Use of aquatic plants of three different ecological types for Escherichia coli removal from pacu breeding effluents

ABSTRACT This study evaluated the water contamination by Escherichia coli in pacu (Piaractus mesopotamicus) breeding ponds and its removal by a constructed wetland system containing macrophytes of three different ecological types (Eichhornia crassipes, Ceratophyllum demersum, and Typha domingensis). The most probable number of E. coli in the water was quantified for supply site, effluent and at each stage of treatment (sedimentation and use of each type of aquatic macrophyte). We conclude that E. coli contamination in water supply and in fishpond can reach the environment through the effluent. The proposed treatment system was efficient in removing E. coli from the water, and when the system was stabilized the average removal efficiency of E. coli was 95%. The tank containing E. crassipes showed the highest removal average, even though it exhibited an efficiency reduction after 60 days of experiment. The average removal of the tanks containing C. demersum and T. domingensis was hampered due to the presence of E. coli in soil used as substrate. However, after the decrease of substrate contamination effect, these two plants were essential for the maintenance of water quality of the treated effluent, indicating the benefits of aquatic macrophytes diversity in treatment systems. The effluent quality was maintained even when some system steps presented a decrease of removal efficiency.