Hybrid Upflow Anaerobic Sludge Blanket (HUASB) reactor filled with rumen liquid associated with cow-dung mixture (3:1) has been fabricated and tested for its performance on the removal of chemical oxygen demand (COD) with different operating conditions for the effluent of pulp and paper industry. The experimental procedure is carried out for a total period of 84 days by applying a COD (attained by trial and error method) range of 11312 kg COD/day in the influent with different Organic Loading Rate (OLR) and Hydraulic Loading Rate (HLR). To test the large scale application of the reactor, the initial COD concentration is not reduced from raw Wastewater value. An efficiency of 85.6% was achieved with respect to COD removal during the study. Kinetic models are fitted to the data obtained and the best fit models are highlighted. Kinetic parameters like decay coefficient, first and second order rate constants, and yield coefficient are determined for the HUASB reactor.