Research Areas

Mechanistic Toxicity Assessment of Emerging Contaminants

The recognized and unknown health risks and the harmful environmental impacts associated with the ever-increasing number of emerging pollutants in our water presents a serious threat to us all. This poses a pressing need for a breakthrough in toxicity-assessment technology because the available methods, such as WET or TIE, are neither feasible nor sufficient to provide the timely information needed for regulatory decision making to eliminate these threats. The emerging field of toxicogenomics (gene-expression profiling technology), which simultaneously examines the toxicity response and global molecular status of an organism that has been exposed to pollutant(s), promises a revolutionary new ground for evaluating toxic effects, understanding toxicity mechanisms, and obtaining pollutant-specific molecular fingerprints (or biomarkers) for compound classification and identification. We proposed and explored the application of prokaryotic real-time gene-expression profiling using whole-cell array for environmental toxicity assessment. Comparing to the existing microarray-based genomic profiling approach, it adds a temporal dimension to the profiling data and therefore allows for more comprehensive and higher-resolution toxicity evaluation of pollutants. Currently, we are focusing on nanomaterials and EDCs.


HCLs (left), SOS network (right).

Funding Source: NSF CAREER

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Ecotoxicity of Engineered Nanomaterials (ENMs)

Further thrive of nanotechnology is likely to be hindered due to a rising public concern unless the possible adverse effects of NMs are understood and potential risks are addressed, and the related regulations are in place. The investigation into the effects of ENMs on organisms in the aquatic environment is of particular interest since water is the main route of exposure and the water cycle ultimately receives runoff and wastewater from domestic and industrial sources. Moreover, nanoecotoxicology, which evaluate the system level toxic impact of an ecosystem, is still in its infancy. We employ a combination of modern techniques including Atomic Force Microscope, Transmission Electron Microscopy, Raman microscopy as well as molecular methods, including ARISA, q-PCR and FISH, to investigate the impact of ENMs on the integrity, activity and structure of ecologically relevant organisms such as algal and the co-reside microbial community.

Experimental set up for ecotoxicity assessment (left), TEM image of our algae (right).

Funding Sources: NSF, CHN-EHS grant

Collaborators:

  • Prof. Max Deim, Chemistry and Biochemistry, NU
  • Prof. Kai-tak Wan, Mechanical Engineering, NU
  • Prof. Dhimiter Bello, School of Health & Environment, UMass-Lowell

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Biosensor and Nano-biosensor for Water Quality Monitoring

High throughput, cost-effective, sensitive and reliable detecting methods/platform for various chemical and biological contaminants is in need to meet the challenges of water quality monitoring. Nanotechnology provides extraordinary physical phenomena that can be utilized for sensing with a potential to reach single molecule sensitivity, allow for compatibility with CMOS microelectronics, and afford in situ simultaneous detection of a large number of targets/endpoints. For example, pathogen detection and identification using virulence and marker genes (VMGs) as genetic targets are receiving considerable interest due to the rapidly increasing availability of gene and whole-genome sequence information for most major pathogens. Our toxicogenomic study of various emerging contaminants led to determination of genetic biomarkers for various (or classes) of contaminants. High-density nano-sensor array integrated with CMOS and micro-fluid technology promises the new-generation of sensing platform for environmental monitoring.


Funding Sources: ITRI scholarship -(CDM Bill & Diane Howard Scholarship)

Collaborators:

  • Prof. Miao He , Tsinghua University, China
  • Prof. Ahmed A. Busnaina, Center for High Rate Nanomanufacturing, NU
  • Prof. Mehmet R. Dokmeci, Electrical and Computer Engineering, NU
  • Prof. Shashi Murthy, Chemical Engineering, NU

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Impact of wastewater-derived refractory organic nitrogen on eutrophication

Dissolved organic nitrogen (DON), which contributes an increasingly larger percentage (up to 85%) to the total N content in highly treated wastewater effluents (relative to 20% of total N in traditional wastewater effluents), is now drawing significant attention from both regulatory agencies and wastewater utilities. For utilities, the concern arises from the substantial capital cost that is required to implement more advanced treatment technologies beyond the current limit of technology (LOT) in order to remove the DON. On the regulatory side, current watershed protection plans (e.g. TMDLs) use total nitrogen for setting limits without considering the possibility that DON and inorganic nitrogen may differ in their bioavailability and therefore their potential to cause cultural eutrophication. This has motivated the regulated community and utilities to assess whether the DON in wastewater effluent is actually labile and therefore harmful to the receiving waters. The overall objective of this study is to investigate the bioavailability of wwDON to both saline and freshwater phytoplankton, assess and quantify the compositions of wwDON and their potential contribution, if any, to primary production and eutrophication.

Funding Sources: NSF –CEBT

Collaborators:

  • Prof. Hans Paerl, University of North Carolina at Chapel Hill
  • Prof. Paul Vorous, Chemistry, NU

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Advanced treatment processes for high-level nutrient removal

Excessive nutrients loading is still one of the main causes for impairment of coastal and freshwater ecosystems. Excess nitrogen (N) and phosphorus (P) can lead to eutrophication and cause water quality and ecosystems integrity deterioration. Nutrients loading come from both point and non-point sources. As part of the point-source control strategy, many public agencies are forced to install and upgrade their wastewater treatment facilities to meet the increasingly stringent effluent N and P limits. The current challenges the environmental engineers/scientists are facing for wastewater nutrient removal include: limits of technologies for achieving extremely low effluent nutrient limits, more environmental-friendly yet efficient and stable treatment processes that can reliably meet compliances, high capacity and small-footprint processes and energy-efficient or energy-recovering processes. Following are some of the examples of how we are working towards addressing some of these challenges.


1. Advanced nutrient removal by IFAS-EBPR-MBR process

We propose the IFAS-EBPR process that combines Integrated Fixed-Film Activated Sludge (IFAS) with EBPR process with the aim to potentially decouple the slow-growing nitrifying populations and other relatively fast growing heterotrophs, including PAOs and denitrifiers, by allowing the former to attach to media (fixed film carrier) and the latter to be in the suspended mixed liquor (ML). This would allow for decoupling and separate control of the SRTs for different microbial populations, and lead to the optimization of different biological processes in BNR systems and therefore improve the overall system reliability and stability.

Using both kinetics testing and molecular techniques we are trying to quantify the abundance, distribution and activity of the different populations involved in the removal of N and P.

A Raman microscopy method was also developed and successfully applied to evaluate the dynamics of intracellular polyphosphate in polyphosphate-accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) processes. Distinctive Raman spectra of polyphosphates allows for both identification of PAOs and quantification of intracellular polyphosphate during various metabolic phases in our lab-scale EBPR process. Observation of polyphosphate at individual cell level indicated that there are distributed states of cells in terms of polyphosphate content at any given time, suggesting that agent-based distributive modeling would more accurately reflect the behavior of an EBPR process than the traditional average-state based modeling.

Laboratory scale IFAS-MBR

Funding Sources: ITRI - Anox-Kaldes, Inc

Collaborators:

  • Prof. Ferdi Hellweger, Department of Civil and Environmental Engineering at Northeastern University
  • Prof. Andrew Schuler, Department of Civil Engineering, University of New Mexico

2. Evaluation of alternative carbon sources for Denitrification

Requirement of external carbon sources for denitrification and for enhancing biological phosphorus removal is becoming more common for POTWs that are facing increasingly stringent effluent nutrient limits. External carbon addition to pre-denitrification anoxic zones can help increase the denitrification rate and nitrogen removal efficiency, addition to post-denitrification zone is required for effluent total nitrogen of less than 6 mg/L, and addition to anaerobic zone for enhanced biological phosphorus removal is shown to improve the system performance and stability. Commonly used external carbon sources include methanol, ethanol, sugar and sludge digestion supernatant. Other alternative carbon sources that have been proposed recently include molasses, glycerol, corn starch and others. MicroC™, MicroCG™ and MicroCGlicerin™ are proprietary wastewater treatment chemicals developed by Environmental Operating Solutions, Inc. and designed specifically for use as an electron donor/carbon source for biological denitrification of wastewater.

Characterization of the carbon sources and their kinetics are being performed and compared to conventional carbon sources (Methanol and acetate). Also study of the microbial community composition changes in the SBR reactors that are fed with the different carbon sources are monitored using ARISA analysis.

SBRs Pilot

Funding Sources: ITRI - Environmental Operation Solution, Inc

Collaborators:

  • Prof. Ferdi Hellweger, Department of Civil and Environmental Engineering at Northeastern University
  • Prof. Andrew Schuler, Department of Civil Engineering, University of New Mexico

3. Phosphorus Speciation and Removal in Wastewater Treatment

Point source control regulates phosphorus (P) in wastewater discharge since P is usually the limiting nutrient for algal growth related to eutrophication in fresh waters. Increasing demand to achieve very low effluent total phosphorus (TP) due to more stringent discharge limits have raised questions on the limits of technologies (LOT) and presented challenges of how to further the removal of phosphorus to extremely low levels at wastewater treatment plants.

Current phosphorus removal technologies target mostly at eliminating ortho-P using chemical and/or biological methods. As more advanced treatment processes are applied to eliminate nearly all the ortho-P in order to meet the extremely low TP limits, other factions of P become relevant and important. The fractional composition of phosphorus and its variations among different wastewater effluent from different treatment processes have hardly been investigated. The treatability of various fractions of P in wastewater effluents is mostly unknown. Questions rise on: what is the lowest level of TP that can be achieved with available treatment technologies? What are the compositions of effluent TP from different treatment processes? What fractions can be further removed and via what mechanisms in order to meet limits that are near or below current LOT?

Funding Sources: WERF

Collaborators:

  • Imre Takács, EnviroSim Associates Ltd.
  • Scott Smith, Department of Chemistry Wilfrid Laurier University, Canada

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Bioremediation- factors affecting microbial migration

Movement and transportation of microbial cells such as virus or bacterial in soil, in subsurface, or in water and wastewater media filters are important because they are directly related to pathogens fate and transport in water, to bioremediation of contaminants in groundwater, and to the pathogen removal efficiency in water treatment processes. Due to the lack of fundamental understanding of the mechanisms and governing factors that dictate the microbial cell movement in porous, we often failed to model, predict and engineer efficient systems for controlling or manipulating these microbes to eliminate risk or to gain benefits. We apply Nano- mechanical methods to quantify the single cellular surface biochemical and mechanical properties and their correlation with cell aggregation and migration behavior. Then the knowledge will be incorporated into mathematical models framework to allow us better understand and predict the cell aggregation, adhesion and attachment in contact with media surface, which will progress our engineering ability for more efficient water and wastewater remediation and treatment.

Funding Sources: DOE- ERSP

Collaborators:

  • Prof. Kai-tak Wan, Mechanical Engineering, NU
  • Dr. YuFeng Yang from DOE Oak Ridge Laboratory

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