This study deals with an Israel-Egypt-USA collaborative project on the health risks and technological options for fish grown in polluted waters.

The fish were grown in aquaculture either with wastewater–enrichment or without. The study included one effluent polishing pond, two fish ponds and two water reservoirs. The fish stock in the ponds and reservoirs consisted mainly of tilapia (usually hybrids of Sarotherodonniloticus × S. aureus). The results of Israeli and Egyptian studies indicated that, on the average, the yields for wastewater aquaculture were higher than the yields without wastewater. However the Egyptian study showed that in areas with inadequate dilution of wastewater by freshwater near to a sewage outfall, there were negative effects on fish production.

Microbiological assays (E.coli and Aeromonas) of water and fish tissues, indicate that the Aeromonas counts were high in the water as well as in the fish tissue. The bacterial count was higher in the digestive tract than in the water in which the fish were grown. In most cases only Aeromonas was detected in muscles. There was no difference between wastewater-enriched and nonwastewater aquacultures for both E.coli and Aeromonas concentrations in fish tissues.

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