In this work, for analysis, one and half liters of (effluent) waste water from paper mill industry was used in batch reactor, to study the variations in DO values under three operating conditions are speed, concentration of effluent in water and time with respect to step change in oxygen feed. The experiment was done 270 trails under specified operating conditions. Experimental data were collected, many trials were done using response surface method (RSM) and respective optimum values of three operating parameters were obtained for DO value ranging from 5 to 6 ppm. In trials, RSM predicted 82.732 % effluent to water concentration, stirrer speed at 150 rpm and at 0.091 min predicted DO is 5.7 ppm, from obtained experimental results shown in figure 3 for 80 % and 90 % concentration. RSM predicted optimal conditions are considered for experimental study and three control strategies such as particle swarm optimization (PSO) based PID control and state feedback controller with Integral action and state observer were used to achieve desired DO value. A comparative study was done among three controllers and it was concluded that state feedback controller with Integral action based control strategy yield better closed loop results in-terms of time-domain and stability analysis.