Nanomaterial Transformation and Association with Fresh and Freeze-Dried Wastewater Activated Sludge: Implications for Testing Protocol and Environmental Fate

• Published in: Environmental science & technology Vol. 46; no. 13; pp. 7046 - 7053
• Main Authors: Kiser, Mehlika A, Ladner, David A, Hristovski, Kiril D, Westerhoff, Paul K
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03.07.2012
• Subjects: Adsorption; Applied sciences; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Biotechnology; Environment and pollution; Exact sciences and technology; Freeze Drying; Fundamental and applied biological sciences. Psychology; General purification processes; Industrial applications and implications. Economical aspects; Nanomaterials; Nanoparticles; Nanostructures - chemistry; Pollutants; Pollution; Sewage - microbiology; Sludge; Surface-Active Agents - chemistry; Test methods; Waste Disposal, Fluid - methods; Wastewaters; Water Pollutants, Chemical - isolation & purification; Water Pollutants, Chemical - metabolism; Water pollution; Water Purification - methods; Water treatment; Water treatment and pollution; Water treatment plants; United States; North America; America; United States > US; Performance evaluation; Activated sludge; Emerging contaminant; Pollutant behavior; Environment impact; Waste water purification; Waste water discharge; Nanostructured materials; Nanotechnology; Biological purification
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es300339x

Engineered nanomaterials (ENMs) are an emerging class of contaminants entering wastewater treatment plants (WWTPs), and standardized testing protocols are needed by industry and regulators to assess the potential removal of ENMs during wastewater treatment. A United States Environmental Protection Agency (USEPA) standard method (OPPTS 835.1110) for estimating soluble pollutant removal during wastewater treatment using freeze-dried, heat-treated (FDH) activated sludge (AS) has been recently proposed for predicting ENM fate in WWTPs. This study is the first to evaluate the use of FDH AS in batch experiments for quantifying ENM removal from wastewater. While soluble pollutants sorbed equally to fresh and FDH AS, fullerene, silver, gold, and polystyrene nanoparticles’ removals with FDH AS were approximately 60–100% less than their removals with fresh AS. Unlike fresh AS, FDH AS had a high concentration of proteins and other soluble organics in the liquid phase, an indication of bacterial membrane disintegration due to freeze-drying and heat exposure. This cellular matter stabilized ENMs such that they were poorly removed by FDH AS. Therefore, FDH AS is not a suitable sorbent for estimating nanoparticle removal in WWTPs, whereas fresh AS has been shown to reasonably predict full-scale performance for titanium removal. This study indicates that natural or engineered processes (e.g., anaerobic digestion, biosolids decomposition in soils) that result in cellular degradation and matrices rich in surfactant-like materials (natural organic matter, proteins, phospholipids, etc.) may transform nanoparticle surfaces and significantly alter their fate in the environment.