| Summary: | ABSTRACT
Black Liquor Waste (BL W) of paper mills is still a big problem related to the enviromental conservation. This research was done in order to search the suitable coagulant which could be applied in the sedimentation process of BL W and to eveluale the characteristics of the coagulants.
BL W as solution material was taken from "Blabak" paper mill factory in Magelang, Central Java. Three type of coagulants (i.e. Kelor Seed Powder (KSP), Chloride Acid (CA) and Ferric Chloride (FC) were used in this investigation. This research was a Batch type by using glass tubes.
The result indicated that application of high concentration of FC (17,5 � 20% per liter BL W) formed flocs. These flocs were floating. Thus formed two significant layers. The same result was obtained in the application of 100 � 125 ml of 10% CA per liter BL W. Application of both coagulants decreased pH level up to 1 � 3.5.
Optimum performance of the KSP coagulant was detected at 10 � 20 g per liter BL W. Another advantage of aplication KSP was the obtained final pH level of the solution that approached neutral condition (pH 8 � 9.5), wherein microorganisms were still active. This would reduce the cost of neutralisation of the secondary treatment.
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