| Eutrophication of water has become a global environmental problem, transition breeding of algae in lakes and reservoirs and other water sources is seriously affected the water supply of the city, and threat of water security. Currently, the methods of removing algae in waterworks has drawbacks in the economic efficiency and safety of the process, it can not meet the needs of urban water supply and requirements, as well as the quality requirements of drinking water. With the promotion and development of ultrasonic technology harmonies chemistry, people attach importance to the ultrasonic techniques for removing algae. Ultrasonic algae algal technology is clean, warm reaction conditions, efficient, fast and other notable features, so it has broad application prospects in algae control field.This study explored the effect and the safety of ultrasound reinforced coagulation and sedimentation removal algae, to find the appropriate frequency, power and time of ultrasonic radiation. It can safely and effectively remove the algae, to protect the safety of water supply. The main conclusions are as follows:(1) Under the certain frequency and power of ultrasound short-term radiation the algae in water samples. Followed by coagulation and sedimentation can remove large amounts of algae, it is effect to remove algae. Frequency of 20KHz ultrasonic with intensity 10-speed, 8-speed,6-speed,5-speed on 20s; Frequency of 40KHz ultrasonic with intensity 10-speed, 8-speed on 15s,and 6-speed,5-speed on 20s,3-spped on 60s; Frequency of 68KHz ultrasonic with intensity 10-speed,8-speed,6-speed on 10s,5-speed and 4-speed on 15s,3-speed on 50s; Frequency of 80KHz ultrasonic with intensity 10-speed,8-speed,6-speed,5-speed and 4-speed on 10s; Frequency of 120KHz ultrasonic with intensity 10-speed,8-speed,6-speed,5-speed and 4-speed on 10s. then coagulating sedimentation algae can achieve good results. The turbidity of precipitation water is less than 1NUT, chlorophyll a is less than 1μg·L-1, more than 98% removal of algae.(2) When with the same input power, the higher of the ultrasonic frequency, the better effect of remove algae.(3) With the depth of water increase, the effect become bad. In 15cm depth the effect of 10-speed of 120KHz and 68KHz is less affected by water depth, influenced by the depth of the rest. With the increasing of depth, it is need longer time to achieve good algaecide effect. So the effect of ultrasonic remove algae is not just by the frequency intensity and time-related radiation, but also affected by the depth of water. When the amount and the depth of water increase, the increase of ultrasonic irradiation time can be guaranteed a good algaecide effect.(4) After ultrasonic irradiation the MCs will be a certain increased, the frequency of 20-120KHz, the strength of 3 to 10 stalls intensity ultrasonic within 10s, the growth rate of MCs is smaller than 5%, and well below the WHO (World Health organization) recommended safety limit of MC-LR is 1.0μg/L in drinking water. After a short time radiation, DOC in water is decreased, with the time prolonged, DOC is concentration.68-120KHz radiate within the 10s, both achieve better results, but also has high security(5) After a short-time ultrasonic coagulating and sedimentation remove algae is obvious effect and safety, it is also an economic and environmentally friendly technology, so it has great potential for development. |
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