The Application Of Carbon Fiber/Electrochemical Process In Eutrophic Water Improvement And Wastewater Treatment

In recent years, the surface water contamination problems were increasingly prominent, especially urban rivers and lakes. Features of polluted urban waters were mainly include high concentrations of nitrogen and phosphorus, low carbon/nitrogen ratio, less biomass and damaged ecosystem etc. Research on treatment of this kind of waters had become a hot and difficult point in water treatment field. Advanced treatment of polluted water provided a crucial way for the solution of water pollution and shortages. Facing the current prominent urban water pollution problems in our country, the application of carbon fiber/electrochemical process in polluted water improvement and wastewater treatment was studied; the research contents were as follows:(1) Using carbon fiber(CF) as a biofilm support, the biofilm characteristics and dynamic features of N/P removal from wastewater by using CF and biological carbon fiber(BCF) were studied, and the effects of aeration rate, pH and HRT on N/P removal were investigated as well. The results were as follows: 1) CF had excellent biological compatibility and the biofilm was thinner and fast-forming, which was favorable to mass transfer; 2) the N/P removal efficiencies of CF and BCF were both preferable. The BCF removal efficiency of TP was above 90%, and the balance time of BCF was shorter than that of CF; 3) the N/P removal dynamic features of CF and BCF fit the exponential model well, and the fitting degree of phosphorus was superior to nitrogen; 4) the optimum operating conditions of aeration rate, pH and HRT were 0.15 L/min, 8 and 6h, respectively.(2) Combined the excellent biological enrichment characteristics of CF with the buffer ability of water velocity buffer, a new kind of biological monitoring device(BMD) was invented. The results showed that: In fast flow waters, BMD had faster biological enrichment speed and good anti-jamming of flow, and the kinds of microorganism were more; the water velocity buffer was in favor of reducing the flow velocity and creating favorable enrichment conditions. In slow flow waters, the protection plate of BMD could prevent the large aquatic animals from eating biofilms, and BMD had outstanding biological enrichment effect, as well.(3) A combined micro-electrolysis reactor(MER)/biofilm-electrode reactor(BER) process was studied for treatment of polluted river water. The results indicated that MER could effectively remove PP, PN, DTP and NH4+-N, and the removal efficiencies of PP, PN, DTP and NH4+-N were 94%, 95%, 93% and 98%, respectively. The removal of NH4+-N was mainly attributed to nitration reaction, and DTP was effectively removed by precipitation reaction with Fe2+ which was produced from micro-electrolysis. Additionally, MER improved the removal efficiency of organic matter as well. However, the removal efficiency of DTN was relatively low. BER was suitable to different influent, and could effectively remove NO3--N from the wastewater. Hydrogenotrophic denitrification process removed the majority of NO3--N, and the remaining organic matter was thoroughly removed by heterotrophic denitrification. NO3--N can be completely removed by the BER if the concentration was below 45.0 mg/L. The optimum operating condition was HRT = 8 h and current density = 0.1 mA/cm2, under which the average effluent concentrations of TN and CODMn were both less than 0.5 mg/L, TP was less than 0.05 mg/L, and the turbidity was below 1.0 NTU. The advanced treatment of polluted water can be achieved by micro-electrolysis/biofilm-electrode process.