| Large surface processing industrial park is the inevitable trend for the development of electroplating industry in China,which can reduce environmental pollution and make better use of resources. Common biological wastewater treatment processes are not suitable for comprehensive electroplating wastewater for the fact that this type of wastewater contains a lot toxic waste especially heavy metals, special larger molecular organics, like surfactants and the biodegradability of this wastewater is not so high. It is essential to develop suitable comprehensive electroplating wastewater treatment process.Hydrolysis-MBR was chose as experimental apparatus to achieve high organic pollutant and nitrogen removal efficienciy. MBR reactor was divided into two regions, and one was kept anoxic and mixed condition. The major tasks were figuring out the optimum operation parameters of the system, the effect of the shock loading(heavy metals, speicial organics and combined load of the two) to the performance of systems and the dominant microflora, the enrichment of the heavy metals in sludge and membrane fouling under the effct of heavy metals.Combined system could start up after 11 days. The optimum parameters of the system were like that: the HRT of the hydrolysis and MBR was 5h and 9h respectively, the aeration rate of MBR was 13.8~16.6L/min and the mixed liquid recycle ratio kept 150%. When the combined system operated at the optimum parameters, the removal efficiency of COD, ammonia and TN were 89.1%, 78.6% and 65.2% respectively, while the average concentration in the effluent were 37.9mg/L, 6.5mg/L and 12.8mg/L, which could meet the level A, first class of the nationnal discharge standard.During the shock load experiment, three level of concentration gradients of heavy metal(Cu2+,Ni2+) and three special organics(poly(ethyleneglycol), sodium dodecyl sulfonate and sodium saccharin) were chosen. The results showed that combined systems showed stronger anti-shock loading capability than the control MBR reactor and the pollutants removal efficiency were higher than that of control group. In addition, the higher concentration of the shock loading, the bigger differences between the two systems. The COD removal efficiency was affected slightly by the concentration of heavy metals for the fact that the effluent COD concentration of combined systems and control group were 75.66% and 68.86%, while the ammonia removal efficiency showed the opposite trends: the efficiency decreased to 35% and 75% in control group and combined systems when the heavy metal loading was 10mg/L, what’s more, the ammonia removal efficiency of the combined systems decreased to 40% when the heavy metals concentration increased to 20mg/L. After the effect of the heavy metals, the microbial secretion, humic acid and fulvic acid in the effluent of control MBR were higher largely than that of MBR in the combined systems(HMBR), while Fluorescent protein were lower. Hydrophobic substance were the main component in the effluent of the HMBR, while the MBR, hydrophilic substance. The aromatic compounds cannot be removed efficiently by aerobic biological treatment. The organic loading had slight effects on the two systems. The COD and TN removal efficiency could kept 82.7% and 63.6% respectively.The SOUR values during the experiment were higher than 17.2mg O2/(g VSS·h). The combined shock laoding experiments showed that the performance of the combined systems were better than the control group.The average COD and TN effluent concentration were 89.4mg/L,65.6mg/L and 18.84mg/L and 16.13mg/L respectively, which could meet the nationnal discharge standard for electroplating wastewater.Both the results of the energy spectrum analysis and the ICP implied that the two systems showed higher enrichment ability of Cu than Ni, and the quantity of the two meavy metals in the sludge of MBR were four times larger than that of HMBR. Bacteria had stronger anti-shock loading capability than protozoan. The larger number of the protozoanand and less number of the filamentous bacterias were showed in HMBR and the plumpnessof the protozoan was higher in HMBR, which was the reason why the removal efficiency and anti-shock loading capability of HMBR were better than that of MBR. Before addition of the heavy metals, the dominant microorganisms remain the same in both reactors, they were mainly seven series, like Proteobacteria,Bacteroidetes and Firmicutes etc. After the effect of heavy metals, the relative abundance ratio of the bacteria changed a lot, and the higher relative abundance ratio of the bacteria in both reactors were Longilinea and Bellilinea. The content of EPS in MBR was higher, while the ratio of EPSp/EPSc showed the opposite trends. During the experiment, the membrane fouling rate in the MBR was much more quickly. The surface of the membrane module in MBR was much rougher than that of HMBR, what is more, the cake layer was thicker and the sizes of particles were larger. These results lead to higher membrane fouling rates in control MBR. |
PDF Full Text Request