Current Research
Project Title:
Membrane Processes for DBP Precursor Control: Effects of Colloid Stability
and Membrane Surface Chemistry on Flux and Rejection
Sponsor: NSF
Background: The use of synthetic polymer membranes in water
treatment is increasing worldwide. Membrane processes for removing disinfection
by-product precursors and pathogens (e.g. viruses) from potable waters
have been designated Best Available Technologies by the U.S. EPA. Membrane
processes are also promising for controlling risk of highly mobile groundwater
contaminants such as perchlorate and methyl tert-butyl ether. Membrane
processes are distinguished by, and derive their unique properties from,
polymeric microporous materials. However, these materials are vulnerable
to fouling by organic macromolecules and other colloids (organic and
inorganic). In both municipal and industrial applications, the efficiency,
reliability, and cost (design and operation) of these processes is controlled
by such fouling. Research to understand mechanisms of fouling and to
develop strategies to control it is needed.
Objectives: The goals of this research are to:
-
understand the interactions between organic macromolecules and other
natural organic and inorganic colloids in nanofiltration systems,
to elucidate how colloid stability influences the performance of membrane
processes designed to control the risk posed by anthropogenic contaminants
and naturally-occurring disinfection by-product precursors; and,
-
understand how membrane flux and rejection are related to membrane
surface chemistry, and identify the efficacy of UV photomodification
as a route to produce nanofiltration membranes that exhibit a resistance
to fouling under water treatment conditions.
back to top ^
Acquisition of Instrumentation
for research on the continuum of Aqueous Colloids and Particles in Natural
and Engineered Environmental Systems
Sponsor: US Bureau of Reclamation, Desalination Research and
Development Program
Co-investigator: Dr. Georges Belfort, Professor & Howard
P. Isermann Department of Chemical Engineering
Membrane fouling by colloidal substances can significantly reduce membrane
performance, increase operating costs, and shorten membrane life. Understanding
fouling mechanisms and developing ways to control them are critical
for the economical development of membrane desalting technologies. Naturally
occurring dissolved and colloidal organic matter
(NOM) is considered a major contributor to membrane fouling in water
treatment applications. Our goal is to understand how organic matter
properties affect the adhesion of these foulant materials to membrane
surfaces, and to develop a procedure to modify commercially available
membranes to reduce their fouling characteristics by NOM. Performance
will be evaluated by measuring flux decline as a function of time, and
the adhesion of NOM to membrane surfaces, as measured by flux recovery
after backwashing and chemical cleaning (NaOH).
back to top ^
Brominated DBP
Formation and Speciation Based on the specific UV Absorbance Distribution
of Natural Waters
Sponsor: US EPA
Co-investigator: Tanju Karanfil, Ph.D., Clemson University,
Clemson, SC
Understanding the factors that influence disinfection byproduct (DBP)
formation and bromine incorporation during disinfection with chlorine
is critical for providing safe water and for meeting current drinking
water regulations (e.g. the D/DBP rule). A good deal of research has
been done showing the effects of primary factors (dissolved organic
carbon, chlorine residual, and bromide concentrations) on DBP formation
and bromine incorporation; however, little is known about how natural
organic matter composition influences such reactions. An important route
to elucidating organic matter composition involves fractionation and
characterization of the reactivity of individual fractions. Another
approach is to use bulk water parameters such as the specific ultraviolet
absorbance (SUVA).
Dr. Kilduff and his team propose to combine these two approaches, under
the hypothesis that fractionation of whole water is required to gain
insight into the reactivity of different components, and that SUVA is
a reliable and robust predictor of reactivity. Current application of
the SUVA measurement yields a single value that represents the response
of a distribution of chromophores within a single organic molecule and
among different molecules. Dr. Kilduff’s proposed approach will
better define how SUVA is distributed in natural waters, and how the
distribution of SUVA in natural waters influences DBP formation and
speciation (including bromine incorporation). Such information will
be critical for optimizing treatment goals, understanding the effects
of treatment processes, and devising strategies to comply with the D/DBP
rule.
back to top ^
Settling Characteristics
of As-Deposited Cryptosporidium Oocysts
Cryptosporidia are pathogenic protozoa found in natural waters from
sources as diverse as small mammals, birds, livestock and humans. The
organisms have a unique life cycle and, outside of the intestinal tract,
form a spore-like body called an "oocyst." The oocyst is resistant
to heat andcold and can stay viable in the environment for months. It
is also resistant to disinfectants like chlorine and is very hard to
remove from water during conventional treatment using filtration. Because
of these characteristics, Cryptosporidia may be the leading cause of
waterborne disease in the US. Although the symptoms of the disease (intestinal
distress and severe diarrhea) are just unpleasant for most healthy individuals,
they may be life threatening for those with an impaired immune response
including the very young, the very old, patients receiving chemotherapy
and those with AIDS.
Dr. Komisar and his team are studying the fundamental behavior of the
oocyst particle in numerous waters in order to understand its basic
hydraulic properties including its settling velocity. They are especially
concerned about the design and implementation of best management practices
for agricultural wastes (like those typically generated at dairy farms)
and hope to use their understanding of Cryptosporidia to protect important
drinking water sources.
back to top ^
|
