Membrane Bioreactor Effluent Research Articles

Optimizing Membrane Bioreactor/ Reverse Osmosis Performance for Municipal Wastewater Treatment

Combining microfiltration (MF) and reverse osmosis (RO) is an accepted practice for treating secondary effluent to allowable levels for common and advanced reuse applications. Several municipalities in the United States and abroad use this combination on a large scale. This leads to the next innovation in treating wastewater—membrane bioreactors (MBRs), the specialized use of MF integrated with activated sludge treatment followed by RO. The Southern Nevada Water Authority has been conducting an ongoing test of such a configuration at the Las Vegas Water Pollution Control Facility since 2009. The study's goal is to better understand the fouling of RO membranes, which directly treat MBR effluent, and to evaluate technologies to minimize RO fouling. The pilot has had stable operation for more than 4,000 hours and has not required RO cleaning when operated at a flux rate of 14 gpd/ft2 (23.8 LMH) and higher. The results have confirmed that MBR–RO is a viable wastewater treatment technology.

Hospital Wastewater Treatment by Membrane Bioreactor: Performance and Efficiency for Organic Micropollutant Elimination

A pilot-scale membrane bioreactor (MBR) was installed and operated for one year at a Swiss hospital. It was fed an influent directly from the hospital's sanitary collection system. To study the efficiency of micropollutant elimination in raw hospital wastewater that comprises a complex matrix with micropollutant concentrations ranging from low ng/L to low mg/L, an automated online SPE-HPLC-MS/MS analytical method was developed. Among the 68 target analytes were the following: 56 pharmaceuticals (antibiotics, antimycotics, antivirals, iodinated X-ray contrast media, antiinflamatory, cytostatics, diuretics, beta blockers, anesthetics, analgesics, antiepileptics, antidepressants, and others), 10 metabolites, and 2 corrosion inhibitors. The MBR influent contained the majority of those target analytes. The micropollutant elimination efficiency was assessed through continuous flow-proportional sampling of the MBR influent and continuous time-proportional sampling of the MBR effluent. An overall load elimination of all pharmaceuticals and metabolites in the MBR was 22%, as over 80% of the load was due to persistent iodinated contrast media. No inhibition by antibacterial agents or disinfectants from the hospital was observed in the MBR. The hospital wastewater was found to be a dynamic system in which conjugates of pharmaceuticals deconjugate and biological transformation products are formed, which in some cases are pharmaceuticals themselves.

Nanofiltration as a Post-Treatmento to Membrane Bioreactor Effluent for Dairy Wastewater Reuse

Nanofiltration as a Post-Treatmento to Membrane Bioreactor Effluent for Dairy Wastewater Reuse

Study on High-strength Anaerobic Landfill Leachate Treatability By Membrane Bioreactor Coupled with Reverse Osmosis

One of the most important concerns in Tehran municipal landfill is the production of leachate and its potential for water resources pollution, this study was undertaken to examine feasibility of biological and physico/chemical treating of high-strength landfill leachate that was collected from Tehran municipal landfill. Average COD of the leachate in aerobic submerged membrane bioreactor is 68000 mg/L. The reactor with a working volume of 175 L, having membrane module (Hollow fiber) with pore size of 0.1 μm coupled with reverse osmosis with pore size of 0.001 μm was used in this study. The dissolved oxygen (DO) concentration was maintained at 3.2 mg/L and solid retention times (SRTs) and hydraulic retention times (HRT) were controlled at 55 and 15 days respectively. the average Membrane Bioreactor effluent COD was 1733 mg/L with average removal efficiency of 97.46%. The average NH 4 –N removal efficiencies was 99%. On the other hand, an almost complete nitrification was achieved during this period. PO4 –P concentration in the effluent was low and its average removal efficiency was as high as 90%; especially during the operation period. The averages reverse osmosis (RO) effluent COD was 335 mg/L with average removal efficiency of 99.13%. PO4-P concentration in the RO effluent was 0.86 mg/L and its average removal efficiency was 99.33%. The use of Membrane technologies, more especially reverse osmosis offers the best solution of achieving full purification with average COD removal efficiency of 99% and solving the problem of water resources pollution.

Removal of Organics and Degradation Products from Industrial Wastewater by a Membrane Bioreactor Integrated with Ozone or UV/H2O2 Treatment

The treatment of a pharmaceutical wastewater resulting from the production of an antibacterial drug (nalidixic acid) was investigated employing a membrane bioreactor (MBR) integrated with either ozonation or UV/H(2)O(2) process. This was achieved by placing chemical oxidation in the recirculation stream of the MBR. A conventional configuration with chemical oxidation as polishing for the MBR effluent was also tested as a reference. The synergistic effect of MBR when integrated with chemical oxidation was assessed by monitoring (i) the main wastewater characteristics, (ii) the concentration of nalidixic acid, (iii) the 48 organics identified in the raw wastewater and (iv) the 55 degradation products identified during wastewater treatment. Results showed that MBR integration with ozonation or UV/H(2)O(2) did not cause relevant drawbacks to both biological and filtration processes, with COD removal rates in the range 85-95%. Nalidixic acid passed undegraded through the MBR and was completely removed in the chemical oxidation step. Although the polishing configuration appeared to give better performances than the integrated system in removing 15 out of 48 secondary organics while similar removals were obtained for 19 other compounds. The benefit of the integrated system was however evident for the removal of the degradation products. Indeed, the integrated system allowed higher removals for 34 out of 55 degradation products while for only 4 compounds the polishing configuration gave better performance. Overall, results showed the effectiveness of the integrated treatment with both ozone and UV/H(2)O(2).

Textile wastewater treatment in a bench-scale anaerobic-biofilm anoxic-aerobic membrane bioreactor combined with nanofiltration

This study evaluated the treatability of textile wastewaters in a bench-scale experimental system, comprising an anaerobic biofilter, an anoxic reactor and an aerobic membrane bioreactor (MBR). The MBR effluent was thereafter treated by a nanofiltration (NF) membrane. The proposed system was demonstrated to be effective in the treatment of the textile wastewater under the operating conditions applied in the study. The MBR system achieved a good COD (90–95%) removal; due to the presence of the anaerobic biofilter, also effective color removal was obtained (70%). The addition of the NF membrane allowed the further improvement in COD (50–80%), color (70–90%) and salt removal (60–70% as conductivity). In particular the NF treatment allowed the almost complete removal of the residual color and a reduction of the conductivity such as to achieve water quality suitable for reuse.

Water reuse: >90% water yield in MBR/RO through concentrate recycling and CO 2 addition as scaling control

Over 1.5 years continuous piloting of a municipal wastewater plant upgraded with a double membrane system (ca. 0.6 m 3 d −1 of product water produced) have demonstrated the feasibility of achieving high water quality with a water yield of 90% by combining a membrane bioreactor (MBR) with a submerged ultrafiltration membrane followed by a reverse osmosis membrane (RO). The novelty of the proposed treatment scheme consists of the appropriate conditioning of MBR effluent prior to the RO and in recycling the RO concentrates back to the biological unit. All the 15 pharmaceuticals measured in the influent municipal sewage were retained below 100 ng L −1, a proposed quality parameter, and mostly below detection limits of 10 ng L −1. The mass balance of the micropollutants shows that these are either degraded or discharged with the excess concentrate, while only minor quantities were found in the excess sludge. The micropollutant load in the concentrate can be significantly reduced by ozonation. A low treated water salinity (<10 mM inorganic salts; 280 ± 70 μS cm −1) also confirms that the resulting product has a high water quality. Solids precipitation and inorganic scaling are effectively mitigated by lowering the pH in the RO feed water with CO 2 conditioning, while the concentrate from the RO is recycled to the biological unit where CO 2 is stripped by aeration. This causes precipitation to occur in the bioreactor bulk, where it is much less of a process issue. SiO 2 is the sole exception. Equilibrium modeling of precipitation reactions confirms the effectiveness of this scaling-mitigation approach for CaCO 3 precipitation, calcium phosphate and sulfate minerals.

Identification of biotransformation products of macrolide and fluoroquinolone antimicrobials in membrane bioreactor treatment by ultrahigh-performance liquid chromatography/quadrupole time-of-flight mass spectrometry

Ultrahigh-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry was applied for the identification of transformation products (TPs) of fluoroquinolone (norfloxacin and ciprofloxacin) and macrolide (azithromycin, erythromycin, and roxitromycin) antimicrobials in wastewater effluents from a Zenon hollow-fiber membrane bioreactor (MBR). The detected TPs were thoroughly characterized using the accurate mass feature for the determination of the tentative molecular formulae and MS-MS experiments for the structural elucidation of unknowns. Several novel TPs, which have not been previously reported in the literature, were identified. The TPs of azithromycin and roxithromycin, identified in MBR effluent, were conjugate compounds, which were formed by phosphorylation of desosamine moiety. Transformation of fluoroquinolones yielded two types of products: conjugates, formed by succinylation of the piperazine ring, and smaller metabolites, formed by an oxidative break-up of piperazine moiety to form the 7-[(2-carboxymethyl)amino] group. A semi-quantitative assessment of these TPs suggested that they might have contributed significantly to the overall balance of antimicrobial residues in MBR effluents and thus to the overall removal efficiency. Determination of TPs during a period of 2 months indicated a conspicuous dynamics, which warrants further research to identify microorganisms involved and treatment conditions leading to their formation.

Influence of seasonal and operating conditions on the rejection of pharmaceutical active compounds by RO and NF membranes

The effect of seasonal changes, ionic strength, effluent dilution, transmembrane pressure and spiked concentration on the rejection of the pharmaceutical active compounds (PhACs), carbamazepine (CBZ) and diatrizoate (DTZ) by reverse osmosis (RO) and nanofiltration (NF), was studied. They represent two families of compounds owning low/medium hydrophobicity and relatively high stability to biological transformation at wastewater treatment plant conditions, frequently present in effluents. Experiments were performed with membrane bioreactor effluents and ultrapure water (UPW) to test the influence of background matrix on the rejection. Three RO (BW, SW and XLE) and two NF (NF90 and NF270) membranes were tested. RO exhibited high rejection of both the compounds (> 98%) regardless of membrane resolution or conditions tested. The loosest membrane tested, NF270, displayed a marked seasonal influence on CBZ rejection from effluents (up to 92% in summer and down to 50% in winter), whereas its rejection from UPW was steady (74 ± 7%). These findings strongly suggest that interactions between low/medium hydrophobicity-PhACs and effluent organic matter (EfOM) took place which markedly changed rejection efficiencies. These interactions seem to be highly correlated to EfOM quality, being enhanced during summer, increasing the removal of small PhACs even by loose nonporous membranes, but decreasing during winter, thus reducing rejection.

Removal and recovery of nutrients by ion exchange from high rate membrane bio-reactor (MBR) effluent

In this study a membrane bioreactor (MBR) with ion-exchange as post-treatment was investigated for organic removal and nutrient recovery. The MBR was operated at a short HRT of 4h in order to mainly remove organic carbon. This was followed by an ion-exchange process to remove and later recover the nitrogen and phosphorus from the MBR effluent. The increase in membrane resistance was reduced by 90% (from 0.061 to 0.006m-1d-1) when the air scouring rate was increased from 0.5 to 1.5m3/m2membrane areah. The organic removal rate in terms of DOC was 85–90%. The bio-polymer in the molecular weight range of 24,500Da was retained by the membrane of the MBR while humic type substances and lower molecular organic matter (molecular weight of 360–60Da) were not effectively removed by the membrane. The ion-exchange process effectively removed the nutrients from the effluent of the MBR. The retention of PO43− and NO3− by the two ion-exchange columns in series was 85% and 95% respectively. Over 95–98% phosphate and nitrate recovery was obtained during regeneration of columns with 1% NaCl of 20 bed volumes. This integrated process can remove pollutants and at the same time recover nutrients and thus open a new source for nitrogen and phosphorous.

Advanced treatment of Membrane Bioreactor (MBR) effluents for effective wastewater reclamation

One of the two main objectives of this work is to oxidize MBR effluents with ozone/peroxide in high pH conditions in order to improve oxidation of pharmaceuticals, which could efficiently be rejected by the nanofiltration (NF) stage. The other main objective is to effectively oxidize of dissolved organic carbon (DOC) in MBR effluents in order to decrease fouling in the filtration stage. In this work, ozone/peroxide oxidation was applied to the MBR effluents in high pH conditions in order to improve the formation of OH radicals, and oxidized effluents were filtered by the NF membrane (NE90) in order to investigate fouling potentials and the removal of pharmaceuticals. Natural and synthetic wastewater samples were used as feed solutions for the MBR system, which was equipped with a U-shaped hollow fiber membrane module. The flux decline was decreased from 29% to 15% when 9 mg/L of ozone was used, the same decline was also observed when 6 mg/L ozone and hydrogen peroxide (1/1 ozone/peroxide mol ratio) were used. A further decrease in flux decline was observed when pH was adjusted to 9.00 (29% to 9%) prior to the ozone/peroxide oxidation. In most cases, the increase in the ozone dose, the addition of hydrogen peroxide and the adjustment of the pH level led to an increase in the removal of pharmaceuticals. Iopromide, TCEP and Naproxen were found to be more resistant to the oxidation when pH was increased.

Advanced treatment of dyeing wastewater towards reuse by the combined Fenton oxidation and membrane bioreactor process

The performance of combined Fenton oxidation and membrane bioreactor (MBR) process for the advanced treatment of an effluent from an integrated dyeing wastewater treatment plant was evaluated. The experimental results revealed that under the optimum Fenton oxidation conditions (initial pH 5, H 2O 2 dosage 17 mmol/L, and Fe 2+ 1.7 mmol/L) the average total organic carbon (TOC) and color removal ratios were 39.3% and 69.5% after 35 min of reaction, respectively. Results from Zahn-Wallens Test also represented that Fenton process was effective to enhance the biodegradability of the test wastewater. As for the further purification of MBR process, TOC removal capacity was examined at different hydraulic retention times (HRT) of 10, 18 and 25 hr. Under the optimum HRT of 18 hr, the average TOC concentration and color of the final MBR effluent were 16.8 mg/L and 2 dilution time, respectively. The sludge yield coefficient was 0.13 g MLSS/g TOC and TOC degradation rate was 0.078 kg TOC/(m 3·day). The final effluent of MBR can meet the reuse criteria of urban recycling water - water quality standard for miscellaneous water consumption GBT18920-2002.

Further treatment of landfill leachate by nanofiltration and microfiltration–PAC hybrid process

Biological treatment is a commonly used process for the treatment of landfill leachate. However, with this treatment process, the permitted discharge limits cannot be consistently met, due to the recalcitrant characteristics of organic carbon in leachate. Therefore, some physico-chemical treatment technologies should be applied for the removal of inert substances, as a refining step. In this study, the main aim was to reduce the Chemical Oxygen Demand (COD) concentration of the jet-loop membrane bioreactor effluent further to meet the COD discharge limit value (700 mg COD/L) determined by the Ministry of Environment and Forestry of Turkey (MoEF). For this purpose, two different systems were used after the jet-loop membrane reactor, namely nanofiltration (NF) unit and microfiltration–powdered activated carbon (MF–PAC) hybrid system. The membranes used in the NF unit were not able to reduce the COD concentration to the desired levels. However, the MF–PAC system achieved to meet the COD discharge limit value, when 8 g PAC/L concentration was used.

Performance of a full-scale membrane bioreactor system in treating municipal wastewater for reuse purposes

The microbial removal efficacy of membrane bioreactor (MBR) technology in a full-scale municipal wastewater treatment plant was evaluated. Total and faecal coliforms, thermo-tolerant coliforms, Escherichia coli, enterococci, somatic coliphages, F-RNA specific bacteriophages and bacteriophages infecting Bacteroides fragilis (BFRPH) were used as bacterial and viral indicators. Reclamation and reuse of MBR effluent were considered. The average Log 10 reductions of the bacterial indicators range from 6 Log 10 for enterococci to 7 Log 10 for E. coli and faecal coliforms. The average removal of FRNA coliphages was similar to that of enterococci. Complete removal of BFRPH was observed. Log 10 reductions of somatic coliphages were significantly lower than those of all other indicators. Somatic coliphages appear to be better indicators of the microbial removal efficiency of the MBR system than faecal bacterial indicators. The quality of the MBR permeate conforms largely with the microbiological standards for urban (e.g. street cleaning, vehicle washing) and agricultural reuse.

Effective organics degradation from pharmaceutical wastewater by an integrated process including membrane bioreactor and ozonation

The enhanced removal of organic compounds from a pharmaceutical wastewater resulting from the production of an anti-viral drug (acyclovir) was obtained by employing a membrane bioreactor (MBR) and an ozonation system. An integrated MBR–ozonation system was set-up by placing the ozonation reactor in the recirculation stream of the MBR effluent. A conventional treatment set-up (ozonation as polishing step after MBR) was also used as a reference. The biological treatment alone reached an average COD removal of 99%, which remained unvaried when the ozonation step was introduced. An acyclovir removal of 99% was also obtained with the MBR step and the ozonation allowed to further remove 99% of the residual concentration in the MBR effluent. For several of the 28 organics identified in the wastewater the efficiency of the MBR treatment improved from 20% to 60% as soon as the ozonation was placed in the recirculation stream. The benefit of the integrated system, with respect to the conventional treatment set-up was evident for the removal of a specific ozonation by-product. The latter was efficiently removed in the integrated system, being its abundance in the final effluent 20-fold lower than what obtained when ozonation was used as a polishing step. In addition, if the conventional treatment configuration is employed, the same performance of the integrated system in terms of by-product removal can only be obtained when the ozonation is operated for longer than 60 min. This demonstrates the effectiveness of the integrated system compared to the conventional polishing configuration.

Membrane Bioreactor Effluent Water Quality and Technology – Organics, Nutrients and Microconstituents Removal

Membrane Bioreactor Effluent Water Quality and Technology – Organics, Nutrients and Microconstituents Removal

Assessment of human adenovirus removal in a full-scale membrane bioreactor treating municipal wastewater

Human adenoviruses (HAdVs) in wastewater samples taken from four different treatment stages of a full-scale municipal wastewater treatment plant (i.e., incoming raw sewage, primary sedimentation effluent, membrane bioreactor (MBR) influent, and MBR effluent) were quantified by real-time PCR assays to further estimate removal efficiency of the HAdVs. Based on hexon gene sequence comparisons, HAdV species A, C, and F were consistently found in the wastewater samples. In general, all three identified HAdV species were detected in most of the wastewater samples using the real-time PCR assays. Overall HAdV concentrations were rather stable over the entire 8-month study period (January–August, 2008) (approximately 10 6–10 7 viral particles/L of wastewater for the raw sewage and primary effluent; 10 8–10 9 viral particles/L for the MBR influent; and, 10 3–10 4 viral particles/L for the MBR effluent). No significant seasonal differences were noticed for the HAdV abundances. Removal efficiencies of the viral particles in the full-scale MBR process were assessed and showed an average HAdV removal of 5.0 ± 0.6 logs over the study period. The removal efficiencies for F species (average log removal of 6.5 ± 1.3 logs) were typically higher ( p-value <0.05) than those of the other two species (average of 4.1 ± 0.9 and 4.6 ± 0.5 logs for species A and C, respectively). These results demonstrate that the full-scale MBR system efficiently removed most HAdV from the wastewater leaving about 10 3 viral particles/L in the MBR effluent.

Comparison of the removal of phthalates and other organic pollutants from industrial wastewaters in membrane bioreactor and conventional activated sludge treatment plants

In recent years greater attention has been paid to the presence of pollutants in wastewater treatment plants, mainly because of strict environmental regulations and the possibility of reusing treated water in industrial processes. Since some organic pollutant compounds are not sufficiently removed in conventional activated sludge treatment (CAST) plants, new treatment processes have been developed, such as membrane bioreactors (MBRs). In this study a submerged membrane bioreactor (MBR) was used to treat mixed industrial wastewaters in parallel with a CAST plant. Two hydraulic retention times (HRT) of wastewater were tested as one of the operational conditions of MBR and the quality of effluents of the two processes were studied and compared. Several general quality parameters were analysed in wastewaters: chemical oxygen demand (COD), pH, conductivity, nitrogen, phosphate, suspended solids (SS) and turbidity. The two systems reduced COD by around 90%. SS was reduced by around 81% in the CAST plant and around 90% in the MBR plant. The results for the other general parameters were similar or better in the MBR process, which worked at a lower HRT. We also studied the removal of a group of six phthalates and bis(2-ethylhexyl)adipate ester by SPME/GC-MS in the two treatment plants. Most of these compounds were not completely removed in the two treatment plants and were identified at low microg l(-1) levels. We also tentatively identify some organic compounds in the wastewaters. Most of the compounds we found in the influent, MBR effluent and CAST effluent were benzene derivates, styrene, naphthalene and naphthalene derivates, and phenol derivates.

Application of MBR for hospital wastewater treatment in China

In China, the number of hospitals has increased to 19,712 in 2008, with the production of hospital wastewater reaching 1.29 × 10 6 m 3/d. Membrane bioreactor (MBR) technology presents a more efficient system at removing pathological microorganism compared with existing wastewater treatment systems. In the past 8 yr, over 50 MBR plants have been successfully built for hospital wastewater treatments, with the capacity ranging from 20 to 2000 m 3/d. MBR can effectively save disinfectant consumption (chlorine addition can decrease to 1.0 mg/L), shorten the reaction time (approximately 1.5 min, 2.5–5% of conventional wastewater treatment process), and attain a good effect of inactivation of microorganism. Higher disinfection efficacy is achieved in MBR effluents at lower dose of disinfectant with less disinfection by-products (DBPs). Moreover, when capacity of MBR plants increases from 20 to 1000 m 3/d, their operating cost decreases sharply.

Hybrid membrane bioreactor technology for small water treatment utilities: Process evaluation and primordial considerations

A hybrid membrane bioreactor (MBR) technology was investigated for treatment of natural waters containing natural organic matter (NOM), nitrate, alachlor and viruses. The NOM are precursors to disinfection byproducts (DBPs) such as trihalomethanes, and potential cause for microbial growth in distribution systems. Batch bioreactor studies optimized the carbon-to-nitrogen (C/N) ratio, temperature and pH for biological denitrification. Mini-pilot MBR studies with ethanol as electron donor were conducted under three scenarios: no powder activated carbon (PAC) or biomass, biomass alone, and combination of PAC and biomass. The removals of nitrate, alachlor, total organic carbon (TOC), trihalomethane formation potential (THMFP) and MS-2 virus were revaluated. Nitrite and ethanol residuals were well below their detection limits in the MBR effluent under steady-state conditions. Using biomass alone, the removal efficiencies for NOM (as TOC), alachlor, and THMFP were 60, 36 and 61%, respectively; whereas, on combining PAC and biomass they increased to 84, 99.8 and 98%. The virus rejection mechanisms postulated were size exclusion, sorption to membrane surface, attachment to bio-particles, and sorption onto foulant or cake layers. The MS-2 removals exceeded 3.8-logs under optimal process conditions. Membrane fouling and flux decline patterns under the three experimental scenarios were well described by the resistance model. The flux decline was characterized by three distinct stages, namely, initial conditioning fouling, rapid fouling, and slow fouling. The Tustin groundwater was associated with lower organic fouling but higher inorganic fouling than the Fountain Valley groundwater.