Biological Fate & Electron Microscopy Detection of Nanoparticles During Wastewater TreatmentEPA Grant Number: R833322
Title: Biological Fate & Electron Microscopy Detection of Nanoparticles During Wastewater Treatment
Investigators: Westerhoff, Paul , Rittman, Bruce , Alford, Terry
Institution: Arizona State University - Main Campus
EPA Project Officer: Hahn, Intaek
Project Period: May 1, 2007 through April 30, 2010
Project Amount: $398,998
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: a Joint Research Solicitation-EPA, NSF, NIOSH, NIEHS (2006) RFA Text | Recipients Lists
Research Category: Health , Safer Chemicals , Nanotechnology , Health Effects
The market for nanomaterials is increasing rapidly, and nanoparticles (NPs) present in consumer products, industrial wastes, biomedical applications, etc., will become significant in the near future for wastewater treatment just as nutrients, pathogens, metals, and synthetic organic chemicals have been important for the last few decades. WWTP discharges (treated effluent, biosolids, and possibly aerosols) may become significant routes for NPs to enter the environment. Today, almost no information is available on the fate of manufactured NPs during biological wastewater treatment.
The goal of this project is to quantify interactions between manufactured NPs and WW biosolids. We will model their fate with a mechanistic model that reflects and helps us gain mechanistic understanding. We hypothesize that dense bacterial populations at WWTPs should effectively remove NPs from sewage, concentrate NPs into biosolids and/or possibly biotransform NPs. The relatively low NP concentrations in sewage should have negligible impact on the WWTPs biological activity or performance.
The project involves environmental engineers and spectroscopy experts who will quantify the removal of four classes of manufactured NPs (metal-oxide, quantum dots, C60 fullerenes, carbon nanotubes) during WW treatment. The unique size and surface characteristics of these NPs are expected to behave differently from >1 μm sized particles currently in wastewaters. The relative importance of four NP removal mechanisms will be quantified: 1) adsorption to the outer cell walls; 2) enmeshment into the extracellular polymeric substances (EPS); 3) partitioning into the cytoplasm; and 4) cellular uptake and synthesis. Batch adsorption experiments will use NPs with whole biosolids, cellular biomass only, and EPS from three types of biological reactors (aerobic heterotrophic, aerobic heterotrophic + autotrophic nitrifying, anaerobic methanogenic) and from full-scale WWTP reactors. NP application to the same three types of laboratory bioreactors operated in a semi-continuous mode will validate adsorption onto biosolids and quantify the NP biotransformation and toxicity to the biological community/activity. Imaging techniques (environmental SEM, TEM) will be developed to understand “where” NPs reside with biosolids. Techniques to extract NPs from complex biological matrices will also be explored. Finally, NP removal reactions will be incorporated into existing mechanistic WWTP models.
The project addresses three broad questions:
- What mechanisms remove NPs?
- Can NPs be imaged within bacteria and WWTP biosolids?
- Do NPs affect biological WW treatment?
Data and mechanistic interpretation/modeling directly supports all four of the stated U.S. EPA interests from the RFP. Experiments will assess the toxicity and biological effects of NPs on the three common mixed WW bacterial communities. The project quantifies the fate (biosorption, biotransformation) of manufactured NPs in contact with complex biological matrices (i.e., WW biosolids). The project will be among the first to apply imaging and extraction procedures for NPs in complex biological matrices. By understanding NP removal in WWTPs, the project helps identify potential NP exposure pathways (effluent discharge to rivers, lakes; land application of biosolids; biosolids incineration) to the environment and provides insight for considerations during life-cycle assessments (e.g., additional treatment requirements at WWTPs).