An investigative study was reported on the wastewater treatment plant (WWTP) in Batna city which is located in the Algerian east, in order to highlight the problem of industrials wastewaters pollution and their impact on WWTP function. The average value of "COD / BOD" was reported as high (3.5) compared to the contract value (2.5) which characterize the biodegradable rejection. In addition the concentrations of industrial discharge were higher than the Algerian’s standards. Our analyses showed that the daily index measurement Mohlman is 200 mg/ml (≥ 150) which confirm the disruption of the biological process; this is why they must be treated before being discharged. Many solutions should be made to lutter against this problem: Applying the rules, additional treatments and rehabilitation of the WWTP in a more conventional extended aeration process for better elimination of pollution. Finally, for a better understanding of the industrial pollution problem, an obligated characterization of wastewater must be made for each industry to improve the discharge quality.