Submerged anaerobic membrane bioreactors for wastewater treatment and membrane fouling characterization and control

This thesis focused on effects of transient conditions (pH shocks, temperature variation and temperature shocks) on the performance and membrane fouling characterization and control of submerged anaerobic membrane bioreactors (SAnMBR) for pulp and paper effluent treatment (thermomechanical whitewater and pressate). A comprehensive characterization of cake layer formed on membrane surfaces was conducted using various techniques. Results show that a pH 8.0 shock had a minor impact, while pH 9.1 and 10.0 shocks exerted significant long-lasting negative impacts on performance of the SAnMBR. The SAnMBR system was highly resilient and could successfully tolerate the 5 °C/10 °C temperatures shocks at 37 °C and the temperature variations from 37 to 45 °C. The temperature shock of 5 °C and 10 °C at 45 °C led to slight disturbance and significant disturbance of the performance, respectively

In-situ polymerization of lignocelluloses of autohydrolysis process with acrylamide

In the present study, the hydrolysates generated via autohydrolysis of spruce wood chips were directly used as feedstock for producing coagulants. The in-situ polymerization of acrylamide (AM) and lignocellulose (LC) of hydrolysates was successfully conducted. The reaction was optimized to generate lignocellulose-acrylamide (LC-AM) with the highest molecular weight (41,060 g/mol) and charge density (–0.25 meq/g) under the optimum conditions, which were 3 h, 60 ℃, 4% (w) initiator based on the dried mass of hydrolysate, and an AM/LC molar ratio of 5.63. A nuclear magnetic resonance (NMR) spectroscopy confirmed the grafting of acrylamide on LC. Other properties of LC-AM were characterized by the elemental analyzer, zeta potential analyzer, gel permeation chromatography (GPC), and particle charge detector (PCD). The LC-AM was applied as a coagulant for removing ethyl violet dye from a simulated dye solution. The results indicated that 47.2% dye was removed from the solution at a low dosage of 0.2 g/g. The dual flocculation of LC-AM with other polymers for dye removal is suggested to further improve its effectiveness

Cationic Lignin Polymers as Flocculant for Municipal Wastewater

The radical polymerization of acid-washed and unwashed softwood kraft lignin with [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was attempted to investigate the production of lignin-based flocculants for simulated wastewater. The incorporation of METAC onto lignin resulted in a cationic charge density (2.3–3.3 meq/g), increased water solubility (89–96% in neutral pH), and increased molecular weight (70,000–210,000 g/mol) of lignin. The lignin–METAC polymers generated from acid-washed lignin had higher molecular weights than those generated from unwashed lignin. The lignin–METAC polymers showed lower resistance to thermal decomposition than unmodified lignin due to the inclusion of PolyMETAC. The unmodified acid-washed lignin samples did not significantly affect the COD of the wastewater, while the unmodified unwashed lignin samples contributed to the COD, implying that unmodified lignin was not suitable for wastewater treatment. The flocculation of wastewater with lignin–METAC led to the chemical oxygen demand (COD) reduction of 17–23% and total organic carbon (TOC) drop of 51–60%. The lignin–METAC polymer with the highest molecular weight (produced from acid-washed lignin) reached the highest COD removal, while lignin–METAC polymer with the highest charge density (produced from unwashed lignin) reached the highest TOC removal. Focused beam reflectance measurement (FBRM) studies revealed that the lignin–METAC polymer produced from acid-washed lignin with a high molecular weight generated larger and more flocs in wastewater than the lignin–METAC polymer produced from unwashed lignin. The comparison of theoretical and experimental dosages required for neutralizing the charges of wastewater demonstrated that charge neutralization was the main flocculation mechanism, although a bridging mechanism was also involved for component removals from wastewater. The use of 1 mg/L of alum along with 65 mg/L lignin–METAC in a dual coagulation–flocculation system led to higher average phosphorous (42%) and COD (44%) removals than the singular flocculation system only using 65 mg/L of lignin–METAC (with phosphorous removals of 3.4% and COD removals of 18.7%). However, lignin–METAC flocculant slightly increased the ammonia–nitrogen content in both singular flocculation and dual coagulation–flocculation systems due to the residual ammonia content of lignin–METAC. The coagulation–flocculation system determined that the use of lignin–METAC (65 mg/L) could reduce the alum dosage significantly while maintaining a similar organic content reduction of 44% for wastewater

Anaerobic MBRs

Anaerobic MBRs (AnMBRs) have been shown to be one of the most promising technologies for sustainable wastewater treatment. It offers several advantages over the aerobic MBRs, namely, requirement of no energy for aeration, low sludge production and energy resource. Compared to the conventional anaerobic processes, AnMBRs can maintain higher biomass concentrations, have higher treatment capacity, excellent effluent quality, and smaller footprint. Compared with the conventional anaerobic digestion, they are relatively robust to cope with variations in organic loading and inhibitory conditions due to complete retention of biomass by membranes. The AnMBR technology is now gaining acceptance by a wide range of industries. The achievements of AnMBRs in pilotscale studies and full-scale applications are surveyed in this chapter. Lab- and pilot-scale studies provide important information to scale up AnMBRs and upgrade the existing anaerobic process into full-scale AnMBR systems. However, membrane fouling is still the major issue limiting its popularity and development in commercialization. The factors affecting the treatment performance and membrane fouling are reviewed along with an in depth discussion of fouling mechanisms, characteristics and control strategies. Moreover, an overview of its commercial potential in water reuse, energy production, and costs of AnMBRs in wastewater treatments is covered. The combination of AnMBRs and other effluent polishing treatments is desirable for the purpose of water reuse. Meanwhile, it is appealing to take advantage of the biogas produced as an energy resource. The lower total cost of AnMBR than that of aerobic MBRs shows its economic feasibility. Finally, the research needs for future developments are summarized based on the state-of-the-art of AnMBR technology

Amphiphilic Lignin Nanoparticles Made from Lignin-Acrylic Acid-Methyl Methacrylate Copolymers

In this study, a novel amphiphilic KL-AA-MMA nanoparticle was prepared through the graft copolymerization of kraft lignin (KL) with acrylic acid (AA) and methyl methacrylate (MMA), using potassium persulfate as an initiator in a water/dimethyl sulfoxide solvent medium, which was followed by the nanoprecipitation technique using dimethylformamide as a solvent and deionized water as an antisolvent. The successful graft polymerization was verified by 1H-nuclear magnetic resonance (NMR), 31P-NMR, and Fourier transform infrared (FTIR) analyses; and the grafting yield of the generated KL-AA-MMA copolymer ranged from 68.2% to 96.5%. Transmission electron microscopy (TEM) observation revealed the formation of amorphous KL-AA-MMA nanoparticles. Additionally, KL-AA-MMA9 nanoparticles with the highest yield exhibited the minimum hydrodynamic diameter and polydispersity of 261 nm and 0.153, respectively. Moreover, the amphiphilicity of KL-AA-MMA nanoparticles was significantly improved by the grafting of MMA monomers. Finally, the adsorption performance of KL-AA-MMA nanoparticles at the xylene interface was evaluated by a quartz crystal microbalance with dissipation (QCM-D). The results demonstrated that the most amphiphilic sample, KL-AA-MMA9 nanoparticles, with the smallest hydrodynamic size displayed the highest adsorption on the oil/water interface. This product provides a wide range of applications in oil/water emulsions.AlumniNon UBCReviewedFacultyResearche

Elevated expression of histone deacetylase HDAC8 suppresses arginine-proline metabolism in necrotizing enterocolitis

Summary: Epigenetic alterations are especially important in necrotizing enterocolitis (NEC). Here, we reported that histone deacetylase 8 (HDAC8) plays a previously unknown role in modulating arginine metabolism via acetylation of histone 3 lysine 9 (acetyl-H3K9) regulation during the pathogenesis of NEC. We found that HDAC8 was upregulated in humans and mice intestinal samples with NEC, while selective inhibition of HDAC8 expression ameliorated NEC. HDAC8 regulates enzymes involved in the metabolic conversion of proline to arginine (PRODH, PRODH2, OAT, and OTC) and arginine to ornithine (ARG1). The results showed that H3K9ac signal in the PRODH/PRODH2 promoter region was mediated by HDAC8. Additionally, the decreased concentration of butyric acid was strongly correlated with elevated HDAC8 levels and circulating arginine, which may result from an unbalanced Firmicutes/Bacteroidetes ratio. These results reveal previously underappreciated roles of microbial metabolites and HDAC8 to coordinate the arginine metabolism during NEC development