Using Oreochromis niloticus for Assessment of Water Quality in Water Treatment Plants

The present study was suggested in order to explore the capability of water treatment plants to induce changes in organisms using the fish as a model. To achieve such a purpose, Oreochromis niloticus were chosen as a test material for the study. Two hundred apparently healthy Oreochromis niloticus were divided into 7 groups (control and 3 different WTPs) to assess differences developed from water treatment and the effect of these differences on the histological aspects of the gills of each group. From the beginning to the end of experiment, water samples were collected and daily analyzed. At the end of experiment, fish from each group were sacrified to assess the heavy metals and histological changes to the gill after 90 days of exposing to different kinds of water from different WTPs. Some heavy metal concentrations (Fe, Mn, Cu, Zn, Pb and Cd) were determined in both water and gill samples. Heavy metals were measured by Flame Atomic Absorption Spectrophotometer. Results of water were compared with national and international water quality guidelines. Also, gill accumulated heavy metals concentrations go parallel with that of water metals. The histological results revealed that the gill tissue of the control and input groups has many histopathological alterations while that of the WTPs output groups were characterized by improvement in the gill histology. The main WTP show normal structure of the gill and the developed one showed irregular shape of the filament, while the compact one were characterized by two states; normal and mucoid metaplasia. The histological alterations nearly agree with the heavy metals measurements. In conclusion, water quality differed by the difference in the design of WTPs. Also, the quality of water treatment affected the histology of the gills of the investigated samples.