(228f) Dewatering Characteristics of Indian Nonwood and Wood BASED PAPER Mill ETP Sludge with Chemical Conditioning

By

H.K.Dhingra, Mohendru V.K.* and A.K.Ray

Department of Paper Technology, IITRoorkee, Saharanpur Campus, India

*Retired Scientist , Central Pulp and paper Research Institute, Saharanpur, India

ABSTRACT

Sludge handling and its disposal from waste water treatment plant is one of the major constraints in any chemical industry in India, pulp and paper industry in particular. This  problem relating to sludge handling can be overcome by applying efficient sludge dewatering techniques. Chemical conditioning of sludge is a commonly applied practice to improve the dewatering characteristics of sludge  to result in improved dried sludge. While doing chemical conditioning of sludge , the understanding of sludge and flocculant characteristics is very much needed for better economical dewatering. However, these chemicals are numerous and generally expensive; thus it increases the cost of operation significantly. Therefore, it is absolute necessary to evaluate the viability of using the chemicals at plant or laboratory scale on the basis of the balancing the gain against cost.

In India effluent treatment plant(ETP) of  paper mill are generally  based on either nonwood or wood fibres or combination of the former two which  generate large amount of primary and secondary sludges in aqueous form. Nonwood based ETP sludges  generally become  more detrimental during handling.  These problems can be overcome by efficient dewatering of sludge for which study of characteristics of sludge and the effect of chemical conditioning is very much needed. The later method is used to improve dewatering of sludge by flocculating the sludge with organic/inorganic flocculants.

An attempt has been made in this present investigation to study  in-depth by laboratory scale experiments, the dewatering characteristics of both primary and secondary sludges of two different Indian mills using different kinds of raw materials, wood and non-wood. The effects of various parameters like, pH, time of agitation, and storage on dewaterability of sludge from wood and nonwood based paper mills during conditioning with inorganic and organic flocculants in terms of specific cake resistance and other filterability parameters..The present investigation also provides a step by step procedure to evaluate the effectiveness of flocculants from the economic standpoint.

KEY WORDS: Primary and secondary sludge, dewatering, chemical conditioning, flocculants, rapid and slow mixing time, pH, storage, optimum dose, under dose, economic analysis.