THE EFFICIENCY OF ULTRASOUND ON ALGAL CONTROL IN A CLOSED LOOP WATER TREATMENT SYSTEM FOR CYPRINID FISH FARMS

摘要

The study has been carried out to evaluate the efficiency of ultrasound (US) on algae control in a fish pond with closed loop water treatment system for cyprinid fish farms consisting of three water treatment devices: glass fibre filters (GFF), US and UV-C (UV) as compared with those of non-treated fish pond. The results showed that sonication caused efficiently sedimentation of planktonic algae. The reduced chlorophyll a concentration and number of total algal species (2.4% and 87% of the control, respectively) was mainly due to the inhibition on the growth of planktonic algal species. Algal cells were not damaged by the US treatment in that proportion that chlorophyll a would be released from the cells. US statistically significantly (p ≤0.05) influenced the algal community structure. The proportion of green algae was 27% higher in non-treated pond, in treated pond diatoms were the predominant group of algae. Species Dictiosphaerium pulchellum, Pediastrum boryanum and Scenedesmus obliquus were "tolerant" to ultrasonic irradiation. The successful control of algae by US suggests that sonication can be a practical method to control algal bloom in fish farms, in case that efficient flushing system for sedimented algae would be developed.