4.7 Article

Partial ozonation of returned sludge via high-concentration ozone to reduce excess sludge production: A pilot study

Journal

SCIENCE OF THE TOTAL ENVIRONMENT
Volume 807, Issue -, Pages -

Publisher

ELSEVIER
DOI: 10.1016/j.scitotenv.2021.150773

Keywords

Wastewater treatment; Partial ozonation; Excess sludge reduction; Nutrient removal capacity; Excess sludge properties

Funding

  1. Mitsubishi Electric Corporation
  2. National Key Research and Development Project [2020YFC1908704]

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By comparing the effects of high and low concentration ozone on partial ozonation of returned sludge, it was found that high concentration ozone can more effectively reduce organic matter and excess sludge production, with stronger nutrient removal capacity. While there were no significant differences in the treatment properties of excess sludge, the advantages of high concentration ozone mainly lie in the sludge solubilization rate and impact on carbon source utilization capacity in bioreactors.
Partial ozonation of returned sludge via high and low concentration of ozone were compared to evaluate their efficiency in excess sludge production reduction. A pilot-scale system of anaerobic/anoxic/oxic (A/A/ O) + ozonated sludge recycle (OSR) process was operated for 97 days, to investigate the effects of different ozone concentration (380 mg/Land 150 mg/L) on the nutrient removal capacity, sludge reduction rate, the excess sludge properties including settling, dewatering and anaerobic digestion (AD) performance. It was found that at the same total ozone dosage (13 mg/g MLSS, 25 mg/g MLVSS), the ozone of 380 mg/L achieved much higher organic matters and total excess sludge reduction (41.6% and 25.9%) than 150 mg/L applied (31.0% and 18.2%). It also laid less deterioration effect on the effluent quality and had better nutrient (COD, NH4+-N, TN) removal capacity than 150 mg/L applied. Meanwhile, little difference was found in the settling, dewatering and AD properties of excess sludge from the two A/A/O + OSR processes. Meanwhile, sludge solubilization rate, BIOLOG ECO microplate, 16S rRNA sequencing were applied comprehensively to illustrate the reasons for above advantages of the elevated ozone dosage applied. It was clarified that compared to 150 mg/L, A/A/O + OSR with ozone of 380 mg/L had higher sludge solubilization rate, less impact on bacterial community distribution and utilization capacity of carbon sources in bioreactors. (C) 2021 Elsevier B.V. All rights reserved.

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