Lime treatment of wastewater in a plywood industry to achieve the zero liquid discharge

Abstract

Abstract The plywood manufacturing process involves debarking of log, peeling and pressing of ribbons of wood after glueing with proper resin, trimming, sanding and finishing. Washings of glue mixer, resin kettle and a glue spreader generate solids and various hazardous chemicals like phenol, sodium hydroxide and formaldehyde. To protect the environment and human health, it is necessary to treat and reuse the wastewater of plywood manufacturing. There are several methods available for the treatment of plywood industries wastewater and use of lime is one of them. In the present study viability of lime treatment was performed to achieve zero liquid discharge in a Plywood Industry. An optimum lime dose of 1.5 g/L was applied to the wastewater of melamine urea formaldehyde and phenol formaldehyde resin units. After treatment, removal of 28.6% and 41.2% total dissolved solid and 36.8% and 37.5% total suspended solid were observed in melamine urea formaldehyde and phenol formaldehyde resin units wastewater. Phenol and chemical oxygen demand removals were more than 38% and 40% from the wastewater of both units. Lime treated wastewater was used to prepare melamine urea formaldehyde and phenol formaldehyde glue/resin by mixing chemicals. The prepared resins exhibit characteristics within prescribed limits of plywood manufacturing. The mechanical and physical properties of plywood specimen have also found satisfactory.