| Relative researches show that ultrasound could increase the pervasion of reactant and produce. At present, the technology of immobiled cell is one of the hotspots in wastewater treatment, but its development is delayed because the carrier materials in use blocks the diffusion of oxygen and product, which makes degradation ratio decreased. Therefore, we researched a new method to decontaminate pollution by combining immobilized cell with Low intensity ultrasound, based on the character of ultrasound. LAS content was a main object of our experiment. The following researches about the effect factors, the stimulating conditions of ultrasound and the kinetic model of LAS degradation would offer some reference for other researches in relation domains.The main research contents and results are as follows:Firstly, four assays of cell immobilized were researched: sodium alginate and calcium chlorate model; sodium alginate, calcium chlorate model and calcium carbonate model; PVA and boric acid model; and PVA and calcium alginate mixed model. The results showed that the second cell immobilization method was the best for us (Table2-3, Fig.2.4).Secondly, four effect factors were studied on the degradation of LAS. Under the condition of the frequency 24kHz, the power 2W, the stimulating time 30s, intermission time 30s, and the total stimulation 20min, the contrast groups without stimulating are also done. The results show: when the LAS concentration is lower than 116mg/L, the increasing of LAS degradation rate is obvious than that of the both contrast groups; when pH chang from 5 to 9, the LAS degradation keeps steady and the degradation rate is high; the supply of oxygen is controlled by increasing the rotary velocity. 200~250rpm is feasible for the immobilized cell, because the disadvantagement will take over inevitably if the rotary velocity is too high, while the oxygen is not sufficient for LAS degradation if the rotary velocity is too low; and the inoculating proportion of cell is about 2~4g percent 100mL carrier materials, because the inoculating proportion inceased highly has a bad effect on the intensity and rigidity of immobilized cell (Table3-4, Fig.3.1~Fig.3.3).Thirdly, the stimulating parameters of ultrasound are researched. Four factors are considered: Ultrasonic frequency being respectively 18kHz, 24kHz,30kHz; Ultrasonic power being 2W, 4W,8W; stimulating time/ intermission time being 10s/30s, 15s/30s,30s/30s; Total stimulating time being respectively 10min, 20min, 30min. At the same time, the other conditions are controlled by LAS concentration 50mg/L, pH neutral, rotary velocity being 200rpm and the inoculating proportion of cell being 2g/100mL. L9(43) orthogonal experiments are designed, and the results show: 1) each of the four factors considered in the orthogonal experiment has different effect on the degradation of LAS, and the trend is C>D>B>A ; The LAS degradation of each stimulated group is more obvious than that of the contrast group without stimulating. 2) The optimal condition of ultrasound is A2B3C1D2, namely frequency 24 kHz, power 8W, stimulation time 10s, intermissive time 30s, and the total stimulation time 20min. (Table3-6, Fig.3.5).Fourthly, at the condition of optimal ultrasound condition (A2B3C1D2) and the other condition are controlled by LAS concentration 50mg/L, pH keeping neutral, rotary velocity being 200rpm and the inoculating proportion of cell being 2g/100mL, the kinetic model were obtained (-rs=r's,maxs/ (ks+s)), and the model is analogous as Michaelis-Menten equation. Moreover, under 30～100mg/L LAS concentration ,the kinetic model equation obtained by experiment data (-rs = 4.05s/ (158.21+s)). The result of F test method and the relation modulus analysis show that the kinetics model equation is effective (Table4-3, Fig.4.2).Lastly, under the optimal conditions, the comparative experiments were done by treating LAS with or without stimulating. The results show that the bioactivity of immobilized cell with stimulating is higher than that of the group without stimula... |
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