Monitoring iohexol and its transformation products as evidence of reclaimed water irrigation input to contiguous waterbodies.

Irrigation with reclaimed water alleviates water supply shortages, but excess application often results in impairment of contiguous waterbodies. This project investigated the potential use of iohexol, an iodinated contrast media used in medical imaging, together with its bio- and phototransformation products as unique reconnaissance markers of reclaimed water irrigation intrusion at three golf courses within the state of Florida. Inter-facility iohexol concentrations measured in reclaimed waters ranged over ~2 orders of magnitude while observed intra-facility seasonal differences were ≤1 order of magnitude. A ~50 % reduction in iohexol was observed post-disinfection for reclaimed water facilities utilizing UV light while none was observed with use of chlorine. Iohexol biotransformation products were observed to decline or shift to lower molecular weight compounds when exposed to UV light but not during disinfection using chlorine. Iohexol biotransformation products were observed in most of the samples but were more prevalent in samples collected during the dry season. Much fewer iohexol phototransformation products were observed in chlorinated reclaimed water, and they were only observed in UV light irradiated reclaimed water when the pre-disinfectant iohexol concentration was ≥5000 ng/L or from solar exposure of reclaimed water spiked with 10 µM of iohexol. For the Hillsborough golf course overlaying an aquifer, the groundwater did not contain iohexol or phototransformation products but did contain biotransformation products. It is not known if these biotransformation products are from active or historical intrusion. The additional presence of sucralose in the aquifer suggests that intrusion has occurred within the past 3 years. This study demonstrates three crucial points in attempting to utilize iohexol to denote reclaimed water intrusion from irrigation overapplication: (1) interpretable results are obtained when iohexol concentrations in the reclaimed water employed for irrigation are ≥1000 ng/L, with higher concentrations in the range of ≥5000 ng/L better able to meet analytical sensitivity requirements after further dilution or degradation in the environment; (2) it is beneficial to assess iohexol transformation products in tandem with iohexol monitoring to account for environmental transformations of iohexol during storage and transport to the receiving water of concern; and (3) inclusion of monitoring for sucralose, an artificial sweetener ubiquitous in wastewater sources that is comparatively stable in the environment, can aid in interpretating whether reclaimed water intrusion based on identification of iohexol and transformation products in the receiving water is attributable to historic or ongoing irrigation overapplications.

Comparative investigation of PFAS adsorption onto activated carbon and anion exchange resins during long-term operation of a pilot treatment plant.

Widespread contamination of groundwater with per- and polyfluoroalkyl substances (PFAS) has required drinking water producers to quickly adopt practical and efficacious treatments to limit human exposure and deleterious health outcomes. This pilot-scale study comparatively investigated PFAS adsorption behaviors in granular activated carbon (GAC) and two strong-base gel anion exchange resin (AER) columns operated in parallel over a 441-day period to treat contaminated groundwater dominated by short-chain perfluorocarboxylic acids (PFCA). Highly-resolved breakthrough profiles of homologous series of 2-8 CF2 PFCA and perfluorosulfonic acids (PFSA), including ultrashort-chain compounds and branched isomers, were measured to elucidate adsorption trends. Sample ports at intermediate bed depths could predict 50% breakthrough of compounds on an accelerated basis, but lower empty bed contact times led to conservative estimates of initial breakthrough. Homologous PFAS series displayed linear (GAC) and log-linear (AER) relationships between chain-length and breakthrough, independent of initial concentration. AERs generally outperformed GAC on a normalized bed volume basis, and this advantage widened with increasing PFAS chain-length. As designed, all treatments would have short full-scale service times (≤142 days for GAC; ≤61 days for AERs) before initial breakthrough of short-chain (2-4 CF2) PFCA. However, AER displayed far longer breakthrough times for PFSA compared to GAC (>3× treatment time), and breakthrough was not observed for PFSA with >4 CF2 in AERs. GAC had a finite molar adsorption capacity for total PFAS, leading to a stoichiometric replacement of short-chain PFCA by PFSA and longer-chain PFCA over time. AERs quickly reached a finite adsorption capacity for PFCA, but they showed substantially greater selectivity for PFSA whose capacity was not reached within the duration of the pilot. Breakthrough characteristics of keto- and unsaturated-PFSA, identified in the groundwater by suspect screening, were also evaluated in absence of reference standards. Modified PFAS structures (branched, keto-, unsaturated-) broke through faster than linear and unmodified perfluorinated structures with equal degrees of fluorination, and the effects were more pronounced in GAC compared to AERs. The results highlight that the design of robust PFAS treatment systems should consider facets beyond current PFAS targets including operational complexities and impacts of unregulated and unmonitored co-contaminants.

Adaptation of selected models for describing competitive per- and polyfluoroalkyl substances breakthrough curves in groundwater treated by granular activated carbon.

Granular activated carbon (GAC) has proven to be a successful technology for per- and polyfluoroalkyl substances (PFAS) removal from contaminated drinking water supplies. Proper design of GAC treatment relies upon characterization of media service-life, which can change significantly depending on the PFAS contamination, treatment media, and water quality, and is often determined by fitting descriptive models to breakthrough curves. However, while common descriptive breakthrough models are favored for their ease-of-use, they have a significant shortcoming in that they are not able to properly fit PFAS desorption in competitive sorption scenarios. The present work adapts three common descriptive models to fit competitive PFAS breakthrough curves from a GAC pilot study. The adapted and original models were fit to the experimental breakthrough curves for 12 common PFAS and evaluated using adjusted R2 and reduced χ2 values. This study found that the novel adaptation of the common descriptive models successfully accounted for desorption of PFAS compounds from the GAC, accurately describing increased exposure risks due to elevated effluent levels during desorption without significantly increasing the complexity of implementing the models.

Energy and water quality management systems for water utility's operations: a review.

Holistic management of water and energy resources is critical for water utilities facing increasing energy prices, water supply shortage and stringent regulatory requirements. In the early 1990s, the concept of an integrated Energy and Water Quality Management System (EWQMS) was developed as an operational optimization framework for solving water quality, water supply and energy management problems simultaneously. Approximately twenty water utilities have implemented an EWQMS by interfacing commercial or in-house software optimization programs with existing control systems. For utilities with an installed EWQMS, operating cost savings of 8-15% have been reported due to higher use of cheaper tariff periods and better operating efficiencies, resulting in the reduction in energy consumption of ∼6-9%. This review provides the current state-of-knowledge on EWQMS typical structural features and operational strategies and benefits and drawbacks are analyzed. The review also highlights the challenges encountered during installation and implementation of EWQMS and identifies the knowledge gaps that should motivate new research efforts.

Impact of MBR cleaning and breaching on passage of selected microorganisms and subsequent inactivation by free chlorine.

Membrane bioreactors (MBRs) produce better quality effluent compared to conventional treatment processes but they are still subjected to the same disinfection requirements as conventional processes by many regulatory agencies. A research study consisting of bench-, pilot- and full-scale studies was conducted to characterize effluents produced from an MBR system operating under routine and challenged conditions and to assess the disinfection requirements for these effluents. Membrane cleaning did not seem to pose a substantial risk with respect to passage of target microorganisms; however, the membrane under breached conditions (turbidity > 0.5 NTU) resulted in an increase in a total coliform bacterial concentration up to 8500 CFU/100 mL. Adenoviruses were always detected in MBR filtrate samples by PCR (method detection limit of 10(3) genome copies per 25 µL reaction) irrespective of the membrane cleaning or breaching status. Passage of MS-2 bacteriophage through a breached membrane was lower compared to total coliform bacteria potentially due to their lower densities in the mixed liquor. Despite an increase in microbial concentration, a free chlorine CT of 30 mg-min/L was sufficient to achieve greater than 5-log removal of seeded MS-2 bacteriophage and removal of total coliform bacteria at or below the method detection limit (2 CFU/100 mL) for samples with a filtrate turbidity of 1.0 NTU. If such lower CT were to be employed, a significant decrease in plant footprint and operational costs could be realized.

Impact of environmental conditions on the suitability of microconstituents as markers for determining nutrient loading from reclaimed water.

Nitrogen and phosphorous loading into waterways from designated beneficial uses of reclaimed water is a growing concern in many parts of the United States. Numerous studies have documented that organic microconstituents present in the reclaimed water can be utilized as indicators of its influence on surface water bodies. However, little to no information is available on the environmental attenuation of these microconstituents relative to the nutrients, which is a critical component in determining the effectiveness or limitations of those markers as a tool for elucidating their origins. In this study, the stability of selected markers (sucralose, carbamazepine, gadolinium anomaly, iohexol, and atenolol) was evaluated through bench-scale studies designed to simulate environmental conditions associated with biodegradation, adsorption, and photolysis. The primary pathway for nitrogen reduction was biodegradation (greater than 99%) while the highest phosphorous removal was due to adsorption (30-80%). Soils with low organic content were selected for this study. Sucralose was the most recalcitrant microconstituent in the environment with less than 15% removal by adsorption, biodegradation, or photolysis. Iohexol was too susceptible to photolysis (90% removal), and atenolol was susceptible to biodegradation (60-80% removal). Gd anomaly was fairly stable (less than 30% removal) in the environment. Carbamazepine was another efficacious marker for wastewater, but was susceptible (50% removal) to photolysis. Of the selected microconstituents, only atenolol showed any similarity with the attenuation observed for nitrate and none of the microconstituents showed any similarity with the attenuation observed for phosphorus.

Characterization of effluent water qualities from satellite membrane bioreactor facilities.

Membrane bioreactors (MBRs) are often a preferred treatment technology for satellite water recycling facilities since they produce consistent effluent water quality with a small footprint and require little or no supervision. While the water quality produced from centralized MBRs has been widely reported, there is no study in the literature addressing the effluent quality from a broad range of satellite facilities. Thus, a study was conducted to characterize effluent water qualities produced by satellite MBRs with respect to organic, inorganic, physical and microbial parameters. Results from sampling 38 satellite MBR facilities across the U.S. demonstrated that 90% of these facilities produced nitrified (NH4-N <0.4 mg/L-N) effluents that have low organic carbon (TOC <8.1 mg/L), turbidities of <0.7 NTU, total coliform bacterial concentrations <100 CFU/100 mL and indigenous MS-2 bacteriophage concentrations <21 PFU/100 mL. Multiple sampling events from selected satellite facilities demonstrated process capability to consistently produce effluent with low concentrations of ammonia, TOC and turbidity. UV-254 transmittance values varied substantially during multiple sampling events indicating a need for attention in designing downstream UV disinfection systems. Although enteroviruses, rotaviruses and hepatitis A viruses (HAV) were absent in all samples, adenoviruses were detected in effluents of all nine MBR facilities sampled. The presence of Giardia cysts in filtrate samples of two of nine MBR facilities sampled demonstrated the need for an appropriate disinfection process at these facilities.

Differentiating sources of anthropogenic loading to impaired water bodies utilizing ratios of sucralose and other microconstituents.

Previous studies have suggested the use of sucralose, a synthetic non-nutritive sweetener, as an indicator of domestic wastewater loading to surface waters. This paper presents a novel flow schematic approach for quantifying volumetric load contributions from different water sources by utilizing sucralose as a master diagnostic variable in combination with other trace compounds. This conceptual approach was validated through demonstration of sucralose presence at positive field sites susceptible to either water reuse or septic infiltration and its absence at negative field sites. Differences in the ratios of carbamazepine to sucralose and gadolinium anomaly to sucralose were demonstrated for eight septic and water reuse effluents. Utilization of these ratios as a means of distinguishing septic and water reuse loading to water bodies merits additional study. In the absence of sustained loading, the use of carbamazepine might be hindered by photolysis and gadolinium anomaly might be hindered when volumetric loading is less than 20%.

Sources of nutrients impacting surface waters in Florida: a review.

The promulgation of numeric nutrient criteria for evaluating impairment of waterbodies in Florida is underway. Adherence to the water quality standards needed to meet these criteria will potentially require substantial allocations of public and private resources in order to better control nutrient (i.e., nitrogen and phosphorus) releases from contributing sources. Major sources of nutrients include atmospheric deposition (195-380 mg-N/m(2)/yr, 6 to 16 mg-P/m(2)/yr), reclaimed water irrigation (0.13-29 mg-N/L, 0.02 to 6 mg-P/L), septic systems (3.3 × 10(3)-6.68 × 10(3) g-N/person/yr, 0.49 × 10(3)-0.85 × 10(3) g-P/person/yr) and fertilizer applications (8 × 10(6)-24 × 10(6) mg-N/m(2)/yr). Estimated nitrogen loadings to the Florida environment, as calculated from the above rates are as follows: 5.9 × 10(9)-9.4 × 10(9) g-N/yr from atmospheric deposition, 1.2 × 10(8)-2.6 × 10(10) g-N/yr from reclaimed water, 2.4 × 10(10)-4.9 × 10(10) g-N/year from septic systems, and 1.4 × 10(11) g-N/yr from fertilizer application. Similarly, source specific phosphorus loading calculations are also presented in this paper. A fraction of those nutrient inputs may reach receiving waterbodies depending upon site specific regulation on nutrient control, nutrient management practices, and environmental attenuation. In Florida, the interconnectivity of hydrologic pathways due to the karst landscape and high volumes of rainfall add to the complexity of tracking nutrient loads back to their sources. In addition to source specific nutrient loadings, this review discusses the merits of source specific markers such as elemental isotopes (boron, nitrogen, oxygen, strontium, uranium and carbon) and trace organic compounds (sucralose, gadolinium anomaly, carbamazepine, and galaxolide) in relating nutrient loads back to sources of origin. Although this review is focused in Florida, the development of source specific markers as a tool for tracing nutrient loadings back to sources of origin is applicable and of value to all other geographical locations.

Occurrence and suitability of sucralose as an indicator compound of wastewater loading to surface waters in urbanized regions.

Urban watersheds are susceptible to numerous pollutant sources and the identification of source-specific indicators can provide a beneficial tool in the identification and control of input loads, often times needed for a water body to achieve designated beneficial uses. Differentiation of wastewater flows from other urban wet weather flows is needed in order to more adequately address such environmental concerns as water body nutrient impairment and potable source water contamination. Anthropogenic compounds previously suggested as potential wastewater indicators include caffeine, carbamazepine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, primidone, sulfamethoxazole, and TCEP. This paper compares the suitability of a variety of anthropogenic compounds to sucralose, an artificial sweetener, as wastewater indicators by examining occurrence data for 85 trace organic compounds in samples of wastewater effluents, source waters with known wastewater point source inputs, and sources without known wastewater point source inputs. The findings statistically demonstrate the superior performance of sucralose as a potential indicator of domestic wastewater input in the U.S. While several compounds were detected in all of the wastewater effluent samples, only sucralose was consistently detected in the source waters with known wastewater discharges, absent in the sources without wastewater influence, and consistently present in septic samples. All of the other compounds were prone to either false negatives or false positives in the environment.

Energy minimization strategies and renewable energy utilization for desalination: a review.

Energy is a significant cost in the economics of desalinating waters, but water scarcity is driving the rapid expansion in global installed capacity of desalination facilities. Conventional fossil fuels have been utilized as their main energy source, but recent concerns over greenhouse gas (GHG) emissions have promoted global development and implementation of energy minimization strategies and cleaner energy supplies. In this paper, a comprehensive review of energy minimization strategies for membrane-based desalination processes and utilization of lower GHG emission renewable energy resources is presented. The review covers the utilization of energy efficient design, high efficiency pumping, energy recovery devices, advanced membrane materials (nanocomposite, nanotube, and biomimetic), innovative technologies (forward osmosis, ion concentration polarization, and capacitive deionization), and renewable energy resources (solar, wind, and geothermal). Utilization of energy efficient design combined with high efficiency pumping and energy recovery devices have proven effective in full-scale applications. Integration of advanced membrane materials and innovative technologies for desalination show promise but lack long-term operational data. Implementation of renewable energy resources depends upon geography-specific abundance, a feasible means of handling renewable energy power intermittency, and solving technological and economic scale-up and permitting issues.

Beneficial phosphate recovery from reverse osmosis (RO) concentrate of an integrated membrane system using polymeric ligand exchanger (PLE).

Phosphorus (P) discharge to surface water is a major environmental problem. Wastewater treatment is targeted towards removal of this nutrient to prevent degradation of surface water. Integrated membrane systems (IMS) are increasingly being considered for wastewater reclamation, and provide excellent removal of P compounds. However, reverse osmosis (RO), which forms an integral part of these IMSs, concentrates most dissolved substances including P-species such as phosphates in the RO waste stream. In this study, removal of phosphate from this stream using polymeric ligand exchange (PLE) resins was investigated. Further, the possibility of phosphate recovery through struvite (MgNH(4)PO(4).6H(2)O) precipitation was tested. Struvite has been promoted as a slow release fertilizer in recent years. This study demonstrates that PLEs can be successfully used to remove phosphate from RO-concentrate, and to recover more than 85% of the adsorbed phosphorus from the exhausted media and precipitated as a beneficial product (struvite). The approach, presented in this study, suggests advantages of providing economic benefit from a waste product (RO) while avoiding phosphorus discharge to the environment.

Characterizing the passage of personal care products through wastewater treatment processes.

Wastewater treatment facilities use secondary treatment to stabilize the effect of discharged effluent on receiving waters by oxidizing biodegradable organic matter and reducing suspended solids and nutrients. The process was never specifically intended to remove trace quantities of xenobiotics, such as endocrine-disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs). Nevertheless, European studies performed at bench-scale or at small facilities have demonstrated that a critical minimum solids retention time (SRT) can achieve good reduction of many EDCs and pharmaceuticals. The objective of this study was to expand these findings to the removal performance for 20 PPCPs commonly found in the influent to full-scale facilities operating in the United States. The participating plants use SRT conditions ranging from 0.5 to 30 days and include facility capacities ranging from 19 000 m3/d (5 mgd) to greater than 1 136 000 m3/d (300 mgd). Two pilot membrane bioreactors were also included in the study. The 20 PPCPs were categorized into nine bin combinations of occurrence frequency and treatment reduction performance. While most compounds were well removed, galaxolide (a musk fragrance) occurred frequently and was resistant to removal. A minimum critical SRT, defined as the minimum SRT, needed to consistently demonstrate greater than 80% removal (SRT80), was compound-dependent, with most compounds removed at 5 to 15 days and a small group requiring longer SRTs. From limited data, no additional removal could be attributed to the use of membrane bioreactors, media filters, or longer hydraulic retention times. Reverse osmosis was effective in removing any remaining compounds.