Removal of microbial biofilm on Water Hyacinth plants roots by ultrasonic treatment

The capacity of floating aquatic plants to purify sewage effluents drops rapidly as a result of biofouling processes that occur on the plant roots. This is due to the high concentration of microorganisms (MO) present in the wastewater. The possibility to apply low frequency (20 kHz) in sonification was examined under laboratory conditions. The ability of US to remove MO from the roots was studied using commercially available sonicators at intensity levels ranging from 2.7 W/cm(2) to 81.4 W/cm(2), (corresponding power levels ranging from 75 W to 500 W) while varying application periods between 5 and 60 min. The results show that MO can be removed effectively (up to 98%) by exposing the Eichhornia crassipes roots to US for 5 min at the intensity level of 64.5 W/cm(2). The efficiency of the wastewater treatment increased with exposure time and power input. The study proved that the US treatment is effective in removing MO that otherwise adhere to the roots, by more then two orders of magnitude. (C) 2008 Elsevier B.V. All rights reserved.