Abstract:
Chlorine is one of the most important disinfectants for purifying water. Purification
of water is a vital concern for mankind since it is directly linked with human
welfare. Many treatment plants use surface water sources for supplying of water.
But this surface water sources carries exccss amount of amonia, organic matter,
turbidity and other impurities due to disposal of untreated waste and wastewater
from industria~ commercial and domestic sources. Removal of these impurities
from raw water is very difficult and quite impossible by plain sedimentation and
even it leads to extra treatment load of the plant. Hence pre-chlorination is
performed in those plants to reduce the extra treatment load and higher removal
efficiency of organic & inorganic impurities. Saidabad Water Treatment Plant is
one example of such pratice. The raw water of Saidabad Water Treatment Plant was
used for this study.
This study is intended to acquire a better understanding the change of behavior of
alum coagulation and sedimentation for use of pre-chlorination in treatment process.
Effectiveness of alum coagulation and sedimentation on removing turbidity and
color was investigated a wide range in this study in both the cases i.e with and
without pre-chlorination condition.
Color removal efficiency is significantly higher in case of pre- chlorination
condition compared to without pre-chlorination condition. But turbidity removal
efficiency IS not significantly higher in case of pre- chlorination condition
compared to without pre-cWorination condition. But pre-chlorination has no
negative impact on removing turbidity and color.
An increase in alum dosage enhances the removal rate of turbidity and color in both
the cases. But it is significantly higher in case of pre-chlorination condition
compared to without pre-chlorination condition. Above all, pre-chlorination has
positive impact on alum coagulation. Turbidity and color removal efficiencies arc directly proportional to contact time of
chlorine. [f the contact time 0f chlorine is increased, then turbidity and co [or
removal efficiency will be increased and vise-versa. On the other hand, contact time
of chlorine is inversely proportional to the amount of applied chlorine doses. If the
contact time of chlorine is increased, then comparatively lower amount of chlorine
dose will remove same amount of turbidity and color and vise-versa.
Ammonia (NH3) concentration of raw water was exhibited a criticality on removing
turbidity and color. Removal efficiencies were higher in case of lower ammonia
(NH3) concentration of raw water compared to higher ammonia (NH3) concentration
of raw water by applying same amount of chlorine doses or same contact time of
chlorine. Increase of chlorine dose corresponds to ammonia (NH3) concentration of
raw water has no significant impact on turbidity removal but has significant impact
on color removal.
