Abstract
A rapid Fenton treatment at second-scale intervals was investigated for further removal of organic compounds in the effluent of bio-treated dyeing and finishing wastewater (BDFW). The decolorization kinetics was studied using a stopped-flow spectrophotometer (SFS) at second-scale intervals. A combined first-order model was found to fit well for the decrease of both methylene blue and rhodamine B in SFS as well as SCOD (soluble chemical oxygen demand) and DOC (dissolved organic carbon) in real BDFW in batch test during Fenton oxidation. A full-scale plant with treatment capacity of 400,000 m3·d−1 was designed and has been run continuously based on the results of the stopped-flow study to treat the effluent of BDFW using Fenton oxidation in 16 pipeline reactors, each with a volume of 6.9 m3 and 24 s of reaction time since 2014. The COD, SCOD and DOC decreased from 140, 110 and 35 mg·L−1 to 77, 71 and 26 mg·L−1 respectively, which can meet the latest strict discharge limitations. The natural fluorescent substances detected in the BDFW were completely removed. The main organic pollutants in the BDFW can be significantly reduced using both gas chromatography-mass spectrometry and ultrahigh-performance liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry. The rapid Fenton reaction applied in pipeline reactors at second intervals has several advantages over the conventional Fenton’s process such as much shorter reaction time at second scale intervals, no need to build extra pH adjustment or reaction tanks, simple operation, low capital cost, etc.
Highlights
Fenton’s reagent, which consists of ferrous ion (Fe2+) and hydrogen peroxide (H2O2), has been widely used to decompose a broad variety of non-biodegradable compounds, including aromatic amines[4], phenols[5], dyes[6] and antibiotics[7]
The SCOD level decreased from 110 mg·L−1 to 71 mg·L−1 with a removal efficiency of 35%, and the dissolved organic carbon (DOC) level decreased from 35 mg·L−1 to 26 mg·L−1 with a removal efficiency of 26%
The relative peak area (RPA) of strong polar species increased, whereas that of medium or weak polar species decreased. These results suggest that medium or weak polar organic pollutants were removed effectively, but the part of them removed were converted into polar organic pollutants in rapid Fenton oxidation
Summary
Fenton’s reagent, which consists of ferrous ion (Fe2+) and hydrogen peroxide (H2O2), has been widely used to decompose a broad variety of non-biodegradable compounds, including aromatic amines[4], phenols[5], dyes[6] and antibiotics[7]. Compared to conventional Fenton reactors, which require the construction of dosing tanks for the adjustment of the pH and occupy a large land[10], the upgraded technology has the advantage of reaching the same removal efficiency at much lower investment and operating cost in significantly shorter reaction time. This is the first study that proposed the application of rapid Fenton oxidation as a tertiary process for BDFW in a full-scale plant
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