-
[show abstract]
[hide abstract]
ABSTRACT: A low-cost and effective iron-chelated catalyst was developed as an electrocatalyst for the oxygen reduction reaction (ORR) in microbial fuel cells (MFCs). The catalyst was prepared by pyrolyzing carbon mixed iron-chelated ethylenediaminetetraacetic acid (PFeEDTA/C) in an argon atmosphere. Cyclic voltammetry measurements showed that PFeEDTA/C had a high catalytic activity for ORR. The MFC with a PFeEDTA/C cathode produced a maximum power density of 1122 mW/m(2), which was close to that with a Pt/C cathode (1166 mW/m(2)). The PFeEDTA/C was stable during an operation period of 31 days. Based on X-ray diffraction and X-ray photoelectron spectroscopy measurements, quaternary-N modified with iron might be the active site for the oxygen reduction reaction. The total cost of a PFeEDTA/C catalyst was much lower than that of a Pt catalyst. Thus, PFeEDTA/C can be a good alternative to Pt in MFC practical applications.
Bioresource technology 01/2011; 102(8):5093-7. · 4.25 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Influence of packing media on nitrogen removal in a subsurface infiltration system was studied. System A was filled with loamy soil and system B was filled with mixed soil of 75% red clay with 25% cinder. Both systems were fed with sewage at the same hydraulic loading of 2 cm/d at continuous operation mode. The same excellent removal performances of COD and T-P could be achieved in both infiltration systems with removal rates about 85% and 98%, respectively. In system A, NH4+ -N removal rate was as high as 96.5% and T-N removal rate was relatively much lower as 55.7%. And in system B, NH4+ -N removal rate was as low as 75.4% and T-N removal rate was relatively much higher as 75.5% . The difference was attributed to different soil oxidation-reduction condition that was greatly influenced by soil texture in subsurface infiltration system. Loamy soil led to oxidative condition that was favorable to nitrification and disadvantageous to denitrification. The results were just adverse to the system filled with clay. Intermittent operation was adopted to improve nitrogen removal in system B. NH4+ -N removal rate could be increased to about 95% and T-N removal rate could be increased to about 90% at intermittent operation mode in system B. Analysis of nitrogen removal mechanisms indicated that nitrification-denitrification was the primary nitrogen removal path in subsurface infiltration system and crop uptake was another important nitrogen removal way. It was the key to improve the total N removal performance that a suitable packing soil was available to present favorable oxidation-reduction condition for simultaneous nitrification and denitrification.
Journal of Environmental Sciences 02/2004; 16(1):153-6. · 1.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The treatment performance, for low concentration rural sewage, through constructed wetlands of different depths(60 cm and 40 cm), was comparatively investigated by using pilot-scale apparatus in Lake Dian-chi area, Yunnan province, China. The experiment results showed, under a high hydraulic loading rate of 30 cm/d, that the removal efficiencies of COD, total nitrogen, ammonia-nitrogen and total phosphorus in the constructed wetland of 60 cm depth were 66.4%, 57.7%, 78.7% and 63.2%, respectively, and were 63.8%, 59.1%, 82.1% and 61.3% in the 40 cm depth, respectively. The removal efficiencies of COD and total phosphorus in the constructed wetland of 60 cm depths were higher than those in the 40 cm depth, but the nitrogen removal efficiency in the latter was higher than that in the former. Nitrogen and phosphorus removal mechanisms were studied. The results showed that nitrogen removal through nitrification/denitrification and the phosphorus removal through absorb and sedimentation were their main removal mechanisms. The nitrogen and phosphorus removed by plant harvesting were amounting to 10% and 9% of input TN and TP, respectively, which was also an important removal pathway for nitrogen and phosphorus.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 10/2003; 24(5):92-6.
-
[show abstract]
[hide abstract]
ABSTRACT: A pilot plant of subsurface wastewater infiltration system (SWIS) filled with red clay was tested to treat rural sewage with hydraulic loading of 2 cm/d. The experiment results showed that average removal rates of COD, NH4(+)-N, total phosphorus, and total nitrogen were 84.7%, 70.0%, 98.0% and 77.7%, with average effluent concentrations of COD, NH4(+)-N, total phosphorus, and total nitrogen being 11.7 mg/L, 4.0 mg/L, 0.04 mg/L and 4.7 mg/L respectively, which met the standard for water reuse issued by the Ministry of Construction of China. Nitrogen removal mechanism analysis revealed that nitrogen in the influent was mainly eliminated through biological removal via nitrification/denitrification processes. In the pilot system, denitrification was well proceeded but nitrification was not satisfactory. How to improve nitrification performance through change of soil environment was the key to enhance nitrogen removal rate. The measurement results of redox potential in the filled soil showed that reductive property of soil was main hindrance to nitrification process.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 12/2002; 23(6):57-61.
-
[show abstract]
[hide abstract]
ABSTRACT: The batch test of oxygen uptake rate (OUR) measurement was used to simulate biochemical reaction process in aerobic reactor treating bleaching liquor from straw pulp process. Lawrence-McCarty kinetic model was used to analyze the biochemical reaction process. The kinetic equation of bleaching liquor biological treatment, v = 0.72 S/(60.43 + S), was deduced from results of the OUR experiment and the bench experiment. The specific substrate degradation rate estimated by the kinetic equation was higher than that of practical wastewater treatment plant. The phenomenon was attributed to the decrease of activated sludge activity caused by cellulose suspended solid accumulation in aerobic reactor of practical plant.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 10/2002; 23(5):84-7.
-
[show abstract]
[hide abstract]
ABSTRACT: A pilot subsurface wastewater infiltration system filled with a mixed soil of red clay + 25% cinder was constructed in a village located in Dianchi valley in south west China to treat rural sewage. At first, the system was continuously fed with rural sewage at a hydraulic loading of 2 cm d−1 for over 4 months. The removal of COD, T-P, NH4+-N, and T-N over the operation period was achieved at average rates of 82.7, 98.0, 70.0, and 77.7%, respectively. Compared to T-P removal, the lower nitrogen removal rates were attributed to reductive soil condition in the system, which was unfavorable for the nitrification process. An intermittent operation was adopted to improve nitrogen removal. The same performances of COD and T-P removal were achieved in the intermittent operation mode. NH4+-N removal was increased from 70% in the continuous feeding mode to over 90%, and T-N removal rate was elevated over 80% even with the average hydraulic loading as high as 8 cm d−1. Nitrogen balance calculation suggested that nitrification–denitrification was the main mechanism of nitrogen removal that eliminated 57–76% of the fed T-N. Soil redox potential measurement showed that the oxidative environment was increased through intermittent operation, encouraging nitrification. Correspondingly, soil nitrification potential was increased from less than 0.8 mg-N kg−1 h−1 in the continuous feeding mode to about 1.6 mg-N kg−1 h−1 in the intermittent operation mode.
Ecological Engineering.
