The Study Of Disinfection Of E.coli In Drinking Water By Coupling Ultrasonic Field With Chemistry

As human activities, industry and agriculture grow rapidly, water quality becomes worse, posing a risk to human health. The existing traditional disinfection technology, in which chloride is chosen as the main disinfectant, bringing about varieties of harmful disinfection by-products, cannot be fully reached the standard of GB/T 5749-2006. It is very necessary to investigate on drinking water disinfection technology with low consumption, high efficiency and security.Physical sterilization method(UV, ultrasonic, etc.) need none or little chemical disinfectants. Ultrasonic coupling with chemical method is expected to significantly increase the efficiency of sterilization, economy and security. Based on the lack of basic research of ultrasonic coupling with chemical method, performance of disinfection in different operating conditions(ultrasonic, chemical disinfection, different ultrasonic frequency, duration, etc.) was researched using the ultrasonic bath and the home-made drinking water treatment device respectively. Results have showed as followed:(1)A sample of 100mL bacteria suspension of E. coli(approximately 104 CFU/ mL) was used for each experiment by single ultrasonic processing. The E. coli inactivation rate is better by ultrasonic frequency of 59 kHz, power of 90 W and ultrasonic time of 60 min. The E. coli inactivation rate is 1.8.(2)A sample of 100mL bacteria suspension of E. coli(approximately 104 CFU/ mL) was used for each experiment by single sodium hypochlorite disinfectant. As the increasing of concentration of sodium hypochlorite, the E.coli inactivated rate can be better. However, the residual chlorine quantity will increase at the same time. If the residual chlorine quantity control within the standard, the optimum operation parameters as follows: at the room temperature, active chlorine concentration was 12.0 mg/L, chlorine reaction time was 30 min. Under the optimum operating conditions, the E. coli inactivation rate can reach 2.9.(3) A sample of 100mL bacteria suspension of E. coli(approximately 104 CFU/ mL) was used for each experiment by ultrasonic field synergic sodium hypochlorite. Compared with single ultrasonic and single sodium hypochlorite disinfectant, we can find that ultrasound can effectively enhance the chlorine disinfection effect. The E. coli inactivation rate increased 95% through 5 min of ultrasonic pretreatment.(4)A lot of imitative water containing E. coli was directly processed by ultrasonic reactor device. The optimum operation parameters as follows: frequency of 70 kHz, power of 20 W/L, volume of 6.5 L and the ultrasonic irradiation time is below 1 hour. Under the optimum operating conditions, the E. coli inactivation rate can reach 1.7. The E.coli sterilization effect is not ideal by ultrasonic alone.(5)Considering the sterilization rate and residual chlorine quantity, The optimum operation parameters of ultrasonic field coupling chemistry method safe drinking water treatment technology as follows: at the room temperature,ultrasonic frequency of 100 kHz, power of 20 W/L, the ultrasonic pretreatment time of 10 min, then the water reacted 30 min in the chemical reaction tank with sodium hypochlorite concentration of 12.0 mg/L. The E. coli inactivation rate can reach 4.52.In conclusion, ultrasonic coupling chemical method has great advantage in drinking water disinfection and has broad application prospects.