RESUMEN
This study was performed to understand the dynamics of the microbial community of submerged membrane bioreactor during the acclimatization process to treat the hospital wastewater. In this regard, three acclimatization phases were examined using a mixture of synthetic wastewater (SWW) and real hospital wastewater (HWW) in the following proportions; In Phase 1: 75:25 v/v (SWW: HWW); Phase 2: 50:50 v/v (SWW: HWW); and Phase 3: 25:75 v/v (SWW: HWW) of wastewater. The microbial community was analyzed using Illumina high throughput sequencing to identify the bacterial and micro-eukaryotes community in SMBR. The acclimatization study clearly demonstrated that shift in microbial community composition with time. The dominance of pathogenic and degrading bacterial communities such as Mycobacterium, Pseudomonas, and Zoogloea was observed at the phase 3 of acclimatization. This study witnessed the major shift in the micro-eukaryotes community, and the proliferation of fungi Basidiomycota was observed in phase 3 of acclimatization.
Asunto(s)
Microbiota , Aguas Residuales , Aclimatación , Reactores Biológicos , Hospitales , Eliminación de Residuos LíquidosRESUMEN
Research on the development of a passive phosphorus entrapment process characterized by biofilters with active wood-based media impregnated with iron hydroxide has been conducted. Phosphorus removal was done by sorption which includes adsorption, exchange of ions and precipitation. Experiments were performed in order to investigate the effect of nitrate, generally present at the end of secondary treatment, on the phosphorus removal performance. Columns tests were performed with anaerobic activated wood-based media and immersion over a period of 150 days. Columns were fed for 32 days with a synthetic solution of 5â mg P L-1. Different concentrations of nitrate (5, 10 and 25â mg N-NO3 L-1) were then applied on three columns (C2, C3 and C4), column C1 serving as a control. Results showed total phosphorus (TP) removal efficiencies of 96.9%, 81.7%, 70.6% and 75.7%, respectively, for C1, C2, C3 and C4. Addition of nitrate increases the oxidoreduction potential (ORP). This results in an inhibition of the reductive dissolution, characterized by a decrease in the release of ferrous ions. Simultaneous denitrification occurs within the columns. It is both biological and chemical through the oxidation of ferrous ions by NO2, produced during biological denitrification. Furthermore, bacterial identification tests have highlighted the presence of iron-related bacteria (Pseudomonas, Thiobacillus, Enteric bacteria, e.g. E. coli), slym forming bacteria, sulphate reducing bacteria and denitrifying microorganisms such as Pseudomonas and E. bacteria in biofilters.
Asunto(s)
Desnitrificación , Fósforo , Reactores Biológicos , Escherichia coli , Nitratos , Nitrógeno , Eliminación de Residuos LíquidosRESUMEN
A combination of processes was required for the proper treatment of old landfill leachate, as it contained a high concentration of pollutants. Humic substances comprised half of the total organic carbon in the raw leachate. Mobility of di(2-ethylhexyl) phthalate (DEHP) and metals could depend on the fate of these substances. Characterization of carbon in raw leachate and effluent of the membrane bioreactor, biofiltration, electro-oxidation, electro-coagulation, and nanofiltration showed complete removal of suspended solids and colloids. Physical processes could not remove the hydrophilic fraction due to its lower molecular weight. However, high removal of the hydrophilic fraction with a molecular weight <500 Da was expected in the biological process. In comparison with fulvic acid, larger sized humic acid resulted in complete removal by physicochemical processes. Because of DEHP partitioning on dissolved organic matter, especially on humic substances, its removal could be correlated with total organic carbon removal. Metals such as iron, aluminum, magnesium, and lead showed removal efficiency >80% in biological processes. Electro-deposition on the surface of an electrode and precipitation by hydroxide resulted in removal efficiencies >90 and >50% in electro-coagulation and electro-oxidation, respectively. Rejection of metals by nanofiltration was >80% and depended on the size and charge of cation. All in all, a combination of membrane bioreactor and nanofiltration seems to be the optimal process configuration for efficient treatment of old landfill leachate.
Asunto(s)
Sustancias Húmicas/análisis , Eliminación de Residuos , Contaminantes Químicos del Agua/análisis , Reactores Biológicos , HierroRESUMEN
In this study, a submerged membrane bioreactor was used to study the effect of low and high bisphenol A (BPA) concentration on the sludge biological activity. The pilot was operated over 540 days with hydraulic retention time and solid retention time of 5.5 hours and 140 days, respectively. As a hydrophobic compound, BPA was highly adsorbed by activated sludge. In lower concentrations, the biodegradation rate remained low, since the BPA concentration in the sludge was lower than 0.5 mg/g TS; yet, at an influent concentration up to 15 mg/L, the biodegradation rate was increasing, resulting in 99% BPA removal efficiency. The result for chemical oxygen demand removal showed that BPA concentration has no effect on the heterotrophic bacteria that were responsible for the organic carbon degradation. In higher concentrations, up to 16 mg of BPA was used for each gram of sludge as a source of carbon. However, the activity of autotrophic bacteria, including nitrifiers, was completely halted in the presence of 20 mg/L of BPA or more. Although nitrification was stopped after day 400, ammonia removal remained higher than 70% due to air stripping. Assimilation by bacteria was the only removal pathway for phosphorus, which resulted in an average 35% of P-PO4 removal efficiency.
Asunto(s)
Compuestos de Bencidrilo/química , Compuestos de Bencidrilo/metabolismo , Reactores Biológicos , Membranas Artificiales , Fenoles/química , Fenoles/metabolismo , Eliminación de Residuos Líquidos/métodos , Amoníaco , Análisis de la Demanda Biológica de Oxígeno , Nitrificación , Fósforo , Aguas del Alcantarillado/química , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/metabolismoRESUMEN
Landfill leachates are known for their high and complex composition of organic, inorganic and microbial pollutants. As a result, it is quite challenging to treat these effluents by using only one treatment process. A combining approach is generally required to treat efficiently these wastewaters and comply with the discharge standards. In this present study, electrocoagulation (EC) and biofiltration (BF) processes were sequentially used to treat landfill leachate. EC process has been able to remove 37⯱â¯2% of the initial total COD. A fractionation of organic compounds showed that EC was particularly efficient to remove insoluble COD and humic acids. In addition, other pollutants such as turbidity, true color, Zn and phosphorus were significantly reduced by EC with 82⯱â¯2.7%, 60⯱â¯13%, 95⯱â¯2.6% and 82⯱â¯5.5% of removal respectively. The subsequent treatment by BF process led to completely removal of ammonia pollution (>99% of NH4 removal) and a partial removal of dissolved organic compounds (42⯱â¯7% of COD removal). The hybrid process EC/BF could form the basis of a process capable of removing organic and inorganic pollutants from many refractory wastewaters (mature landfill leachates, industrial and municipal wastewaters).
Asunto(s)
Electrocoagulación , Instalaciones de Eliminación de Residuos , Contaminantes Químicos del Agua/química , Filtración , Sustancias Húmicas , Compuestos Orgánicos , FósforoRESUMEN
In this work, the combination of membrane bioreactor (MBR) and electro-oxidation (EO) process was studied for the treatment of a synthetic hospital wastewater fortified with four pharmaceutical pollutants namely carbamazepine (CBZ), ibuprofen (IBU), estradiol (E-E) at a concentration of 10 µg L-1 venlafaxine (VEN) at 0.2 µg L-1. Two treatment configurations were studied: EO process as pre-treatment and post-treatment. Wastewater treatment with MBR alone shows high removal percentages of IBU and E-E (â¼90%). Unlikely for CBZ and VEN, a low elimination percentage (â¼10%) was observed. The hydraulic and the solid retention times (HRT and SRT) were 18 h and 140 d respectively, while the biomass concentration in the MBR was 16.5 g L-1. To enhance pharmaceuticals elimination, an EO pretreatment was conducted during 40 min at 2 A. This configuration allowed a 92% removal for VEN, which was far greater than both treatments alone, with lower than 30% and 50% for MBR and EO, respectively. The MBR-EO coupling (EO as post-treatment) allows high removal percentages (â¼97%) of the four pharmaceutical pollutants after 40 min of treatment at a current intensity of 0.5 A with Nb/BDD as electrodes. This configuration appears to be very effective compared to the first configuration (EO-MBR) where EO process is used as a pre-treatment. Toxicity assessment showed that the treated effluent of this configuration is not toxic to Daphnia magna except at 100% v/v. The MBR-EO coupling appears to be a promising treatment for contaminated hospital effluents.
Asunto(s)
Reactores Biológicos , Eliminación de Residuos Líquidos/métodos , Aguas Residuales/química , Contaminantes Químicos del Agua/análisis , Biomasa , Carbamazepina , Hospitales , Cinética , Eliminación de Residuos Sanitarios , Membranas Artificiales , Oxidación-Reducción , Contaminantes Químicos del Agua/toxicidadRESUMEN
Electrocoagulation (EC) was employed to treat residual organic matter from a landfill leachate pretreated by an aerated bio-filter system. Organic matter (humic acids (HA), fulvic acids (FA) and hydrophilic compounds (Hyl)) was fractionated using DAX-8 resin in order to estimate the efficiency of EC on each fraction. Initial characterization of the bio-filtrated landfill leachate showed that humic substances (HA + FA) represented nearly 90% of TOC. The effects of current densities, type of anode (Aluminum versus iron), and treatment time on the performance of COD removal were investigated. The best COD removal performances were recorded at a current density ranging between 8.0 and 10 mA cm-2 during 20 min of treatment time. Under these conditions, 70% and 65% of COD were removed using aluminum and iron electrodes, respectively. The fractionating of organic matter after EC treatment revealed that HA was completely removed using either aluminum or iron anode. However, FA and Hyl fractions were partially removed, with the percentages varying from 57 to 60% and 37-46%, respectively. FA and Hyl removal were quite similar using either aluminum or iron anode. Likewise, a significant decrease in 254-nm absorbance was recorded (UV254 removal of 79-80%) using either type of anode. These results proved that EC is a suitable and efficient approach for treating the residual refractory organic matter from a landfill leachate previously treated by a biological system.
Asunto(s)
Benzopiranos/análisis , Electrocoagulación/métodos , Sustancias Húmicas/análisis , Contaminantes Químicos del Agua/análisis , Aluminio/química , Benzopiranos/química , Fraccionamiento Químico , Electrodos , Filtración , Hierro/química , Eliminación de Residuos/métodos , Instalaciones de Eliminación de ResiduosRESUMEN
The presence of recalcitrant dissolved organic matter (DOM) could have a significant effect on the adsorption mechanism and capacity of the sludge for many trace organic carbons (TrOCs). In this study, adsorption of three TrOCs on the sludge and HA was investigated. The results revealed that neutral hydrophilic compounds had an insignificant interaction with both sludge and HA. Positively charged compounds, such as fluoranthene, had more affinity toward HA than sludge with solid/liquid partitioning of 57 and 3.2â L/g, respectively. The adsorption intensity (Kf) of di-2-ethyl hexyl phthalate was 0.5 and 1.13 for the HA and the sludge, respectively. By introducing the sludge to the solution of HA and TrOCs that already reached equilibrium, the sludge adsorption capacity in the presence of HA was investigated. The finding showed that at the lower concentration, adsorption of HA on the sludge was considered as the main removal pathway for the adsorbed emerging contaminants, as 70 mg of HA was adsorbed by a gram of sludge. For the higher concentration, desorption of TrOCs from DOM into the sludge comprised 15-30% of total removal efficiency. ABBREVIATIONS: CBZ: carbamazepine; DEHP: di-2-ethyl hexyl phthalate; DOM: dissolved organic matter; FLAN: fluoranthene; foc: fraction of organic carbon; HA: humic acid; Log Kow: octanol-water partition coefficient; PAH: polycyclic aromatic hydrocarbon TS: total solid; TrOCs: trace organic carbons VS: volatile solid.
Asunto(s)
Carbono , Aguas del Alcantarillado , Adsorción , Sustancias Húmicas , Compuestos Orgánicos , Contaminantes Químicos del AguaRESUMEN
Combination of high performance membrane bioreactor (MBR) equipped with ultrafiltration and electro-oxidation process (EOP) by boron-doped diamond electrode (BDD) was used to effectively treat highly contaminated old landfill leachate. MBR and EOP were optimized for raw and pretreated landfill leachate. Seasonal changes dramatically affected the both processes' performance, as the landfill leachate was ¾ more concentrated in winter. For MBR, organic load rate of 1.2 gCOD/L/day and sludge retention time of 80 days was considered as the optimum operating condition in which COD, TOC, NH4+ and phosphorous removal efficiencies reached the average of 63, 35, 98 and 52%, respectively. The best performance of EOP was in current intensity of 3 A with treatment of time of 120 min. Effluent of electro-oxidation was more toxic due to the presence of radicals and organochlorinated compounds. These compounds were removed by stripping or assimilation of sludge if EOP was used as a pretreatment method. Furthermore, the energy consumption of EOP was decreased from 22 to 16 KWh/m3 for biologically treated and raw landfill leachate, respectively.
Asunto(s)
Reactores Biológicos , Eliminación de Residuos Líquidos/instrumentación , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/química , Análisis de la Demanda Biológica de Oxígeno , Boro , Diamante , Electrodos , Diseño de Equipo , Sustancias Húmicas , Oxidación-Reducción , Quebec , Aguas del Alcantarillado , Ultrafiltración , Contaminantes Químicos del Agua/metabolismoRESUMEN
A combined upflow anaerobic sludge blanket (UASB)-trickling biofilter (TBF) process was constructed to treat swine wastewater, a typical high-strength organic wastewater with low carbon/nitrogen ratio and ammonia toxicity. The results showed that the UASB-TBF system can remarkably enhance the removal of pollutants in the swine wastewater. At an organic loading rate of 2.29â kg/m(3)â d and hydraulic retention time of 48â h in the UASB, the chemical oxygen demand (COD), Suspended Solids and Total Kjeldahl Nitrogen removals of the combined process reached 83.6%, 84.1% and 41.2%, respectively. In the combined system the UASB served as a pretreatment process for COD removal while nitrification and denitrification occurred only in the TBF process. The TBF performed reasonably well at a surface hydraulic load as high as 0.12â m(3)/m(2)â d. Since the ratio of influent COD to total mineral nitrogen was less than 3.23, it is reasonable to suggest that the wood chips in TBF can serve as a new carbon source for denitrification.
Asunto(s)
Filtración/instrumentación , Nitrógeno/aislamiento & purificación , Eliminación de Residuos Líquidos/instrumentación , Aguas Residuales/análisis , Aguas Residuales/microbiología , Contaminantes Químicos del Agua/aislamiento & purificación , Amoníaco/aislamiento & purificación , Amoníaco/metabolismo , Anaerobiosis , Crianza de Animales Domésticos , Animales , Bacterias/metabolismo , Análisis de la Demanda Biológica de Oxígeno , Reactores Biológicos/microbiología , Desnitrificación , Diseño de Equipo , Filtración/métodos , Residuos Industriales/análisis , Nitrificación , Nitrógeno/metabolismo , Aguas del Alcantarillado/análisis , Aguas del Alcantarillado/microbiología , Porcinos , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/metabolismo , Purificación del Agua/instrumentación , Purificación del Agua/métodosRESUMEN
Highly hydrophobic Di 2-ethyl hexyl phthalate (DEHP) is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25days, it can be used as an efficiency indicator of wastewater treatment plant for the removal of hydrophobic emerging contaminants. In this study, the performance of submerged membrane bioreactor was monitored to understand the effect of DEHP on the growth of aerobic microorganisms. The data showed that the chemical oxygen demand (COD) and ammonia concentration were detected below 10 and 1.0mg/L, respectively for operating conditions of hydraulic retention time (HRT)=4 and 6hr, sludge retention time (SRT)=140day and sludge concentration between 11.5 and 15.8g volatile solid (VS)/L. The removal efficiency of DEHP under these conditions was higher and ranged between 91% and 98%. Results also showed that the removal efficiency of DEHP in biological treatment depended on the concentration of sludge, as adsorption is the main mechanism of its removal. For the submerged membrane bioreactor, the pore size is the pivotal factor for DEHP removal, since it determines the amount of soluble microbial products coming out of the process. Highly assimilated microorganisms increase the biodegradation rate, as 74% of inlet DEHP was biodegraded; however, the concentration of DEHP inside sludge was beyond the discharge limit. Understanding the fate of DEHP in membrane bioreactor, which is one of the most promising and futuristic treatment process could provide replacement for conventional processes to satisfy the future stricter regulations on emerging contaminants.