake (5.7%). Different microalgae-based processes including that of this study were compared in terms of tolerances to a high dissolved TKN concentration and strong light. Our system showed a relatively higher resistance to not only light exposure but also TKN because the nitrification process decreased the free ammonia level to less than 0.25 mg L-1, which allowed microalgae to grow despite the high ammonium concentration.
Assuntos
Microalgas , Lagoas , Anaerobiose , Fotobiorreatores , Eliminação de Resíduos LíquidosRESUMO
Novel Gram-stain-negative, non-spore-forming, vibrio-shaped, anaerobic, alkaliphilic, sulfate-reducing bacteria, designated strains PAR180T and PAR190, were isolated from sediments collected at an alkaline crater lake in Guanajuato (Mexico). Strain PAR180T grew at temperatures between 15 and 40 °C (optimum 35 °C), and at pH between 8.3 and 10.4 (optimum 9). It was halotolerant, growing with up to 8â% (w/v) NaCl. Lactate, formate, pyruvate and ethanol were used as electron donors in the presence of sulfate and were incompletely oxidized to acetate and CO2. The isolate was able to grow with hydrogen and with CO2 as a carbon source. Beside sulfate, sulfite and thiosulfate were used as terminal electron acceptors. The isolate was able to grow by disproportionation of sulfite and thiosulfate, but not elemental sulfur, using acetate as a carbon source. The predominant fatty acids were C16â:â0, C16â:â1ω7c and summed feature 10 (C18â:â1ω7c and/or C18â:â1ω9t and/or C18â:â1ω12t). The DNA G+C content was 56.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that it belongs to the genus Desulfonatronum, class Deltaproteobacteria. Its closest relative is Desulfonatronum thiosulfatophilum (98.7â% 16S rRNA gene sequence similarity). The DNA-DNA relatedness value between strain PAR180T and the type strain of D. thiosulfatophilum was 37.1±2.5â%. On the basis of phylogenetic, phenotypic and chemotaxonomic characteristics, the isolates is considered to represent a novel species of the genus Desulfonatronum, for which the name Desulfonatronum parangueonense sp. nov. is proposed. The type strain is PAR180T (=DSM 103602T=JCM 31598T).
Assuntos
Deltaproteobacteria/classificação , Sedimentos Geológicos/microbiologia , Lagos/microbiologia , Filogenia , Álcalis , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Deltaproteobacteria/genética , Deltaproteobacteria/isolamento & purificação , Desulfovibrio/genética , Ácidos Graxos/química , Concentração de Íons de Hidrogênio , México , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
The aim of this work was to evaluate the impact generated by ZnO NPs on the activated sludge process treating raw (RWW) and filtered wastewater (FWW). It was analyzed the oxygen uptake rate, nutrient removal, flocs characteristics and the morphological interactions between activated sludge and ZnO NPs, in presence of 450-2000 mg/L. The results showed that the presence of more than 450 mg/L of ZnO NPs in raw and filtered wastewater inhibited the oxygen uptake by activated sludge. The highest inhibition was 35% in presence of 1500 mg/L in RWW. The organic matter removal was only inhibited in the presence of 450 and 900 mg/L of ZnO NPs; while ammonia removal decreased for all concentrations of ZnO NPs in both types of wastewater, around 13% for RWW and up to 9% for FWW. The orthophosphate removal improved as the concentration of ZnO NPs increased for both wastewater types, enhancing up to 8% for RWW and 17% for FWW. The flocs size of activated sludge exposed to ZnO NPs in RWW decreased as the concentration of ZnO NPs increased; while for FWW, an opposite effect was observed. The elemental mapping allowed detect the Zn inside of microorganisms, which may correspond to a toxicity mechanism in RWW and FWW. These results indicated that the changes in nutrient removal and flocs characteristics caused by the presence of ZnO NPs on the activated sludge are related to wastewater characteristics, such as suspended solids, type of substrate and concentration of ZnO NPs.
Assuntos
Nanopartículas Metálicas/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Amônia , Águas Residuárias/química , Óxido de Zinco/químicaRESUMO
Physicochemical characteristics of wastewater have a relationship with the stability of TiO2 nanoparticles (NPs). This in turn has an effect on the toxicity of TiO2 NPs in microorganisms. In this work, the effect of TiO2 NPs on activated sludge process was evaluated using three different types of wastewater: synthetic, raw, and filtered. The results showed that aggregate size of TiO2 NPs and their specific adsorption of substrates were influenced by the type of substrates and the presence of suspended solids in the wastewater. It was also shown that TiO2 NPs in raw wastewater severely inhibited oxygen uptake by microorganisms as compared to uptake in synthetic or filtered wastewater. The attachment of TiO2 NP aggregates on cell membranes was observed for all types of wastewater. However, the internalization of TiO2 NPs by microorganisms was observed only for raw and filtered wastewater. These results indicate that the effects caused by TiO2 NPs on activated sludge were different depending on the wastewater used for the experiment.
Assuntos
Nanopartículas Metálicas , Titânio , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Adsorção , Análise da Demanda Biológica de Oxigênio , Nanopartículas Metálicas/química , Oxigênio/metabolismo , Esgotos/química , Esgotos/microbiologia , Titânio/químicaRESUMO
Freshwater contamination usually comes from runoff water or direct wastewater discharges to the environment. This paper presents a case study which reveals the impact of these types of contamination on the sediment bacterial population. A small stretch of Lerma River Basin, heavily impacted by industrial activities and urban wastewater release, was studied. Due to industrial inputs, the sediments are characterized by strong hydrocarbon concentrations, ranging from 2 935 to 28 430µg·kg(-1) of total polyaromatic hydrocarbons (PAHs). These sediments are also impacted by heavy metals (e.g., 9.6µg·kg(-1) of Cd and 246µg·kg(-1) of Cu, about 8 times the maximum recommended values for environmental samples) and polychlorinated biphenyls (ranging from 54 to 123µg·kg(-1) of total PCBs). The bacterial diversity on 6 sediment samples, taken from upstream to downstream of the main industrial and urban contamination sources, was assessed through TRFLP. Even though the high PAH concentrations are hazardous to aquatic life, they are not the only factor driving bacterial community composition in this ecosystem. Urban discharges, leading to hypoxia and low pH, also strongly influenced bacterial community structure. The bacterial bioprospection of these samples, using PAH as unique carbon source, yielded 8 hydrocarbonoclastic strains. By sequencing the 16S rDNA gene, these were identified as similar to Mycobacterium goodii, Pseudomonas aeruginosa, Pseudomonas lundensis or Aeromonas veronii. These strains showed high capacity to degrade naphthalene (between 92 and 100% at 200mg·L(-1)), pyrene (up to 72% at 100mg·L(-1)) and/or fluoranthene (52% at 50mg·L(-1)) as their only carbon source on in vitro experiments. These hydrocarbonoclastic bacteria were detected even in the samples upstream of the city of Salamanca, suggesting chronical contamination, already in place longer before. Such microorganisms are clearly potential candidates for hydrocarbon degradation in the treatment of oil discharges.
Assuntos
Metais Pesados/toxicidade , Bifenilos Policlorados/toxicidade , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Poluentes Químicos da Água/toxicidade , Monitoramento Ambiental , Metais Pesados/análise , México , Bifenilos Policlorados/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Rios/química , Rios/microbiologia , Microbiologia da ÁguaRESUMO
Los Azufres spa consists of a hydrothermal spring system in the Mexican Volcanic Axis. Five samples (two microbial mats, two mud pools and one cenote water), characterized by high acidity (pH between 1 and 3) and temperatures varying from 27 to 87 °C, were investigated for their microbial diversity by Terminal-Restriction Fragment Length Polymorphism (T-RFLP) and 16S rRNA gene library analyses. These data are the first to describe microbial diversity from Los Azufres geothermal belt. The data obtained from both approaches suggested a low bacterial diversity in all five samples. Despite their proximity, the sampling points differed by their physico-chemical conditions (mainly temperature and matrix type) and thus exhibited different dominant bacterial populations: anoxygenic phototrophs related to the genus Rhodobacter in the biomats, colorless sulfur oxidizers Acidithiobacillus sp. in the warm mud and water samples, and Lyzobacter sp.-related populations in the hot mud sample (87 °C). Molecular data also allowed the detection of sulfate and sulfur reducers related to Thermodesulfobium and Desulfurella genera. Several strains affiliated to both genera were enriched or isolated from the mesophilic mud sample. A feature common to all samples was the dominance of bacteria involved in sulfur and iron biogeochemical cycles (Rhodobacter, Acidithiobacillus, Thiomonas, Desulfurella and Thermodesulfobium genera).