Study On Hybrid Anaerobic Baffled Reactor (HABR)Treating Printing And Dyeing Wastewater Containing Anthraquinone Dyes

In this research, the two sets of equipment-anaerobic baffled reactor (ABR) and hybrid anaerobic baffled reactor (HABR) fitted with multi-surface hollow packing are used to investigate the treatment of simulated printing and dyeing wastewater. Making soluble starch and polyvinyl alcohol (PVA) as a mixed sizing agent, the simulated wastewater also adds some reactive brilliant blue (KN-R) of Anthraquinone dye to it. The study includes four parts:the start-up phase of reactors under low loading; the stages of influent loading increasing gradually; the study of treating printing and dyeing wastewater on different hydraulic retention time (HRT); study about the performance of anaerobic sludge on degradation of organic pollutants. Through the indicators’determination of COD, PVA, KN-R, pH and so on, the study analyses and discusses the running conditions of printing and dyeing wastewater in the two reactors. The results show that:(1)When the start-up phase with low loading, the reactors are inoculated with mixed anaerobic sludge, the starting volume loading is0.28kgCOD/(m3d), HRT is maintained at48h and the influent temperature is controlled at35degrees centigrade. After50days, COD removal efficiency in HABR reactor reach85%, which is slightly higher than the reactor of ABR. In the two reactors, the removal efficiency of PVA and KN-R are not significantly different, and the ultimately removal rates are around70%and50%respectively. The effluent pH is stable, which is demonstrated that acidification does not appear, and the reactors start up successfully.(2)When the influent loading is increasing, the reactor of HABR only shows a little stronger stability than ABR, but the final results don’t appear the obvious advantages. With the influent PVA concentration increasing, the corresponding organic loading is climbing from0.5kgCOD/(m3d) to0.73kgCOD/(m3·d). The treatment effects of printing and dyeing wastewater are reduced, and COD, PVA, KN-R removal rate are kept at55%,35%and30%respectively. The proportion of soluble starch in simulative printing and dyeing wastewater is so large that the wastewater has good biodegradability. In addition, there are a large number of unacclimated sludge during the reactor start-up phase, and their large specific surface area makes it has strong adsorption capacity. Therefore, removal effects of PVA and KN-R are obvious, at the same time, COD removal rate is quite high. While with the proportion of PVA increasing in the mixed sizing agents, the wastewater becomes more difficult to degrade. The adsorption capacity of the reactor sludge also reduces greatly with the reactor running. All of them will decrease the removal effects of organic pollutants in wastewater treatment. Activity brilliant blue KN-R has some biological toxicity, which will have some inhibited effect on the microorganism’ biological activity when the concentration of KN-R over a critical value. Therefore as the influent KN-R concentration increasing from20mg/L to35mg/L, the removal rate of COD, PVA and KN-R arrived at about55%,10%and20%respectively, and the removal of PVA fluctuates on a large scale. The effect of this process does not ideal.(3)Extending the HRT from36h to48h, after keeping running for some time, COD removal rate rose, and it will stabilize at around60%finally. The removal of PVA and KN-R also have slightly increase. When HRT keep for48h, the removal efficiency of PVA fluctuate at25%up and down; while when HRT is36h, the lowest degradation rate of PVA in ABR reactor is12.28%, but the highest will arrive at33.56%. It does not improve the reactor operating conditions significantly by extending HRT to48h. From the experiment, it can be inferred that the influent loading increases so quickly and heavily as to lead to the irreversible inhibition of microbial activity. Moreover, according to analyze the water quality from different compartments, it can be concluded that the increase of HRT will strengthen the release of PVA and KN-R from anaerobic sludge and packing to liquid phase after the adsorption is saturated. The effluent water quality will be effected ultimately.(4)As the reactor running and the influent loading increasing, anaerobic sludge particle sizes become lager gradually. At the end of the experiment, the proportion of sludge particle size less than0.125mm is significantly less than the beginning. In the reactor compartment, because of adequate nutrition, the sludge of front compartment has more granular sludge, and the proportion of sludge whose particle size is greater than0.5mm is significantly higher than the behind compartment. In the back compartment, the relative lack of nutrition, combined with the hydraulic shearing action, makes the sludge difficult to gather into larger particles.(5)The study of anaerobic sludge degrading PVA and KN-R showed that the acclimated sludge includes a small number of specific bacteria which can degrade KN-R. However, the removal efficiency of PVA indicates that it is removed mainly through biological adsorption, and a little for biodegradation. The performance of acclimated sludge degrading PVA and KN-R is totally different under the different temperatures and pH conditions. The high temperature of45℃is conducive to the degradation of dye, however, the temperature will accelerate the solution of PVA, making the acclimated sludge release some PVA and resulting in rapid increase of effluent PVA concentration. Similarly, when the pH is6.5, KN-R has the highest removal rates, however, the best pH value for the PVA removal is7.5. It is can be seen that the conditions for the treatment of simulate printing and dyeing wastewater still require further research and discussion.