Enhancement of Quality of Secondary Industrial Wastewater Effluent by Coagulation Process: A Case Study1255
that ferrous sulfate-flocs have the better settlabilty among
other flocs. Within 15 minutes the sludge reached its
lowest volume compared to 22 and 28 minutes for alum
and ferric chloride, respectively. The final sludge volume
is another indication about the excellent characteristics of
ferrous sulfate as a coagulant. This volume was 50 ml
compared to 100 and 110 ml for alum and ferric chloride
respectively. The sludge volume index (SVI) for the
three coagulants are 25, 55 and 50 ml/l, respectively in-
dicate good settling properties.
4. Conclusions and Recommendations
The removal efficiency of turbidity from industrial waste-
water was experimentally investigated using coagulation
technique. Four different coagulants were tested. The
temperature did not have a preannounced effect on the
coagulation process. The pH of the wastewater had an
important effect on turbidity removal efficiency. The
highest removal efficiency was found at higher pH. Even
without the addition of coagulant a considerable part of
the turbidity would precipitate at elevated pH. The Stir-
ring rate also does not have an effect either. Consequ-
ently, the slow and fast steps of stirring can be consoli-
dated in just one step with moderate velocity to save
money and time. Ferrous sulfate and polymer were found
to be the best polymers. Even at very low doses (in the
range of 1 - 5 mg/lit) the turbidity was reduced to much
lower than that required by the governmental agencies.
The settling rate for ferrous sulfate was 15 minutes com-
pared to 4 minutes for the polymer. The jar test must be
applied regularly to keep up with the continuous changes
of the properties of the received industrial wastewater
which ensures good quality of the treated water.
5. Acknowledgements
The authors are grateful to the local wastewater treat-
ment facility for supplying the industrial wastewater, and
polymer used in this work. The authors would like to
thank Mr. AbdelRahman Mohanna and Mr. Samy Jaber
for their help through this work.
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