Oscar Quiñones

Pilot-scale evaluation of ozone and biological activated carbon for trace organic contaminant mitigation and disinfection.

In an effort to validate the use of ozone for contaminant oxidation and disinfection in water reclamation, extensive pilot testing was performed with ozone/H(2)O(2) and biological activated carbon (BAC) at the Reno-Stead Water Reclamation Facility in Reno, Nevada. Three sets of samples were collected over a five-month period of continuous operation, and these samples were analyzed for a suite of trace organic contaminants (TOrCs), total estrogenicity, and several microbial surrogates, including the bacteriophage MS2, total and fecal coliforms, and Bacillus spores. Based on the high degree of microbial inactivation and contaminant destruction, this treatment train appears to be a viable alternative to the standard indirect potable reuse (IPR) configuration (i.e., membrane filtration, reverse osmosis, UV/H(2)O(2), and aquifer injection), particularly for inland applications where brine disposal is an issue. Several issues, including regrowth of coliform bacteria in the BAC process, must be addressed prior to full-scale implementation.

Occurrence of perfluoroalkyl carboxylates and sulfonates in drinking water utilities and related waters from the United States.

The prevalence and persistence of perfluoroalkyl compounds (PFCs) in environmental and biological systems has been well documented, and a rising number of reports suggest that certain PFCs can result in adverse health effects in mammals. As traditional water sources become increasingly impacted by waste discharge and the demand for planned potable reuse grows, there is recent interest in determining PFC occurrence in drinking water supplies. Here we report monitoring results from drinking water treatment facility samples collected across the United States, and from associated surface, ground, and wastewater sources. Using automated solid phase extraction (SPE) and isotope-dilution liquid chromatography/tandem mass spectrometry (LC/MS-MS), samples were screened for perfluorohexanoic acid (PFHxA), perfluorohexanesulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), perfluorononanoic acid (PFNA) perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUdA), and perfluorododecanoic acid (PFDoA). Method reporting limits (MRLs) were established at 1.0 ng/L for all monitored PFCs except PFOA, for which the MRL was set at 5.0 ng/L given elevated procedural and instrumental background levels. PFOS was the only investigated PFC detected in minimally impacted surface waters, with individual site averages of 2.0 ng/L and lower. Conversely, wastewater treatment plant (WWTP) effluents and other highly impacted waters had almost 100% detection frequency for all PFCs except PFUdA and PFDoA, which were not detected above MRL in any samples. Of the investigated PFCs, PFOA averaged the highest overall concentration at any site at 115 ng/L. Substantial impacts from treated wastewater generally caused increased summed PFC concentrations at downstream drinking water facilities, although levels and distribution suggest geographical variability. No discernible differences between influent and effluent PFC levels were observed for drinking water facilities. Removal of PFCs, however, was observed at an indirect potable reuse facility using microfiltration and reverse osmosis for wastewater treatment, in which case all PFC levels in effluents were below the MRL.

Rapid analysis of perchlorate, chlorate and bromate ions in concentrated sodium hypochlorite solutions

A sensitive, rapid, and rugged liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for measuring concentrations of perchlorate, chlorate, and bromate ions in concentrated sodium hypochlorite solutions is presented. The LC-MS/MS method offers a practical quantitation limit (PQL) of 0.05 microg L(-1) for ClO(4)(-), 0.2 microg L(-1) for BrO(3)(-), and 0.7 microg L(-1) for ClO(3)(-) and a sample analysis time of only 10 min. Additionally, an iodometric titration technique was compared with the LC-MS/MS method for measurement of chlorate ion at high concentration. The LC-MS/MS method was the most reproducible for chlorate concentrations below 0.025 M while the iodometric titration method employed was the most reproducible above 0.025 M. By using both methods, concentrations of chlorate can be measured over a wide range, from 0.7 microg L(-1) to 210 g L(-1) in hypochlorite ion solutions. Seven quenching agents were also evaluated for their ability to neutralize hypochlorite ion, thereby stopping formation of perchlorate ion in solution, without adversely impacting the other oxyhalide ions. Malonic acid was chosen as the quenching agent of choice, meeting all evaluation criteria outlined in this manuscript.

Titanium distribution in swimming pool water is dominated by dissolved species

The increased use of titanium dioxide nanoparticles (nano-TiO2) in consumer products such as sunscreen has raised concerns about their possible risk to human and environmental health. In this work, we report the occurrence, size fractionation and behavior of titanium (Ti) in a childrens swimming pool. Size-fractionated samples were analyzed for Ti using ICP-MS. Total titanium concentrations ([Ti]) in the pool water ranged between 21 μg/L and 60 μg/L and increased throughout the 101-day sampling period while [Ti] in tap water remained relatively constant. The majority of [Ti] was found in the dissolved phase (<1 kDa), with only a minor fraction of total [Ti] being considered either particulate or microparticulate. Simple models suggest that evaporation may account for the observed variation in [Ti], while sunscreen may be a relevant source of particulate and microparticule Ti. Compared to diet, incidental ingestion of nano-Ti from swimming pool water is minimal.

The Effects of Solids Retention Time in Full-Scale Activated Sludge Basins on Trace Organic Contaminant Concentrations

Although pharmaceuticals and personal care products (PPCPs) and endocrine disrupting compounds (EDCs) are largely unregulated, water resource recovery facilities are increasingly using advanced chemical/physical treatment technologies (e.g., advanced oxidation and reverse osmosis) to remove or destroy these trace organic contaminants (TOrCs). This can both reduce potential adverse human health effects in reuse applications and mitigate environmental effects on aquatic ecosystems. Unfortunately, advanced treatment technologies are typically energy intensive and costly to implement, operate, and maintain. The goal of this study was to determine whether optimization of solids retention time (SRT) provided sufficient benefits to warrant such operational strategies for TOrC mitigation. Specifically, SRTs of 5.5, 6, and 15 days were evaluated to determine the effects on several standard wastewater parameters (e.g., nitrite, nitrate, and ammonia concentrations) and the degradation of TOrCs. The experimental SRTs were operated simultaneously in parallel, full-scale activated sludge basins. The results indicate that it can be beneficial to implement biological process optimization strategies using existing infrastructure while reducing reliance on advanced treatment technologies. This study also identified potential operational issues that might arise in activated sludge systems operating at extended SRTs.

Biotransformation and sorption of trace organic compounds in biological nutrient removal treatment systems

This study determined biotransformation rates (kbio) and sorption-distribution coefficients (Kd) for a select group of trace organic compounds (TOrCs) in anaerobic, anoxic, and aerobic activated sludge collected from two different biological nutrient removal (BNR) treatment systems located in Nevada (NV) and Ohio (OH) in the United States (US). The NV and OH facilities operated at solids retention times (SRTs) of 8 and 23 days, respectively. Using microwave-assisted extraction, the biotransformation rates of the chosen TOrCs were measured in the total mixed liquor. Sulfamethoxazole, trimethoprim, and atenolol biotransformed in all three redox regimes irrespective of the activated sludge source. The biotransformation of N, N-diethyl-3-methylbenzamide (DEET), triclosan, and benzotriazole was observed in aerobic activated sludge from both treatment plants; however, anoxic biotransformation of these three compounds was seen only in anoxic activated sludge from NV. Carbamazepine was recalcitrant in all three redox regimes and both sources of activated sludge. Atenolol and DEET had greater biotransformation rates in activated sludge with a higher SRT (23 days), while trimethoprim had a higher biotransformation rate in activated sludge with a lower SRT (8 days). The remaining compounds did not show any dependence on SRT. Lyophilized, heat inactivated sludge solids were used to determine the sorption-distribution coefficients. Triclosan was the most sorptive compound followed by carbamazepine, sulfamethoxazole, DEET, and benzotriazole. The sorption-distribution coefficients were similar across redox conditions and sludge sources. The biotransformation rates and sorption-distribution coefficients determined in this study can be used to improve fate prediction of the target TOrCs in BNR treatment systems.

Two New Methods of Synthesis for the Perbromate Ion: Chemistry and Determination by LC-MS/MS

Historically, the synthesis of perbromate ion through conventional oxidation routes has proven elusive. Herein, we report perbromate ion formation through the reaction of hypobromite and bromate ions in an alkaline sodium hypobromite solution. Formation was established via LC-MS/MS analysis of the bromate and perbromate ions in the reaction solutions over a 13-day period. Furthermore, it was discovered that the perbromate ion was also formed as a result of the electrospray ionization process. Selective reduction of the bromate ion prior to analysis was used to confirm the two formation pathways.

Removal of perfluoroalkyl and polyfluoroalkyl substances in potable reuse systems

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a group of persistent contaminants that have been identified throughout the aquatic environment. In this study, ten targeted perfluoroalkyl acids (PFAAs), three targeted PFAA precursors, and non-targeted PFAA precursors were monitored in four full- and pilot-scale potable reuse plants at each stage of advanced treatment. Non-targeted PFAA precursors were quantified by applying a total oxidizable precursor assay in which PFAA precursors are oxidized by hydroxyl radicals to targeted PFAAs. Two of the potable reuse systems had membrane-based treatments with reverse osmosis and UV-advanced oxidation (RO-UV/AOP) and two used ozone, biological activated carbon filtration and granular activated carbon adsorption (O3-BAC-GAC). The total targeted PFAAs in the four tertiary effluents, the influent sources for the potable reuse systems, ranged from 52 to 227 ng/L with non-targeted PFAA precursors accounting for 30-67% of total PFASs on a molar basis. The RO-UV/AOP treatment trains reduced PFAAs and PFAA precursors to below their method reporting limits through the barrier provided by RO. The O3-BAC-GAC based treatment trains reduced, but did not completely remove PFAAs or PFAA precursors and the PFASs present in the product water were primarily shorter-chain PFAAs, some of which lack human health guidance values for drinking water. The relative fraction of targeted shorter-chain PFAAs increased after each treatment step indicating that there was preferential removal of the PFAA precursors and longer-chain PFAAs. This study provides new insight on the concentrations and treatment of PFAA precursors through potable reuse treatment systems.

Solids retention time, influent antibiotic concentrations, and temperature as selective pressures for antibiotic resistance in activated sludge systems

This study evaluated the occurrence and potential proliferation of antibiotic resistance during biological wastewater treatment as a function of solids retention time (SRT), influent antibiotic concentrations, and temperature. Two phases of experiments were performed in laboratory-scale sequencing batch reactors (SBRs) fed with primary effluent from a full-scale wastewater treatment plant. Phase 1 evaluated SRTs of 2, 7, and 20 days with ambient antibiotic concentrations, and phase 2 evaluated a constant SRT of 7 days with influent antibiotic concentrations of 1×, 10×, and 100× relative to ambient levels. Ampicillin, sulfamethoxazole/trimethoprim, tetracycline, and vancomycin resistance were evaluated among Gram positive cocci (Staphylococcus and Streptococcus) using spread plate and minimum inhibitory concentration (MIC) assays. The laboratory-scale data demonstrated that biological treatment, in addition to longer SRTs, higher influent antibiotic concentrations, and higher temperatures, often resulted in greater relative prevalence of antibiotic resistance (up to 35% of the target population), and antibiotic resistant isolates were generally resistant to antibiotic concentrations 32 times higher than their baseline MICs. Some of these relationships were antibiotic-specific, with SRT having no significant impact on tetracycline resistance, influent antibiotic concentration having no significant impact on sulfamethoxazole/trimethoprim resistance, and temperature having no significant impact on vancomycin resistance.