Advanced oxidation of raw and biotreated textile industry wastewater with O3, H2O2 /UV-C and their sequential application

Abstract

The advanced chemical oxidation of raw and biologically pretreated textile wastewater by (1) ozonation, (2) H 2 O 2 /UV À C oxidation and (3) sequential application of ozonation followed by H 2 O 2 / UV À C oxidation was investigated at the natural pH values (8 and 11) of the textile ef¯uents for 1 h. Analysis of the reduction in the pollution load was followed by total environmental parameters such as TOC, COD, UV±VIS absorption kinetics and the biodegradability factor, f B . The successive treatment combination, where a preliminary ozonation step was carried out prior to H 2 O 2 /UV À C oxidation without changing the total treatment time, enhanced the COD and TOC removal ef®ciency of the H 2 O 2 /UV À C oxidation by a factor of 13 and 4, respectively, for the raw wastewater. In the case of biotreated textile ef¯uent, a preliminary ozonation step increased COD removal of the H 2 O 2 /UV À C treatment system from 15% to 62%, and TOC removal from 0% to 34%. However, the sequential process did not appear to be more effective than applying a single ozonation step in terms of TOC abatement rates. Enhancement of the biodegradability factor (f B ) was more pronounced for the biologically pretreated wastewater with an almost two-fold increase for the optimized Advanced Oxidation Technologies (AOTs). For H 2 O 2 /UV À C oxidation of raw textile wastewater, apparent zero order COD removal rate constants (k app ), and the second order OH . formation rates (r i ) have been calculated. NOTATION AOXAdsorbable organic halogens BOD 5, o 5-day Biochemical Oxygen Demand at time t = 0 (mg dm À3 ) BOD 5, t 5-day Biochemical Oxygen Demand at treatment time t (mg dm À3 ) COD o Chemical Oxygen Demand at time t =0 (mg dm À3 ) COD t Chemical Oxygen Demand at treatment time t (mg dm À3 ) C OH Concentration of OH . (mol dm À3 ) d Effective path length of UV-C light in the reactor (cm) f B Biodegradability factor (dimensionless) F H Fraction of incident radiation at 254 nm absorbed by H 2 O 2 (dimensionless) I o Incident light¯ux of the UV-C lamp (Einstein dm À3 s À1 ) k app Apparent zero order rate constant for COD abatement (mg dm À3 min À1 ) k OH Rate constant for reaction of pollutants with OH . (dm 3 mol s À1 ) r i Second order rate of initiation of OH . formation (mol dm À3 s À1 ) UV-C Light emission in the spectral wavelength region 180 nm`l`290 nm UV H 2 O 2 Absorbance of H 2 O 2 at 254 nm wavelength (m À1 ) UV T Total absorbance at 254 nm wavelength (m À1 ) UV 254 Absorbance of the wastewater at 254 nm wavelength (m À1 ) f Quantum yield for H 2 O 2 photolysis (dimensionless)

Photocatalytic Properties of Co3O4-Coated TiO2 Powders Prepared by Plasma-Enhanced Atomic Layer Deposition

“…Moreover, most textile dyes show recalcitrance towards chemical oxidation and other traditional wastewater treatment. Fortunately, TiO 2 -based photocatalysts exhibit excellent degradation towards organic dyes [4]. TiO 2 has been extensively and intensively studied as one of popular photocatalytic materials due to its low toxicity, high chemical stability, and catalytic activity in elimination of a large range of organic pollutants [5–7].…”

Decolorisation and mineralisation of homo‐ and hetero‐bireactive dyes under Fenton and photo‐Fenton conditions

“…Among these treatments, advanced oxidation processes (AOPs) have been used for pollutant abatement due to the high oxidative power (2.8 V vs NHE) of the hydroxyl radical, the main reactive species generated by such processes. The most widely known AOPs include heterogeneous photocatalytic oxidation [6][7][8][9][10][11], treatment with ozone in basic or neutral media [often combined with hydrogen peroxide, ultraviolet (UV) light or both] [12][13][14], hydrogen peroxide/UV systems [2,[15][16][17][18], and Fenton [4,9,[19][20][21][22] and photo-Fenton reactions [9,20,[23][24][25].…”

Review: Photocatalytic Degradation of Textile Azo Dyes

“…The effects of pH on photo-catalytic degradation of dyes have been studied by many researchers. In studying the effects of Ph on the photo-catalytic degradation of dyes, two things must be borne in mind; one, industrial effluents may not be neutral, and two; pH of the reaction mixture influences the surface-charge -properties of the photo-catalysts [13] .Sleiman et al [11] reported that influence of pH on the photo-catalytic degradation of Metanil Yellow, an anionic dye with a sulphonate group, over TiO 2 photo-catalyst under UV illumination. The result shows that the process efficiency is not over a wide range of pH (4)(5)(6)(7)(8).…”

“…Which will add more cost to the process. Bio-degradation [9] , Ozonation [10] and advanced oxidation processes [4,11] have also been use for dyes removal.…”