In this study, the survival of E. coli O157:H7 (EcO157) in the vertical layers of a black soil column under FTCs conditions was investigated. The survival parameters including ttd (time needed to reach detection limit), p (shape parameter) and delta (time needed to first decimal reduction) were obtained. Compared with non-FTCs control, FTCs resulted in a rapid decline in EcO157 cell counts across all vertical soil layers, and a greater ttd tended to correspond to a deeper vertical layer. FTCs increased soil NO3 (-)-N, NH4+-N, and neutral phosphatase activity (P < 0.01), and decreased soil moisture content, available phosphorus (AP), and microbial biomass carbon in vertical soil layers in comparison with non-FTCs control. The results of the coexistence network analysis and Mantel test showed that soil physicochemical properties, enzyme activities, and bacterial communities correlated (P < 0.05) with the survival of EcO157. Structural equation model further revealed that AP and bacterial communities directly and positively related to EcO157 survival (P < 0.01). NO3-N directly and negatively correlated ttd (P < 0.01), and indirectly influenced ttd via shifting the structure and composition of bacterial communities. In summary, our results revealed the survival profiles of EcO157 in vertical soil layers under FTCs, and provided additional insights into the mechanisms of bacterial pathogens survival in seasonally frozen soils.

The occurrence and dissemination of resistomes within environmental compartments are worrisome, considering the huge public health challenge they may pose. Treated wastewater from wastewater treatment plants (WWTPs) has been shown to contain enormous and diversified bacterial communities with antibiotic resistance gene (ARG) profiles, and it provides tolerable environments for their prefoliation and dissemination. This study considered the ARG profiles of a municipal WWTP that also collects wastewater from diverse production factories with the aim to determine the efficacy of the wastewater treatment plant and the prevalence of ARGs in the various compartments. The WWTP employs the conventional activated sludge system in its treatment. Our study employed metagenomic screening of ARGs and mobile genetic elements (MGEs), using different PCR assays of untreated wastewater (UTW) and treated wastewater (TWW) from the WWTP. Downstream- (RWD) and upstream- (RWU) receiving river water was also screened. Twenty-nine ARGs and two mobile genetic elements (MGEs) were screened for. Antibiotic resistance genes to all the classes of antibiotics studied were detected in all the samples. Of the twenty-nine ARGs screened for, twenty-four (82.8%) were detected, and one MGE was detected from the two screened for in the samples with the highest ARG prevalence detected in the UTW. This study shows that ARGs proliferate in every compartment of the WWTP, even in the treated water and the receiving rivers, portraying that the WWTP system was not efficient in getting rid of the resistomes, creating an important channel for human acquisition of resistant determinants to antibiotics.

Antibiotic-resistance genes (ARGs) in wastewater may promote antibiotic resistance in consumers of crops irrigated with wastewater. Removal of DNA from wastewater may thus mitigate potential environmental risks associated with irrigation and environmental release of recycled wastewater. Although biochar adsorbents are a potentially cost-effective strategy for removing DNA from water, biochar feedstock influence on performance has not been studied across a range of feedstock classes. Our objective was to produce biochar from 5 distinct feedstocks (manure (MN), black mustard (Brassica nigra) (MU), orange peel (OP), pine pellet (PP) and macadamia nutshell (MNS)) at a fixed pyrolysis temperature (500 °C), characterize biochars and relate characteristics to DNA adsorption. Adsorption reached equilibrium within two hours and kinetics fit the pseudo-second order model. Adsorption rates increased from MNS, PP, OP, MN to MU, with rates of 3.06 × 10−2, 5.65 × 10−2, 1.78 × 10−1, 4.00 × 10−1 and 5.05 × 10−1 mg g−1 min−1, respectively. Adsorption isotherms fit the Freundlich model, with affinities increasing from PP, MNS, OP, MN to MU (Kd = 1.30 × 10−2, 1.35 × 10−2, 1.27 × 10−1, 1.96 × 10−1 and 1.42, respectively). DNA adsorption on biochars increased with ionic strength from I = 0 – 0.10 M except for MN. Ca2+ addition increased adsorption for biochars at I = 0.01 and 0.10 M, except for MN, which increased only with I = 0.10 M. Lower sensitivity of adsorption on MN biochar to ionic conditions indicates a different mechanism may control adsorption. The high ash content of MN biochar may favor direct bonding of DNA to ash minerals compared to π-π interactions likely driving DNA adsorption to structural carbon. These findings help understand how feedstock-driven variability in biochars translates to DNA immobilization and will assist researchers and stakeholders in determining the most suitable feedstocks for this purpose.

Different anthropogenic sources can have a significant influence on bacterial populations and their antimicrobial activities. In this study, the impact of anthropogenic activities on Enterococcus species was studied in an urban watershed in southern California affected by concentrated animal feeding operations (CAFOs), recreational activities, wastewater treatment plants (WWTPs), urban runoff, and control sites. Water samples were collected quarterly for two years for the enumeration of Enterococcus species based on the Enterolert most probable-number (MPN) assay. Concentrations of enterococci were higher in the sediment compared to surface water (4.5 × 106 CFU/g of sediment vs. 2.3 × 105 MPN/100 mL of water). The species diversity was dominated by E. mundtii (32%), E. faecalis (27%), and E. faecium (25%). E. faecium exhibited the highest antibiotic-resistant phenotype. Resistances were mostly to ciprofloxacin, erythromycin, and tetracycline. Tetracycline and erythromycin resistance genes, encoded by tet (C, K, O, S) and ermB, respectively, were more common in isolates from sediment (42.9%) compared to water (12.7%). E. mundtii was sensitive to ampicillin, chloramphenicol, gentamicin, and high levels of vancomycin. A significant percentage of E. faecalis were also resistant to these antibiotics. E. faecium and E. faecalis exhibited resistance to multiple antibiotics. Our data suggest that resistant Enterococcus species within the watershed might provide some useful data to determine pollutant types and sources in that watershed. Therefore, the widespread occurrence and abundance of E. faecium and E. faecalis, and their resistance genes associated with multiple antibiotics may potentially pose risks to the local populations exposed to these water sources during recreational activities.

The antibiotic cephalexin binds to DOM under environmentally-relevent solution conditions through π–π bonding. Under conditions where cephalexin–DOM binding occurs, cephalexin adsorption by biochar and clay is impeded by DOM addition.

The spread of antimicrobial resistance (AMR) in agricultural systems via irrigation water is a serious public health issue as it can be transmitted to humans through the food chain. Therefore, understanding the dissemination routes of antibiotic resistance genes (ARGs) in agricultural systems is crucial for the assessment of health risks associated with eating fresh vegetables such as spinach and radish irrigated with treated municipal wastewater (TMW). In this study, we investigated the bacterial community structure and resistome in the soil -plant -earthworm continuum after irrigation of spinach and radish with TMW containing the antibiotics trimethoprim (TMP), sulfamethoxazole (SMZ), and sulfapyridine (SPD) using 16S rRNA gene sequencing and high throughput quantitative PCR (HT-qPCR). The study was conducted in two phases: Phase I involved eight weeks of spinach and radish production using TMW for irrigation, whereas Phase II entailed three weeks of earthworm exposure to contaminated plant material obtained in Phase I. The 16S data indicated that the rhizosphere bacterial community composition and structure were more resilient to antibiotic residuals in the irrigated water, with radish showing less susceptibility than spinach than those of bulk soils. The HT-qPCR analysis revealed that a total of 271 ARGs (out of 285) and 9 mobile genetic elements (MGEs) (out of 10) were detected in all samples. Higher diversity and abundance of ARGs were observed for samples irrigated with higher concentrations of antibiotics in both spinach and radish treatments. However, compared to spinach, radish ARG dynamics in the soil biome were more stable due to the change of antibiotic introduction to the soil. At the class level, multi -drug resistance (MDR) class was altered significantly by the presence of antibiotics in irrigation water. Compared to earthworm fecal samples, their corresponding soil environments showed a higher number of detected ARGs, suggesting that earthworms could play a role in reducing ARG dissemination in the soil environments. These findings will not only provide insight into the dissemination of ARGs in agricultural environments due to antibiotic residuals in irrigated water but could help understand the potential human health risks associated with ARGs.

Antimicrobial resistance (AMR) is a world-wide public health threat that is projected to lead to 10 million annual deaths globally by 2050. The AMR public health issue has led to the development of action plans to combat AMR, including improved antimicrobial stewardship, development of new antimicrobials, and advanced monitoring. The National Antimicrobial Resistance Monitoring System (NARMS) led by the United States (U.S) Food and Drug Administration along with the U.S. Centers for Disease Control and U.S. Department of Agriculture has monitored antimicrobial resistant bacteria in retail meats, humans, and food animals since the mid 1990’s. NARMS is currently exploring an integrated One Health monitoring model recognizing that human, animal, plant, and environmental systems are linked to public health. Since 2020, the U.S. Environmental Protection Agency has led an interagency NARMS environmental working group (EWG) to implement a surface water AMR monitoring program (SWAM) at watershed and national scales. The NARMS EWG divided the development of the environmental monitoring effort into five areas: (i) defining objectives and questions, (ii) designing study/sampling design, (iii) selecting AMR indicators, (iv) establishing analytical methods, and (v) developing data management/analytics/metadata plans. For each of these areas, the consensus among the scientific community and literature was reviewed and carefully considered prior to the development of this environmental monitoring program. The data produced from the SWAM effort will help develop robust surface water monitoring programs with the goal of assessing public health risks associated with AMR pathogens in surface water (e.g., recreational water exposures), provide a comprehensive picture of how resistant strains are related spatially and temporally within a watershed, and help assess how anthropogenic drivers and intervention strategies impact the transmission of AMR within human, animal, and environmental systems.

Identification of methods for the standardized assessment of bacterial pathogens and antimicrobial resistance (AMR) in environmental water can improve the quality of monitoring and data collected, support global surveillance efforts, and enhance the understanding of environmental water sources. We conducted a systematic review to assemble and synthesize available literature that identified methods for assessment of prevalence and abundance of bacterial fecal indicators and pathogens in water for the purposes of monitoring bacterial pathogens and AMR. After screening for quality, 175 unique publications were identified from 15 databases, and data were extracted for analysis. This review identifies the most common and robust methods, and media used to isolate target organisms from surface water sources, summarizes methodological trends, and recognizes knowledge gaps. The information presented in this review will be useful when establishing standardized methods for monitoring bacterial pathogens and AMR in water in the United States and globally.

The sequencing platform and workflow strongly influence microbial community analyses through potential errors at each step. Effective diagnostics and experimental controls are needed to validate data and improve reproducibility. This cross-laboratory study evaluates sources of variability and error at three main steps of a standardized amplicon sequencing workflow (DNA extraction, polymerase chain reaction [PCR], and sequencing) using Oxford Nanopore MinION to analyze agricultural soils and a simple mock community. Variability in sequence results occurs at each step in the workflow with PCR errors and differences in library size greatly influencing diversity estimates. Common bioinformatic diagnostics and the mock community are ineffective at detecting PCR abnormalities. This work outlines several diagnostic checks and techniques to account for sequencing depth and ensure accuracy and reproducibility in soil community analyses. These diagnostics and the inclusion of a reference soil can help ensure data validity and facilitate the comparison of multiple sequencing runs within and between laboratories. A soil bacterial amplicon sequencing study using the Nanopore MinION platform suggests that common diagnostics are insufficient to detect irregular community results and recommends further diagnostics and the use of a reference soil as a mock community.

Developing effective and sensitive detection methods for antimicrobial resistant Salmonella enterica from surface water is a goal of the National Antimicrobial Resistance Monitoring System (NARMS). There are no specified methods for recovery of S. enterica in surface waters in the U.S. A multi-laboratory evaluation of four methods - bulk water enrichment (BW), vertical Modified Moore Swab (VMMS), modified Standard Method 9260.B2 (SM), and dead-end ultrafiltration (DEUF) - was undertaken to recover S. enterica from surface water. In Phase 1, one-liter volumes of water were collected from the same site on five different dates. Water was shipped and analyzed at four different laboratory locations (A, B, C, and D) for recovery of 1) inoculated fluorescent S. Typhimurium strain (ca. 30 CFU/L) and 2) Salmonella present in the water sampled. At each location, BW, VMMS, or SM recovery was performed on five separate 1 L water samples. Twenty 1 L water samples were subjected to each recovery method, and overall, sixty 1 L samples were assayed for Salmonella. Inoculated, fluorescent Salmonella Typhimurium and environmental Salmonella spp. were recovered from 65 % (39/60) and 45 % (27/60) of water samples, respectively. BW, VMMS, and SM recovered fluorescent S. Typhimurium from 60 %, 60 %, and 75 % of inoculated samples, respectively. Analysis by Chi-squared test determined laboratory location had a significant (p < 0.05) effect on fluorescent S. Typhimurium recovery compared to method or date of water collection. In Phase 2, recovery of inoculated fluorescent S. Typhimurium from 1 L samples by SM and DEUF was compared at laboratory locations B and D. SM and DEUF recovered fluorescent S. Typhimurium from 100 % (20/20) and 95 % (19/20) of inoculated water samples, respectively; laboratory location (p > 0.05) did not affect Salmonella recovery. Uniform laboratory methodology and training should be prioritized in conducting Salmonella recovery from surface water in laboratories.

This study implemented biochars produced from two arid agricultural byproducts, date palm leaves and pistachio shells, at pyrolysis temperatures from 400 to 800 degrees C to remove trimethoprim, sulfamethoxazole and sulfapyridine antibiotics from mixed solutions. By altering pyrolysis temperature and feedstock, produced biochars yielded a range of physicochemical properties resulting in distinct antibiotic adsorption. Antibiotic adsorption capacity generally decreased with increasing pyrolysis temperature, while adsorption affinities were temperature independent for trimethoprim and increased with pyrolysis temperature for sulfamethoxazole and sulfapyridine. Correlation against biochar properties suggested cation exchange capacity and functional group composition related well to adsorption capacity and polarity/hydrophobicity was linked to adsorption affinities. Antibiotic removal efficiencies by biochars from both feedstocks compared favorably against previous reports, with up to 97.6, 98.1 and 99.5 % of trimethoprim, sulfamethoxazole and sulfapyridine removed, respectively. This work relates biochar production conditions to properties and subsequent antibiotic adsorption, demonstrating application of these materials for removing antibiotics from wastewater.

Soilborne pathogen infections are increasingly reported globally in recent years. Infectious agents have contaminated most of seasonal frozen zone and have been found in permafrost due to the effects of intensified human activities on global warming. Therefore, in regard to sustainable agriculture, it is particularly important to assess the environmental behavior of those pathogens in frozen soils. Due to high pathogenicity and low infection threshold, E. coli O157:H7 (EcO157) is a worldwide public health concern, and recent studies have focused more on its fate in the environment. The survival of this serotype in a large variety of environmental media under temperature above 0 °C has been investigated, while its persistence in frozen soils has received less attention. In this study, we collected soils with different textures from a seasonally frozen zone in northeast China and investigated the persistence of EcO157 in soils at freezing temperatures (−5 °C and −15 °C) and moisture content (30% and 60% water holding capacity (WHC)) of the soils. By fitting the survival data with a Weibull model, we obtained three parameters: first log reduction time (δ in days), survival curve shape parameters (p), and monthly average reduction in EcO157 (MAR, log·gdw−1·mon−1). The results showed that temperature has a major impact on persistence, while moisture content has less effect on the survival of EcO157. Further multi-variable analysis revealed that the physical and chemical properties (e.g., sand fraction) of soil play an important role in survival. Certain bacterial groups are significantly correlated with the survival of EcO157 in frozen soils at −5 °C but not for the ones incubated at −15 °C. Our data could provide background data to evaluate the health risk associated with EcO157. The results could be helpful to improve sustainable soil practices and to develop regulations and policies aiming to achieve sustainable agriculture.

The increased recycling of treated municipal wastewater (TMW) to agricultural land is potentially hampered by the presence of antibiotic compounds, which may lead to the spread of antibiotic resistance. Biochar-based adsorption has been widely assessed as a means of polishing TMW to remove antibiotics prior to use; however, relatively little is known about how acid and base modification of biochar impacts its antibiotic retention capabilities, especially under the dynamic (flow-through) conditions inherent in proposed polishing systems. Using small columns of sand mixed with dairy manure or rice husk biochars (initial pH = 8.48 and 8.91, respectively) modified with acid or base, the retention of trimethoprim (TMP), sulfamethoxazole (SMZ), and sulfapyridine (SPD) was assessed. For SMZ and SPD, retention by the columns was consistently markedly lower than that measured in batch studies, indicating that equilibrium data may overestimate the retention of more realistic (dynamic) systems. TMP was completely retained by all biochars under both conditions. In columns, SMZ retention was strongly controlled by its pH-dependent speciation (greater retention at low pH, i.e., in acid modified biochars). SPD retention was strongly controlled by biochar surface area, which was markedly increased in the acid-modified dairy manure biochar and base-modified rice husk biochar. The findings indicate that acid or base modification of certain biochars may improve retention of sulfonamide antibiotics (which are known to be particularly difficult to remove from TMW) even under dynamic conditions. Biochar-based polishing systems comprising such biochars may offer potential in mitigating the spread of antibiotics, and hence antibiotic resistance, in agricultural settings.

Livestock manure, dairy lagoon effluent, and treated wastewater are known reservoirs of antibiotic resistance genes (ARGs), antibiotic-resistant bacteria (ARB), and virulence factor genes (VFGs), and their application to agricultural farmland could be a serious public health threat. However, their dissemination to agricultural lands and impact on important geochemical pathways such as the nitrogen (N) cycle have not been jointly explored. In this study, shotgun metagenomic sequencing and analyses were performed to examine the diversity and composition of microbial communities, ARGs, VFGs, and N cycling genes in different livestock manure/lagoon and treated wastewater collected from concentrated animal feeding operations (CAFOs) and a municipal wastewater treatment plant along the west coast of the United States. Multivariate analysis showed that diversity indices of bacterial taxa from the different microbiomes were not significantly different based on InvSimpson (P = 0.05), but differences in ARG mechanisms

Treated municipal wastewater (TMW) can provide a reliable source of irrigation water for crops, which is especially important in arid areas where water resources are limited or prone to drought. Nonetheless, TMW may contain residual antibiotics, potentially exposing the crops to these substances. The goal of this study was to investigate the dissemination of antibiotics resistance genes (ARGs) in the soil-plant-earthworm continuum after irrigation of spinach and radish plants with TMW containing trimethoprim, sulfamethoxazole, and sulfapyridine in a greenhouse experiment, followed by feeding of earthworms with harvested plant materials. Our results showed that antibiotic resistance genes (ARGs) were enriched in the soil-plant-earthworm microbiomes irrigated with TMW and TMW spiked with higher concentrations of antibiotics. The number of ARGs and antibiotic-resistant bacteria (ARB) enrichment varied with plant type, with spinach harboring a significantly higher amount of ARGs and ARB compared to radish. Our data showed that bulk and rhizosphere soils of spinach and radish plants irrigated with MilliQ water, TMW, TMW10, or TMW100 had significant differences in bacterial community (p < 0.001), ARG (p < 0.001), and virulence factor gene (VFG) (p < 0.001) diversities. The abundance of ARGs significantly decreased from bulk soil to rhizosphere to phyllosphere and endosphere. Using metagenome assembled genomes (MAGs), we recovered many bacterial MAGs and a near complete genome (>90 %) of bacterial MAG of genus Leclercia adecarboxylata B from the fecal microbiome of earthworm that was fed harvested radish tubers and spinach leaves grown on TMW10 irrigated waters, and this bacterium has been shown to be an emerging pathogen causing infection in immunocompromised patients that may lead to health complications and death. Therefore, crops irrigated with TMW containing residual antibiotics and ARGs may lead to increased incidences of enrichment of ARB in the soil-plant-earthworm continuum.

2In this study, we investigated the persistence of Salmonella Typhimurium in 26 soil samples from apple-pear orchards in Yanji, Longjing and Helong in northeastern China. The time to reach detection limit (ttds) of Salmonella Typhimurium in soils varied from 20 to 120 days. Redundancy analysis and variation partition analysis elucidated that bacterial communities, clay content, pH, electrical conductivity (EC) salinity, and NO3--N could explain more than 85% of overall variation of the persistence behaviors. Results of structural equation models and Mantel tests revealed that clay content and EC displayed both direct and indirect effect on ttds, while NO3--N and pH exhibited direct and indirect effect on the survival patterns, respectively. Furthermore, Actinobacteria, Acidobacteria and Deltaproteobacteria at class level showed highly close correlations with ttds. Our results revealed that certain biotic and abiotic factors could greatly contribute to the overall persistence of Salmonella in apple-pear orchard soils.

Antimicrobial resistance associated with the spread of plasmid-encoded extended-spectrum β-lactamase (ESBL) genes conferring resistance to third generation cephalosporins is increasing worldwide. However, data on the population of ESBL producing E. coli in different animal sources and their antimicrobial characteristics are limited. The purpose of this study was to investigate potential reservoirs of ESBL-encoded genes in E. coli isolated from swine, beef, dairy, and poultry collected from different regions of the United States using whole-genome sequencing (WGS). Three hundred isolates were typed into different phylogroups, characterized by BOX AIR-1 PCR and tested for resistance to antimicrobials. Of the 300 isolates, 59.7% were resistant to sulfisoxazole, 49.3% to tetracycline, 32.3% to cephalothin, 22.3% to ampicillin, 20% to streptomycin, 16% to ticarcillin; resistance to the remaining 12 antimicrobials was less than 10%. Phylogroups A and B1 were most prevalent with A (n = 92, 30%) and B1 (87 = 29%). A total of nine E. coli isolates were confirmed as ESBL producers by double-disk synergy testing and multidrug resistant (MDR) to at least three antimicrobial drug classes. Using WGS, significantly higher numbers of ESBL-E. coli were detected in swine and dairy manure than from any other animal sources, suggesting that these may be the primary animal sources for ESBL producing E. coli. These isolates carry plasmids, such as IncFIA(B), IncFII, IncX1, IncX4, IncQ1, CollRNAI, Col440I, and acquired ARGs aph(6)-Id, aph(3″)-Ib, aadA5, aph(3′)-Ia, blaCTX-M-15, blaTEM-1B, mphA, ermB, catA1, sul1, sul2, tetB, dfrA17. One of the E. coli isolates from swine with ST 410 was resistant to nine antibiotics and carried more than 28 virulence factors, and this ST has been shown to belong to an international high-risk clone. Our data suggests that ESBL producing E. coli are widely distributed in different animal sources, but swine and dairy cattle may be their main reservoir.

Pharmaceutical wastewaters are recognized as reservoirs of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB), and also as hotspots for their horizontal gene transfer (HGT) using mobile genetic elements. Our study employed the use of PCR analysis of metagenomic DNA samples obtained from four pharmaceutical wastewaters using known primers to study the prevalence of thirty-six ARGs and four MGEs active against the commonly used antibiotics in Nigeria. The ARGs most frequently detected from the metagenomic DNA samples in each of the antibiotic classes under study include tetracycline [tet(G)], aminoglycoside [aadA, strA and strB], chloramphenicol [catA1], sulphonamides [sulI and sulII], and β-lactams and penicillins [blaOXA]. The ARGs showed a 100% prevalence in their various environmental sources. The pharmaceutical facility PFIV showed the highest concentration of ARGs in this study. The highest concentration for MGEs was shown by pharmaceutical facility PFIII, positive for intl1, intl2, and IFS genes. This study highlights the wide distribution of ARGs to the antibiotics tested in the wastewater, making pharmaceutical wastewater reservoirs of ARGs which could potentially be transferred from commensal microorganisms to human pathogens.

Background: Utilization of animal wastes in algal culture has proven to be challenging. The utilization of “free” nutrients has drawn researchers and industry to develop business models that call for the use of these free nutrients, which comes at a cost. Some of these costs include reduced productivity, increased contamination, lower value target markets, and lower treatment capabilities (for wastewater treatment applications). This paper evaluates the impact of dairy lagoon effluent on productivity and wastewater treatment ability. Methods: Screened dairy lagoon wash water was fed to four three square meter outdoor open paddlewheel algal cultivation reactors. The units were operated semi-continuously for one and a half years. Seasonal productivity and nutrient uptake rates, for nitrogen (N) and phosphorous (P) were measured against wastewater dilution requirements. Seasonal algal species dominance was also recorded. Wastewater was added at two levels, and the lower level was supplemented with synthetic fertilizer. Results: Seasonal N uptake rates ranged from 0.5 to 1.2 grams of N uptake per square meter per day, while P uptake ranged from 0.17 to 0.3 grams of P per square meter per day depending on season and Hydraulic Residence Time (HRT). N removal efficiency ranged at 40 to 70% for semicontinuous operation, depending on HRT, season, and dilution of influent wastewater, which was made up from 1.5% to 13% of the daily water exchange. Conclusion: Algal reactors tended to be N limited due to the inability to add enough dairy wastewater to mitigate the high turbidity and dark color. Treatments with lower levels of added dairy wastewater tended to show higher nutrient removal. Algal culture from dairy wash water could benefit from a pretreatment step to reduce turbidity and color, thereby promoting algal growth and productivity.