Ecological Studies on Treatment of Polluted Drainage Water of Fish Farms using Nano-composites and Protozooplankton

Abstract

The present study was planned to treat polluted drainage water of fish farms using three nano-composite and protozooplanktons to remove heavy metals and control the physicochemical parameters of wastewater. Field study was carried out in three different fish farms in Khafr El-Sheikh governorate; El- Abbassia (EL-Reyad), Eizbat Ghabayshah (Motobas), and El- Shakhlopa (Sidi Salem). Water samples were collected during three fish growth seasons; spring, summer and autumn, 2018. The present study showed that fish farms drainage water was contaminated with heavy metals in all studied areas. Also, these metal ions were detected in collected fish samples with varying concentrations during studied seasons. Examination of water samples showed presence 16 genera of protozooplankton in the water of fish farms, especially Euglena, Paramecium and Euplotes, and their densities increased in fishponds than in source and wastewater. In the laboratorial study, three nanocomposites were prepared, which are chitosan nanoparticles, magnetic iron oxide-EDTA nano- compound, and a combination of both to produce more stable nano- compound, magnetic-EDTA@chitosan (ME@CS NC). The study provides success of fabrication of compounds in the nanoscale and the incorporation of chitosan with stable bonds with the magnetic- EDTA. The ability of the three nano-composites to remove heavy metals from fish farm wastewater was tested. The results of the study showed the great ability of ME@CS NC to reduce these ions from fish farms wastewater under the optimum conditions, which are a dose of 0.5 g/l, water pH of 7.0 and a treatment time of one hour only, where 99.9, 99.5, 99.3, and 99.1% of Al, Pb, Cd, and Mn ions were removed under these conditions, respectively. Also, concentrations of nitrates, chemical oxygen demand (COD), ammonia, phosphate and nitrite were reduced by 63.6, 57.0, 28.0, 21.4, and 11.8%, respectively.

Our results revealed that magnetic-EDTA@chitosan nano- composite was safe for the biological indicator Daphnia magna, which indicated that this nano-composite is safe for all aquatic life. The study proved that the combined treatment of protozooplankton with ME@CS nano-composite was more efficient to remove pollutants from fish farm wastewater, especially heavy metals and ammonia. Therefore, this combined treatment is environmentally safe and can be applied to reuse fish farm wastewater many times and save water, especially in semi-intensive and intensive systems