Chloride or sulfate? Consequences for ozonation of textile wastewater

Ozonation of chloride-rich textile wastewater is a common pretreatment practice in order to increase biodegradability and therefore meet the discharge limits. This study is the first to investigate ozone-chloride/bromide interactions and formation of hazardous adsorbable organic halogens (AOX) in real textile wastewater. Initially effect of ozonation on chloride-rich real textile wastewater samples were investigated for adsorbable organic halogens (AOX) formation, biodegradability and toxicity. After 15 min of ozonation, maximum levels of chlorine/bromine generation (0.3 mg/l) and AOX formation (399 mg/l) were reached. OUR and SOUR levels both increased by approximately 58%. Daphnia magna toxicity peaked at 100% for 10 min ozonated sample. Considering adverse effects of ozonation on chloride-rich textile industry effluents, we proposed replacement of NaCl with Na2SO4. Comparative ozonation experiments were carried out for both chloride and sulfate containing synthetic dyeing wastewater samples. Results showed that use of sulfate in reactive dyeing increased biodegradability and decreased acute toxicity. Although sulfate is preferred over chloride for more effective dyeing performance, the switch has been hampered due to sodium sulfate's higher unit cost. However, consideration of indirect costs such as contributions to biodegradability, toxicity, water and salt recovery shall facilitate textile industry's switch from chloride to sulfate.TUBITAK (117Y194

Comparison of ozonation and coagulation decolorization methods in real textile wastewater

Several treatment approaches such as ozonation, metal coagulation, (ferric chloride and alum), polymer treatment (Polyethylene polyamine, PP, and Cyanoguanidine Polymer, CP) and their combinations for decolarization of biologically treated textile wastewater (BTTWW) were applied. Wastewater samples were taken from effluent stream of an activated sludge treatment system in a synthetic-cotton textile factory. Absorbance, color, chemical oxygen demand (COD) measurements were done to determine optimum conditions. At coagulation experiments, neither ferric chloridenoralum decreased the color parameter below the discharge standard. Ozonation was found to be efficient in removing color from BTTWW as color degradation reached steady-state after 10 min. However color standard was met at higher ozone dosages (20 min). Polymer coagulation (200 mg/L) was found to be practical in removing color from BTTWW. Ozonation prior to polymer coagulation (pre-ozonation) not only improved the color removal efficiency but also decreased the required polymer dosage by 75%. Operational costs of ozonation, PP and pre-ozonation-subsequently PP were found to be 0.37 €/m3, 0.50 €/m3, and 0.26 €/m3, respectively

Photocatalytic, self-cleaning and antibacterial properties of Cu(II) doped TiO2

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