The results of the characterization of the wastewater from the industrial zone of the city of El Jadida show that parameters such as pH, electrical conductivity, total Kjeldahl nitrogen (NTK), and nitrates (NO3−) are very high and vary significantly throughout the day. The pollutant loads are also highly variable in terms of chemical oxygen demand (COD) and biochemical oxygen demand (BOD5), with values ranging from 1152 to 8064 mg O2/L for COD and from 581 to 1674 mg O2/L for BOD5. The concentrations of suspended solids (SS) in this effluent are notably high, reaching a maximum of 1540 mg/L. These variations depend on the intense industrial activities across the different factories. Various treatment trials using activated carbon, lime, fly ash, slag, raw chitin, and chitosan resulted in clear waters with significantly reduced dissolved organic matter, demonstrating high treatment efficiency. On the other hand, the use of biological supports (palm bark, sugarcane bagasse, and corn cobs) resulted in effluents that remained heavily loaded with organic matter, showing very low treatment efficiency. Coagulation-flocculation using aluminum sulfate and ferric chloride produced clear water with low levels of organic matter after treatment at optimal pH values of approximately 8.1 for aluminum sulfate and 6.1 for ferric chloride. The residual organic matter and turbidity in the treated water were low; however, the quantities of coagulants used were very high.