Domestic wastewater treatment employing a novel baffled osmotic membrane bioreactor-microfiltration hybrid system

University of Technology Sydney. Faculty of Engineering and Information Technology.A novel baffled osmotic membrane bioreactor microfiltration (OMBR-MF) hybrid system was proposed for the domestic wastewater treatment with specific focus on nutrient and organic micropollutant (OMPs) removal. This baffled OMBR-MF hybrid system was first applied in laboratory scale conditions to treat simulated wastewater. Insertion of baffles in the aerobic reactor, created separate oxic and anoxic zones. In particular, simultaneous nitrification and denitrification (SND) was achieved in a single baffled OMBR-MF hybrid system. Thus, this reactor design enables both aerobic and anoxic processes reduce the process footprint and energy costs associated with pumping the mixed liquor in-between the oxic and anoxic tanks and chemical dosing costs for pH adjustment. The bioreactor was operated under four different oxic-anoxic cycle time at constant flux operation employing thin film composite-forward osmosis (TFC-FO) and polyether sulfone-microfiltration (PES-MF) membranes. At 65 d sludge retention time (SRT) 86-92 % COD, 63-76 % TN and 57-63 PO₄-P % removal was achieved during Run 1 to Run 4 in a bioreactor. The oxic-anoxic cycle time of 0.5-1.5 h appeared to be an appropriate choice for the process. Incorporation of MF membrane effectively alleviated salinity build up in the reactor, allowing stable operation of the system. Based on outstanding SND performance using baffled OMBR-MF hybrid system test at different oxic-anoxic conditions long-term OMBR-MF hybrid system performance was evaluated at optimum oxic-anoxic (0.5-1.5 h) cycle time. The process performance was evaluated in terms of water flux, salinity build up in the bioreactor, organic and nutrient removal and microbial activity using synthetic reverse osmosis (RO) brine as draw solution (DS). The incorporation of MF membrane was effective in maintaining a reasonable salinity level (612–1434 mg/L) in the reactor which resulted in a much lower flux decline (i.e. 11.48–6.98 LMH) as compared to previous studies. An average of 8.56 LMH FO flux was achieved during 38 days of continuous operation. The stable operation of the osmotic membrane bioreactor–forward osmosis (OMBR-FO) process resulted in an effective removal of both organic matter (97.84%) and nutrient (phosphate 87.36% and total nitrogen 94.28%), respectively. The dissolved oxygen profile during aerobic-anoxic cycle confirmed < 0.5 mg/L oxygen favourable for denitrification. To further investigate novel baffled OMBR-MF system performance in particular the efficiency of OMPs removal under unique redox environment (oxic-anoxic conditions) were evaluated. The performance of OMBR-MF system was examined employing three different draw solutes (DS), and three model OMPs. The DS employed in this study were sodium chloride (NaCl), potassium chloride (KCl) and sodium acetate (CH₃COONa). Three model organic micropollutants used were caffeine, atenolol and atrazine respectively. The highest forward osmosis (FO) membrane rejection was attained with atenolol (100%) due to its higher molar mass and positive charge. With inorganic DS caffeine (94–100%) revealed highest removal followed by atenolol (89–96%) and atrazine (16–40%) respectively. All three OMPs exhibited higher removal with organic DS as compared to inorganic DS. Significant anoxic removal was observed for atrazine under very different redox conditions with extended anoxic cycle time. This can be linked with possible development of different microbial consortia responsible for diverse enzymes secretion. Overall, the OMBR-MF process showed effective removal of carbonaceous matter, nutrient and organic micropollutants (OMPs). Membrane biofouling is an inevitable phenomenon in any membrane process. Therefore real-time membrane fouling characterization without affecting continuous operation would be helpful in devising efficient antifouling strategy. Further, real wastewater exhibits entirely different foultants and very diverse bacterial community. So, it would be more interesting to study foulant and microbial interaction with membrane employing real wastewater. So, in order to study the biofouling development on forward osmosis membranes optical coherence tomography (OCT) technique was employed. On-line monitoring of biofilm growth on a flat sheet cellulose triacetate forward osmosis (CTA-FO) membrane was conducted for 21 days with three different draw solutes. Further, the process performance was evaluated in terms of water flux, organic and nutrient removal, microbial activity in terms of soluble microbial products (SMP) and extracellular polymeric substance (EPS), and floc size. The measured biofouling layer thickness was in the order sodium chloride (NaCl) > ammonium sulfate (SOA) > potassium dihydrogen phosphate (KH₂PO₄). Very high organic removal (96.9 ± 0.8%) and reasonably good nutrient removal efficiency (85.2 ± 1.6% TN) was achieved. The sludge characteristics and biofouling layer thickness suggest that less EPS and higher floc size were the governing factors for less fouling. Osmotic membrane bioreactor for wastewater treatment is very attractive and emerging process. It has shown very promising results for organic, nutrient and trace organics removal. With current technological advances, employing hybrid OMBR-MF have potential to produce fresh water at less cost than conventional desalination/water recovery technologies (i.e. ultrafiltration/RO systems). Main benefits of using baffled OMBR-MF hybrid system are better removal efficiency in terms of nutrient and micropollutants, saving in energy and pH adjustment costs, reduced process piping costs as SND takes place in single reactor and more flexible treatment unit. The major challenges of OMBR to be a techno-economically viable technology are developing a high performance low cost forward osmosis membrane with higher flux and high selectivity with less internal concentration polarization (ICP) effect, and the availability of suitable draw solutions (to explore other divalent organic DS with lower RSF and lower fouling propensity and to compare their performance in baffled OMBR-MF system). It would be interesting to address microbial community dynamics in oxic and anoxic zone in the baffled bioreactor to elucidate its impact on nutrient and OMPs removal. Besides, most of studies of OMBR have been performed at lab-scale. Therefore, more studies both in pilot and in full-scale plants are necessary to gain knowledge to achieve a better OMBR performance. In order to commercialise OMBR, full scale benchmarking and efficient process controls intensification are major challenges. Looking to the present progresses in FO membrane development (outer selective hollow fiber and nanomaterials made) in order to meet similar flux of existing porous membranes and very high performance of FO membranes in rejection of nutrients and micropollutants as compared to MF/UF membranes, OMBR can become techno- economically viable alternative for waster reuse applications in near future

A novel approach in crude enzyme laccase production and application in emerging contaminant bioremediation

Laccase enzyme from white-rot fungi is a potential biocatalyst for the oxidation of emerging contaminants (ECs), such as pesticides, pharmaceuticals and steroid hormones. This study aims to develop a three-step platform to treat ECs: (i) enzyme production, (ii) enzyme concentration and (iii) enzyme application. In the first step, solid culture and liquid culture were compared. The solid culture produced significantly more laccase than the liquid culture (447 vs. 74 μM/min after eight days), demonstrating that white rot fungi thrived on a solid medium. In the second step, the enzyme was concentrated 6.6 times using an ultrafiltration (UF) process, resulting in laccase activity of 2980 μM/min. No enzymatic loss due to filtration and membrane adsorption was observed, suggesting the feasibility of the UF membrane for enzyme concentration. In the third step, concentrated crude enzyme was applied in an enzymatic membrane reactor (EMR) to remove a diverse set of ECs (31 compounds in six groups). The EMR effectively removed of steroid hormones, phytoestrogen, ultraviolet (UV) filters and industrial chemical (above 90%). However, it had low removal of pesticides and pharmaceuticals

Critical flux on a submerged membrane bioreactor for nitrification of source separated urine

Membrane fouling is the biggest challenge in membrane based technology operation. Studies on critical flux mainly focused on membrane bioreactor for municipal wastewater and/or greywater treatment, which can significantly differ from the ultrafiltration membrane bioreactor (UF-MBRs) to treat source separated urine. In this work, the inhibitory factors on nitrifying bacteria activity were investigated for fast acclimation of nitrifying bacteria with high ammonium concentration and optimization of a high-rate partial nitrification MBR. The maximum nitrification rate of 447 +/- 50 mgN L-1 d(-1) was achieved when concentration of ammonia in feed urine is approximately 4006.3 +/- 225.8 mg N L-1 by maintaining desired pH around 6.2 and FA concentrations below 0.5 mgL(-1). Furthermore, for the first time, the impact of different operational and filtration conditions (i.e. aeration intensity, filtration method, imposed flux, intermittent relaxation, biomass concentration) on the reversibility of membrane fouling was carried out for enhancement of membrane flux and fouling mitigation. Fouling mechanisms for minor irreversible fouling observed under sub-critical condition were pore blocking and polarization. To mitigate membrane fouling, the UF module with effective membrane surface area of 0.02 m(2) is recommended to be operated at the aeration intensity of 0.4 m 3 h(-1), intermittent relaxation of 15 min, biomass concentration of 3.5 g L-1. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved

Removal of organic micro-pollutants by conventional membrane bioreactors and high-retention membrane bioreactors

The ubiquitous presence of organic micropollutants (OMPs) in the environment as a result of continuous discharge from wastewater treatment plants (WWTPs) into water matrices&mdash;even at trace concentrations (ng/L)&mdash;is of great concern, both in the public and environmental health domains. This fact essentially warrants developing and implementing energy-efficient, economical, sustainable and easy to handle technologies to meet stringent legislative requirements. Membrane-based processes&mdash;both stand-alone or integration of membrane processes&mdash;are an attractive option for the removal of OMPs because of their high reliability compared with conventional process, least chemical consumption and smaller footprint. This review summarizes recent research (mainly 2015&ndash;present) on the application of conventional aerobic and anaerobic membrane bioreactors used for the removal of organic micropollutants (OMP) from wastewater. Integration and hybridization of membrane processes with other physicochemical processes are becoming promising options for OMP removal. Recent studies on high retention membrane bioreactors (HRMBRs) such as osmotic membrane bioreactor (OMBRs) and membrane distillation bioreactors (MDBRs) are discussed. Future prospects of membrane bioreactors (MBRs) and HRMBRs for improving OMP removal from wastewater are also proposed

A novel approach in crude enzyme laccase production and application in emerging contaminant bioremediation

© 2020 by the authors. Laccase enzyme from white-rot fungi is a potential biocatalyst for the oxidation of emerging contaminants (ECs), such as pesticides, pharmaceuticals and steroid hormones. This study aims to develop a three-step platform to treat ECs: (i) enzyme production, (ii) enzyme concentration and (iii) enzyme application. In the first step, solid culture and liquid culture were compared. The solid culture produced significantly more laccase than the liquid culture (447 vs. 74 μM/min after eight days), demonstrating that white rot fungi thrived on a solid medium. In the second step, the enzyme was concentrated 6.6 times using an ultrafiltration (UF) process, resulting in laccase activity of 2980 μM/min. No enzymatic loss due to filtration and membrane adsorption was observed, suggesting the feasibility of the UF membrane for enzyme concentration. In the third step, concentrated crude enzyme was applied in an enzymatic membrane reactor (EMR) to remove a diverse set of ECs (31 compounds in six groups). The EMR effectively removed of steroid hormones, phytoestrogen, ultraviolet (UV) filters and industrial chemical (above 90%). However, it had low removal of pesticides and pharmaceuticals