Study On The Treatment Efficiency Of Different Dye Wastewater By Bioelectrochemical Technology

Dye wastewater is more difficult to be treated among all kinds of industrial wastewater, it has a wide range of varieties and complex chemical compositions. Most of the dyes cannot be degraded directly in the nature, and it will do great harm to both human body and ecological environment if it is directly discharged into the water. Bioelectrochemical technology is a new type of water treatment technology and is still in the exploratory stage at present. The method is already used to deal with dye wastewater, but the studies are mainly focused on single dyes and comparative studys on different dye wastewater are relatively rare. The experiment made a comparative study on treatment efficiency of different dye wastewater by Bioelectrochemical technology, hoping to find an efficient dye wastewater treatment method, and hoping to enrich the mechanism of Bioelectrochemical technology.The experiment made a comparative study on treatment efficiency of monoazo dye(Acid Red 3R), polyazo dye(Direct Fast Black G) and anthraquinone dye(Reactive Brilliant Blue X-BR) using Electro-biological coupling hydrolysis-biological contact oxidation method.Meanwhile, as a comparative trial,Acid Red 3R is treated by Biological hydrolysis-biological contact oxidation method. Bioelectrochemical system is conducted under the condition of direct current and the current densities are 0.024mA/cm2,0.048mA/cm2,0.071mA/cm2 and 0.095mA/cm2 respectively. At the end of the trial, a supplemental test was carried out with the current density 0.024mA/cm2. The main analysis items are dye concentration, chroma, CODCr and ammonia nitrogen respectively. Microorganism and absorption spectra are supervised, too.The results of the trial are as follows:(1)Treatment effect of different dye waste water. Bioelectrochemical technology has good treatment effect on dye concentration, chroma and CODcr for all the dyes used in the trial, and has some treatment effect on ammonia nitrogen, too. The comparison of the overall treatmet effect of the three kinds of dyes shows that the treatment effect from good to bad are respectively anthraquinone dye, monoazo dye and polyazo dye.(2)Effect of current density on Bioelectrochemical system. Within the scope of the curent density selected in the trial, the treatment effect of all the items increase while the current densities increase. The treatment effect come to the best when the current density is 0.095mA/cm2, at this period, the removal rate of dye concentration of monoazo dye, polyazo dye and anthraquinone dye are 98.70%,94.30% and 99.68% respectively; the removal rate of chroma are 95.67%,95.31% and 96.59% respectively; the removal rate of CODCr are 90.06%,88.27% and 94.05% respectively; the removal rate of ammonia nitrogen are 53.15%,60.69% and 60.32% respectively. The supplemental test which is carried out with the current density 0.024mA/cm2 at the end of the trial shows that the treatment effect have improved to a certain extent which is due to the influence of temperature and microbial activity.(3)Microbiological analysis. The comparative analysis of microorganism shows that the microbial species, quantity and activity are consistent with the treatment results of dye wastewater. The microorganism in the reactor of anthraquinone dye is large in quantities, abundant in species and strong in activity, so it has better treatment effect. The microorganism in the reactor of monoazo dye is not better than the microorganism in the reactor of anthraquinone dye, and the microorganism in the reactor of polyazo dye is not as good as the microorganism in the reactor of monoazo dye. The appearance of protozoa in all the three dye wastewater suggests that the treatment effect is fine.(4)Spectra analysis. The comparative analysis of absorption spectra shows that the shape of absorption spectra, the position of absorption peak and the intensity of absorption have changed greatly when the current density is 0.095mA/cm2. The stage of Electro-biological coupling hydrolysis plays a main role in the course of degradation of dye wastewater. The stage of Electro-biological coupling hydrolysis has improved the biodegradability of dye wastewater, which contributes to the further removal of organic matter in the stage of biological contact oxidation.Compared with Biological system, The absorption spectrum of wastewater treated by Bioelectrochemical system is more flat.(5)Comparative analysis of Bioelectrochemical system and Biological system. The comparative analysis of Bioelectrochemical system and Biological system dealing with monoazo dye (Acid Red 3R) shows that Bioelectrochemical system is obviously superior to Biological system. Bioelectrochemical system and Biological system achieved the best treatment condition when the trial was running from the 105th days to the 136th days. At this period, the average removal rate of the two systems are as follows:98.70% and 66.02% for dye concentration, 95.67% and 58.90% for chroma,90.06% and 75.93% for CODCr,53.15% and 44.74% for ammonia nitrogen respectively.There are rich microbes in both Bioelectrochemical system and Biological system. The growth of the microbes in Bioelectrochemical system is in good condition, but the biological film in the Biological system is loose.