Degradation Of Organic Wastewater Using Gliding Arc Discharge Plasma And Biochemical Technology

This dissertation launched a series of exprimental study, which aims at the effect of gas-liquid gliding arc discharge (GAD) degrading organic wastewater. The objectives of the current research incolved as follows:(1) The mechanisms of gliding arc disposing wastewater are analysed.(2) With Acid Orangeâ…¡solution as objective pollutant, the influences of the nature of reactor parameters, the nature of wastewater, inorganic ions contained in the wastewater, the gas flow and the structure and type of organic matter on the degradation rate are studied. The results show that: considering energy efficiency, the gas-liquid GAD is fit for treating high concentration level organic wastewater, and the influences of pH value and temperature are not apparent, and butanol has an obvious impact on the degradation rate at 5min, and the effects of CO₃^2- and high concentration Cl^- is obvious, and the effect of NO₃^- can be ignored, and the effect of PO₄^3- is not apparent after 10min, and the higher gas flow rate, and the higher degradation rate. The different structure of the organic dyes have a wide range of adaptability.(3) Degradation kinetics and degradation mechanism of Acid Orangeâ…¡, the solution biodegradability, the toxicity of intermediate products are investigated. The results indicate that the degradation reaction of Acid Orangeâ…¡follows the first-order law, and the kinetic pathway could be expressed as follows: dC/dt= - 0.7587C₀ ^-0.2889C. The solution biodegradability was significantly improved, and the toxicity of intermediate products is lower than that of the initial Acid Orangeâ…¡. The possible degradation pathway of Acid Orangeâ…¡is proposed through the analysis of the main intermediates detected by ultraviolet-visible (UV-Vis) spectrum, ion chromatograph (IC) and gas chromatograph coupled with mass spectrophotometer (GC-MS) and fourier transform infrared spectroscopy(FTIR) techniques. The main intermediates are detected during the decomposition such as acetic acid, oxalic acid, malonic acid, phenol, 3-hydroxyhypnone, naphthalene, benzene sulfonic acid, near benzene dicarboxylic acid (anhydride), 8-naphthalene etc. The possible degradation channel of Acid Orangeâ…¡is that hydroxyl radicals react with the azo linkage-bearing carbon of a hydroxy substituted ring, with which process substituted phenyldiazene and naphthoxy radical are produced. Both of them are unstable extremely and could react further with hydroxyl radicals resulting in the degradation of aromatic ring.(4) To make full use of UV light produced in GAD, H₂O₂ and TiO₂ are added when plasma discharges. The results show that: when H₂O₂ are added, the initial pH has a little impact on the degradation rate, and oxygen atmosphere and higher discharge voltage are conducive to raise the degradation efficiency of pollutants. The combination H₂O₂ with GAD has a synergetic effect obviously, which increases remarkably decomposition rate and decreases treatment time. When the concentration of TiO₂ is 1.0 g/L, the degradation rate of Acid Orangeâ…¡is the hightest, because photovoltaic electron energy is used to fully and the more active particles are produced. Oxygen can increase degradation rate. The amount of H₂O₂ and the relative quantity OH^* are the greatest. The removals of COD and TOC increase, and treatment time becomes shorten, and treatment cost has been saved.(5) The industral waste is degraded by gas-liquid GAD. CO₃^2- existing in the wastewater consumes free radicals and decreases degradation rate, and changing initial pH or adding calcium oxide to the wastewater can get rid of CO₃^2-. Without the influence of CO₃^2-, the degradation kinetics also follow first-order law.(6) The industral waste decomposed by the combination GAD with biological treatment is studied. COD removal achieves the relative second and first State Effluent Standard, GB8978-1996, respectively, after biological treatment for 5min treatment and 10min GAD treatment. The removal of color achieves the relative first State Effluent Standard, GB8978-1996.(7) Finally, with COD concentration of 20-30 g/L as objective pollutant, operating costs are estimated for the GAD/H₂O₂/activated sludge, and compared with other existing technology. The results show that the technology has a good prospect for development.