| Steroid hormones are widely used in the field of medicine(e.g., for improving metabolism and immune systems). The synthesis of steroids hormonesproduces wastewater which is difficult to manage and characterized by complex components, high organic concentrations, toxicity, and bio-refractory compounds. The economic and effective treatment of wastewater has become a key link in the healthy development of pharmaceutical enterprises and the water environment security. And it is crucial to explore the characteristics and optimization of process operating conditions on the removal of pollutants with high efficiency and stability. So in this paper, we have investigated the influencing factors, operation condition optimization and water quality characteristics before and after pretreatment in the pretreatment of interior micro-electrolysis(IME)/ Fenton in batch tests. And demonstrating the removal efficiency of pollutants and the operating stability of continuous flow experiments using IME/Fenton oxidation(FO) pretreatment and hydrolysis acidification(HA)- biological contact oxidation(BCO) treatments.The main research contents of this paper is as follows:(1) Batch tests of IME-FO pretreatment at the bench-scaleEvaluating the COD removal effects, Fe2+ yield and IME–Fenton oxidation coagulation(FOC) process performance in batch tests with different operating parameters(initial pH, Fe-C/water(V/V) and air/water ratios, reaction time, H2O2 dosage, etc.). Based on the single factor experiment, the suitable operating conditions for the pretreatment process of IME/Fenton are obtained. IME achieved a COD removal efficiency of 31.8% and a 1.7-fold increase in the BOD5/COD(B/C) ratio of wastewater at the initial pH of 4, Fe-C/water(V/V) ratio of 1:1, air/water ratio of 10, and reaction time of 180 min. The Fe2+ concentration of 458.5 mg/L in the IME effluent meets the requirements of the FO process. FOC further reduced the COD with an efficiency of 30.1%, and the B/C ratio of the wastewater reached 0.59 with the initial pH=4, H2O2 dosage of 6.6 g/L and reaction time of 40 min. The concentration of metal compounds such as Cr6+, Zn2+, and Al3+ in the raw wastewater(RW) was greatly reduced by adsorption, electrophoresis and coagulation during the IME-FOC process.(2) Preliminarily exploring the characteristics and degradation pathway of characteristic pollutantsThe characteristics of influent and effluent of pretreatment was detected by excitation-emission matrix(EEM). EEM analysis showed that complex higher molecular weight organic compounds(i.e. fulvic-like compounds and humic acid compounds) were degraded into small molecular degradable organic matterafter the pretreatment process. A pyridine simulated wastewater was prepared based on the concentration level of the characteristic pollutants in the actual wastewater, and the degradation pathway of characteristic pollutant-pyridine was detected by gas chromatography mass spectrometer(GC-MS). GC-MS detection shows that breakdown products of pyridine are compounds with low toxicity, such as acetic acid and acetamide and further completely decomposed into H2 O and CO2 in oxidation reaction of IME and FO process. Which consequently reduced the toxicity and loading shock of the subsequent biochemical treatment units.(3) Field experiments with continuous flow of pretreatment-biotreatment combined processA field experiment with a continuous flow of 96m3/d was conducted for over 90 d based on the batch experiments. Before the continuous tests, biofilm formation was activated in the biological tank with inoculated sludge from aerobic sediments of local wastewater treatment plant. During the activation, the bioreactors were operated with a mixture of domestic sewage and RW in an intermittent operating mode to ensure adequate nutrition for microorganism growth. After the successful activation, biofilm formation and certain superior flora of the HA-BCO process are in good condition. After the stable operation of the system, theCOD and BOD5 concentrations in the finaleffluent were less than 90 mg/L and 15 mg/L, respectively, and the residual metal ions in the effluent of the pretreatment were almost completely removed.Which can met the requirements of the Discharge standards of water pollutants for pharmaceutical industry chemical synthesis products category(GB21904-2008, China). The operated efficiency and stability, though the Fe-Cfillings should be soaked in a sulfuric acid solution(5‰) for 12 hours to recover activityevery two weeks. In the field experiments, the pretreatment system operation cost 28.47-32.56 yuan/m3, which has a good economic applicability.Studies on the treatment of refractory organic wastewater by IME-FOC combined with biochemical process in the present stage is basically at the bench-scale, in a laboratory matrix. And few studies have investigated the treatment efficiency of the combination of IME-FOC and biological treatments for synthetic steroid hormone pharmaceutical wastewater. It has a good theoretical and practical significance for similar refractory organic industrial wastewater and provides some theoretical support and technical referenceto evaluate the influence factor of IME–FOC pretreatment and combined process performance, based on the actual production of wastewater characterized due to its complex componentsand the fluctuation of the water quality in the field experiment. |
PDF Full Text Request