The role of online analyzers in the industrial process control varies from real-time feedback for controlling product quality to compliance monitoring of the final discharge. Manual operation has been the traditional method for wastewater treatment process control. Manual adjustments of control elements or intermittent operation are made to maintain parameters within desirable ranges. Frequent adjustments are impossible such that the system is never optimized. Despite this major disadvantage, manual operation is still the most common control method today. To meet the increasing level of automation in water treatment plants as, reliable real-time information is indispensable for optimizing treatment processes and ensuring stable operation. Without timely process monitoring, it is hard to know the effectiveness of process control decisions. Proportional-integral-derivative (PID) controller ensures to maintain the process closer to setpoints and more closely match the responses to the demand. Good process control keeps several factors in balance such that WWTP operators can achieve compliance with discharge limits for TOC, TN and TP. Reliable continuous monitoring of parameters is critical for optimizing the wastewater treatment system.