Treatment of Textile Effluents by H2O2/ UV Oxidation Combined with RO Separation for Reuse

• Main Authors: Hsing-Yuan Yen, 顏幸苑
• Other Authors: Shyh-Fang Kang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/89134406673787005455

博士 === 淡江大學 === 水資源及環境工程學系 === 91 === In this study, real textile effluents were sampled from three textile factories and 158 sets effluents totally. The range of COD, color, conductivity and hardness of the textile effluent are 37-97 mg/L, 79-547 unit, 2300-5000 μs/cm and 30-89 mg/L as CaCO3, respectively. The correlation among COD and DOC, conductivity and TDS, turbidity and SS are good agreement, but there are poor relation between UV254 and COD&DOC. The results showed that all of the water qualities of 158 sets real effluents comply with the effluent standards enforced by Taiwan EPA. However, there are residual organics and inorganic salts remaining in the effluent. Thus, advanced treatment is needed as to further reduce organics, e.g., DOC, and inorganic salts, e.g., conductivity, as to meet the water quality criteria for water reuse in the textile industry. DOC and color can be removed efficiently from textile effluent when oxidized by UV 128W, H2O2 100 mg/L, and oxidation time 60 minutes. The DOC in the effluent decreased from 15.7 mg/L to 3.8mg/L with a mineralized efficiency 76%. Most of residual DOC concentrates in low molecular weight. The color in the effluent decreased from 77 unit to 3 unit. All of the residual color concentrates in high molecular weight. The SDI of the effluent after use of a 1μm pre-filter was 7.4. Through H2O2/UV oxidation, it dropped to 4.4. Although the textile effluents were treated by H2O2/UV can effectively remove color and organics, the conductivity and hardness cannot be removed. Thus, the textile effluents were treated by H2O2/UV oxidation cannot comply with the quality of reuse in textile factory. Three types of membranes were used in this study: UF, NF and RO membrane. The separation ability of three membranes decreases in the following order:RO>NF>UF. The rejection of color is higher than COD, and the rejection of conductivity is highter than hardness for all the three types of membrane. It is found while the textile effluent was treated by RO separation, the transport of solvent (water) and solute (conductivity, COD) corrospond with Sourirajan solution-diffusion model and Yang & Chu modified solution-diffusion model. We calculated the activation energy by Arrhenius Equation. The activation energy of diffusivity for water is 57.4 kJ/mole. Moreover, The activation energies of permeability of conductivity and COD were 84.8 kJ/mole and 79.1 kJ/mole, respectively. It indicates that the solvent permeability is higher than solute and COD permeability is higher than conductivity. The experimental formula developed by Sourirajan was used for calculating the transport parameters A and B of solution; a and b of membrane. A-value increased and B-value decreased with an increase of the temperature. For a-value and b-value decreased with an increase of the temperature for the conductivity and COD, respectively. Moreover, A modified solution-diffusion model developed by Yang & Chu was used for describing the textile effluents transport through a membrane under various operating pressures and temperatures. It was found that the diffusivity for water increased with increasing temperature. The permeability for solute increased with increasing the temperature. According to these two solution-diffusion models, the transport parameters for solution, solvent and solute were calculated for describing the case of the textile effluents transport through a membrane under various operating pressure and temperature, which can be evaluated the quality and amount of water reuse for programming of water recycling in textile factory. H2O2/UV pre-oxidation promoted the ability of RO for further treatment of DOC, color and conductivity, increasing the permeate flux, decreasing the osmotic pressure, FDIw decreased from 0.1106 to 0.0672, and effectively improving the water flux decline that is caused by operated time. Thus, combining H2O2/UV pre-oxidation and RO post-process to treat textile effluents is effective and is capable of elevating water quality for the reuse in textile factory.