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1764776 
Journal Article 
Comparison of efficiency between poly-aluminium chloride and aluminium sulphate coagulants during full-scale experiments in a drinking water treatment plant 
Zouboulis, A; Traskas, G; Samaras, P 
2008 
1 
Separation Science and Technology
ISSN: 0149-6395
EISSN: 1520-5754 
43 
6 
1507-1519 
WOS:000254822300013 
The efficiency of poly-aluminium chloride (PACl) and of
aluminium sulphate (alum), two commonly applied coagulant agents, was studied comparatively in
this work, during full-scale experiments in a drinking water treatment plant. The removal of
suspended solids (turbidity) and the residual aluminium concentrations were carefully monitored
and they were used for the evaluation of effectiveness for each coagulant, as well as for the
determination of optimal operative conditions. Two alternative treatment processes were examined:
(a) the conventional coagulation-flocculation-sedimentation process, followed by gravity
filtration through sand filter beds, and (b) the direct filtration process, i.e., coagulation-
flocculation and sand filtration, but without the intermediate sedimentation step. PACl proved to
be a more efficient coagulant than alum, as lower dosages of PACl, about 1.35mg Al/L in this
case, resulted to the production of treated water with low turbidity and residual aluminium
content. In addition, the direct filtration process through dual sand-anthracite filter beds was
found to be equally sufficient, as the conventional one, i.e., when applying the sedimentation
step; in this case, 0.70mg Al/L of PACl resulted in low turbidity water (around 0.1 NTU) and
residual aluminium content (lower than 150g/L). In addition, the operation time of filters was
extended to more than 24 hours. 
PACl; alum; coagulation; direct filtration; residual aluminium concentration; drinking water treatment; full-scale experiments