| The present paper deals with two important kinds of waste waters including dyeing and phenol-containing wastewaters. Due to the fact they are frequently and in huge quantities produced by industries through the entire world, they represent imminent threats for the ecosystem, terrestrial lives as well as aquatic ones. They are of great interests for environmentalists nowadays since researches can be done about them in order to improve our environment. Here, we present them with studies done about them.Dyeing wastewater is one kind of wastewaters with high color concentration, and refractory7 organic wastes. After being discharged in water, it can seriously harm natural sceneries as well as many other things by pollutants distortion threatening human health and ecosystem.With the rapid development of textile industries, it is creating more and more serious environmental concerns. With its deep color concentration, complicated structure, plus its complicated chains of nitrogen, it can undergo common methods of treatment such as physico-chemical and biological treatment, but it is very difficult to reach satisfying results. Here, it has also stimulated people's attention towards improved treatment techniques of dyeing wastewater.Phenol is found naturally in decaying dead organic matter like rotting vegetables and in coal. It was first isolated in 1834 from coal tar and this remained the main source of phenol until the First World War. Phenol is a well-known environmental pollutant. It has been found in the wastewaters of many industrial processes. Removal of phenol from wastewater, therefore, has been a major environmental concern.Phenols are considered as primarily pollutant components in wastewater due to their high toxicity, high oxygen demand (theoretically. 2.4 mg O2 mg-1 phenol) and low biodegradability over 2mg I-1 phenol concentration is toxic to fish and concentrations between 10-and 100mgl-1 result in death of aquatic life within 96 h.Being considered as one of the best oxidants in drinking water and wastewater treatments by producing less harmful by-products, ozone has been used uniquely and in combination with other treatment processes such as biological treatment in our experiments.Oxidation with ozone has particular points; high cost of the treatment, in general it is not used solely in wastewater treatment plants, but frequently combined with other methods, and how to do this combination is very important. Using ozone in the pre-treatment followed by biological treatment or first use biological treatment for color removing followed by ozonation to also remove color make it worth for researches. According to the former method, a small amount of ozone can be used for organic pollutants formation, and it is possible to increase its biological and chemical regeneration, with these one can completely remove pollutants from the environment. According to the latter one, the removal of color is successful. In order to do researches (or investigation) on other combined methods, we carried out ozonation and biological treatment combination with different techniques.In the present paper, the unique use of ozone and its combination with the biological treatment were investigated on dyeing wastewater and phenol containing-wastewater. We used the ozonation process before and after biologicaltreatment in the degradation experiment of dyeing and phenol-containing wastewaters at laboratory scale under conditions such as initial concentrations of dye and phenol, temperature, ozone flow. pH values, and ozonation time. Comparison between experimental results and theoretical ones has been realized. Experimental results indicated that the use of ozonation in first position did not change significantly the dyeing wastewaters BOD/COD. Using ozonation as last step of the process gave satisfying results.Good rates of CODcr removal and color removal were obtained in the case of dyeing wastewater allowing a reuse of treated waters.Concerning the phenol-containing wastewater. the use of ozone ahead of the biologi...
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