| With the rapid development in scale and intensification of pig farming industry in China, copper, zinc and other elements are widely used in pig feed’s additives as efficient,inexpensive and operational convenient growth promoter, which leads to a large number of unabsorbed and untransformed copper, zinc and other heavy metals existing in pig manure and swine wastewater. In order to explore the effect of copper on microbial community diversity in anaerobic sludge and its relationship with the treatment efficiency of the reactor, PCR-DGGE and Real-time PCR technology were employed to investigate the changes of microbial community during acclimation period of activated sludge and copper stress period in swine wastewater treatment by the upflow anaerobic sludge blanket reactor(UASB) basing on the comparison of the related properties of the anaerobic sludge in the running process of two UASB reactors.These results could identify the microbial flora survived under the high concentration of copper, in the swine wastewater, further provide the theoretical basis for improving the efficiency in swine wastewater treatment by UASB. Meanwhile, in view of the treatment status of biogas slurry from swine wastewater, the simulated slightly polluted swine wastewater was treated by the artificial wetlands barricading and the migration and transformation of copper and zinc among reed, sediment and water was explored to reveal the fate of heavy metals in the water- plant- sediment system. Then the mechanism that reed planting inhibited heavy metals moving from the sediments to the overlying water was probed basing on the effect of reed planting on heavy metals distribution in surface sediments with different particle sizes.The main results are as follows:1. Taking vesicular feces wastewater as the object, the COD removal rate of swine wastewater by UASB was more than 80 % after a total of 86 days treatment including the adaptation period, the loading increase period and stable period, when the process conditions was controlled in the hydraulic retention time(HRT) of 48 h, organic loading of 3.00~5.00 kg COD/(m3·d), the operating temperature of 35°C~37°C., This indicated that UASB reactor had good effect on swine wastewater treatment and was worthy of popularization as a swine wastewater treatment process. Due to transformation of organicnitrogen into ammonium nitrogen by ammonifiers, the concentration of NH3-N in the effluent was up to 84.16% higher than that of the influent during the reactor running. It indicated that the ammonium nitrogen could not be removed by anaerobic process alone in swine wastewater. Thus other processes needed to be combined in ammonium nitrogen treatment. During acclimation process, the copper content of sludge was up to 0.42 mg/g due to accumulation in the case of influent copper concentration of 0.1~4.2 mg/L and the removal of COD in UASB could be accelerated by exogenous copper under 1.0 mg/L.However when the copper addition was higher than 1.0 mg/L, the COD removal by reactors decreased by 20%, indicating that influent copper with concentration higher than1.0 mg/L would restrain the COD removal in the process of UASB treatment on swine wastewater.2. The analysis of PCR-DGGE based the methanogen 16 S r RNA indicated that the addition of exogenous copper to the UASB mainly affected the number of the group of methanogens, not the diversity of the fiora species and the addition of exogenous copper disrupted the structural stability of the methane producing bacteria. When the concentration of exogenous copper was less than 1 mg/L, the promoting effect on MBT was the greatest among the three kinds of methanogen. When the concentration of exogenous copper reached 1.5 mg/L, only MBT was promoted When the exogenous copper reached 4 mg/L, both MMB and MCC were inhibited obviously, but MBT was still in the process of improvement and MCC could not survive in the UASB reactor. The quantity of MBT and MSL were both higher than that of MMB. Among the three kinds of methanogenic bacteria, MSL’s quantity was maximum without exogenous copper addition.Beside, the average concentration of the 16 S r RNA gene in MSL accounted for 49.6% of the total concentration of 16 S r RNA gene in methanogenic bacteria, MBT and MMB were42.5%,and 7.9%, respectively, In addition, the quantity and the average concentration of the 16 S r RNA gene of MBT were highest with the exogenous copper exist.The average concentration of the 16 S r RNA gene of MSL and MMB were 36.7%and 5.0%,respectively.3. Studies on the treatment of simulated slightly polluted swine wastewater by artificial wetland ecological process implied that the concentration of Zn and Cu could bereduced via reed planting in short time. After 5 days, the Cu concentrations of the upper and lower water samples were 1.20 mg/L and 0.40 mg/L, respectively. While the Cu concentrations of the upper and lower water samples with reed planting were 0.52 mg/L and 0.37 mg/L, respectively. under the same condition, the Zn concentrations of the upper and lower water samples without reed planting were 1.55mg/L and 0.69mg/L,respectively. And those with reed planting were 0.68mg/L and 0.52mg/L, respectively.The contents of Zn and Cu in different parts of the reed followed the order of roots >stem>leaves, which increased gradually with the growth of the reed The content of Zn was higher than that of Cu in different parts of the reed. Reed could significantly reduce the contents of Zn and Cu in sediments and had great effect on the contents of heavy metals in different particle sizes of sediments. In the case of the same sizes, reed planting could largely cut down the content of heavy metals of sediment. Accordingly, the artificial wetland treatment could be effectively applied as an ecological measurement in slightly polluted swine wastewater treatment through sedimentation of heavy metals from wastewater. Reed planting could inhibit sediment resuspension when the wetland disturbance by the external force and reduce the content of heavy metals in the sediments of small particle size significantly, thus reduced the content of heavy metals in water effectively due to the movement of heavy metal by resuspension of sediment into the water. |
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