The effect of thermal hydrolysis pretreatment on the anaerobic degradation of nonylphenol and short-chain nonylphenol ethoxylates in digested biosolids

P. J. McNamara, C. A. Wilson, M. T. Wogen, S. N. Murthy, J. T. Novak, Paige J Novak

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33 Scopus citations


The presence of micropollutants can be a concern for land application of biosolids. Of particular interest are nonylphenol diethoxylate (NP2EO), nonylphenol monoethoxylate (NP1EO), and nonylphenol (NP), collectively referred to as NPE, which accumulate in anaerobically digested biosolids and are subject to regulation based on the environmental risks associated with them. Because biosolids are a valuable nutrient resource, it is essential that we understand how various treatment processes impact the fate of NPE in biosolids. Thermal hydrolysis (TH) coupled with mesophilic anaerobic digestion (MAD) is an advanced digestion process that destroys pathogens in biosolids and increases methane yields and volatile solids destruction. We investigated the impact of thermal hydrolysis pretreatment on the subsequent biodegradation of NPE in digested biosolids. Biosolids were treated with TH, anaerobic digestion, and aerobic digestion in laboratory-scale reactors, and NPE were analyzed in the influent and effluent of the digesters. NP2EO and NP1EO have been observed to degrade to the more estrogenic NP under anaerobic conditions; therefore, changes in the ratio of NP:NPE were of interest. The increase in NP:NPE following MAD was 56%; the average increase of this ratio in four sets of TH-MAD samples, however, was only 24.6±3.1%. In addition, TH experiments performed in pure water verified that, during TH, the high temperature and pressure alone did not directly destroy NPE; TH experiments with NP added to sludge also showed that NP was not destroyed by the high temperature and pressure of TH when in a more complex sludge matrix. The post-aerobic digestion phases removed NPE, regardless of whether TH pretreatment occurred. This research indicates that changes in biosolids processing can have impacts beyond just gas production and solids destruction.

Original languageEnglish (US)
Pages (from-to)2937-2946
Number of pages10
JournalWater Research
Issue number9
StatePublished - Jun 1 2012

Bibliographical note

Funding Information:
PJM was supported by the National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) under Grant No. DGE-0504195, and the Water Environment Federation Canham Graduate Studies Scholarship. MW was partially supported by DC WASA. We would like to thank Matt Simcik for the use of his LC/MS. Much appreciation is given to Nancy Love and Michael Dodd for providing the recombinant yeast strain used in the YES assay.


  • Anaerobic digestion
  • Biosolids
  • Estrogenicity
  • Nonylphenol
  • Nonylphenol ethoxylates
  • Thermal hydrolysis


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