Acclimatization of microbial community of submerged membrane bioreactor treating hospital wastewater

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.

Passive phosphorus capture in biofiltration context: nitrate impact on the performance

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 5 mg P L^-1. Different concentrations of nitrate (5, 10 and 25 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.

The bacterial community structure of submerged membrane bioreactor treating synthetic hospital wastewater

The pharmaceuticals are biologically active compounds used to prevent and treat diseases. These pharmaceutical compounds were not fully metabolized by the human body and thus excreted out in the wastewater stream. Thus, the study on the treatment of synthetic hospital wastewater containing pharmaceuticals (ibuprofen, carbamazepine, estradiol and venlafaxine) was conducted to understand the variation of the bacterial community in a submerged membrane bioreactor (SMBR) at varying hydraulic retention time (HRT) of 6, 12 and 18 h. The variation in bacterial community dynamics of SMBR was studied using high throughput sequencing. The removal of pharmaceuticals was uniform at varying HRT. The removal of both ibuprofen and estradiol was accounted for 90%, whereas a lower removal of venlafaxine (<10%) and carbamazepine (>5%) in SMBR was observed. The addition of pharmaceuticals alters the bacterial community structure and result in increased abundance of bacteria (e.g., Flavobacterium, Pedobacter, and Methylibium) reported to degrade toxic pollutant.

Hybrid process, electrocoagulation-biofiltration for landfill leachate treatment

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 ± 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 ± 2.7%, 60 ± 13%, 95 ± 2.6% and 82 ± 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 ± 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).

Removal of Pollutants in Different Landfill Leachate Treatment Processes on the Basis of Organic Matter Fractionation

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.

Performance of a membrane bioreactor in extreme concentrations of bisphenol A

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.

Synthetic hospital wastewater treatment by coupling submerged membrane bioreactor and electrochemical advanced oxidation process: Kinetic study and toxicity assessment

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 (∼90%). Unlikely for CBZ and VEN, a low elimination percentage (∼10%) 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 (∼97%) 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.

Insight into the adsorption mechanisms of trace organic carbon on biological treatment process

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 3.2 L/g, respectively. The adsorption intensity (K_f) 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; f_oc: 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.

Electrocoagulation of bio-filtrated landfill leachate: Fractionation of organic matter and influence of anode materials

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.

Landfill leachate treatment by sequential membrane bioreactor and electro-oxidation processes

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.

Effect of bioavailability on the fate of hydrophobic organic compounds and metal in treatment of young landfill leachate by membrane bioreactor

Complex dissolved organic matter (DOM) present in landfill leachate provides reliable media for adsorption of highly hydrophobic contaminants, such as Di 2-ethyl hexyl phthalate (DEHP). In this research, the feasibility of submerged membrane bioreactor (SMBR) for treatment of landfill leachate (LFL) was determined. Later, the operating conditions were optimized for removal of DEHP, COD, NH4(+) and PO4(3-), and finally the effect of bioavailability was examined by introduction of different concentrations of humic acid into the influent. The result revealed that presence of complex agglomerated organic compounds increased the removal efficiency of DEHP and COD, even though DEHP biodegradation rate in sludge dramatically decreased (from 58.8% to 12.8%). MBR retention of different metals in the absence and in the presence of recalcitrant DOM was also studied. Like DEHP, ternary interaction between metals, DOM, and sludge play a pivotal role in their removal efficiency and their concentration in sludge.

A combined upflow anaerobic sludge bed and trickling biofilter process for the treatment of swine wastewater

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 2.29 kg/m(3) d and hydraulic retention time of 48 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 0.12 m(3)/m(2) 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.

Investigation on removal pathways of Di 2-ethyl hexyl phthalate from synthetic municipal wastewater using a submerged membrane bioreactor

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.

Occurrence, fate and effects of Di (2-ethylhexyl) Phthalate in wastewater treatment plants: a review

Phthalates, such as Di (2-ethylhexyl) Phthalate (DEHP) are compounds extensively used as plasticizer for long time around the world. Due to the extensive usage, DEHP is found in many surface waters (0.013-18.5 μg/L), wastewaters (0.716-122 μg/L), landfill leachate (88-460 μg/L), sludge (12-1250 mg/kg), soil (2-10 mg/kg). DEHP is persistent in the environment and the toxicity of the byproducts resulting from the degradation of DEHP sometime exacerbates the parent compound toxicity. Water/Wastewater treatment processes might play a key role in delivering safe, reliable supplies of water to households, industry and in safeguarding the quality of water in rivers, lakes and aquifers. This review addresses state of knowledge concerning the worldwide production, occurrence, fate and effects of DEHP in the environment. Moreover, the fate and behavior of DEHP in various treatment processes, including biological, physicochemical and advanced processes are reviewed and comparison (qualitative and quantitative) has been done between the processes. The trends and perspectives for treatment of wastewaters contaminated by DEHP are also analyzed in this review.

The effect of race and sex on physicians' recommendations for cardiac catheterization

BACKGROUND

Epidemiologic studies have reported differences in the use of cardiovascular procedures according to the race and sex of the patient. Whether the differences stem from differences in the recommendations of physicians remains uncertain.

METHODS

We developed a computerized survey instrument to assess physicians' recommendations for managing chest pain. Actors portrayed patients with particular characteristics in scripted interviews about their symptoms. A total of 720 physicians at two national meetings of organizations of primary care physicians participated in the survey. Each physician viewed a recorded interview and was given other data about a hypothetical patient. He or she then made recommendations about that patient's care. We used multivariate logistic-regression analysis to assess the effects of the race and sex of the patients on treatment recommendations, while controlling for the physicians' assessment of the probability of coronary artery disease as well as for the age of the patient, the level of coronary risk, the type of chest pain, and the results of an exercise stress test.

RESULTS

The physicians' mean (+/-SD) estimates of the probability of coronary artery disease were lower for women (probability, 64.1+/-19.3 percent, vs. 69.2+/-18.2 percent for men; P<0.001), younger patients (63.8+/-19.5 percent for patients who were 55 years old, vs. 69.5+/-17.9 percent for patients who were 70 years old; P<0.001), and patients with nonanginal pain (58.3+/-19.0 percent, vs. 64.4+/-18.3 percent for patients with possible angina and 77.1+/-14.0 percent for those with definite angina; P=0.001). Logistic-regression analysis indicated that women (odds ratio, 0.60; 95 percent confidence interval, 0.4 to 0.9; P=0.02) and blacks (odds ratio, 0.60; 95 percent confidence interval, 0.4 to 0.9; P=0.02) were less likely to be referred for cardiac catheterization than men and whites, respectively. Analysis of race-sex interactions showed that black women were significantly less likely to be referred for catheterization than white men (odds ratio, 0.4; 95 percent confidence interval, 0.2 to 0.7; P=0.004).

CONCLUSIONS

Our findings suggest that the race and sex of a patient independently influence how physicians manage chest pain.

[Hyperactivity in children: a valid diagnosis?]

Research has documented differences between hyperactive and normal children. However, to be valid, a diagnostic entity must differ in etiology, course, characteristics, or treatment response from other behavior problems as well as from normality. In order to demonstrate the validity of this syndrome, the research has followed three lines: the search for a biological marker, the study of symptoms and the evaluation of the suspected cognitives deficits. No final answers have been obtained yet but understanding of this clinical entity is still progressing.

Agalactosyl IgG in inflammatory bowel disease: correlation with C-reactive protein

The proportion of oligosaccharide chains on the Fc fragment of IgG which terminate with N-acetylglucosamine (GlcNAc) rather than galactose is increased in rheumatoid arthritis and tuberculosis, and in sera from patients with Crohn's disease, probably because of decreased activity of a galactosyltransferase in B lymphocytes. We have assayed the prevalence of agalactosyl oligosaccharides on IgG in sera from 67 patients with inflammatory bowel disease (32 ulcerative colitis and 35 Crohn's disease). The prevalence of agalactosyl IgG significantly increases in the majority of Crohn's patients (19/35 patients), and correlates with the level of C-reactive protein (r = 0.79), and inversely with the concentration of serum albumin. Sera from ulcerative colitis patients show less frequent (nine of 32) and less marked rises in agalactosyl IgG, and sera with high C-reactive protein values can contain normal levels. Thus in ulcerative colitis no correlation was seen between the two assays. The diseases in which the percentage of agalactosyl IgG is raised (rheumatoid arthritis, tuberculosis, Crohn's disease and some ulcerative colitis) are characterised by simultaneous T cell mediated granulomatous tissue damage, and acute phase responses. Levels are normal in less tissue damaging granulomatous conditions, including sarcoidosis, and leprosy (except during episodes of erythema nodosum leprosum). We suggest therefore that a raised percentage of agalactosyl IgG is a correlate of a particular type of T cell mediated pathology which may be relevant to the pathogenesis of inflammatory bowel disease.