Impact/Purpose:

The goal of this project is to test the hypothesis that engineered nanoparticles (ENP) tend to be collected at solid particulates in wastewater treatment and that physico-chemical properties of the dissolved organic matter (DOM) and solids (both ENP and sludge) play important roles in the distribution of ENP in wastewater treatment plants (WWTP). To achieve this goal, three specific objectives will be pursued: 1) to study the distribution of ENP in wastewater treatment plants, 2) to study the uptake of ENP by wastewater particulates, and 3) to predict the distribution of ENP in wastewater treatment plants.

Description:

This research project will be among the first attempts to study the distribution of ENP at major municipal wastewater treatment plants.  A new technique, EATF-EAA-NMAS, will be used to monitor free ENP in field and laboratory wastewater samples. The uptake isotherm of ENP as a function of DOM and type of sludge particulates will enable the prediction of the distribution of ENP at WWTP. The results will provide a new technology for studying the distribution of ENP in natural as well as built environment. Results also will assist wastewater process design engineers in the development of treatment processes for the elimination of solids from wastewater and help decision makers in the revision of effluent quality standards for total solids.

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Four regional municipal wastewater treatment plants (WWTP) will serve as the study sites: the city of Wilmington, DE; the city of Philadelphia, PA; the Beck River Plant of the city of Baltimore, and the Blue Plant of Washington, DC.  Wastewater and sludge samples will be collected and characterized for general physico-chemical properties. A new technique involving the application of electrically-assisted tangential flow (EATF) membrane filtration and electrospray aerosol analysis (EAA) coupled with a nano aerosol mass spectrometer (NAMS) will be used to isolate, identify and quantify ENP in the four WWTP. Additionally, the following surface analysis techniques will be used to characterize ENP for crystal structure by XRD, morphology by SEM/TEM, chemical composition by EDS and chemical state by XPS. The DOM will be extracted and fractionalized using resin chromatographic separation technique into hydrophobic (HPO), transhydrophlic (TPI) and hydrophilic (HPI) fractions for use in DOM sorption on ENP experiments. The sludge particulates will be classified into three fractions of “settle-able (>100 mm), “super colloidal” (10-100 mm) and colloidal (1-10 mm) using the cone differential sedimentation technique for use in experiments of ENP uptake by sludge particulates.   Both DOM sorption on ENP and ENP uptake experiments will be conducted at various values of temperature, pH and concentrations of Ca²⁺ and Mg²⁺ while keeping the ionic strength constant at 0.01 M. The sorption results of DOM on ENP and ENP on sludge particulates will be analyzed according to stoichiometry of association as to establish ENP uptake isotherm for various sludge particulates (source and size fraction) and DOM sorption isotherm for various fractions of DOM. Based on the sorption results and field observation, the distribution of ENP in the wastewater treatment system will be calculated, predicted and verified.

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