Poly dimethyldiallylammonium chloride (PDMDAAC) was applied in a membrane bioreactor (MBR) to study its effects on mitigation of MBR membrane fouling. Floc size, zeta potential, soluble microbial substances (SMP) and extracellular polymeric substances (EPS) secretion were studied with respect to PDMMAAC-dosing operations. Results demonstrated that a sustainable filtration cycle extended 3.3 times with the optimal PDMDAAC dosage of 90 mg L. The addition of PDMDAAC could increase zeta potential of sludge floc, which led to the decrease in repulsive electrostatic interactions between flocs, as well as the facilitation of flocs-to-flocs aggregation. With the optimal dosage of PDMDAAC, the mean size of sludge was 3.23 ± 0.55 times higher than the control group, resulting in higher impact resistance and better adaptive capacity to the changing environment, which led to less SMP secretion. Moreover, a high contaminants removal rate was achieved in the reactor that was dosed with PDMDAAC. The average effluent concentrations of chemical oxygen demand and total nitrogen were less than 45.6 ± 2.85 and 5.23 ± 0.61 mg L, respectively, and the corresponding removal rates were 93.1 ± 5.81% and 89.1 ± 9.61%.
This study used hexadecyl trimethyl ammonium bromide (CTAB) to organically modify orange peel biochar (OBC) to produce CTAB-modified orange peel biochar (NOBC), the adsorption performance of NOBC on Congo red dye in water and the influencing factors were investigated.
Membrane bioreactors (MBRs) are frequently used to treat municipal wastewater, but membrane fouling is still the main weakness of this technology. Additionally, the low carbon-nitrogen (C/N) ratio influent has been shown to not only increase the membrane fouling, but also introduce challenges to meet the effluent discharge standard for nitrogen removal. Herein, the authors addressed the challenges by adding cost-effective biochar. The results suggested that the biochar addition can enable membrane fouling alleviation and nitrogen removal improvement. The reduced membrane fouling can be ascribed to the biochar adsorption capacity, which facilitates to form bigger flocs with carbon skeleton in biochar as a core. As a result, the biochar addition significantly altered the mixed liquor suspension with soluble microbial product (SMP) concentration reduction of approximately 14%, lower SMP protein/polysaccharide ratio from 0.28 ± 0.02 to 0.22 ± 0.03, smaller SMP molecular weight and bigger sludge particle size from 67.68 ± 6.9 μm to 113.47 ± 4.8 μm. The nitrogen removal is also dramatically improved after biochar addition, which can be due to the initial carbon source release from biochar, and formation of aerobic–anaerobic microstructures. Microbial diversity analysis results suggested more accumulation of denitrification microbes including norank_f__JG30-KF-CM45 and Plasticicumulans. Less relative abundance of Aeromonas after biochar addition suggested less extracellular polymer substance (EPS) secretion and lower membrane fouling rate.
The oxidation of chloramphenicol (CAP) by potassium ferrate (VI) in test solution was studied in this paper. A series of jar tests were performed at bench scale with pH of 5-9 and molar ratio [VI/CAP] of 16.3:1-81.6:1. Results showed that raising VI dose could improve the treatment performance and the influence of solution pH was significant. VI is more reactive in neutral conditions, presenting the highest removal efficiency of CAP. The rate law for the oxidation of CAP by VI was first order with respect to each reactant, yielding an overall second-order reaction. Furthermore, five oxidation products were observed during CAP oxidation by VI. Results revealed that VI attacked the amide group of CAP, leading to the cleavage of the group, while benzene ring remained intact.
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