| With the continuous improvement of wastewater discharge standards in our country, reverse osmosis(RO), which can stably get high quality permeate water, has been gradually applied to the treatment of landfill leachate in industry scale. However, the RO brine produced simultaneously is a kind of low biodegradability waste water which contains high organic concentration, high chroma and high salinity, and has become the main technical problems restricting the application of membrane technology. Therefore, it is urgent to work out an efficient, economic, practical and feasible treatment technique for RO brine. In this thesis, a combined process of polyferric sulphate(PFS) coagulation-Fenton oxidation-biological aerobic filter(BAF) was used for treatment of landfill leachate RO brine from Guangzhou Likeng Leachate Treatment Plants, and a 12 m3/d pilot plant was carried out.PFS, polyaluminium chloride(PAC) and ferric chloride(FC) was chosen as flocculant in coagulation test to remove chemical oxygen demand(COD) and chroma of RO brine respectively. Results showed that PFS was superior to PAC and FC in removal of both COD and chroma, and best removal rate, 56.7% of COD and 80.5% of chroma, was obtained under the condition of 5.5 of p H value, 1000 mg/L of PFS.After coagulation, Fenton and BAF process were carried out for advanced treatment of RO brine. In Fenton treatment, with 60 min reaction time, initial p H=3.92(that of coagulation effuent), 80 mmol/L hydrogen peroxide(H2O2), n(H2O2):n(Fe2+)=2 and two steps dosing ratio of 4:1, the optimal average removal efficiencies of COD and chroma were 51.0% and 92.0%, respectively, and BOD5/COD increased from 0.01 to 0.32. In addition, the optimal operating parameters of BAF were gas-water ratio about 4:1 to 6:1, and hydraulic retention time(HRT) about 10 to 12 hours, and then effluent COD below 300 mg/L and chroma below 40 times could be obtained stably after 10 days continuous operation.UV-vis absorbance and three-dimensional excitation emission matrix fluorescence spectroscopy(EEM) were used to analyze effluent from each unit of PFS coagulation-Fenton-BAF. E253/E203 ratio of effluent after combination processes decreased from 0.497 to 0.0313 which meant that the organic substituents gradually were transfered to aliphatic chain. According to the EEM of dissolved organic matter(DOM), the concentrations of fulvic-like and humic-like compounds decreased and the degree of aromatization was reduced in the combined process.Results of pilot plant study showed that these processes could be carried out stably under the condition of 12 m3/d of inflow, 1 kg/m3 of PFS and 7.8~8 L/m3 of H2O2(27.5%), n(H2O2):n(Fe2+)=2 and 12 hours of hydraulic retention time(HRT) in BAF, respectively, and COD, chroma and ammonia nitrogen(NH3-N) of the effluent was less than 300 mg/L, 60 times and 10 mg/L, respectively, meeting the second period level 3 discharge standards of <The water pollutents discharge limits>(DB 44/26-2001) and level 3 standards of <Table of wastewater discharged into urban sewage>(CJ 3082-1999). The chemical compositions of slag were analyzed by energy dispersion spectrum(EDS) and X-ray fluorescence(XRF), and results indicated that the effluent was also available for reuse in refrigeration of incineration slag. |
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