MORTALITY RATE OF TILAPIA ZILLII GERV. EXPOSED TO RAW AND TREATED TANNERY WASTEWATER.

MORTALITY RATE OF TILAPIA ZILLII GERV. EXPOSED TO

RAW AND TREATED TANNERY WASTEWATER.

HAMED SALEH, AHMED HAMZA*, MAKA WY AKEL*
AND MOUHAMED MOURAD*.
Alexandria Institute of Oceanography and Fisheries. Egypt.
*High Institute of Public Health. Alexandria. Egypt.
ABSTRACT
The waste water from tanneries at Max industrial complex
are discharged directly without pretreatment to Western
Harbour (Mediterranean Sea).
laboratory experiments using Tilapia zillii Gerv and
tannery waste water and its dilutions ( 0% (control). 3%.
5%. 10%. 20%. 30%. 40%. 60%. 80% and 100% ) had proved the
high toxicity of such waste water and its dilutions.
The hi gh 1etha1ity of tannery waste water is attri buted
mainly to it~ high content of ammonia. suspended organic
matter. sulphides and heavy metals.
Treatment of tannery waste water by plain sedimentation
decreased its lethality to fishes. i.e. 96 h – lCSO for
Tilapia zillii became 40% tannery waste water, which was
probably due to moderate removal of suspended organic matter
and heavy metals mainly Cr.
Insignificant improvement of mortality rate was achieved
by chemical coagulation using alum (A12 (504)3′ 18 H20).
inspite of the improvement in chemical characteristics of
the raw waste.
The 96 h-lC50 for Tilapia zillii exposed to tannery
waste water with activated sludge and sand filtration was
80%. which was attributed to effective removal of ammonia.
suspended organic matter and heavy metals.