Enhanced treatment of nitroaniline-containing wastewater by a membrane-aerated biofilm reactor: Simultaneous nitroaniline degradation and nitrogen removal

Lumen air pressure regulated multifunctional microbiotas in membrane-aerated biofilm reactors for simultaneous nitrogen removal and antibiotic elimination from aquaculture wastewater

In this study, two membrane-aerated biofilm reactors (MABRs) were constructed: one solely utilizing biofilm and another hybrid MABR (HMABR) incorporating both suspended-sludge and biofilm to treat low C/N aquaculture wastewater under varying lumen air pressure (LAP). Both HMABR and MABR demonstrated superior nitrogen removal than conventional aeration reactors. Reducing LAP from 10 kPa to 2 kPa could enhance denitrification processes without severely compromising nitrification, resulting in an increase in total inorganic nitrogen (TIN) removal from 50.2±3.1 % to 71.6±1.0 %. The HMABR exhibited better denitrification efficacy than MABR, underscoring its potential for advanced nitrogen removal applications. A decline in LAP led to decreased extracellular polymeric substance (EPS) production, which could potentially augment reactor performance by minimizing mass transfer resistance while maintaining microbial matrix stability and function. Gene-centric metagenomics analysis revealed decreasing LAP impacted nitrogen metabolic potentials and electron flow pathways. The enrichment of napAB at higher LAP and the presence of complete ammonia oxidation (Comammox) Nitrospira at lower LAP indicated aerobic denitrification and Comammox processes in nitrogen removal. Multifunctional microbial communities developed under LAP regulation, diversifying the mechanisms for simultaneous nitrification-denitrification. Increased denitrifying gene pool (narGHI, nirK, norB) and enzymatic activity at a low LAP can amplify denitrification by promoting denitrifying genes and electron flow towards denitrifying enzymes. Sulfamethoxazole (SMX) was simultaneously removed with efficiency up to 80.2 ± 3.7 %, mainly via biodegradation, while antibiotic resistome and mobilome were propagated. Collectively, these findings could improve our understanding of nitrogen and antibiotic removal mechanisms under LAP regulation, offering valuable insights for the effective design and operation of MABR systems in aquaculture wastewater treatment.

Efficiency, Kinetics and Mechanism of 4-Nitroaniline Removal from Aqueous Solutions by Emulsion Liquid Membranes Using Type 1 Facilitated Transport

4-Nitroaniline (4NA) is a common organic pollutant that is released into the environment during the manufacture and processing of a wide variety of industrial products. This article describes the use of an emulsion liquid membrane process to remove 4NA from aqueous solutions using a type 1 facilitated transport mechanism. Optimization of the removal process was carried out by analyzing the efficiency of 4NA removal from the feed phase and the initial apparent feed/membrane fluxes and permeabilities under different experimental conditions. The kinetics of the removal process was analyzed using a simplified mass transfer model involving an empirical mass transfer coefficient calculated from experimental data, assuming that the concentrations of 4NA in the external aqueous phase and in the internal w/o emulsion are uniform. The results show that there is a very good fit between the experimental and model data and that the variation in the values of the overall mass transfer coefficients with the experimental conditions coincides with that of the removal efficiency mentioned above. The transport mechanism was studied by identifying the rate-controlling step of the removal process, using models described for adsorption processes, due to the strong parallelism between the transport mechanisms in adsorption and emulsion liquid membrane processes.

Effects of salinity on the performance, microbial community, and functional genes among 4-chlorophenol wastewater treatment

Chlorophenols frequently occur alongside salinity in industrial wastewater; thus, the effects of low concentrations of salinity (NaCl, 100 mg/L) on sludge performance, microbial community, and functional genes were deeply analyzed among 4-chlorophenol (4-CP, 2.4-4.0 mg/L) wastewater treatment. The influent 4-CP was effectively degraded, but the efficiencies for PO₄^3--P, NH₄⁺-N, and organics reduction were slightly inhibited by NaCl stress. Long-term NaCl and 4-CP stress significantly stimulated the secretion of extracellular polymeric substances (EPS). The abundances of predominant microbes at different taxonomic levels were affected by NaCl, and the increased relative abundances of functional genes encoding proteins contributed to resist NaCl and 4-CP stress. The functional genes associated with phosphorus metabolism and nitrogen metabolism in nitrification were unaffected, but the functional genes in denitrification increased in diversity under NaCl stress in 4-CP wastewater treatment. This finding acquires useful insight into the wastewater treatment with low chlorophenols and low salinity.

Understanding the role of sorption and biodegradation in the removal of organic micropollutants by membrane aerated biofilm reactor (MABR) with different biofilm thickness

The role of sorption and biodegradation in a membrane aerated biofilm reactor (MABR) were investigated for the removal of 10 organic micropollutants (OMPs) including endocrine disruptors and pharmaceutical active compounds. The influence of the biofilm thickness on the mechanisms of removal was analyzed via kinetic test at three different stages. At all biofilm stages, biodegradation was demonstrated to dominate the removal of selected OMPs. Higher OMPs rates of removal via biodegradation (K_biol) were achieved when biofilm increased its thickness from (stage T1) 0.26 mm, to (stage T2) 0.58 mm and (stage T3) 1.03 mm. At stage T1 of biofilm, heterotrophs contribute predominantly to OMPs degradation. Hydrophilic compounds removal (i.e., acetaminophen) continue to be driven by heterotrophic bacteria at the next stages of biofilm thickness. However, for medium hydrophobic neutral and charged OMPs, the combined action of heterotrophic and enriched nitrifying activity at stages T2 and T3 enhanced the overall removal. A degradation pathway based on heterotrophic activity for acetaminophen and combined action of nitrifiers-heterotrophs for estrone was proposed based on identified metabolites. Although biodegradation dominated the removal of most OMPs, sorption was also observed to be essential in the removal of biologically recalcitrant and lipophilic compounds like triclosan. Furthermore, sorption capacity of apolar compound was enhanced as the biofilm thickness grew and increased in EPS protein fraction. Microbial analysis confirmed the higher abundance of nitrifying and denitrifying activity at stage T3 of biofilm, which not only facilitated near complete ammonium removal but also enhanced degradation of OMPs.

Coupling of (methane + air)-membrane biofilms and air-membrane biofilms: Treatment of p-nitroaniline wastewater

Membrane biofilm (MBf) technology is a promising biological water treatment process that combines membrane aeration with biofilms. To expand its application in the treatment of toxic organic wastewater, methane/air gas mixture-MBfs ((CH₄ + Air)-MBfs) and air-MBfs were coupled to enhance the treatment of p-nitroaniline (PNA) wastewater. Based on exploration of the membrane permeability of methane and oxygen, a hybrid MBf reactor was constructed, and the degradation characteristics of PNA and the coupling effects of (CH₄ + Air)-MBfs and air-MBfs were studied. The permeation flux of methane was found to be 1.114 g/(m² d) when using a methane/air gas mixture at an aeration pressure of 10 kPa, and this result was better than that when methane was used as the aeration gas alone. Aeration with a methane/air gas mixture provided conditions for realizing aerobic methane oxidation; the aerobic methane oxidation that occurred in the (CH₄ + Air)-MBfs promoted the reduction of PNA, and the intermediates of PNA degradation were further degraded by the air-MBfs. At an influent PNA membrane area load of 1.67 g/(m² d), the PNA removal load reached 187.30 g/(m³ d). The coupling of MBfs took advantage of different matrix-based MBfs and promoted the degradation of PNA by utilizing the synergistic effects of various functional microorganisms.

Biodegradation of 4-nitroaniline by novel isolate Bacillus sp. strain AVPP64 in the presence of pesticides

In this study, Bacillus sp. strain AVPP64 was isolated from diuron-contaminated soil. It showed 4-nitroaniline (4-NA) degradation, pesticide tolerance, and self-nutrient integration via nitrogen (N)-fixation and phosphate (P)-solubilization. The rate constant (k) and half-life period (t_1/2) of 4-NA degradation in the aqueous medium inoculated with strain AVPP64 were observed to be 0.445 d^-1 and 1.55 d, respectively. Nevertheless, in the presence of chlorpyrifos, profenofos, atrazine and diuron pesticides, strain AVPP64 degraded 4-NA with t_1/2 values of 2.55 d, 2.26 d, 2.31 d and 3.54 d, respectively. The strain AVPP64 fixed 140 μg mL^-1 of N and solubilized 103 μg mL^-1 of P during the presence of 4-NA. In addition, strain AVPP64 produced significant amounts of plant growth-promoting metabolites like indole 3-acetic acid, siderophores, exo-polysaccharides and ammonia. In the presence of 4-NA and various pesticides, strain AVPP64 greatly increased the growth and biomass of Vigna radiata and Crotalaria juncea plants. These results revealed that Bacillus sp. strain AVPP64 can be used as an inoculum for bioremediation of 4-NA contaminated soil and sustainable crop production even when pesticides are present.

High performance polyvinylidene fluoride (PVDF) mixed matrix membrane (MMM) doped by various zeolite imidazolate frameworks

Zeolitic imidazolate framework (ZIF-8) in three particle sizes (40, 70 and 100 nm) was prepared through both solvothermal and hydrothermal methods and employed to decorate polyvinylidene fluoride (PVDF). The finger-like macro-voids, sponge-like poly-porous morphology and surface roughness of prepared membranes were characterized by SEM and AFM microscopy. The FTIR spectrum and XPS analysis bear out the chemical component. ZIF-8 has the characteristics of higher porosity and appropriate pore size, which is a condition for improving the permeability and pollution resistance of the modified membrane. Results indicated that different ZIF-8s have different enhancement effects on PVDF MMM. 100 nm ZIF-8 membrane possessed pure water flux (PWF) of 350 L m−2h−1, which was 10 times more than the bare membrane (30 L m−2h−1), and OVA flux recovery ration (FRR%) is 98%. 40 nm ZIF-8 membrane owned BSA FRR% of 98.4%. The 70 nm ZIF-8 showed the best mechanical properties. The dynamic contact angles of UP-Z70 ranged from 104.5° to 62.5° within 180 s. Furthermore, pore size distribution, molecular weight cut-off (MWCO) and porosity were also researched to evaluate the MMM. The dislodge of Reactive Black KN-B, Reactive Red 3BS and Reactive Brilliant Blue KN-R dyes by MMM were studied under different dye concentrations and transmembrane pressures. The membrane can provide selective separation methods for dyes and Reactive Brilliant Blue KN-R up to 99%. Overall, the permeability, hydrophilicy, anti-fouling performance and wastewater treatment of modified membranes were regulated by the ZIF-8 in a steerable blending reaction modification process.