Resource recovery from septic tank effluent using duckweed-based tilapia aquaculture

Abstract

Two parallel duckweed ponds were deployed to utilize nutrients from the effluent of a septic tank treating domestic wastewater. The effluent and fresh biomass of duckweed pond were fed to two subsequent fish ponds stocked with Nile tilapia (Oreochromis niloticus). Fish ponds receiving freshwater and commercial feed were used as control. The results of specific growth rate and feed conversion ratio showed no significant difference between the control ponds and treatment ponds. On the other hand, the total and net fish yields were significantly higher in the control. Microbial analysis revealed contamination of gills, intestine and liver of fish in the treatment ponds. The activity of the immune response genes was up-regulated in the brain and liver of the treatment samples. A micronucleus assay revealed a similar percentage of micronuclei in the polychromatic erythrocytes of blood in the control and treatment samples, while the treatment samples a had higher incidence of micronuclei in the polychromatic erythrocytes of gills, compared with the control.

Keywords:

• duckweed wastewater
• micronucleus
• nutrients
• septic tank
• Nile tilapia

Acknowledgements

This research was carried out and financially supported by the Department of Water Pollution Research, National Research Centre, Egypt. The authors would like to thank M.Sc. students at the Genetic of Hydrobiology Laboratory, Department of Water Pollution Research. I would like also to thank Dr. Bahman Sheikh and Prof. Slav Hermanowicz for their editing. Great thanks to the Prince Khalid Bin Sultan Chair (PKC) for Water Research, College of Engineering, King Saud University, for Internet access and support during the office-work phase of this research.