Organic matter extracted from activated sludge with ammonium hydroxide and its characterization

In order to characterize the organic properties of waste activated sludge in a wastewater treatment plant, organic matter within sludge was extracted with NH₃·H₂O preferentially, and subsequently fractionated into five fractions using XAD-8/XAD-4 resins. Up to a 63.8%-71.1% of organic matter within the sludge could be efficiently extracted by NH₃·H₂O. Fractionation results showed that hydrophobic acid and hydrophilic fraction were two main components among the sludge organic matter (accounting for 32.2% and 48.0% of the bulk organic matter, respectively), whereas transphilic acid, hydrophobic neutral and transphilic neutral were quite low (accounting for 9.2%, 5.8% and 4.8%, respectively). Despite that the extractant of NH₃·H₂O showed a relatively higher extraction efficiency of the aromatic components, the relatively low aromaticity of the organic fractions implied that those non-aromatic components could also be effectively extracted, especially for neutral and hydrophilic fractions. In addition, acidic fractions contained more aromatic humic-like components, whereas the neutral fractions had a greater content of aromatic proteins and soluble microbial byproduct-like components. Extraction of sludge organics with NH₃·H₂O and subsequential fractionation using XAD resins could be a novel method for further characterization of sludge organics.