A STUDY ON THE FISH CULTURE IN INDUSTRIAL WASTE WATER
Huang Yuyao Zhao Zhongxian Guo Hongliang (institute of Zoology, Academic Sinica, Beijing)
This paper deals with the possibility of fish culture in the effluent purified by simulation stabilization pond which is consisted of 4 cells with 45 days of hydraulic retention time. The effluent quality is improved remarkbly through simulation pond. Before purifying, the raw waste water contains high levels of BOD5, COD, NH3-N, PO4-P, chloride, mercury etc (Table 2.).Some 50 young fish (Tilapia mossambica) are reared in the effluent. 2 or 3 fish are caught out in different sampling time for examination of growth and mercury content. No food has been added to the fish outside the simulation pond system during experimental interval of 132 days. The results obtained are as followss1. The growth and breeding behavoir of the T.mossambica are quite well. No dead sample has been found in the effluent during the exposed test. It indicates that the effluent quality is good for fish growth and reproduction.2. The mercury content of T.mossambica is slightly increased with increasing exposure time. The average mercury contents vary between 0.35 and 0,40 Hg/g including initial mercury content of 0.14Hg/g of test fish. This mercury contents of test fish are much lower than those of crucian carp (Carassius aura-tus) living in Hangu Sewage Lagoon which receives the same kind of waste water as the simulation pond and the mercury content of crucian carp reaches to 7.7μg/g through 100 day exposure time.3. The biological productivity of effluent is very high because of high levels of nitrogen and phosphorus. The potential fish productivity in designing fish pond is estimated based on the data of the primary production of phytoplankton and biomass of benthos. If some fish contains mercury too high for human consumption, it still could be used as food for mink.4. Data obtained indicate that the fish culture is one of the important approaches in the reuse of industrial waste water which contains high concentrations of nitrogen,phosphorus,chloride and mercury through purifying by multicell stabilization pond.