| In this paper, to treat the ecological environmental pollution caused by rural sewage, a combination of anaerobic baffled reactor(ABR) and constructed wetland with the enhanced wetland media was employed for rural sewage disposal, of which dynamic features were explored. The ABR start-up experiment was also conducted by adding Fe3+and Fe2+, respectively. Furthermore, the feasibility of the ABR-constructed wetland and the effect of key controlling factors on the performance of the wetland as well as the corresponding mechanism were investigated. The results of this paper would provide technical support for improving the rural ecological environment. The results were as follows:Under the condition of COD of200-1200mg/L,TN of100-150mg/L, NH3-N of50-150mg/L in the influent, the start-up time lasted130d and the CODcr in the effluent of ABR reached the second discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002)49-day later, and the corresponding average TN and TP removal was10.28%and12.49%,respectively. The effluent was discharged to the simulated apparatus of constructed wetland for the further purification. In the apparatus, reed was planted and water treatment residual (WTR) was considered to be the enhanced wetland media. Due to the presence of Al and Fe in WTR, its maximum adsorption capacity of phosphorus was13.07mg(PO43--P)/g, which was higher than that of normal constructed wetland substrate, like zeolite, steel slag, coal ash etc. The effluent COCr of the simulated apparatus was stable at about20mg/L, and the corresponding CODCr removal was about80%. The effluent CODcr ranged from2.05mg/L to6.51mg/L, and the average TP removal was about39.2%. The nitrogen removal was only in the range of10%to20%, which was due to the influence of the microbial and growth of wetland plants.During the ABR start-up and running process, the partial microbial separation in ABR sludge was observed. The aspect ratio of the granules in ABR firstly increased followed by a dramatically decreasing, then tended to be stable. The anaerobic granules produced in ABR became more and more regular in surface and compact in structure. The size of the granules increased to0.54-0.92mm after a duration of stable running. The corresponding settling velocity and the effective density of these granules ranged from1.8mm/s to29.1mm/s and from2.82kg/m3-71.32kg/m3,respectively. Based on Logan’s equation, the porosity of these granules was in the range of0.60-0.95, whereas the average porosity of these granules was only0.66-0.81determined from the paraffin section image.Adding Fe3+alone did not improve the performance. By comparison, when ABR was dosed Fe2+by the iron carbon micro electrolysis device, it took ten days shorter to start up the ABR than the control one which lasted45days. Meanwhile, the CODCr was120mg/L in the effluent and the removal efficiency increased by10percent. Dosing Fe2+to ABR accelerated the granulation, improved the capability of resistance to shear deformation, and promoted the growth of granular sludge in the length direction and the width direction. Finally, the sphere-like granule formed, which had smooth surface and dense structure. The average size of the granules in the five compartment was0.28-0.73mm, while it was only in the range from0.04mm to0.20mm for the control ABR and the ABR dosed Fe3+.The protein and a-polysaccharide might be the main contributor to the formation of anaerobic granule hydrogel. Under conditions of neutral pH and high ionic strength, the storage modulus(G’), energy of cohesion(E) and yield stress(τ) of the granules were higher, which indicated that the granules exhibited stronger elasticity and strength. The equilibrium water content (EWC) of the anaerobic granules kept almost stable when the temperature was in the range of25℃and75℃. As pH<4, the sharp decrease of the EWC indicated the decrease of the water content in sludge. While the EWC increased rapidly when pH>10. The high concentration of NaCl in the solution led to the reduction of the EWC. Under these conditions, the osmotic pressure was negative, which showed that the granules tended to release water. This tendency was controlled by Donnan equilibrium.Adding Fe2+to ABR by control the Fe2+concentration of150mg/L, maintained the pH in ABR at about7.0, under which the methane-producing bacteria grew well. Through the PCR-DGGE technology, the distribution of microbial community in the ABR was characterized, and the results was as following. A variation in the microbial community in the ABR compartments was observed with the addition of Fe2+. In the ABR dosing with Fe2+, the dominant species was Uncultured Sulfuricurvum sp in the first and second compartment, and its quantity decreased in the latter three compartments. However, in the control ABR, a great number of Uncultured Sulfuricurvum sp. and Chlorobium limicola was observed in all the five compartments. In addition, Uncultured Clostridiales bacterium and Tolumonas auensis dominated in the second compartment, Uncultured Sulfuricurvum sp and great quantity of Uncultured Sulfuricurvum sp was observed in the fifth compartment. The microbial diversity analysis showed that the microbial diversity decreased in ABR apart from in the first compartment due to the Fe2+dosing.In this paper, ABR-constructed wetland was employed for decentralized treating rural domestic sewage. The ABR start-up was strengthed by Fe2+produced in the iron carbon micro electrolysis device, and the wetland was strengthed by WTR and typical plants, through which the start-up period of key unit was shortened and the removal efficiency of polluant in sewage was increased. The combination of ABR-constructed wetland could be recommended techniques for improving rural ecological environment. Based on the results of the above-mentioned and the analysis about the water quantity and wastewater characterization of the low-strength rural sewage produced in Kang Ling Village in Beijing, the ABR that was celebrated start-up by Fe2+was considered as the pretreatment unit. A constructed subsurface wetland that contained WTR to ennaced phosphorus removal was employed as the advanced treament unit. An4.0m/d pilot-scale improved ABR-constructed’ wetland and iron carbon micro electrolysis device were designed, and the draft was drawn after calculating the structure parameters of every unit. In addition, the improved ABR-constructed wetland with enhanced media was compared with other technology used in rural sewage disposal. |
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