Fate and biotransformation of phytosterols during treatment of pulp and paper wastewater in a simulated aerated stabilization basin

Pulp and paper wastewater (PPW) contains significant concentrations of phytosterols, suspected of inducing endocrine disruption in aquatic species. Aerated stabilization basins (ASBs) are commonly used for the treatment of PPW, but phytosterol removal varies among treatment systems. The objective of...

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Bibliographic Details
Published inWater research (Oxford) Vol. 68; pp. 589 - 600
Main Authors Dykstra, Christy M., Giles, Hamilton D., Banerjee, Sujit, Pavlostathis, Spyros G.
Format Journal Article
LanguageEnglish
Published England Elsevier Ltd 01.01.2015
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Summary:Pulp and paper wastewater (PPW) contains significant concentrations of phytosterols, suspected of inducing endocrine disruption in aquatic species. Aerated stabilization basins (ASBs) are commonly used for the treatment of PPW, but phytosterol removal varies among treatment systems. The objective of this study was to better understand the removal processes and biotransformation of phytosterols within an ASB treatment system fed with untreated PPW. PPW settled solids and supernatant fractions showed that phytosterols are primarily associated with settleable solids, which carry phytosterols to ASB sediment where anoxic/anaerobic conditions prevail. Bioassays with supernatant and settled PPW fractions of the raw wastewater conducted under aerobic and anaerobic conditions, respectively, showed that solids disintegration and hydrolysis results in phytosterol release in ASBs. A simulated ASB, fed with PPW and operated for 2.4 years at three hydraulic retention times (HRTs; 22.2, 11.1 and 5.6 d) with total phytosterol and solids loading rates from 10 to 42 μg/L-d and 44–178 mg/L-d, respectively, was used to determine the steady-state effluent quality and sediment characteristics. Although effluent COD and phytosterol concentrations were relatively low and stable (84–88% total COD removal; 82–94% total phytosterol removal) across the range of HRTs tested, sediment COD and phytosterol concentrations increased with increasing loading rate. On average, 51% of the phytosterols entering the ASB were removed via biotransformation, 40% were retained in the sediment, and the remaining 9% exited with the effluent. This study demonstrates the role of sediment as a source of phytosterol release in ASBs and highlights the importance of HRT and the PPW characteristics for predicting phytosterol fate in ASBs. [Display omitted] •Pulp and paper wastewater settleable fraction carries ca. 58% of total phytosterols.•A simulated aerated stabilization basin (ASB) was operated for 2.4 years.•ASB total phytosterol removal was 82–94% at three hydraulic retention times.•Breakdown of settled solids in ASB sediments releases phytosterols.•Biotransformation/settling account for 51/40% phytosterols removal, respectively.
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ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2014.10.030