Treatment Of Antibiotic Fermentation Wastewater Using Combined Coagulationhydrolysis/Aerobic Moving Bed Biofilm Reactor-Fenton Process

As for most pharmaceutical enterprises, high concentration pharmaceutical wastewater is one kind of refractory industry wastewater due to the complicated components, high quantity organic compounds, deep color and low biodegradability. Furthermore, it is difficult to biodegrade the antibiotic wastewater and single wastewater treatment has been imperfect. Hence, it is imperative to develop a series effective new process for wastewater treatment, which can meet the increasing strict discharge standards. The combined coagulation-hydrolysis/oxidation MBBR-Fenton process was adopted for the treatment of high concentration antibiotic fermentation wastewater which was originated from a workshop of some pharmaceutical factory of Harbin (COD 14700¹7600mg·L^-1; BOD5/COD ratio 0.25⁰.26).According to colloid charge charactes in antibiotic fermentation wastewater, the coagulation efficiencies of six kinds of selected coagulants were compared. The results indicated that Polyferric Sulfate (PFS) was the best compared to the others, so it was chosen as the coagulant for the pharmaceutical wastewater. The effects of PFS dosage, initial pH, strring time and settling time in coagulation process were investigated. The relationship between PFS coagulation mechanisms and PFS modalities were discussed by SEM, TEM, FT-IR and XRD characterization of PFS. The effects of the fractal dimension of PFS floccules and the distribution of different size particles after coagulation to sedimentation performances were also studied. The optimal operational parameters of coagulation were determined as follows: PFS dosage of 135.26mg/gCOD, initial pH of 4.0 around, high speed agitation of 300r·min-1 with 1min, low speed agitation of 50r·min-1 with 12min and sedimentation time of 60min. After coagulation, 62.2% COD and 88.2% SS removal were achieved, and the organic load was evidently decreased, but B/C ratio only increased from 0.25 to 0.28.Hydrolysis/aerobic MBBR were applied to treat antibiotic fermentation wastewater, and the correlative operational parameters were investigated. The start of hydrolysis/aerobic MBBR was studied. On the one hand, the pH,HRT and OLR of hydrolysis MBBR were optimized; On the other hand, the HRT, aeration rate and OLR of aerobic MBBR were also optimized. The microorganisms and biofilms which were in hydrolysis/aerobic MBBR were observed. Hydrolysis/acidification bacteria and aerobic bacteria were characterized by SEM. The thickness of biofilm that was in aerobic MBBR carries was measured, and then flow status which was inside carries were simulated by the computed fluid dynamics software Fluent. The simulated results were used to analyze the relationship between distributions of flow field and distributions of biofilm thickness. The experimental results showed when COD of influent were 6000⁷000mg·L^-1, the COD removal efficiency could reach 93.09% after series hydrolysis/oxidation MBBR treatment. And the final COD of effluent was 449.3mg·L^-1. In addition, when the pH was in 5.5-7.0 range, the hydrolysis/acidification bacteria were suitable to survive, i.e., it would be good at hydrolysis reaction. At pH 6.5, the hydrolysis efficiency was upmost, and the VFAs production could reach 741.12mg·L^-1 accompanying with 11.4% acidification degree and 15.38% of COD removal. At HRT 12h,the hydrolysis efficiency was optimum, and B/C was improved from 0.28 to 0.40 accompanying with 931.75mg·L^-1 of VFAs, 14.33% acidification degree and 26.59% of COD removal, which were very benefit for the latter biological treatment. Although the pH and HRT were influenced the treatment efficiency, the type of hydrolysis was not changed basically. Acetate was the main composition of VFAs. The Propionate was the second, butyrate and valerate were lowest. At HRT 12h of aerobic MBBR, the COD removal efficiency could reach 89.6%. At aeration rate 1.5m³Â·h^-1, the COD removal efficiency could reach 91%. The feasible OLR of whole MBBR process was 13kgCOD·(m3·d)^-1. The results of biofilm measures showed hydrolysis/acidification bacteria mainly were bacilli. From the observations by SEM, some fields mainly contained zoogloea; some fields mainly contained filamentous bacteria. Aerobic bacteria mainly were cocci and short bacilli. From the observations by SEM, some fields mainly contained short bacilli; some fields mainly contained cocci; in addition, some fields mainly contained bacilli and cocci. The experimental results showed the thickness of aerobic biofilms was thicker than hydrolysis/acidification biofilm. The thickness of aerobic biofilms was 1.0¹.2mm and was asymemetry. The simulated results showed the distributions of flow filed of inside carriers in accordance with thickness of biofilms. Hence, it could use the Fluent-software to simulate the distributions of thickness of biofilms.Batch tests were carried out to investigate the COD degradation kinetics of antibiotic fermentation wastewater by aerobic MBBR and a modified bio-kinetic model was set up to describe the biological reaction, that is, S=(S0-Sn)exp(-K2Xt)+Sn. The experimental results obtained from different initial concentration and different bio-carrier volume showed that the model could well describe the biodegradation of antibiotic fermentation wastewater, and the kinetic parameter K2 could be used as indicator of degradation rate and Sn could be used to estimate the biodegradability of antibiotic fermentation wastewater.The oxidation effects of three kinds of Fenton systems were compared. The effect of initial Fe2+ dosage, pH, reaction time, agitation time, the sedimentation pH, carrier gas and manner of H2O2 addition were investigated. The kinetics of Fenton process was also studied. The hydroxyl radical of Fenton system were measured by EPR. The continuous running experiments were conducted, and the qualities of influent and effluent in different process were analyzed. The different combined processes were compared and estimated. The Optimum conditions of Fenton process for treating the effluent of coagulation were determined as: adjusting initial pH of wastewater about 3.0, controlling initial Fe2+ concentration of 60.8mg·L^-1, adding half the stoichiometric calculated quantities (Qth) of H2O2, using air as carrier gas, reacting for 1h, pH was then adjusted to 7.0, in which Fe2+ and H2O2 were added every 20 minutes during the first hour of reaction. Under these conditions, 80% of COD removal was obtained. Finally,the application ranges of different combined processes were given by comparisons. It was feasible to apply coagulation-hydrolysis/aerobic MBBR-Fenton process to treat antibiotic fermentation wastewater.