Chloride or sulfate? Consequences for ozonation of textile wastewater. (1st October 2019)

• Record Type: Journal Article
• Authors: Oktem, Yalcin Askin; Yuzer, Burak; Aydin, Muhammed Iberia; Okten, Hatice Eser; Meric, Sureyya; Selcuk, Huseyin
• Is Part Of: Journal of environmental management. Volume 247(2019)
• Page Start: 749
• Page End: 755
• Publication Date: 2019-10-01
• Subjects: Adsorbable organic halogens -- Ozonation -- Reactive dye -- Treatment -- Textile wastewater -- Toxicity; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2019.06.114
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: 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 Na2 SO4 . 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. Graphical abstract: Image 1 Highlights: Use of sulfate in reactive dyeing increased biodegradability and decreased acute toxicity. Although use of sulfate has a high cost, also subjects such as biodegradability, low toxicity, water and salt recovery have advantages. Ozonation is as an auxiliary process that increased biological degradability, it also caused increased toxicity for textile wastewaters.