Degradation of Organic Pollutants, Comparative Study Between the Results of the Jar-Test Pilot Unit and the IGF Coagulation-Flocculation Unit of the Arzew Refinery

The main purpose of the Jar-test laboratory scale tests is to improve knowledge on the theory of primary settling in the treatment of industrial wastewater in order to optimize the coagulation-flocculation processes of the liquid effluent treatment units of the Arzew refinery. This study attempts to develop the coagulation and flocculation process for primary settling and to choose the best coagulant and reactive flocculant. To do this, the study of different treatment characteristics of a decanter, including the impact of adding chemical reagents such as coagulant and flocculant is necessary. These products improve the efficiency of the unit operation by making the coagulation and flocculation phase more efficient. The Arzew refinery is equipped with two industrial liquid effluent treatment units, U1800 and Z27, whose liquid effluent nature is almost identical. Unit 1800 uses two reagents KEMAZUR and PROSEDIM CS53 as coagulant and flocculant respectively, while in unit Z27 the coagulants used are aluminum sulfates, N8186, N8187 and N77135 as well as flocculants N71456 and N71305. The objective of the Jar-test is to optimize the necessary doses, increase the efficiency of primary decantation and apply the best reagents in both units in order to have more efficient coagulation and flocculation. This is a way to simulate, on a small scale, the coagulation/flocculation process that takes place in a treatment plant. This study shows that the coagulation phase, i.e., the coagulation time and speed, and the concentration of the coagulating reagents, are the most important factors to consider when optimizing the results of jar tests for wastewater treatment, where the rotation speed of the coagulation phase is around 200 rpm (rotation per minute). The effects of the flocculation phase, i.e., the addition time of the polymer reagent, the flocculation time and speed, and the polymer concentration, can be considered negligible. Similarly, the water quality, which can be variable, does not influence the results of jar tests, under certain storage and handling rules during the latter. Regarding the significant factors, it seems that the optimal coagulation speed is around 30 rotations per minute. Beyond this, coagulation is not improved. The coagulation time required to have a good reaction mechanism is 3 minutes, with the optimum concentration of KEMAZUR and CS53 coagulants around 420 mg/l, while the optimal concentration, optical density and turbidity of: Aluminum sulfates, N8186, N8187, N77153, N71456 and N71305 are between 12 and 16 mg/l of the doses of coagulants and flocculants. On the other hand, COD and yields are better depending on the upward increase in the doses of the reagents. Applying the same doses to the IGF coagulation-flocculation process of unit Z27 actually significantly reduced COD, resulting in yields exceeding 42%. The constraints encountered by the IGF process were the high furfural levels in the influent, pH variations, high variable hydrocarbon levels, and the flow rate of the coagulant and flocculant dosing pumps. This experiment showed us that the best coagulant and flocculant chosen for the best treatment were N8187 and N71456, respectively.