Extended field investigations of ozone-biofiltration advanced water treatment for potable reuse.

Recovering and reusing treated wastewater effluent is a sustainable and cost-effective practice for addressing global water sustainability. To date, most potable reuse advanced water treatment (AWT) solutions are based on reverse osmosis (RO), which generates a continuous reject stream of concentrated brine waste. Ozone-biofiltration based solutions have been investigated as a potential alternative for RO. However, implementation of ozone-biofiltration for potable reuse projects around the world has been limited. The goal of this study was to conduct an extended field investigation of ozone-biofiltration treatment to address regulatory, design, and operational hurdles that may hinder implementation in water-short areas. For 16 months, two parallel biological activated carbon (BAC) filters were operated at empty bed contact times (EBCTs) of 10 min and 20 min treating up to 60,000 and 30,000 bed volumes (BVs), respectively, of sand filtered effluent from a municipal wastewater treatment process. BAC 1 (EBCT = 10 min) and BAC 2 (EBCT = 20 min) used Calgon Filtrasorb 400 granular activated carbon (GAC) as filter media, with equal bed depths of 0.8 m. Increasing the specific ozone dose from 0.9 to 2.0 provided a muted response with respect to oxidation of contaminants of emerging concern (CECs) that are resistive to ozonation. N-Nitrosodimethylamine (NDMA) was generated during ozonation, with the average concentration of NDMA in ozonated effluent being 40.4 ng/L. In BAC 1 (EBCT = 10 min), NDMA was fully removed during the first month of study (<2000 BVs), partially removed between 2000 and 20,000 BVs, and completely removed when monitored between 57,000 and 62,000 BVs. These trends clearly reveal time-dependent interactions between carbon-based (e.g., adsorption) and non-carbon-based (e.g., biodegradation) removal mechanisms. In BAC 2 (EBCT = 20 min), almost all CECs, excluding NDMA, were removed consistently throughout the study (through ∼30,000 BVs). This indicates a somewhat different interaction between carbon-based and non-carbon-based removal in the more lightly loaded BAC 2, compared to BAC 1. After 482 days of operation, BAC 1 (EBCT = 10 min) produced effluent with lower NDMA concentration (<2 ng/L) than BAC 2 (10 ng/L), confirming prior evidence of cometabolic NDMA biodegradation pathways operable in more heavily loaded BACs. These findings emphasize the need for extended field testing (50,000 BVs or greater). BAC 1 removed TOC in effluent until it plateaued at around 6 mg/L after 60,000 BVs, whereas BAC 2 effluent plateaued at around 4 mg/L. Under plateau conditions, BAC 1 and BAC 2 with sand filter pretreatment and ozonation appear to have a gross TOC removal potential of around 0.2-0.3 kg of TOC removed per day per cubic meter of carbon media (kg/d/m3). A comparative analysis of findings from this study and results from a past ozone-BAC study in the Reno area (termed BAC 3 operated downstream of membrane filter with an EBCT of 30 min) shows that higher TOC removal was observed in BAC with shorter EBCT and upstream sand filter compared to BAC with longer EBCT and upstream membrane filter. The present study addresses the regulatory and financial concerns associated with ozone-BAC performance in potable reuse applications. Improved comprehension of ozone-BAC performance, coupled with its reduced capital and operations and maintenance (O&M) costs compared to RO, may accelerate the full-scale implementation of ozone-BAC treatment as a sustainable solution for the rapidly emerging potable reuse market.

Decomposition of Iodinated Pharmaceuticals by UV-254 nm-assisted Advanced Oxidation Processes.

Iodinated pharmaceuticals, thyroxine (a thyroid hormone) and diatrizoate (an iodinated X-ray contrast medium), are among the most prescribed active pharmaceutical ingredients. Both of them have been reported to potentially disrupt thyroid homeostasis even at very low concentrations. In this study, UV-254 nm-based photolysis and photochemical processes, i.e., UV only, UV/H2O2, and UV/S2O82-, were evaluated for the destruction of these two pharmaceuticals. Approximately 40% of 0.5µM thyroxine or diatrizoate was degraded through direct photolysis at UV fluence of 160mJcm-2, probably resulting from the photosensitive cleavage of C-I bonds. While the addition of H2O2 only accelerated the degradation efficiency to a low degree, the destruction rates of both chemicals were significantly enhanced in the UV/S2O82- system, suggesting the potential vulnerability of the iodinated chemicals toward UV/S2O82- treatment. Such efficient destruction also occurred in the presence of radical scavengers when biologically treated wastewater samples were used as reaction matrices. The effects of initial oxidant concentrations, solution pH, as well as the presence of natural organic matter (humic acid or fulvic acid) and alkalinity were also investigated in this study. These results provide insights for the removal of iodinated pharmaceuticals in water and/or wastewater using UV-based photochemical processes.

In vivo and In vitro neurochemical-based assessments of wastewater effluents from the Maumee River area of concern.

Wastewater treatment plant (WWTP) effluents contain potentially neuroactive chemicals though few methods are available to screen for the presence of such agents. Here, two parallel approaches (in vivo and in vitro) were used to assess WWTP exposure-related changes to neurochemistry. First, fathead minnows (FHM, Pimephales promelas) were caged for four days along a WWTP discharge zone into the Maumee River (Ohio, USA). Grab water samples were collected and extracts obtained for the detection of alkylphenols, bisphenol A (BPA) and steroid hormones. Second, the extracts were then used as a source of in vitro exposure to brain tissues from FHM and four additional species relevant to the Great Lakes ecosystem (rainbow trout (RT), river otter (RO), bald eagle (BE) and human (HU)). The ability of the wastewater (in vivo) or extracts (in vitro) to interact with enzymes (monoamine oxidase (MAO) and glutamine synthetase (GS)) and receptors (dopamine (D2) and N-methyl-D-aspartate receptor (NMDA)) involved in dopamine and glutamate-dependent neurotransmission were examined on brain homogenates. In vivo exposure of FHM led to significant decreases of NMDA receptor binding in females (24-42%), and increases of MAO activity in males (2.8- to 3.2-fold). In vitro, alkylphenol-targeted extracts significantly inhibited D2 (66% in FHM) and NMDA (24-54% in HU and RT) receptor binding, and induced MAO activity in RT, RO, and BE brains. Steroid hormone-targeted extracts inhibited GS activity in all species except FHM. BPA-targeted extracts caused a MAO inhibition in FHM, RT and BE brains. Using both in vivo and in vitro approaches, this study shows that WWTP effluents contain agents that can interact with neurochemicals important in reproduction and other neurological functions. Additional work is needed to better resolve in vitro to in vivo extrapolations (IVIVE) as well as cross-species differences.

Assessment of the abiotic transformation of 17ß-estradiol in the presence of vegetable matter--II: the role of molecular oxygen.

This study characterizes the effect of oxygen in the abiotic transformation of estrogens when they are contacted with a surrogate of the vegetable wastes found in sewage. 17ß-Estradiol (E2) and 17ß-(14)C(4)-estradiol ((14)C-E2) were utilized as model compounds. Batch experiments were run under both oxic and anoxic conditions. In order to accomplish an accurate mass balance of the target estrogen, two analyses were performed simultaneously: first, radioactivity counting, and second, quantitation of E2 and (14)C-E2, as well as their transformation product estrone and (14)C(4)-estrone, by Liquid Chromatography tandem Mass Spectrometry. Under oxic conditions, the total concentration of (14)C-E2 was found to decrease by 78% in 72 h (15% and 7% remained in the liquid and solid phases, respectively). Conversely, when the estrogens were contacted with the synthetic influent under anoxic conditions, E2 was quantitatively recovered after 72 h (70% and 22% in aqueous and solid matrices, correspondingly). These results suggest that when the concentration of dissolved oxygen is null or limited, catalysis through an oxidative coupling mechanism is halted. Moreover, it was confirmed that the catalytic reaction occurred solely in the presence of the solid phase of the model vegetable matter.

Assessment of the abiotic transformation of 17ß-estradiol in the presence of vegetable matter.

A study using 17 ß-(14)C(4)-estradiol ((14)C-E2) was performed to confirm and characterize the catalytic transformation of estrogens in the presence of a model vegetable matter (namely rabbit food) as a surrogate material for vegetable wastes found in sewage. Results corroborated the occurrence of an abiotic transformation. Unknown transformation byproduct(s) accounted, respectively, for 38% and 9% of the initial radioactivity in liquid and extractable solid phases after 72 h; on the other hand, only 15% and 7% of this radioactivity corresponded to (14)C-E2 in those same matrices. Mass balance was closed including the radioactivity irreversibly bounded to the solid phase. Formation of (14)C(4)-estrone was monitored by Liquid Chromatography with tandem Mass Spectrometry detection; negative results were found in all sampling events. This process could be harnessed to optimize sustainable technologies for the removal of phenolic microcontaminants from wastewater.

Abiotic transformation of estrogens in synthetic municipal wastewater: an alternative for treatment?

The abiotic transformation of estrogens, including estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2), in the presence of model vegetable matter was confirmed in this study. Batch experiments were performed to model the catalytic conversion of E1, E2, E3 and EE2 in synthetic wastewater. Greater than 80% reduction in the parent compounds was achieved for each target chemical after 72h with the remaining concentration distributed between aqueous and solid phases as follows: 13% and 7% for E1, 10% and 2% for E2, 6% and 2% for E3, and 8% and 3% for EE2, respectively. Testosterone, androstenedione and progesterone were also monitored in this study, and their concentrations were found to be in agreement with initially spiked amount. Data collected under laboratory conditions provided the basis for implementing new abiotic wastewater treatment technologies that use inexpensive materials.

Fate of sex hormones in two pilot-scale municipal wastewater treatment plants: conventional treatment.

The fate of seven sex hormones (estrone (E1), estradiol (E2), estriol (E3), ethinylestradiol (EE2), testosterone, androstenedione, and progesterone) was determined in two pilot-scale wastewater treatment plants operated under conventional loading conditions. The levels of hormones in both the liquid and the solid matrixes of the plants were determined. Each of the two 20-l/h pilot-scale plants consisted of a primary clarifier followed by a three-stage aeration tank and a final clarifier. The primary sludge and the waste activated sludge (WAS) were digested anaerobically in one pilot plant and aerobically in the other. The pilot plants were fed a complex synthetic wastewater spiked with the hormones. Levels of testosterone, androstenedione and progesterone were close to method detection limit (MDL) concentrations in the final and digester effluents (both liquid and solid phases) and were considered as completely removed. Average mass flux removals from the liquid streams (plant influent minus secondary clarifier effluent) for the natural estrogens were 82% for E1, 99% for E2, and 89% for (E1+E2). An average overall removal of only 42% was achieved for EE2. These values reflect removals averaged for the two pilot plants.