Comparison of calcium carbonate production by bacterial isolates from recycled aggregates.

The new technology of microbially induced calcium carbonate precipitation (MICP) has been applied in construction materials as a strategy to enhance their properties. In pursuit of solutions that are more localized and tailored to the study's target, this work focused on isolating and selecting bacteria capable of producing CaCO3 for posterior application in concrete aggregates. First, eleven bacterial isolates were obtained from aggregates and identified as genera Bacillus, Lysinibacillus, Exiguobacterium, and Micrococcus. Then, the strains were compared based on the quantity and nature of calcium carbonate they produced using thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy with energy dispersive spectroscopy. Bacillus sp. dominated the cultured isolates and, along with Lysinibacillus sp., exhibited the highest CaCO3 conversion (up to 80%). On the other hand, Exiguobacterium and Micrococcus genera showed the poor ability to MICP (21.3 and 20.3%, respectively). Calcite and vaterite were the dominant carbonate polymorphs, with varying proportions. Concrete aggregates have proven to be a source of microorganisms capable of producing stable calcium carbonates with a high conversion rate. This indicates the feasibility of using microorganisms derived from local sources for application in construction materials as a sustainable way to enhance their characteristics.

Effects of solid retention time and exposure mode to electric current on Remazol Brilliant Violet removal in an electro-membrane bioreactor.

The performance of an electrochemically assisted anoxic-oxic membrane bioreactor (A/O-eMBR) was assessed as an alternative for azo dye (Remazol Brilhant Violet (RBV)) removal from simulated textile wastewater. The A/O-eMBR was operated under three experimental conditions (runs I, II, and III), in which different solids retention time (SRT) (45 and 20 d) and exposure mode to electric current (6'ON/30'OFF and 6'ON/12'OFF) were assessed. The reactor exhibited excellent decolorization performance for all runs, with average dye removal efficiency ranging from 94.3 to 98.2%. Activity batch assays showed that the dye removal rate (DRR) decreased from 16.8 to 10.2 mg RBV L-1 h-1 when the SRT was reduced from 45 to 20 d, likely attributed to the lower biomass content under lower sludge age. At the electric current exposure mode of 6' ON/12'OFF, a more substantial decrease of DRR to 1.5 mg RBV L-1 h-1 was noticed, suggesting a possible inhibitory effect on dye removal via biodegradation. By reducing the SRT to 20 d, a worse mixed liquor filterability condition was observed, with a membrane fouling rate (MFR) of 0.979 kPa d-1. In contrast, using the electric current exposure mode of 6'ON/12'OFF resulted in lower membrane fouling propensity, with an MFR of 0.333 kPa d-1. A more attractive cost-benefit ratio for dye removal was obtained using the exposure mode of 6'ON/30'OFF, for which the energy demand was estimated at 21.9-22.6 kWh kg dye-1 removed, almost two times lower than that observed for the mode of 6'ON/12'OFF.

Electrochemical degradation of psychotropic pharmaceutical compounds from municipal wastewater and neurotoxicity evaluations.

Contaminants of emerging concern (CECs) are released daily into surface water, and their recalcitrant properties often require tertiary treatment. Electrochemical oxidation (EO) is often used as an alternative way to eliminate these compounds from water, although the literature barely addresses the neurotoxic effects of residual by-products. Therefore, this study investigated the performance of EO in the removal of five CECs (alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine) and performed neurotoxicity evaluations of residual EO by-products in Wistar rat brain hippocampal slices. Platinum-coated titanium (Ti/Pt) and boron-doped diamond (BDD) electrodes were studied as anodes. Different current densities (13-75 A m-2), pH values (3-10), electrolyte dosages (NaCl), and matrix effects were assessed using municipal wastewater (MWW). The drugs were successfully degraded after 5 min of reaction for both the Ti/Pt and BDD electrodes when a current density of 75 A m-2 was applied. For Ti/Pt and BDD, neutral and acidic pH demonstrated better CEC removal performance, respectively. Compound degradation using MWW achieved 40% removal after 120 min for Ti/Pt and ranged between 33 and 52% for the BDD anode. For Ti/Pt, neurotoxicity studies using MWW indicated a decrease in reactive oxygen species (ROS) signals. However, when an artificial cerebrospinal fluid (ACSF) medium was reapplied, the signal recovered and increased to a value above the baseline, indicating that cells recovered part of their normal activity but remained in a different condition. For the BDD anode, the treated MWW did not cause significant ROS production variations, suggesting that he EO was effective in eliminating the toxicity of the treated solution.

Treatment of a slaughterhouse wastewater by anoxic-aerobic biological reactors followed by UV-C disinfection and microalgae bioremediation.

In this study, removal of organic matter and nitrogen from a cattle slaughterhouse wastewater was investigated in a two-stage anoxic-aerobic biological system, followed by UV-C disinfection. Ecotoxicity of the raw, biotreated, and disinfected wastewater against the microalgae Scenedesmus sp. was evaluated in short-term tests, while the potential of the microalgae as a nutrient removal step was addressed in long-term experiments. Throughout 5 operational phases, the biological system was subjected to gradual reduction of the hydraulic retention time (8-1.5 day), increasing the organic (0.21-1.11 kgCOD·m-3 ·day-1 ) and nitrogen (0.05-0.28 kgN·m-3 · day-1 ) loading rates. COD and total ammoniacal nitrogen (TAN) removal ranged within 83%-97% and 83%-99%, respectively. While providing alkalinity source, effluent TAN concentrations were below 5 mg·L-1 . Nitrate was the main nitrification product, while nitrite levels remained low (<1 mgN·L-1 ). Upon supplementation of external COD as ethanol, total nitrogen removal reached up to 90% at the highest load (0.28 kgN·m-3 ·day-1 ). After UV-C treatment, 3-log reduction of total coliforms was attained. The 96-hr ecotoxicity tests showed that all non-diluted samples tested (raw, biologically treated and UV-C irradiated wastewater) were toxic to microalgae. Nevertheless, these organisms were able to acclimate and grow under the imposed conditions, allowing to achieve nitrogen and phosphorous removal up to 99.1% and 43.0%, respectively. PRACTITIONER POINTS: The treatment of a slaughterhouse wastewater in an anoxic-aerobic biological system followed by a UV-C disinfection step was assessed. The pre-denitrification system showed efficient simultaneous removal of organic matter and nitrogen from the wastewater under increasing applied loads. UV-C disinfection worked effectively in reducing coliforms from the biotreated effluent, boosting the performance of microalgae on nutrients removal. Despite the toxicity to microalgae, they were capable to acclimate to the aqueous matrices tested, reducing efficiently the nutrients content. The combined stages of treatment presented great capacity for depleting up to 97% COD, 99% nitrogen, and 43% phosphorous.

Treatment of real domestic sewage in a pilot-scale aerobic granular sludge reactor: Assessing start-up and operational control.

Aerobic granular sludge (AGS) has been considered a breakthrough in the wastewater treatment sector given its key characteristics, such as excellent settleability, simultaneous removal of organic and nutrient pollutants, and compactness. However, the formation of granules often delays the start-up of granular-based systems, especially in large-scale settings. This study addressed the start-up of a pilot-scale AGS sequencing batch reactor (SBR) treating domestic sewage, monitored for over 280 days. The challenges faced during aerobic granulation using a mixture of activated sludge and anaerobic granular sludge as inoculum and the performance of the reactor on organic matter, nitrogen, and phosphorus removal were discussed. Results showed that robust and stable granules were formed after an initial period of around six months, with the settling time playing a key role on granules development. At least 80% of granules had a diameter greater than 0.2 mm and 60% >1 mm. In general, the reactor achieved high nitrogen removal efficiency, as well as satisfactory removal of soluble COD. However, total COD abatement was impaired by the various episodes of suspended solids loss with the effluent. Overall, this study demonstrated that the reactor was efficient in the treatment of domestic sewage, but its performance was adversely affected from sudden changes in the influent quality. PRACTITIONER POINTS: Aerobic granular sludge (AGS) applied to small-scale domestic sewage treatment. The control of sludge age in AGS can be a problem due to short sedimentation times. High DO to maintain aerobic granulation can economically make the process economically unfeasible in tropical countries. A sludge with excellent sedimentation properties was obtained. However, maintaining the granule over time is a challenge.

Assessing the impact of synthetic estrogen on the microbiome of aerated submerged fixed-film reactors simulating tertiary sewage treatment and isolation of estrogen-degrading consortium.

17α-ethinylestradiol (EE2) is a synthetic estrogen that can cause harmful effects on animals, such as male feminization and infertility. However, the impact of the EE2 contamination on microbial communities and the potential role of bacterial strains as bioremediation agents are underexplored. The aim of this work was to evaluate the impact of EE2 on the microbial community dynamics of aerated submerged fixed-film reactors (ASFFR) simulating a polishing step downstream of a secondary sewage treatment. For this purpose, the reactors were fed with a synthetic medium with low COD content (around 50 mg l-1), supplemented (reactor H) or not (reactor C) with 1 µg l-1 of EE2. Sludge samples were periodically collected during the bioreactors operation to assess the bacterial profile over time by 16S rRNA gene amplicon sequencing or by bacterial isolation using culture-dependent approach. The results revealed that the most abundant phyla in both reactors were Proteobacteria and Bacteroidetes. At genus level, Chitinophagaceae, Nitrosomonas and Bdellovibrio predominated. Significant effects caused by EE2 treatment and bioreactors operating time were observed by non-metric multidimensional scaling. Therefore, even at low concentrations as 1 µg l-1, EE2 is capable of influencing the bioreactor microbiome. Culture-dependent methods showed that six bacterial isolates, closely related to Pseudomonas and Acinetobacter genera, could grow on EE2 as the sole carbon source under aerobic conditions. These organisms may potentially be used for the assembly of an EE2-degrading bacterial consortium and further exploited for bioremediation applications, including tertiary sewage treatment to remove hormone-related compounds not metabolized in secondary depuration stages.

Removal of bromate from drinking water using a heterogeneous photocatalytic mili-reactor: impact of the reactor material and water matrix.

The main goal of this study was to evaluate the removal of bromate from drinking water using a heterogeneous photocatalytic mili-photoreactor, based on NETmix technology. The NETmix mili-reactor consists of a network of channels and chambers imprinted in a back slab made of acrylic (AS) or stainless steel (SSS) sealed, through mechanical compression and o-rings, with an UVA-transparent front borosilicate glass slab (BGS). A plate of UVA-LEDs was placed above the BGS window. TiO2-P25 thin films were immobilized on the BGS (back-side illumination, BSI) or SSS (front-side illumination, FSI) by using a spray deposition method. The photoreduction rate of a 200 µg L-1 (1.56 µM) BrO3- solution was assessed taking into account the following: (i) catalyst film thickness, (ii) catalyst coated surface and illumination mechanism (BSI or FSI), (iii) solution pH, (iv) type and dose of sacrificial agent (SA), (v) reactor material, and (vi) water matrix. In acidic conditions (pH 3.0) and in the absence of light/catalyst/SA, 28% and 36% of BrO3- was reduced into Br- only by contacting with AS and SSS during 2-h, respectively. This effect prevailed during BSI experiments, but not for FSI ones since back SSS was coated with the photocatalyst. The results obtained have demonstrated that (i) the molar rate of disappearance of bromates was similar to the molar rate of formation of bromides; (ii) higher BrO3- reduction efficiencies were reached in the presence of an SA using the FSI at pH 3.0; (iii) formic acid ([BrO3-]:[CH2O2] molar ratio of 1:3) presented higher performance than humic acids (HA = 1 mg C L-1) as SA; (iv) high amounts of HA impaired the BrO3- photoreduction reaction; (v) SSS coated catalyst surface revealed to be stable for at least 4 consecutive cycles, keeping its photonic efficiency. Under the best operating conditions (FSI, 18 mL of 2% wt. TiO2-P25 suspension, pH 3.0), the use of freshwater matrices led to (i) equal or higher reaction rates, when compared with a synthetic water in the absence of SA, and (ii) lower reaction rates, when compared with a synthetic water containing formic acid with a [BrO3-]:[CH2O2] molar ratio of 1:3. Notwithstanding, heterogeneous TiO2 photocatalysis, using the NETmix mili-reactor can be used to promote the reduction of BrO3- into Br-, attaining concentrations below 10 µg L-1 (guideline value) after 2-h reaction. Graphical Abstract .

Investigating the most appropriate methods for attached solids determination in moving-bed biofilm reactors.

Moving-bed biofilm reactors (MBBR) have been employed worldwide as an efficient technology for the treatment of a diverse set of wastewaters. Although the attached biomass represents the major fraction of solids in MBBR systems, there is still no standard for its reliable quantification. An extensive literature review indicated that several methods for attached biomass assessment are applied, hindering the comparability of results issued from different studies. Therefore, the most reported methods for biofilm quantification in the MBBR literature were compared using three different carriers. The results revealed that the performance of each method was biased depending on the carrier type and shape. Moreover, differences in total attached solids (TAS) concentrations varied from 13% up to more than 90%, depending on the employed method for a given carrier. Overall, direct weighing of the carrier containing the biofilm, accounting for the clean carrier weight, and manual extraction of the biofilm, preceded or not by sonication for at least 15 min, were the most suitable techniques for assessing TAS and the volatile/total solids ratio in non-porous medias, respectively. The results here presented may be used as a frame of reference for standardization of the methods for assessing the biofilm mass in MBBR carriers.

Effect of the gradual increase of salt on stability and microbial diversity of granular sludge and ammonia removal.

Two sequential batch reactors were operated, aiming at forming aerobic granular sludge and studying the effects of the gradual increase of the NaCl concentration on the granule. structure and microbial diversity, and on the efficiency of ammonia removal. The reactors were fed with ammonia-enriched synthetic effluent and 5 g L-1 of NaCl per week were applied. A decrease in the size of the granules was observed until they were completely disintegrated as the salt concentration increased up to 10 g L-1. However, the ammonia removal efficiency remained high in all the salinities applied. By sequencing the 16S rRNA amplicon gene, the microbial community structure allowed the verification of the presence of several genera affiliated with the bacteria that perform both heterotrophic nitrification and aerobic denitrification, besides those involved in the conventional nitrification and denitrification and the ANAMMOX process. Salinity affected the microbial population related to the formation and stability of the granules.

Insights into estrogenic activity removal using carbon nanotube electrochemical filter.

This study reports the performance of a carbon nanotube (CNT) electrochemical filter applied to 17ß-estradiol (E2) and 17α-ethinylestradiol (EE2) degradation and their estrogenic activity removal (calculated in terms of E2 equivalent, EQ-E2). The performance of CNT electrochemical filter was assessed at different applied voltages (0-2.5 V) and aqueous matrices (ultrapure water and urban wastewater), using 37 µM of E2 and EE2, a flow rate of 1.5 mL min-1 and 10 mM of Na2SO4, used as supporting electrolyte. Surface characterization of CNT anodic filters was completed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) was used to investigate electron transfer mechanisms. The CNT electrochemical filter was successfully applied to E2 and EE2 degradation and removals higher than 95.3% (oxidative fluxes >2.94 ±â€¯0.05 mmol h-1 m-2) were achieved when 2.5 V was applied for both ultrapure water and urban wastewater. CV results indicate that the oxidation in the CNT electrochemical filter is an irreversible process. SEM and XPS results showed evidence of the polymer formation on the CNT surface after 300 min of reaction, which probably reduced the efficiency of the process under low applied voltages. Estrogenic activity was considerably reduced and minimal EQ-E2 levels were observed when 2.5 V was applied. A residual EQ-E2 was observed, likely due to the presence of estrogens, which suggests the non-formation of estrogenic intermediates. At 2.5 V total cell potential, the energy required to remove estrogenic activity was 0.014 ±â€¯0.001 kWh m-3 for ultrapure water and 0.021 ±â€¯0.001 kWh m-3 for post-secondary wastewater. These results suggest a CNT electrochemical filter may have potential to effectively and efficiently remove estrogenic activity and may be a feasible process for wastewater polishing treatment.

Influência da idade do lodo na colmatação das membranas em um biorreator à membrana tratando esgoto sanitário / Effect of solids retention time on membrane fouling in a membrane bioreactor treating municipal wastewater

RESUMO O presente estudo avaliou o efeito da idade do lodo (θc) no potencial incrustante do licor misto em um biorreator à membrana (BRM) tratando esgoto sanitário. Tal avaliação foi conduzida em BRM construído em escala de bancada, com volume útil de 15 L, operado por 420 dias na modalidade de batelada sequencial. Durante o período experimental, foram aplicadas 3 estratégias operacionais, E-1, E-2 e E-3, em que foram testadas as idades de lodo de 80, 40 e 20 dias, respectivamente. Os resultados revelaram que a utilização da idade de lodo de 20 dias resultou em licor misto com maior potencial incrustante, apresentando, neste caso, uma velocidade de colmatação (VC) das membranas de 1,95 mbar dia-1, aproximadamente 2 vezes maior do que a observada nas idades de lodo de 80 e 40 dias. A maior colmatação observada foi atribuída a maior concentração de produtos microbianos solúveis (PMSs) no licor misto e a maior relação proteínas/polissacarídeos (PN/PS) dos flocos biológicos nesse período em questão. Por outro lado, a aplicação da idade de lodo de 80 dias resultou em menor VC das membranas do BRM, com valor de 0,82 mbar dia-1. Contudo, no período final dessa estratégia foi observado crescimento excessivo de bactérias filamentosas, que se refletiu em piora da filtrabilidade do licor misto e aumento da VC das membranas. De maneira geral, os resultados obtidos mostraram que a aplicação da idade de lodo de 40 dias resultou em licor misto com menor potencial incrustante.

ABSTRACT This study evaluated the effect of solids retention time (SRT) on membrane fouling rate in a membrane bioreactor (MBR) treating municipal wastewater. The evaluation was conducted in a membrane bioreactor built in bench scale, with a volume of 15 L, operated for 420 days in the sequential batch regime. During this period, three experimental runs were applied, E-1, E-2 and E-3, in which the solids retention time of 80, 40 and 20 days, respectively, were tested. The results showed that use of 20-days solids retention time resulted in a higher membrane fouling rate (MFR), with value of 1,95 mbar d-1, approximately two times higher than observed in the solids retention time of 80 and 40 days. The higher membrane fouling rate observed was attributed to a higher concentration of soluble microbial products (SMP) in the mixed liquor and to the higher proteins/polysaccharides ratio of the biological flocs in this period. On the other hand, the use of 80-days solids retention time resulted in a lower membrane fouling rate, with a value of 0.82 mbar d-1. However, it was observed in the final period of this experimental run an excessive growth of filamentous bacteria, which was reflected in a deterioration of the mixed liquor filterability and an increase of membrane fouling rate. Overall, the results showed that the 40-days solids retention time resulted in a mixed liquor with lower fouling propensity.

Removal of pharmaceutically active compounds from synthetic and real aqueous mixtures and simultaneous disinfection by supported TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A processes.

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A, using sunlight and artificial irradiation. While using TiO2 in suspension, best results were found at [TiO2] = 0.1 g L-1. H2O2/UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO2/UV-A and H2O2/UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H2O2/UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO2-photocatalysis.

Comparative study on treatment performance, membrane fouling, and microbial community profile between conventional and hybrid sequencing batch membrane bioreactors for municipal wastewater treatment.

A sequencing batch conventional membrane bioreactor (SB-CMBR) and sequencing batch hybrid membrane bioreactor (SB-HMBR) were operated in parallel under two different hydraulic retention times (HRTs) (namely 12 h and 6 h), and their chemical oxygen demand (COD) and nutrient removal performance, membrane fouling behavior, and microbial community characteristics were compared. Both systems exhibited high organic matter (> 95%) and ammonium (> 98%) removal performance regardless of the HRT applied. As the HRT was reduced from 12 to 6 h, total nitrogen removal slightly increased in both reactors, being higher in the carrier-based MBR, where anoxic zones may have been established within the biofilm. Conversely, total phosphorus removal improved only in the SB-CMBR at the shorter HRT. Moreover, activity batch assays have shown a faster P uptake rate in the SB-CMBR than in the SB-HMBR, a result likely associated with the lower relative abundance of phosphate-accumulating organisms in both adhered and suspended biomass fractions in the hybrid MBR. The results also revealed that more pronounced increases in the transmembrane pressure and, consequently, in the membrane fouling rate at higher COD loading rates were observed in the SB-CMBR, where the soluble microbial products (proteins, polysaccharides, and especially, transparent exopolymer particles), supernatant turbidity, and filamentous bacteria were more significant. Overall, as compared to the conventional MBR, the plastic media-based SB-HMBR showed a lower fouling propensity at all hydraulic conditions tested.

Fluorene oxidation by solar-driven photo-Fenton process: toward mild pH conditions.

Polycyclic aromatic hydrocarbons (PAHs) are on the list of priority pollutants to be eliminated from the environment due to their carcinogenic and mutagenic action, chemical stability, and resistance to biodegradation. The aim of this study was to evaluate the degradation of fluorene, a well-known PAH, in aqueous solutions (0.03 and 0.08 mg L-1), by means of a solar-driven conventional (PF) and modified photo-Fenton mediated by ferrioxalate complexes (PFF). Photolysis was also employed for comparison purposes. PF reaction was evaluated at different pH values (2.8, 3.5, and 4.0) and iron concentrations (2, 5, 10, and 20 mg L-1). On the other hand, PFF studies were conducted at mild pH conditions (4.0, 5.0, and 6.0) and iron content of 2 mg L-1, keeping initial iron/oxalate molar ratio at 1:3. In both PF and PFF, the initial hydrogen peroxide/iron molar ratio was maintained at 5. In the presence of methanol as cosolvent for fluorene dissolution, the PF reaction was hampered and no consumption of H2O2 was observed during the reaction carried out at constant pH (2.8). This led to low degradation rates, similar to those achieved by photolysis. Under the same pH but using acetonitrile as cosolvent for fluorene dissolution, fluorene degradation was found to be proportional to the iron content used in the PF experiments. On the other hand, at an invariable iron concentration of 5 mg Fe2+ L-1, the increase in pH was accompanied by a decrease in the molar fraction of the most photoactive iron complex (FeOH2+) and ferric hydroxides precipitation, leading to a reduction in the fluorene degradation rate. With regard to the PFF tests, similar fluorene degradation performance was achieved at pH 4 and 5, while at pH 6 iron precipitation became relevant and the degradation rate was slightly slower. PFF has shown to be more efficient than the PF under the same pH (4) and iron concentration (2 mg L-1). Moreover, even at near neutral pH (6), fluorine degradation was shown to be feasible by using ferrioxalate complexes.

Water contamination by endocrine disruptors: Impacts, microbiological aspects and trends for environmental protection.

Hormone active agents constitute a dangerous class of pollutants. Among them, those agents that mimic the action of estrogens on target cells and are part of the group of endocrine-disruptor compounds (EDCs) are termed estrogenic EDCs, the main focus of this review. Exposure to these compounds causes a number of negative effects, including breast cancer, infertility and animal hermaphroditism. However, especially in underdeveloped countries, limited efforts have been made to warn people about this serious issue, explain the methods of minimizing exposure, and develop feasible and efficient mitigation strategies at different levels and in various environments. For instance, the use of bioremediation processes capable of transforming EDCs into environmentally friendly compounds has been little explored. A wide diversity of estrogen-degrading microorganisms could be used to develop such technologies, which include bioremediation processes for EDCs that could be implemented in biological filters for the post-treatment of wastewater effluent. This review describes problems associated with EDCs, primarily estrogenic EDCs, including exposure as well as the present status of understanding and the effects of natural and synthetic hormones and estrogenic EDCs on living organisms. We also describe potential biotechnological strategies for EDC biodegradation, and suggest novel treatment approaches for minimizing the persistence of EDCs in the environment.

Treatment of a simulated textile wastewater containing the Reactive Orange 16 azo dye by a combination of ozonation and moving-bed biofilm reactor: evaluating the performance, toxicity, and oxidation by-products.

In this study, an aqueous solution containing the azo dye Reactive Orange 16 (RO16) was subjected to two sequential treatment processes, namely: ozonation and biological treatment in a moving-bed biofilm reactor (MBBR). The most appropriate ozonation pretreatment conditions for the biological process and the toxicity of the by-products resulting from RO16 ozone oxidation were evaluated. The results showed that more than 97 % of color removal from the dye solutions with RO16 concentrations ranging from 25 to 100 mg/L was observed in 5 min of ozone exposure. However, the maximum total organic carbon removal achieved by ozonation was only 48 %, indicating partial mineralization of the dye. Eleven intermediate organic compounds resulting from ozone treatment of RO16 solution were identified by LC/MS analyses at different contact times. The toxicity of the dye-containing solution decreased after 2 min of ozonation, but increased at longer contact times. The results further demonstrated that the ozonolysis products did not affect the performance of the subsequent MBBR, which achieved an average chemical oxygen demand (COD) and ammonium removal of 93 ± 1 and 97 ± 2 %, respectively. A second MBBR system fed with non-ozonated dye-containing wastewater was run in parallel for comparison purposes. This reactor also showed an appreciable COD (90 ± 1 %) and ammonium removal (97 ± 2 %), but was not effective in removing color, which remained practically invariable over the system. The use of short ozonation times (5 min) and a compact MBBR has shown to be effective for the treatment of the simulated textile wastewater containing the RO16 azo dye.

Effect of solids retention time on nitrogen and phosphorus removal from municipal wastewater in a sequencing batch membrane bioreactor.

This study evaluated the removal of organic matter, nitrogen and phosphate from a municipal wastewater in a sequencing batch membrane bioreactor (SBMBR) operated at different solids retention times (SRTs) and subjected to different aeration profiles. The results demonstrated that SRT reduction from 80 to 20 d had a negligible effect on chemical oxygen demand (COD) removal and only a slight negative effect on nitrification. COD removal efficiency remained stable at 97%, whereas ammonium removal decreased from 99% to 97%. The total nitrogen removal efficiency was improved by SRT reduction, increasing from 80% to 86%. Although the total phosphorus (TP) removal was not significantly affected by the SRT reduction, ranging from 40-49%, the P-release and P-uptake processes were observed to increase as the SRT was reduced. The implementation of a pre-aeration phase in the SBMBR operating cycle allowed a higher TP removal performance, which reached up to 76%. Batch tests suggested that the fraction of phosphate removed anoxically from the total (anoxic + aerobic) phosphate removal decreased with the SRT reduction.

Ammonium removal from high-salinity oilfield-produced water: assessing the microbial community dynamics at increasing salt concentrations.

Water generated during oil exploration is chemically complex and contains high concentrations of ammonium and, in some cases, high salinity. The most common way to remove ammonium from effluent is a biological process, which can be performed by different routes and different groups of microorganisms. However, the presence of salts in the effluents could be an inhibiting factor for biological processes, interfering directly with treatment. This study aimed to evaluate changes in the profile of a microbial community involved in the process of ammonium removal when subjected to a gradual increase of salt (NaCl), in which the complete inhibition of the ammonium removal process occurred at 125 g L-1 NaCl. During the sludge acclimatization process, samples were collected and submitted to denaturing gradient gel electrophoresis (DGGE) and massive sequencing of the 16S ribosomal RNA (rRNA) genes. As the salt concentration increased in the reactor, a change in the microbial community was observed by the DGGE band profiles. As a result, there was a reduction in the presence of bacterial populations, and an increase in archaeal populations was found. The sequencing data suggested that ammonium removal in the reactor was carried out by different metabolic routes by autotrophic nitrifying bacteria, such as Nitrosococcus, Nitrosomonas, Nitrosovibrio, Nitrospira, and Nitrococcus; ammonium-oxidizing archaea Candidatus nitrosoarchaeum; ANAMMOX microorganisms, such as Candidatus brocadia, Candidatus kuenenia, and Candidatus scalindua; and microorganisms with the potential to be heterotrophic nitrifying, such as Paracoccus spp., Pseudomonas spp., Bacillus spp., Marinobacter sp., and Alcaligenes spp.

Effect of different salt adaptation strategies on the microbial diversity, activity, and settling of nitrifying sludge in sequencing batch reactors.

The effect of salinity on the activity of nitrifying bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ hybridization and polymerase chain reaction-denaturing gradient gel electrophoresis techniques was investigated. Two sequencing batch reactors (SRB1 and SBR2) treating synthetic wastewater were subjected to increasing salt concentrations. In SBR1, four salt concentrations (5, 10, 15, and 20 g NaCl/L) were tested, while in SBR2, only two salt concentrations (10 and 20 g NaCl/L) were applied in a more shock-wise manner. The two different salt adaptation strategies caused different changes in microbial community structure, but did not change the nitrification performance, suggesting that regardless of the different nitrifying bacterial community present in the reactor, the nitrification process can be maintained stable within the salt range tested. Specific ammonium oxidation rates were more affected when salt increase was performed more rapidly and dropped 50% and 60% at 20 g NaCl/L for SBR1 and SBR2, respectively. A gradual increase in NaCl concentration had a positive effect on the settling properties (i.e., reduction of sludge volume index), although it caused a higher amount of suspended solids in the effluent. Higher organisms (e.g., protozoa, nematodes, and rotifers) as well as filamentous bacteria could not withstand the high salt concentrations.