Abstract
Improvement of sludge dewaterability is important for reducing the total costs for the treatment and disposal of sludge in wastewater treatment plants. In this study, we investigate the use of hydrogen peroxide as an oxidizing reagent for the conditioning of waste activated sludge. Significant improvement to sludge dewaterability was attained after the addition of hydrogen peroxide at 30 mg/g TS and 28 mg/g TS under acidic conditions (pH = 3.0), with the highest reduction of capillary suction time being 68% and 56%, respectively, for sludge containing an iron concentration of 56 mg Fe/g TS and 25 mg Fe/g TS, respectively. The observations were due to Fenton reactions between the iron contained in sludge (indigenous iron) and hydrogen peroxide. For the sludge with an insufficient level of indigenous iron, the addition of ferrous chloride was found to be able to improve the sludge dewaterability. The results firstly indicated that indigenous iron can be utilized similarly as the externally supplied iron salt to improve sludge dewaterability through catalyzing the Fenton reactions.
Highlights
Role of indigenous iron in improving sludge dewaterability through peroxidation Xu Zhou, Guangming Jiang, Qilin Wang & Zhiguo Yuan
Significant improvement to sludge dewaterability was attained after the addition of hydrogen peroxide at 30 mg/g TS and 28 mg/g TS under acidic conditions, with the highest reduction of capillary suction time being 68% and 56%, respectively, for sludge containing an iron concentration of 56 mg Fe/g TS and 25 mg Fe/g TS, respectively
We firstly investigate if the indigenous iron in activated sludge is available for the Fenton reaction following the addition of hydrogen peroxide, which would improve the dewaterability of waste activated sludge (WAS)
Summary
Role of indigenous iron in improving sludge dewaterability through peroxidation Xu Zhou, Guangming Jiang, Qilin Wang & Zhiguo Yuan. Improvement of sludge dewaterability is important for reducing the total costs for the treatment and disposal of sludge in wastewater treatment plants. Significant improvement to sludge dewaterability was attained after the addition of hydrogen peroxide at 30 mg/g TS and 28 mg/g TS under acidic conditions (pH 5 3.0), with the highest reduction of capillary suction time being 68% and 56%, respectively, for sludge containing an iron concentration of 56 mg Fe/g TS and 25 mg Fe/g TS, respectively. The water in WAS could be classified as free water and bound water[2] The former combines with the sludge loosely and could be removed with the mechanical dewatering methods. The bound water is hard to be removed mechanically because it combines with the sludge structure by capillary forces or chemical bonds. Many conditioning approaches, involving physical, chemical or enzymatic treatment of sludge, have been developed for improving the WAS dewaterability. Physical treatment includes various mechanical methods such as ultrasonic treatment and pressure homogenization[5]
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