ABSTRACT
A novel magnetic carrier with surface magnetic field of 4 mT was developed for studying the magnetic enhanced bio-effect on nitrification. The bio-effect on nitrificaton induced by the magnetic carrier was studied by comparing the performance of sequencing batch biofilm reactors filled with magnetic (MC) and non-magnetic (NMC) carriers. The result showed that the bioreactor with MC had better performance for nitrification than bioreactor with NMC. During the biofilm culturing period, the time required for nitrification formation in biofilm of the MC reactor was 25% less than that for the NMC reactor. The results also showed that the ammonium oxidation rate of the MC reactor was 1.6-fold faster than that in the NMC reactor at high influent NH4-N concentration, while nitrite oxidation rate was always accelerated regardless of influent NH4-N concentration. The specific oxygen uptake rate analysis revealed that ammonia and nitrite oxidation activities in biofilm of the MC reactor were 1.65 and 1.98 times greater than those of the NMC reactor, respectively.
Subject(s)
Biofilms , Bioreactors , Magnetic Fields , NitrificationABSTRACT
The comparative study on the electro-generation of H2O2 using an activated carbon fiber cathode and graphite cathode was investigated. The effect of the operating parameters on the H2O2 generation concentration and current efficiency, such as the initial pH, current density and electrolyte concentration, was also evaluated. The results revealed that the activated carbon fiber cathode was more effective compared to the graphite cathode. The maximum value of H2O2 concentration could be achieved with pH 3.00, current density 8.89 mA/cm2 and electrolyte concentration 0.05 mol/L. However, due to the formation of competitive electrode reactions, the current efficiency of this electrolysis system is lower than other electrolysis system. In addition, a new kinetic model was established to well describe the electro-generation of H2O2. The experimental data were fitted well using the kinetic model.
Subject(s)
Carbon/chemistry , Charcoal/chemistry , Hydrogen Peroxide/chemistry , Waste Disposal, Fluid/methods , Carbon Fiber , Electrodes , Electrolytes , Oxidation-Reduction , Waste Disposal, Fluid/instrumentationABSTRACT
Seven ultrasonic energy levels ranging from 0 to 26 000 kJ x kg(-1) were used to disintegrate excess sludge to investigate the changes in physical characteristics. The results indicated that the ultrasonication process destroys floc structure, facilitates the transfer of matter into the aqueous phase, and breaks up cell walls, which facilitated the improvement of settleability and biodegradability. Low ultrasonic energies could improve the settleability and supernatant turbidity. When the energy of 1 000 kJ x kg(-1) was applied into the sludge, the maximal settling velocity of sludge at 45 min was increased by 18.58% and the supernatant turbidity at 24 h was decreased by 43.52%, compared to the control. However, high ultrasonic energies deteriorated the characteristics. The maximal settling velocity was reduced by 37.03% and the supernatant turbidity was increased by 10 times in comparison to the control when the energy dose of 26 000 kJ x kg(-1) was applied. With the increases in ultrasonic energies, the particle size was significantly decreased, the soluble solids increased and the floc clusters dispersed. These changes in sludge characteristics were directly dependent upon the amount of ultrasonic energy applied. Furthermore, these characteristics correlated significantly to the ultrasonic energy. 1000 kJ x kg(-1) was the optimal energy that improved the settleability and the supernatant turbidity, and that destructed the floc structure of sludge. On the other hand, particle size was an important factor affecting sludge settleability and supernatant turbidity. The optimal values led to best settleability and turbidity.
Subject(s)
Sewage/chemistry , Sonication/methods , Waste Disposal, Fluid/methods , Wastewater/chemistry , Cities , Particle SizeABSTRACT
A novel bioflocculant ZS-7 produced by Bacillus licheniformis X14 was investigated with regard to its synthesis and application to low temperature drinking water treatment. The effects of culture conditions including pH, carbon source, nitrogen source, temperature, inoculum size and shaking speed on ZS-7 production were studied. The purified bioflocculant was identified as a glycoprotein consisting of polysaccharide (91.5%, w/w) and protein (8.4%, w/w), with an approximate molecular weight of 6.89 x 10(4)Da. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) indicated the presence of amino, amide, carboxyl, methoxyl and hydroxyl groups. This bioflocculant showed good flocculating performance and industrial potential for treatment of low temperature drinking water, and the maximum removal efficiencies of COD(Mn) and turbidity were 61.2% and 95.6%, respectively, which were better than conventional chemical flocculants. Charge neutralization and bridging were proposed as the reasons for the enhanced performance based upon the experimental observations.
