Recycled
water is an increasingly important water supply component
for many communities. Widespread success with nonpotable reuse, and
indirect potable reuse (IPR) such as groundwater injection, has an
increasing number of municipalities considering potable reuse without
the use of an environmental buffer [direct potable reuse (DPR)]. Previous
risk assessment studies have evaluated the microbiological risks associated
with potable reuse. However, no studies have rigorously evaluated
the potential public health implications of known, infrequent, and
short duration, off-specification conditions in advanced water treatment
facilities (“off-spec events”). Herein, we couple previously
reported data describing the frequency and severity of off-spec events
with a microbial risk assessment methodology to quantitatively characterize
the public health implications of these off-spec events. The results
indicate that these low-probability, short duration, off-spec events
in a potable reuse treatment system can drive annual risks; predicted
annual median risk differences were increased by up to ∼4 orders
of magnitude. The use of accurate monitoring of performance surrogates
and diversion [e.g., engineered storage buffer (ESB)] allows for these
increased risks to be minimized. These results highlight the importance
of understanding water treatment system operations on a real-time
basis and point toward managing plant operations and off-spec events
in real time to maintain public health protection.
The removal of emerging contaminants during water treatment is a current issue and various technologies are being explored. These include UV- and ozone-based advanced oxidation processes (AOPs). In this study, AOPs were explored for their degradation capabilities of 25 chemical contaminants on the US Environmental Protection Agency's Contaminant Candidate List 3 (CCL3) in drinking water. Twenty-three of these were found to be amenable to hydroxyl radical-based treatment, with second-order rate constants for their reactions with hydroxyl radicals (OH) in the range of 3-8 × 10(9) M(-1) s(-1). The development of biological activity of the contaminants, focusing on mutagenicity and estrogenicity, was followed in parallel with their degradation using the Ames and YES bioassays to detect potential changes in biological effects during oxidative treatment. The majority of treatment cases resulted in a loss of biological activity upon oxidation of the parent compounds without generation of any form of estrogenicity or mutagenicity. However, an increase in mutagenic activity was detected by oxidative transformation of the following CCL3 parent compounds: nitrobenzene (OH, UV photolysis), quinoline (OH, ozone), methamidophos (OH), N-nitrosopyrolidine (OH), N-nitrosodi-n-propylamine (OH), aniline (UV photolysis), and N-nitrosodiphenylamine (UV photolysis). Only one case of formation of estrogenic activity was observed, namely, for the oxidation of quinoline by OH. Overall, this study provides fundamental and practical information on AOP-based treatment of specific compounds of concern and represents a framework for evaluating the performance of transformation-based treatment processes.
Chromophores ranging from simple small molecule π-conjugated systems comprised of phenylene ethynylene or fluorenylethynyl units to cross-conjugated Bunz-type cruciforms have been derivatized to include 1,3-bis(dimethylaminomethyl)phenyl moieties. The photophysical responsiveness of these diamino-substituted chromophores to metal ions has been examined. Both emission enhancement (turn-on) and ratiometric fluorescence detection of Cu(2+) and Zn(2+) ions have been achieved in THF.
Advanced oxidation processes (AOPs) are utilized due to their ability to treat emerging contaminants with the fast reacting and non-selective hydroxyl radical (OH). Organophosphorous insecticides are common drinking water contaminants, with 12 different compounds of this class being found on the US EPA's most recent Candidate Contaminant List (CCL4). The use of the AOP UV/HO for the treatment of organophosphorous insecticides was explored in this study, by coupling biological and analytical tools to follow the abatement of the target compounds. Four insecticides were explored for advanced oxidation treatment: acephate, dicrotophos, fenamiphos, and methamidophos. All four compounds were fast reacting with OH, all reacting with second order rate constants ≥5.5 × 10 Ms. Three major endpoints of toxicity were studied: estrogenicity, genotoxicity (mutagenicity) and neurotoxicity. None of the target compounds showed any estrogenic activity, while all compounds showed an active genotoxic (mutagenic) response (AMES II assay) and most compounds had some level of neurotoxic activity. AOP treatment did not induce any estrogenic activity, and reduced the compounds' neurotoxicity and genotoxicity in all but one case. Methamidophos degradation by UV/HO resulted in an increase in genotoxicity, likely due to the formation of toxic transformation products. The increase in toxicity gradually decreased with time, possibly due to hydrolysis of the transformation products formed. This study provides insights into parent compound abatement and the changes in toxicity due to transformation products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.