Textile waste water resulting from finishing of textile materials has a complex and diverse composition, due to a variety of raw materials and technological processes used. General characteristics of waste water for textile dyeing are related to a high content of organic matter (dyes, auxiliary agents) being very colourful and toxic [1]. The aim of this thesis is to study experimentally on model systems, the influence of DEG diethylen glycol on the coagulation of active (Active Red-AR120) and direct (Direct Blue- DB 71) dyes. The pH value and the concentration of aluminium ions are the main parameters influencing the coagulation process. From the experimental studies it was determined that the optimal pH for the coagulation of the DEG with a concentration of 60 mg/L is 5.5 and the Al3+ concentration is 1.62 mg/L. Under such conditions, a high efficiency of the coagulation process was obtained (90-93%). In actual fact, waste water is a complex system that contains dyes and various toxic auxiliary substances. In order to optimize the process of coagulation of the textile waste water, various systems similar to their composition have been modeled. The experimental studies in coagulation of the AR - DEG and DB - DEG model systems, with a 200 mg/L dye level, found that the optimal pH is 5.0-5.5 and pH ~ 4.5 respectively. And the optimal Al3+ concentration is 2.7 mg/L for the AR-DEG model system and 5.40 mg/L for the DB - DEG system, taking into account the rational use of the reagents. From the experimental researches of the coagulation process of AR and DB, it has been established that maximum efficacy is obtained at pH as compared to systems containing DEG. And the optimum concentration of Al3+ is 1.35 mg/L for AR and 2.7 mg/L for DB [2]. So we conclude that DEG has no influence on the optimum pH in the systems containing dyes. The coagulation of DB and AR dyes has been studied according to Al3+ concentration and it has been found that the [Al3+]/[Col.] ratio depends on the nature of the dyes: for AR is 0.006 and for DB is 0.013. However, in the presence of DEG this ratio increases (DB - 0.020, and for RA-0.010).The dyes in model systems with DEG behave differently because they have different coagulation nature and structure. DB dye has higher removal efficiency compared to the model system containing AR. For purification by coagulation of the model system composed of DB - DEG, a double coagulant concentration is required compared to the model system consisting of AR and DEG. This process takes place because there are several negatively charged polar groups in the structure of the AR dye, which more easily interact with the colloidal micelles of the positively charged coagulant. Based on the electrostatic effect, large agglomerates are formed, which are eliminated by filtering the model system [3].