CHEMICAL PRETREATMENT OF A SPENT DISPERSE DYEBATH ANALOGUE BY COAGULATION AND ELECTROCOAGULATION


Arslan-Alaton I., Tuerkoglu G. , Kabdasli I.

FRESENIUS ENVIRONMENTAL BULLETIN, cilt.17, ss.1809-1815, 2008 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 17
  • Basım Tarihi: 2008
  • Dergi Adı: FRESENIUS ENVIRONMENTAL BULLETIN
  • Sayfa Sayıları: ss.1809-1815

Özet

Coagulation and electrocoagulation (EC) using aluminum (Al) and stainless steel (SS) electrodes were investigated for color and COD removal from a simulated spent disperse dyebath analogue (COD0 = 3300 mg/L; apparent color in absorbance (A) units at the wavelengths 436, 525 and 620 nm: A(436) = 0.992 cm(-1), A(525) = 0.910 cm(-1): A(620) = 0.616 cm(-1), respectively : original pH = 3.0). In the first part of the study, coagulation experiments were carried out with aluminum sulphate, ferrous sulfate and ferric chloride at their optimum pH's and varying coagulant doses (200-2000 mg/L). In the second part of the study., the EC process using, Al electrodes was optimized for initial reaction pH (3.5-11.5) in the presence of 2500 mg/L NaCl electrolyte and an electrical current density of 44 mA/cm(2). Thereafter, EC experiments using SS as the electrode material were also conducted at varying pH's (3.5-11.5) in the presence of 2000 mg/L NaCl and an electrical current density of 44 mA/cm(2) Coagulation experiments indicated that aluminum sulphate was the most effective coagulant in terms of color (100%) and COD (64%) removals. According to the chemical pretreatment results obtained with EC using Al electrodes, color and COD removals occurred almost instantaneously and highest removal rates were achieved at an initial pH of 7.0, resulting in complete color and 61 % COD removals. In the case of EC with SS electrodes, color and COD removal rates were relatively slow and highest treatment efficiencies (complete color and 55% COD removals) could be obtained at an initial pH of 7.3. The variation in treatment performance was attributable to the different reaction mechanisms taking place during EC with Al and SS electrodes. In the last part of the study, the effect of chemical pretreatment EC with Al and SS electrodes under optimized working conditions) on the biodegradability of the total. combined textile wastewater was examined. Activated sludge experiments run for 24 It at an initial food-to-microorganisms ratio of 0.18 g COD0/g MLVSS indicated that the final effluent COD of biotreated textile waste-water decreased below 100 mg/L when the spent disperse dye-bath was subjected to chemical pretreatment with EC.