A Caustic Recovery Plant is typically a multiple effect evaporation plant which will re-concentrate the weak lye by heating it in exchanger and when it reaches evaporator vapour is released due to water evaporation that increases its concentration. This Process repeats itself by circulating in caustic recovery plant till the desired concentration reached. Textile Mills involved in mercerizing of (Yarn, Woven, Knitted, Denim) cotton use caustic (NaOH) in mercerizing machines. After process in mercerizing machine this dilute caustic soda solutions come out form mercerizing machines as drain. The density of drain caustic solution veries from 3% to 8% (31 to 87 gm/It)). The drained weak lye also causes financial los not only by removal but also by process incurred to remove it, i.e. expense incurred in treating (neutralizing) at ETP as per pollution laws.