Study On Removal Of Sulfamethazine From Sewage By UASB-SBR Process

Lab-scale experiments were conducted to investigate the removal property of sulfamethazine(SM2) by UASB-SBR process and optimum conditions of the process were confirmed. On the base of previous research, the adsorption characteristics of trace sulfamethazine by the sludge in the two reactors(anaerobic granular sludge and aerobic sludge) were investigated. Furthermore, a sulfamethazine degrading bacterial strain was isolated from aerobic activated sludge and identified. The degradation conditions of the strain were also optimumed.Firstly, a quantitative analysis method has been developed for determination of sulfamethazine in anqueous environment by using Solid-phase Extraction Coupled to High Performance Liquid Chromatography(HPLC). HLB (Hydrophile-Lipophile Balance) cartridges were used to enrich and purify the antibiotics in water. C18 column was applied for separation of the investigated sulfamethazine. Acetonitrile and ultrapure water(V:V=2:8) were used as the mobile phases. The results showed that the concentration of the sulfamethazine(range from 1 to 20mg/L) and peak area have a good linear relationship with the correlation coefficient R2=0.9962. The average recovery of the method was 93.68%.Then lab-scale experiments were conducted to investigate the removal efficiency of SM2 by UASB-SBR process. When the HRT was 8h, volume loading ranged from 0.5 to 1.2 kgCOD/(m3·d), COD and SM2 concentration of influent was 200～500mg/L and 40～80μg/L, the average removal efficiency of COD and SM2 were 70% and 35%, respectively, and the removal efficiency inscreased with the increase of influent COD concentration. The effluent VFA was 50～120mg/L, alkalinity was 220～350mg/L, which indicated the UASB reactor runned well and there was no phenomenon of acidification. The SBR reactor were followed the UASB when the nitrogen, phosphorus and SM2 had low removal efficiency due to the ammoniation in anaerobic condition and phosphorus release effect by phosphorus release bacteria. When the aeration time and SRT of SBR reactor were 3h,20d, respectively, the effluent concentration of COD, TN and TP reached the First Grade of the National Standard for Wastewater Discharge and the total removal efficiency of SM2 was 90%. COD was mainly removed by UASB, while nitrogen, phosphorus and SM2 were greatly removed by SBR, which meaned SM2 was more likely to be degraded in the condition of aerobic and removal of COD and SM2 had not a positive relation.The adsorption characteristics of trace sulfamethazine by the sludge in the two reactors(anaerobic granular sludge and aerobic sludge) were investigated. The effect of adsorption equilibrium time and temperature on the adsorption of SM2 by inactivated sludge were studied. The research also compared the adsorption characteristics of inactivated and activated sludge. The results showed that the adsorption of SM2 by two kinds of sludge was a rapid process. The adsorption by two kinds of sludge fitted both Freundlich and Langumir model,but Freundlich model fitted better than Langumir model(RF2>RL2). The adsorption of SM2 by the two sludge is the common results of surface adsorption and distribution effect rather than simple monolayer adsorption. The temperature had same effect on the adsorption by two kinds of sludge and the capacity parameter KF (15℃)>KF(25℃)>KF(35℃). This showed that the adsorption was exothermic and low temperatures favored adsorption reaction. According to the fitting results, two kinds of inactivated sludge had little adsorption difference from activated sludge, which also fitted Freundlich model. The removal of SM2 by two kinds of activated sludge is the combined effect of adsorption and degradation,and degradation played the leading role. What's more, the degradation efficiency of aerobic sludge was better than anaerobic granular sludge.On the base of previous research, a sulfamethazine degrading bacterial strain was isolated from aerobic activated sludge. According to the morphological character and 16S rDNA gene sequencing analysis, the strain was identified as genus Achromobacter and named S-3. In order to research the biodegradation characteristics of S-3, temperture, pH and rotation speed were examined. The results showed that when temperture was 30℃, pH was 7.0, rotation speed was 150r/min, about 33% SM2 was degraded by S-3 in mineral medium containing 5 mg/L SM2.