| Anaerobic membrane bioreactor (AnMBR) which combined with the advantages of the anaerobic biotechnology and the membrane filtration technology had a widely application prospect in the energy-scarce world. The advantages of AnMBR for the treatment of wastewater containing suspended solids are divided into HRT and SRT to reduce the reactor volume, conducive to speed up the rate of hydrolysis of liquefied to increase its efficiency and recycling of resources.In this study, AnMBR which combined with ultrasonic equipment to control anaerobic membrane fouling were used for the treatment of the wastewater containing suspended solids with sewage sludge as the representative. Two AnMBR process configurations which were Up-Flow and CSTR bioreactor coupled with ultrasonic equipment as on-line membrane fouling control were designed and built. The Up-Flow bioreactor was designed to reduce the concentration of sludge into the membrane module so as to reduce membrane fouling tendency. With two sets of system, a series of experiments were carries out to explore their abilities of sludge digestion and the methods and mechanisms of membrane fouling control by ultrasound. We can come to the conclusions as follow.Experimental results of sludge digestion showed that VS degradation rate reached 55.0%～72.8% when HRT was 6 days in the Up-Flow bioreactor. In the ultrasound system, VS degradation rate which compared with that in the non-ultrasound system had improved 18.0% was 72.8% under the condition of 90W, 5min/h. When the sludge concentration increased, the sludge in the settling zone was gradually in line with the lower part, which could not reach the goal of reducing the concentration of sludge into the membrane module. During the whole operation process, the system could not stir adequately and the gas production was low, which indicated that the Up-Flow bioreactor was not suitable for the treatment of sewage sludge. For the CSTR bioreactor, VS degradation rate was 47.2%～52.3% when HRT was shorten from 8 days to 5 days. When HRT was 5 days, VS degradation rate was 52.3% that was the highest in the whole process under the ultrasonic condition of 90W, 5min/h. During the whole operation process, the system was running well which indicated that the CSTR bioreactor could be used for the treatment of sludge.Experimental results of membrane fouling controlled by ultrasound showed that ultrasound had a control effect on membrane fouling. Membrane fouling in the Up-Flow bioreactor could be effectively controlled under the ultrasonic condition of 90W, 3min/h, while the membrane material was not damaged. But in the ultrasonic condition of 90W, 5min/h, though the membrane fouling was effectively controlled, the membrane was damaged. For the CSTR bioreactor, the ultrasound controlled membrane fouling worked best in the ultrasonic condition of 90W, 5min/h, which the membrane was well compared with the Up-Flow bioreactor.Experimental results indicated that the membrane was damaged when the ultrasonic power intensity was over high. The cake layer that was approximately 97% of the total filtration resistance was the main constituent of the membrane fouling in the two kinds of structure of anaerobic membrane bioreactor without on-line ultrasound; but for the bioreactors with on-line ultrasound, although the cake layer and the biofouling had the different proportion of the total filtration resistance, both of them were still the main constituent of the membrane fouling, at the same time, the concentration of the sludge that entered the membrane module had the obvious influence function to the ultrasound. When applying ultrasound to clean the membrane fouling, the cake layer that was the main object can be removed. The membrane fouling control and membrane damage were both explained by the mechanism of acoustic streaming and microstreaming, microstreamers, micro-jets caused by acoustic cavitations.
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