Treatment of aqueous per- and poly-fluoroalkyl substances: A review of biochar adsorbent preparation methods.

Per- and poly-fluoroalkyl substances (PFAS) are synthetic chemicals widely used in everyday products, causing elevated concentrations in drinking water and posing a global challenge. While adsorption methods are commonly employed for PFAS removal, the substantial cost and environmental footprint of commercial adsorbents highlight the need for more cost-effective alternatives. Additionally, existing adsorbents exhibit limited effectiveness, particularly against diverse PFAS types, such as short-chain PFAS, necessitating modifications to enhance adsorption capacity. Biochar can be considered a cost-effective and eco-friendly alternative to conventional adsorbents. With abundant feedstocks and favorable physicochemical properties, biochar shows significant potential to be applied as an adsorbent for removing contaminants from water. Despite its effectiveness in adsorbing different inorganic and organic contaminants from water environments, some factors restrict its effective application for PFAS adsorption. These factors are related to the biochar properties, and characteristics of PFAS, as well as water chemistry. Therefore, some modifications have been introduced to overcome these limitations and improve biochar's adsorption capacity. This review explores the preparation conditions, including the pyrolysis process, activation, and modification techniques applied to biochar to enhance its adsorption capacity for different types of PFAS. It addresses critical questions about the adsorption performance of biochar and its composites, mechanisms governing PFAS adsorption, challenges, and future perspectives in this field. The surge in research on biochar for PFAS adsorption indicates a growing interest, making this timely review a valuable resource for future research and an in-depth exploration of biochar's potential in PFAS remediation.

Comparison of Legionella pneumophila and Pseudomonas fluorescens Quantification Methods for Assessing UV LED Disinfection.

This study assesses the efficacy of ultraviolet light-emitting diodes (UV LEDs) for deactivating Legionella pneumophila (pure culture) and Pseudomonas fluorescens (pure culture and biofilms) on relevant drinking water distribution system surfaces (cast iron and stainless steel). UV LED treatment at 280 nm demonstrated superior performance compared to that at 365 nm, achieving a 4.8 log reduction value (LRV) for P. fluorescens pure cultures and, for biofilms, 4.02 LRV for stainless steel and 2.96 LRV for cast iron at 280 nm. Conversely, the results were less effective at 365 nm, with suspected photolytic reactions on cast iron. Quantification of L. pneumophila yielded varying results: 4 LRV using standard plate counts, 1.8 LRV with Legiolert, and 1 LRV with quantitative polymerase chain reaction at 280 nm, while the results were less than 1.5 LRV at 365 nm. This study provides insights into managing opportunistic pathogens and biofilms, emphasizing the need for improved quantification tools to better assess treatment efficacy.

Enhanced detection of viruses for improved water safety.

Human viruses pose a significant health risk in freshwater environments, but current monitoring methods are inadequate for detecting viral presence efficiently. We evaluated a novel passive in-situ concentration method using granular activated carbon (GAC). This study detected and quantified eight enteric and non-enteric, pathogenic viruses in a freshwater recreational lake in paired grab and GAC passive samples. The results found that GAC passive sampling had a higher detection rate for all viruses compared to grab samples, with adenovirus found to be the most prevalent virus, followed by respiratory syncytial virus, norovirus, enterovirus, influenza A, SARS-CoV-2, and rotavirus. GAC in-situ concentration allowed for the capture and recovery of viral gene copy targets that ranged from one to three orders of magnitude higher than conventional ex-situ concentration methods used in viral monitoring. This simple and affordable sampling method may have far-reaching implications for reducing barriers associated with viral monitoring across various environmental contexts.

Biodegradation of 1,4-dioxane in a continuous-flow bioelectrochemical reactor by biofilm of Pseudonocardia dioxanivorans CB1190 and microbial community on conductive carriers.

Bioelectrochemical degradation is an environmentally friendly, cost-effective and controllable way of providing electron acceptor to the microorganisms. A two-chamber continuous-flow bioelectrochemical reactor (BER) was developed in this study. The objective was to investigate the potential for enhancing the bioelectrochemical degradation of 1,4-dioxane (DX) by Pseudonocardia dioxanivorans CB1190 (CB1190) and microbial community biofilm on conductive and non-conductive carriers in low potentials (1.0-1.2 V) and currents (<2 mA). In the case of CB1190, biodegradation experiments at 1.0 V did not result in any observable change in DX removal efficiency (32.63 ± 2.48%) compared to the 0.0 V (31.69 ± 2.33%). However, the removal efficiency was much higher at 1.2 V (59.08 ± 0.86%). The higher removal at 1.2 V was attributed to an increase in dissolved oxygen (DO) concentration from 3.77 ± 0.33 mg/L at 0.0 V to 5.40 ± 0.11 mg/L at 1.2 V, which resulted from water electrolysis. In the case of microbial community, on the other hand, DX removal efficiency increased at 1.0 V (30.98 ± 1.10%) compared to 0.0 V (23.40 ± 1.02%) that can be attributed to a simultaneous increase in microbial activity from 2389 ± 118.5 ngATP/mgVSS at 0.0 V to 2942 ± 109 ngATP/mgVSS at 1.0 V. Analysis of the changes in microbial composition indicated enrichment of Alistipes and Lutispora at 1.0 V due to the ability of these genera to directly transfer electrons with conductive surface. On the other hand, no change was observed in the microbial community in the case of non-conductive carriers. Results of this study showed that electro-assisted biodegradation of DX at low potentials is possible through two different mechanisms (oxygen production and direct electron transfer with electrode) which makes this technique flexible and cost-effective. The novelty of this work lies in exploring the use of electrical assistance to enhance the biodegradation of DX in the presence of CB1190 and the microbial community. This study more specifically investigated lower potential than required water electrolysis potential, allowing microorganisms to be stimulated through mechanisms unrelated to oxygen generation.

An innovative passive sampling approach for the detection of cyanobacterial gene targets in freshwater sources.

Cyanotoxins pose significant human health risks, but traditional monitoring approaches can be expensive, time consuming, and require analytical equipment or expertise that may not be readily available. Quantitative polymerase chain reaction (qPCR) is becoming an increasingly common monitoring strategy as detection of the genes responsible for cyanotoxin synthesis can be used as an early warning signal. Here we tested passive sampling of cyanobacterial DNA as an alternative to grab sampling in a freshwater drinking supply lake with a known history of microcystin-LR. DNA extracted from grab and passive samples was analyzed via a multiplex qPCR assay that included gene targets for four common cyanotoxins. Passive samples captured similar trends in total cyanobacteria and the mcyE/ndaF gene responsible for microcystin production when compared to traditional grab samples. Passive samples also detected genes associated with the production of cylindrospermopsin and saxitoxin that were not detected in grab samples. This sampling approach proved a viable alternative to grab sampling when used as an early warning monitoring tool. In addition to the logistical benefits of passive sampling, the detection of gene targets not detected by grab samples indicates that passive sampling may allow for a more complete profile of potential cyanotoxin risk.

Raw water biofiltration for surface water manganese control.

Manganese (Mn) control in surface water systems is a challenge for the drinking water industry, especially through a sustainability framework. Current methods for removing manganese from surface water use strong oxidants that embed carbon and can be expensive and harmful to human health and the environment. In this study, we used a simple biofilter design to remove manganese from lake water, without conventional surface water pre-treatments. Biofilters with aerated influent removed manganese to concentrations below 10 µg/L when receiving influent water containing > 120 µg/L of dissolved manganese. Manganese removal was not inhibited by high iron loadings or poor ammonia removal, suggesting that removal mechanisms may differ from groundwater biofilters. Experimental biofilters also achieved lower effluent manganese concentrations than the full-scale conventional treatment process, while receiving higher manganese concentrations. This biological approach could help achieve sustainable development goals.

Improved disinfection performance for 280 nm LEDs over 254 nm low-pressure UV lamps in community wastewater.

Ultraviolet (UV) disinfection has been incorporated into both drinking water and wastewater treatment processes for several decades; however, it comes with negative environmental consequences such as high energy demands and the use of mercury. Understanding how to scale and build climate responsive technologies is key in fulfilling the intersection of UN Sustainable Development Goals 6 and 13. One technology that addresses the drawbacks of conventional wastewater UV disinfection systems, while providing a climate responsive solution, is UV light emitting diodes (LEDs). The objective of this study was to compare performance of bench-scale 280 nm UV LEDs to bench-scale low pressure (LP) lamps and full-scale UV treated wastewater samples. Results from the study demonstrated that the UV LED system provides a robust treatment that outperformed LP systems at the bench-scale. A comparison of relative energy consumptions of the UV LED system at 20 mJ cm-2 and LP system at 30 and 40 mJ cm-2 was completed. Based on current projections for wall plug efficiencies (WPE) of UV LED it is expected that the energy consumption of LED reactors will be on par or lower compared to the LP systems by 2025. This study determined that, at a WPE of 20%, the equivalent UV LED system would lead to a 24.6% and 43.4% reduction in power consumption for the 30 and 40 mJ cm-2 scenarios, respectively.

Simultaneous detection of SARS-CoV-2, influenza A, respiratory syncytial virus, and measles in wastewater by multiplex RT-qPCR.

A multiplex quantitative reverse transcription polymerase chain reaction (RT-qPCR)-based method was designed for the simultaneous detection of influenza A, SARS-CoV-2, respiratory syncytial virus, and measles virus. The performance of the multiplex assay was compared to four monoplex assays for relative quantification using standard quantification curves. Results showed that the multiplex assay had comparable linearity and analytical sensitivity to the monoplex assays, and the quantification parameters of both assays demonstrated minimal differences. Viral reporting recommendations for the multiplex method were estimated based on the corresponding limit of quantification (LOQ) and the limit of detection at 95 % confidence interval (LOD) values for each viral target. The LOQ was determined by the lowest nominal RNA concentrations where %CV values were ≤35 %. Corresponding LOD values for each viral target were between 15 and 25 gene copies per reaction (GC/rxn), and LOQ values were within 10 to 15 GC/rxn. The detection performance of a new multiplex assay was validated in the field by collecting composite wastewater samples from a local treatment facility and passive samples from three sewer shed locations. Results indicated that the assay could accurately estimate viral loads from various sample types, with samples collected from passive samplers showing a greater range of detectable viral concentrations than composite wastewater samples. This suggests that the sensitivity of the multiplex method may be improved when paired with more sensitive sampling methods. Laboratory and field results demonstrate the robustness and sensitivity of the multiplex assay and its applicability to detect the relative abundance of four viral targets among wastewater samples. Conventional monoplex RT-qPCR assays are suitable for diagnosing viral infections. However, multiplex analysis using wastewater provides a fast and cost-effective way to monitor viral diseases in a population or environment.

A review of long-term change in surface water natural organic matter concentration in the northern hemisphere and the implications for drinking water treatment.

Reduced atmospheric acid deposition has given rise to recovery from acidification - defined as increasing pH, acid neutralization capacity (ANC), or alkalinity in surface waters. Strong evidence of recovery has been reported across North America and Europe, driving chemical responses. The primary chemical responses identified in this review were increasing concentration and changing character of natural organic matter (NOM) towards predominantly hydrophobic nature. The concentration of NOM also influenced trace metal cycling as many browning surface waters also reported increases in Fe and Al. Further, climate change and other factors (e.g., changing land use) act in concert with reductions in atmospheric deposition to contribute to widespread browning and will have a more pronounced effect as deposition stabilizes. The observed water quality trends have presented challenges for drinking water treatment (e.g., increased chemical dosing, poor filter operations, formation of disinfection by-products) and many facilities may be under designed as a result. This comprehensive review has identified key research areas to be addressed, including 1) a need for comprehensive monitoring programs (e.g., larger timescales; consistency in measurements) to assess climate change impacts on recovery responses and NOM dynamics, and 2) a better understanding of drinking water treatment vulnerabilities and the transition towards robust treatment technologies and solutions that can adapt to climate change and other drivers of changing water quality.

Impacts of orthophosphate-polyphosphate blends on the dissolution and transformation of lead (II) carbonate.

Orthophosphate-polyphosphate blends are commonly used to control lead release into drinking water, but little is known about how they interact with lead corrosion scale. Conventional corrosion control practice assumes that orthophosphate controls lead release by forming insoluble Pb-phosphate minerals, but this does not always occur, and under certain conditions, phosphate blends may increase lead release. Here, we used continuously-stirred tank reactors to compare orthophosphate-polyphosphate blends with orthophosphate on the basis of lead (II) carbonate dissolution and transformation at environmentally relevant phosphate concentrations. Three model polyphosphates-tripoly-, trimeta- and hexametaphosphate-were used. Hexametaphosphate was the strongest complexing agent (1.60-2.10 molPb/molPolyphosphate), followed by tripolyphosphate and trimetaphosphate (1.00 and 0.07 molPb/molPolyphosphate, respectively. At equivalent orthophosphate and polyphosphate concentrations (as P), orthophosphate-trimetaphosphate had minimal impact on lead release, while orthophosphate-tripolyphosphate increased dissolved lead. Orthophosphate-hexametaphosphate also increased dissolved lead, but only over a 24-h stagnation. Both orthophosphate-tripolyphosphate and orthophosphate-hexametaphosphate increased colloidal lead after 24-h. Increasing the concentrations of hexameta- and tripoly-phosphate increased dissolved lead release, while all three polyphosphates inhibited the formation of hydroxypyromorphite and reduced the phosphorus content of the resulting lead solids. We attributed the impacts of orthophosphate-polyphosphates to a combination of complexation, adsorption, colloidal dispersion, polyphosphate hydrolysis, and lead mineral precipitation.

Enhanced Reproducibility and Precision of High-Throughput Quantification of Bacterial Growth Data Using a Microplate Reader.

This study aimed to develop a repeatable, reliable, high-throughput protocol to monitor bacterial growth in 96-well plates and analyze the maximum growth rate. The growth curves and maximum growth rates of two bacterial species were determined. Issues including (i) lid condensation, (ii) pathlength correction, (iii) inoculation size, (iv) sampling time interval, and (v) spatial bias were investigated. The repeatability of the protocol was assessed with three independent technical replications, with a standard deviation of 0.03 between the runs. The maximum growth rates of Bacillus mycoides and Paenibacillus tundrae were determined to be (mean ± SD) 0.99 h-1 ±  0.03 h-1 and 0.85 h-1 ± 0.025 h-1, respectively. These bacteria are more challenging to monitor optically due to their affinity to clump together. This study demonstrates the critical importance of inoculation size, path length correction, lid warming, sampling time intervals, and well-plate spatial bias to obtain reliable, accurate, and reproducible data on microplate readers. The developed protocol and its verification steps can be expanded to other methods using microplate readers and high-throughput protocols, reducing the researchers' innate errors and material costs.

Immersive ultraviolet disinfection of E. coli and MS2 phage on woven cotton textiles.

Immersive ultraviolet disinfection provides a chemical-free technology for safer textiles, surfaces, and public spaces by inactivating communicable pathogens. This study examined immersive UV disinfection, using a disinfection cabinet, of E. coli and MS2 that was inoculated on white cotton T-shirts. The impact that porous materials have on UV disinfection is poorly understood with the majority of previous surface disinfection research focusing on hard, smooth surfaces. Several approaches were used in this study to characterize the light dynamics within the disinfection cabinet including colorimetric dosimetry coupons, biodosimetry, and spectroradiometry. Micro and macro geometry of porous surfaces are important factors to consider when using immersive UV technologies. The geometry of the cabinet impacted the distribution of emitted UV light within the disinfection cabinet and the physical properties of a porous material, such as the woven pattern of cotton, both contribute to UV disinfection efficiency. This work identified that light distribution is crucial for immersive UV technologies as the delivered fluence was highly variable within the disinfection cabinet and resulted in a difference of several logs of reduction for adjacent areas of T-shirt samples. Other inoculated areas achieved upwards of 1-log reductions values for MS2 and upwards of 2-log reductions for E. coli.

Early phase effects of silicate and orthophosphate on lead (Pb) corrosion scale development and Pb release.

Orthophosphate is widely used to control lead (Pb) release in drinking water distribution systems, but phosphorus addition is not sustainable. Alternative corrosion control treatments are needed, and sodium silicate is one possibility. Here, pre-corroded Pb coupons-with and without free chlorine-were used to examine early-phase corrosion scale development after silicate addition, with orthophosphate as a reference corrosion inhibitor. Scale development was evaluated in terms of total Pb release, phase transformation, electrochemical impedance, morphological changes, Pb dissolution kinetics, and short-term Pb-Cu galvanic corrosion. Elevated Pb release occurred for approximately one month after silicate addition, and total Pb release peaked at 1968.1 µg/L and 1176.9 µg/L from systems with and without free chlorine, respectively. In contrast, orthophosphate-treated coupons exhibited fewer, less pronounced spikes in Pb release. By day 354, the median total Pb release from orthophosphate-treated coupons with and without free chlorine had decreased to 3.7 and 5.0 µg/L, respectively, while the median total Pb release from corresponding silicate-treated coupons was much higher, at 44.9 µg/L and 34.3 µg/L. Calcium lead apatite (Ca0.56Pb3.77(PO4)3OH0.67) was identified in orthophosphate-treated scales, with hydroxylpyromorphite (Pb5(PO4)3OH) present in the absence of free chlorine. Plattnerite occurred on coupons in all chlorinated systems. Pb silicate compounds were not detected, but Ca2SiO4 and Na2Ca2(SiO3)3 were identified by X-ray powder diffraction. The charge transfer: film resistance ratio characterizing the orthophosphate-treated coupons decreased slowly while that of the silicate-treated coupons increased after silicate was added. These variations suggest orthophosphate provided better corrosion control than silicate did. Silicate treatment generally caused degradation of the top Pb scale layer, resulting in elevated Pb release, while orthophosphate encouraged the growth of more structured, generally thicker, corrosion scales that were effective in limiting Pb release.

Adsorption of SARS-CoV-2 onto granular activated carbon (GAC) in wastewater: Implications for improvements in passive sampling.

Based on recent studies, passive sampling is a promising method for detecting SARS-CoV-2 in wastewater surveillance (WWS) applications. Passive sampling has many advantages over conventional sampling approaches. However, the potential benefits of passive sampling are also coupled with apparent limitations. We established a passive sampling technique for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater using electronegative filters. Though, it was evident that the adsorption capacity of the filters constrained their use. This work intends to demonstrate an optimized passive sampling technique for SARS-CoV-2 in wastewater using granular activated carbon (GAC). Through bench-scale batch-adsorption studies and sewershed deployments, we established the adsorption characteristics of SARS-CoV-2 and two human feacal viruses (PMMoV and CrAssphage) onto GAC. A pseudo-second-order model best-described adsorption kinetics for SARS-CoV-2 in either deionized (DI) water and SARS-CoV-2, CrAssphage, and PMMoV in wastewater. In both laboratory batch-adsorption experiments and in-situ sewershed deployments, the maximum amount of SARS-CoV-2 adsorbed by GAC occurred at ~60 h in wastewater. In wastewater, the maximum adsorption of PMMoV and CrAssphage by GAC occurred at ~60 h. In contrast, the adsorption capacity was reached in DI water seeded with SARS-CoV-2 after ~35 h. The equilibrium assay modeled the maximum adsorption quantity (qmax) in wastewater with spiked SARS-CoV-2 concentrations using a Hybrid Langmuir-Freundlich equation, a qmax of 2.5 × 109 GU/g was calculated. In paired sewershed deployments, it was found that GAC adsorbs SARS-CoV-2 in wastewater more effectively than electronegative filters. Based on the anticipated viral loading in wastewater, bi-weekly sampling intervals with deployments up to ~96 h are highly feasible without reaching adsorption capacity with GAC. GAC offers improved sensitivity and reproducibility to capture SARS-CoV-2 RNA in wastewater, promoting a scalable and convenient alternative for capturing viral pathogens in wastewater.

Seasonal Lead Release into Drinking Water and the Effect of Aluminum.

Monitoring lead in drinking water is important for public health, but seasonality in lead concentrations can bias monitoring programs if it is not understood and accounted for. Here, we describe an apparent seasonal pattern in lead release into orthophosphate-treated drinking water, identified through point-of-use sampling at sites in Halifax, Canada, with various sources of lead. Using a generalized additive model, we extracted the seasonally varying components of time series representing a suite of water quality parameters and we identified aluminum as a correlate of lead. To investigate aluminum's role in lead release, we modeled the effect of variscite (AlPO4·2H2O) precipitation on lead solubility, and we evaluated the effects of aluminum, temperature, and orthophosphate concentration on lead release from new lead coupons. At environmentally relevant aluminum and orthophosphate concentrations, variscite precipitation increased predicted lead solubility by decreasing available orthophosphate. Increasing the aluminum concentration from 20 to 500 µg L-1 increased lead release from coupons by 41% and modified the effect of orthophosphate, rendering it less effective. We attributed this to a decrease in the concentration of soluble (<0.45 µm) phosphorus with increasing aluminum and an accompanying increase in particulate lead and phosphorus (>0.45 µm).

Comparing quantitative probability of occurrence to a risk matrix approach: A study of chlorine residual data.

Implementation of water safety planning methods globally has focused primarily on developing an evidence base to demonstrate the benefits of the WSP methodology for risk management in water systems. However, little work has been completed to understand the appropriateness of the risk matrix method currently used to capture levels of risk for system-specific hazardous events. This study examines two quantitative risk calculations (probability density functions and event trees) compared to the risk matrix method employed in water safety planning. This analysis was undertaken to understand if the risk matrix provides an accurate estimation of risk in a water system. Two data sets were collected from nine water supply systems, both continuous inline monitoring and grab samples collected in water distribution systems (discrete events) for chlorine residual data. Using quantitative risk calculations, our study found the risk matrix does not accurately estimate risk compared to water quality data from a water system. In thirty-four (77%) of the forty-four possible scenarios investigated, the risk matrix method provided an underestimation or overestimation compared to the probability calculated using water quality data. The probabilities calculated using continuous data and the event tree method provided the closest estimations to the risk matrix, indicating larger data sets with simpler methods may be more likely to match WSP results. The lack of accuracy obtained reveals the need for a re-evaluation of the risk matrix within a water safety plan (WSP), particularly for systems with data available to perform advanced risk analysis. The risk matrix method has been used historically for systems with little data; however, for water systems with advanced water quality monitoring, adding quantitative probability calculations to a water safety plan has the potential to increase accuracy of risk assessment in water safety planning.

Co-development of a risk assessment tool for use in First Nations water supply systems: A key step to water safety plan implementation.

Despite several years of targeted interventions, First Nations drinking water systems in Canada remain under-resourced and require substantial improvements in both infrastructure and management to provide communities with safe drinking water. The purpose of this study was to co-develop a risk assessment process integral to the water safety planning methodology to determine if proactive risk assessment provides a beneficial management tool for First Nations water systems. We co-developed a risk assessment web-application with First Nations stakeholders to identify hazards and assess risk in six Atlantic region First Nations communities. Using this application, we were able to successfully identify high-risk hazards in each community, both risks specific to individual systems, and risks common at a regional level. Through semi-structured interviews we identified the following benefits of a risk assessment web application: increased communication, data ownership and centralized data management. However, challenges remain, including current fragmented governance realities, and liability concerns associated with adopting a new risk management strategy. Successful adoption of proactive risk management strategies in First Nations communities will depend on strong co-development of risk assessment tools, transparent communication between stakeholders and clearly defined data ownership and management practices.

Operational Constraints of Detecting SARS-CoV-2 on Passive Samplers using Electronegative Filters: A Kinetic and Equilibrium Analysis.

In developing an effective monitoring program for the wastewater surveillance of SARS-CoV-2 ribonucleic acid (RNA), the importance of sampling methodology is paramount. Passive sampling has been shown to be an effective tool to detect SARS-CoV-2 RNA in wastewater. However, the adsorption characteristics of SARS-CoV-2 RNA on passive sampling material are not well-understood, which further obscures the relationship between wastewater surveillance and community infection. In this work, adsorption kinetics and equilibrium characteristics were evaluated using batch-adsorption experiments for heat-inactivated SARS-CoV-2 (HI-SCV-2) adsorption to electronegative filters. Equilibrium isotherms were assessed or a range of total suspended solids (TSS) concentrations (118, 265, and 497 mg L-1) in wastewater, and a modeled qmax of 7 × 103 GU cm-2 was found. Surrogate adsorption kinetics followed a pseudo-first-order model in wastewater with maximum concentrations achieved within 24 h. In both field and isotherm experiments, equilibrium behavior and viral recovery were found to be associated with wastewater and eluate TSS. On the basis of the results of this study, we recommend a standard deployment duration of 24-48 h and the inclusion of eluate TSS measurement to assess the likelihood of solids inhibition during analysis.

Specificity of UV-C LED disinfection efficacy for three N95 respirators.

The recent surge in the use of UV technology for personal protective equipment (PPE) has created a unique learning opportunity for the UV industry to deepen surface disinfection knowledge, especially on surfaces with complex geometries, such as the N95 filter facepiece respirators (FFR). The work outlined in this study addresses the interconnectedness of independent variables (e.g., UV Fluence, respirator material) that require consideration when assessing UV light efficacy for disinfecting respirators. Through electron microscopy and Fourier-transform infrared (FTIR) spectroscopy, we characterized respirator filter layers and revealed that polymer type affects disinfection efficacy. Specifically, FFR layers made from polypropylene (PP) (hydrophobic in nature) resulted in higher disinfection efficiency than layers composed of polyethylene terephthalate (PET-P) (hygroscopic in nature). An analysis of elastic band materials on the respirators indicated that silicone rubber-based bands achieved higher disinfection efficiency than PET-P bands and have a woven, fabric-like texture. While there is a strong desire to repurpose respirators, through this work we demonstrated that the design of an appropriate UV system is essential and that only respirators meeting specific design criteria may be reasonable for repurposing via UV disinfection.