Anion Exchange Resin and Inorganic Anion Parameter Determination for Model Validation and Evaluation of Unintended Consequences during PFAS Treatment

When implementing anion exchange (AEX) for per- and polyfluoroalkyl substances treatment, temporal drinking water quality changes from concurrent inorganic anion (IA) removal can create unintended consequences (e.g., corrosion control impacts). To understand potential effects, four drinking water-relevant IAs (bicarbonate, chloride, sulfate, and nitrate) and three gel-type, strong-base AEX resins were evaluated. Batch binary isotherm experiments provided estimates of IA selectivity with respect to chloride (K x ∕ C ) for IA/resin combinations where bicarbonate < sulfate ≤ nitrate at studied conditions. A multi-IA batch experiment demonstrated that binary isotherm-determinedK x ∕ C values predicted competitive behavior. Subsequent column experiments with and without natural organic matter (NOM) allowed for the validation of a new ion exchange column model (IEX-CM; https://github.com/USEPA/Water_Treatment_Models). IA breakthrough was well-simulated using binary isotherm-determinedK x ∕ C values and was minimally impacted by NOM. Initial AEX effluent water quality changes with corrosion implications included increased chloride and decreased sulfate and bicarbonate concentrations, resulting in elevated chloride-to-sulfate mass ratios (CSMRs) and Larson ratios (LRs) and depressed pH until the complete breakthrough of the relevant IA(s). IEX-CM utility was further illustrated by simulating the treatment of low-IA source water and a change in the source water to understand the resulting duration of changes in IAs and water quality parameters.

Effectiveness of biosurfactant for the removal of trihalomethanes by biotrickling filter

In this study, the biodegradation of a mixture of two trihalomethane (THM) compounds, chloroform (CF) and dichlorobromomethane (DCBM), was evaluated using two laboratory-scale biotrickling filters (BTFs). The two BTFs, hereby designated as "BTF-A" and "BTF-B," were run parallel and used ethanol as co-metabolite at different loading rates (LRs), and a lipopeptide-type biosurfactant that was generated by the gram-positive bacteria, Surfactin, respectively. The results using BTF-A showed that adding ethanol at a higher rate of 4.59 g/(m³ h) resulted in removal efficiencies of 85% and 87% for CF and DCBM, respectively. Conversely, for the same LR, the use of Surfactin without ethanol (BTF-B) showed comparable removal efficiencies of 85% and 80% for CF and DCBM, respectively. The maximum rate constant for CF and DCBM for the BTF-A was 0.00203 s^-1 and 0.0022 s^-1, respectively. For the same THMs LR, similar reaction rate constants resulted for the BTF-B. Further studies were conducted to investigate and understand the microbial diversity within both BTFs. The result indicated that for BTF with co-metabolite, Fusarium sp. was the most dominant fungi over 98% followed by F. Solani with less than 2%. F. oxysporum and Fusarium sp. were instead the dominant fungi for the BTF with Surfactin. Before introducing the Surfactin into the BTF, the batch experiment was conducted to evaluate the effectiveness of synthetic surfactant as compared to a biosurfactant (Surfactin). In this regard, vials with Surfactin showed better performance than vials with Tomadol 25-7 (synthetic surfactant).

Application of the CANARY event detection software for real-time performance monitoring of decentralized water reuse systems

Real-time monitoring of water reuse systems ensures the production of high quality water to protect human health at the point-of-use. In this study, several online real-time sensors were utilized to monitor effluent from a wastewater fed laboratory-scale membrane bioreactor (MBR) under natural and simulated failure conditions. These simulated failures included adding reactor mixed liquor to emulate a membrane breach, and spiking MS2 bacteriophage into the reactor to create a high viral load, which might be observed during an outbreak. The CANARY event detection software was used to analyze sensor data and report changes in water quality that might be indicative of poor system behavior. During simulated failure conditions, CANARY reported 20 alarms, accurately detecting each failure. During natural operating conditions, 219 alarms were produced and 189 were attributed to known events (e.g., system and sensor maintenance). The remaining alarms (23) during natural operating conditions were considered to have an unknown cause. However, 13 of those had signal deviations similar to known events, but could not be definitively linked to a source. The results of this study suggest that real-time monitoring in conjunction with CANARY analysis may be useful as an early warning system for monitoring the effluent of water reuse systems, and may help to quickly identify treatment malfunctions or other abnormal conditions.

Characterization and potential environmental implications of select Cu-based fungicides and bactericides employed in U.S. markets

This exploratory study aimed to examine the extent and mineral speciation of nanosized Cu in two fungicide products (A and B) available in the U.S. markets. Electron microcopy results demonstrated the presence of spherical and polydisperse <100 nm Cu particles in product B. Other elements (e.g., Pb, Na, Ca, and S) were found in both products. Mineral speciation analysis indicated the dominance of spertiniite followed by cornetite and then malachite in product A. In product B, spertiniite and tenorite were the dominant Cu species followed by cornetite and malachite. Tenorite in product B (∼30%, <450 nm) has the potential for stronger toxicological impacts relative to those of other Cu minerals in the tested products. For both products, the particle hydrodynamic diameter was impacted by changes in environmental parameters (pH, ionic strength, and background electrolyte) in Milli-Q water and humic acid suspensions. However, a minimal impact was observed in polyvinylpyrrolidone suspensions. The findings are critically important for estimating the fate and transport of Cu particles in different environmental scenarios as well as allowing a more accurate assessment of their risk that is largely impacted by chemical speciation and size.

Biological treatment of benzene in a controlled trickle bed air biofilter

Trickle bed air biofilters (TBABs) are suitable for treatment of relatively high volumes of volatile organic compounds due to their controlled environment. A laboratory-scale TBAB was used for the treatment of an air stream contaminated with benzene under different loading rates (LRs) ranging from 7.2 to 76.8 gm(-3)h(-1). The TBAB was operated at pH 7 and 25 degrees C. Consistent long-term performance of the benzene TBAB depends on various factors one of which is the excess amount of biomass accumulated within the bed. Three experimental strategies for biomass control were employed in the study: weekly backwashing for 1h, starvation (no benzene feed for a period of 2d/week) and stagnation (no benzene, air and nutrient flow for a period of 2d/week). The experimental plan was designed to investigate the long-term performance of the TBAB with emphasis on the empty bed resident time (EBRT), different benzene LRs, removal efficiency with TBAB depth, volatile suspended solids and carbon mass balance closure. For benzene loading up to 34.1gm(-3)h(-1), removal efficiency consistently over 98% was achieved. At the maximum LR 76.8 gm(-3)h(-1) the removal efficiency was still above 80% by utilizing stagnation strategy for 2d and gas flow switching once per week as means of biomass control. Backwashing once per week provided less efficient performance as compared to stagnation while starvation showed the worst performance. EBRT at 120 s provided the best performance while EBRT at 90 s showed slightly lower performance.

The application of a mulch biofilm barrier for surfactant enhanced polycyclic aromatic hydrocarbon bioremediation

Lab scale mulch biofilm barriers were constructed and tested to evaluate their performance for preventing the migration of aqueous and surfactant solubilized PAHs. The spatial distribution of viable PAH degrader populations and resultant biofilm formation were also monitored to evaluate the performance of the biobarrier and the prolonged surfactant effect on the PAH degrading microorganism consortia in the biobarrier. Sorption and biodegradation of PAHs resulted in stable operation of the system for dissolved phenanthrene and pyrene during 150 days of experimentation. The nonionic surfactant could increase the solubility of phenanthrene and pyrene significantly. However, the biobarrier itself couldn't totally prevent the migration of micellar solubilized phenanthrene and pyrene. The presence of surfactant and the resultant highly increased phenanthrene or pyrene concentration didn't appear to cause toxic effects on the attached biofilm in the biobarrier. However, the presence of surfactant did change the structural composition of the biofilm.

Electrochemical pilot scale study for reduction of 2,4-DNT

An electrochemical pilot scale reactor was used to treat simulated munitions wastewater containing 100 mg/L of 2,4-dinitrotoluene (DNT). Experiments were conducted by using a glassy carbon (zero porosity) coated graphite cylinder as the cathode and a platinum wire as the anode. All experiments were conducted under dissolved oxygen concentration of less than 1.5 mg/L. Initially, simulating batch conditions were conducted to obtain the optimum operating conditions for the reactor. During this batch-mode study, the effects of various parameters such as applied current, electrolyte concentration, and type of electrolyte on the reduction of DNT were evaluated. Results obtained showed that the rates of reduction of DNT increased with an increase in current or concentration of electrolyte. Based on the results obtained from the batch simulation experiments, continuous flow experiments were conducted at three different currents. The ionic strength of the feed solution was maintained at 0.027 M. A current of 200 mA was found to provide a stable reduction of DNT at the 80% level for a period of 14 days after which reactor cleaning is necessary for removal of solids that were formed within the reactor. End products determined for the continuous flow experiments showed 100% molar balance conversion.