Septic Effluent Research Articles

Modeling Escherichia coli concentrations for health risk analysis in the Three Gorges Reservoir Region, Chongqing, China

Escherichia coli (E. coli), a typical fecal coliform, can enter surface rivers through daily wastewater and septic effluents, as well as the use of fecal fertilizers. Pathogenic strains of E. coli pose a significant public health risk. Despite China’s rapid economic and social development, sanitation and watershed management still face challenges. In this study, we employ a combined model of the Soil and Water Assessment Tool and Quantitative Microbial Risk Assessment to predict pollution changes, considering social development and climate change. Our aim is to quantify the risks and assess pollution prevention strategies for E. coli in the Three Gorges Reservoir (TGR) region. The results indicated that under moderate development, the average E. coli concentrations and disease burdens were 367 ± 75 CFU/100 mL and 23.4 (95 % Confidence Interval (CI): 2.8–72.6) Disability-Adjusted Life Years (DALYs, per 1,000,000 population per year), respectively. Under rapid development, these values were 330 ± 58 CFU/100 mL and 21.2 (95 % CI: 2.6–65.1) DALYs, respectively. Implementing a point strategy, mainly increasing sewage collection rates, could reduce E. coli concentrations by approximately 30 % and disease burdens by 27–28 %. For a diffuse strategy, primarily extending composting duration, reductions of 9 % in E. coli concentrations and 7–8 % in disease burdens were observed. Combining both strategies resulted in a 40 % decrease in E. coli concentrations and 35–36 % reduction in disease burdens. This model, incorporating social development, climate change, and microbial risk, provides insights into predicting pollution changes and evaluating the effectiveness of prevention strategies for E. coli in the TGR region and similar watersheds.

Local factors and sources affecting freshwater chloride concentrations in the Toronto region

Increasing chloride concentrations in freshwater streams throughout many areas of North America have raised concern over freshwater salinization. Road salt has been implicated; however, chloride source identification is lacking in the Toronto region. We assessed trends in chloride concentrations in streams and groundwater between 2000 and 2021 within the Toronto region and identified factors contributing to trends. Chloride concentrations increased in 36 of 47 streams and in 5 of 13 groundwater wells. There were no significant relationships between changes in stream chloride concentrations and changes in winter climatic conditions over the study period; however, changes in stream chloride concentrations were positively related to changes in road density. Chloride:bromide ratios indicated that road salt and/or septic effluent was the dominant source of chloride in streams. Inputs varied throughout the year with road salt and/or septic effluent having a higher proportion of inputs during the salting season compared to the non-salting season where a higher proportion of inputs were from basin brines and/or animal waste, landfill leachate, and pristine aquifer. Commercial, industrial, institutional, and medium density residential land uses were also positively correlated with stream chloride. Parking lot cover increased in several catchments suggesting that these too may contribute to trends. These results highlight the importance of continued and enhanced investment in long-term monitoring of freshwater ecosystems. It also highlights the need for urgent action to better control and monitor road salt usage by public and private applicators since urban growth continues to drive increasing chloride trends.

Antimicrobial Resistance Linked to Septic System Contamination in the Indiana Lake Michigan Watershed.

Extended-spectrum β-lactamases confer resistance to a variety of β-lactam antimicrobials, and the genes for these enzymes are often found on plasmids that include additional antimicrobial resistance genes (ARG). We surveyed aquatic environments in the Indiana Lake Michigan watershed in proximity to areas with high densities of residential septic systems to determine if human fecal contamination from septic effluent correlated with the presence of antimicrobial resistance genes and phenotypically resistant bacteria. Of the 269 E. coli isolated from environmental samples and one septic source, 97 isolates were resistant to cefotaxime, a third-generation cephalosporin. A subset of those isolates showed phenotypic resistance to other β-lactams, fluoroquinolones, sulfonamides, and tetracyclines. Quantitative PCR was used to quantify human-associated Bacteroides dorei gene copies (Human Bacteroides) from water samples and to identify the presence of ARG harbored on plasmids from E. coli isolates or in environmental DNA. We found a strong correlation between the presence of ARG and human fecal concentrations, which supports our hypothesis that septic effluent is a source of ARG and resistant organisms. The observed plasmid-based resistance adds an additional level of risk, as human-associated bacteria from septic systems may expand the environmental resistome by acting as a reservoir of transmissible resistance genes.

Optimizing Scale for Decentralized Wastewater Treatment: A Tool to Address Failing Wastewater Infrastructure in the United States

Wastewater systems (sewered or on-site septic tanks) are failing across the U.S. Economically disadvantaged populations, communities of color, tribal lands, and rural/peri-urban areas are especially vulnerable. Efficient deployment of public and private capital to assure appropriate service levels and affordability is a critical need. We present a modeling framework to identify economically optimal wastewater network layout and component sizes. Six system configurations are considered, which include gravity versus pressurized collection system flow and treatment of septic effluent versus raw wastewater. A case study for Uniontown, Alabama─a community that has been in national news for the failure of their wastewater infrastructure─is presented. We find that a decentralized network that separates and stores solids on-site, prior to conveyance to a cluster-scale treatment site, has a fraction of the capital and operating cost of a centralized system that is currently proposed. Broader implications are discussed.

Septic system-groundwater-surface water couplings in waterfront communities contribute to harmful algal blooms in Southwest Florida.

As human population growth has expanded in Southwest Florida, water quality has become degraded with an increased occurrence of harmful algal blooms (HABs). Red tide (Karenia brevis) originating offshore, intensifies in nearshore waters along Florida's Gulf Coast, and blue-green algae (Microcystis spp.) originating in Lake Okeechobee is discharged into the Caloosahatchee River. These HABs could be enhanced by anthropogenic nitrogen (N) and phosphorus (P) from adjacent watersheds. North Fort Myers is a heavily developed, low-lying city on the Caloosahatchee River Estuary serviced by septic systems with documented nutrient and bacterial pollution. To identify sources of pollution within North Fort Myers and determine connections with downstream HABs, this multiyear (2017-2020) study examined septic system- groundwater- surface water couplings through the analysis of water table depth, nutrients (N, P), fecal indicator bacteria (FIB), molecular markers (HF183, GFD, Gull2), chemical tracers (sucralose, pharmaceuticals, herbicides, pesticides), stable isotopes of groundwater (δ15N-NH4, δ15N-NO3) and particulate organic matter (POM; δ15N, δ13C), and POM elemental composition (C:N:P). POM samples were also collected during K. brevis and Microcystis spp. HAB events. Most (>80%) water table depth measurements were too shallow to support septic system functioning (<1.07 m). High concentrations of NH4+ and NOx, up to 1094 μM and 482 μM respectively, were found in groundwater and surface water. δ15N values of groundwater (+4.7‰) were similar to septic effluent (+4.9‰), POM (+4.7‰), and downstream HABs (+4.8 to 6.9‰), indicating a human waste N source. In surface water, FIB were elevated and HF183 was detected, while in groundwater and surface water sucralose, carbamazepine, primidone, and acetaminophen were detected. These data suggest that groundwater and surface water in North Fort Myers are coupled and contaminated by septic system effluent, which is negatively affecting water quality and contributing to the maintenance and intensification of downstream HABs.

Variation in septic system effluent inputs to tributaries in multiple subwatersheds and approaches to distinguish contributing pathways and areas

Quantifying the contribution of septic systems to contaminant, including nutrient, loading to streams is needed in many watersheds to inform water quality management programs. However, this quantification is challenging due to the distributed locations of septic systems and uncertainties regarding the pathways delivering effluent from septic systems (functioning and failing) to a stream. The objectives of this study were firstly to evaluate how septic effluent inputs to streams vary with stream discharge conditions for multiple subwatersheds with different characteristics (i.e., geology, septic system density, and typical age), and secondly to examine new approaches for distinguishing the pathways and the contributing areas delivering septic effluent to streams. These approaches use the artificial sweetener acesulfame as a conservative tracer for septic effluent in applications of: (i) stream concentration-discharge (C-Q) relationships using low frequency sampling data, (ii) hysteresis behavior in event-based C-Q relationships, and (iii) longitudinal stream sampling. For all nine subwatersheds studied, the amount of septic effluent reaching the subwatershed outlets was considerably higher during high stream discharge (event) conditions compared to low discharge (baseflow) conditions, suggesting pathways other than groundwater may also be important. Generally, the percentage of septic effluent reaching the outlets was less for subwatersheds with newer households compared to those with older households. The combined interpretation of low frequency and event-based C-Q relationships indicate that complex pathways control the delivery of septic effluent to the subwatershed outlets. The interpretations suggest that groundwater pathways may dominate in some subwatersheds, while more rapid pathways associated with failing septic systems (e.g., overland runoff) may be important in others. Finally, longitudinal stream sampling illustrate the potential of acesulfame data to identify key areas contributing septic effluent to the stream. The novel approaches used here can be applied to guide future investigations aiming to quantify and manage water quality impairment from septic systems.

Comparative evaluation of the macrophytes in the constructed wetlands for the treatment of combined wastewater (greywater and septic tank effluent) in a sub-tropical region

The role of macrophytes in constructed wetlands (CW) has been studied extensively in the last three decades. The remediating effect of macrophytes in CWs depends on whether the species is suitable for the given climatic and operational conditions and on the morphological traits of the species. This study experimentally investigated and compared the contribution of three macrophytes, namely Phragmites karka, Iris kashmiriana, and Sagittaria latifolia in removing pollutants from combined wastewater (greywater and septic effluent) using horizontal sub-surface flow type constructed wetlands (HSSF-CW) under sub-tropical conditions. The study monitored the standard wastewater parameters (COD, Nitrogen, Phosphorus, and Solids) in the inlet and outlet of the CW microcosms, the fate of nutrients through the planted microcosms, and the growth rate of the selected species. Phragmites karka showed better removal efficiencies than the other two species, with organic loading removal rates of 10 ± 1.3 gm−2d−1, nitrogen removal rates of 2.6 ± 0.4 gm−2d−1, phosphorus removal rates of 1.3 ± 0.2 gm−2d−1, and solids removal rates of 3.6 ± 1.2 gm−2d−1. Mass balance showed that the nutrient uptake by species Sagittaria latifolia (TP – 9.3 g and TN – 48.2 g) was the most, followed by Phragmites karka (TP – 8.6 g and TN – 47.9 g) and Iris kashmiriana (TP – 4.4 g and TN – 29.1 g). Biomass analysis revealed that Phragmites karka had the maximum biomass growth rate with an increment of 1383 gm−2: 524 gm−2 in the above-ground: below ground dry biomass weight, while as Sagittaria latifolia and Iris kashmiriana showed an increase of 1299 gm−2: 866 gm−2 and 663 gm−2: 1312 gm−2, respectively. The macrophytes with well-developed root systems (Phragmites karka) had a better pollutant remediating effect. The nutrient uptake by macrophytes depended on the total dry biomass increase and the nutrient content of the biomass. The CW beds of the three macrophytes need nutrient pre- or post-treatment to comply with the irrigation reuse and conventional sewage treatment plant (STP) discharge regulations in India.

Growth of Chlorella pyrenoidosa on different septic tank effluents from rural areas for lipids production and pollutants removal

Septic tank effluent from rural areas was an ideal medium for cultivating oleaginous microalgae. However, the characteristics of septic tank effluents varied greatly due to the different incoming wastewater, and bring uncertain risks for algal growth. In this study, an oleaginous microalgae was cultivated in septic effluents from different mixed wastewater. The results showed that the effluent from pure toilet wastewater was the best medium to achieve the highest biomass yield (1.68 g·L-1) and productivity (154.6 mg·L-1·d-1). In contrast, the discharge of kitchen or laundry wastewater reduced the biomass production by 50.5–79.1%. That caused much lower lipids production in effluents from mixed wastewater regardless of its high lipids content and saturation degree. The results suggest that the discharge of kitchen or laundry wastewater bring risks for biomass and lipids production, and should be separated from the toilet wastewater before entering into septic tank.

Estimation of phosphorus loads from septic systems to tributaries in the Canadian Lake Erie Basin

The contribution of septic systems to watershed nutrient loads is poorly quantified although they are often cited as potentially important nutrient sources. The study used a geospatial model to estimate P loads from septic systems to the tributaries of the Canadian Lake Erie Basin to inform Lake Erie nutrient management initiatives. There is currently no inventory of septic systems in the Lake Erie Basin (e.g., numbers and locations of septic systems). Therefore a geospatial model was developed to automatically locate individual septic systems and to use these locations to estimate P load contributions to tributaries. The model was first tested on three subwatersheds in the Canadian Lake Erie Basin before being applied across the Basin. Present-day basin-wide P load estimates reveal that: (i) only a fraction of septic effluent is currently reaching the tributaries due to slow transport and other delays, as well as (ii) P attenuation in the subsurface, range from 23 ± 11 to 68 ± 32 MT/yr. Based on these estimates, septic systems may currently contribute 1.7 ± 0.8–5 ± 2.3% of the P loads to Lake Erie from Canada. However, maximum P load estimates and transient model results show that the contribution of septic systems to P loads will increase over time as slow moving septic-derived groundwater P plumes reach tributaries if aging septic systems are not maintained. This study provides widely applicable new knowledge and methodology; as well as specific findings needed to inform nutrient and septic system management in the Lake Erie Basin.

Investigating the use of the artificial sweetener acesulfame to evaluate septic system inputs and their nutrient loads to streams at the watershed scale

Septic systems are often cited as an important contributor to rural watershed nutrient loads despite limited quantitative evidence regarding their actual contribution. The measurement of the artificial sweetener acesulfame in streams to quantify upstream inputs of septic system effluent has recently been proposed. However, there is a lack of detailed study on this application, including temporal variability, influence of dry and wet weather conditions, and disentangling the contributions from functioning versus failing septic systems. Further, this approach has not been applied to assess the relative contribution of septic systems to nutrient watershed loads. Here we conducted artificial sweetener and nutrient stream measurements in three watersheds with no other identified sources of acesulfame (e.g., no municipal wastewater treatment plants, landfills) over a 10-month period. Measured acesulfame stream concentrations varied from below detection (<2 ng/L) to 87 ng/L with acesulfame stream loads revealing that septic system inputs to streams vary considerably between low and high stream discharge conditions. Positive acesulfame concentration-stream discharge relationships for all three watersheds reveal the potentially important contributions from failing septic systems and surface flow pathways (i.e., effluent breakout from septic drain field) under high discharge conditions. Further they indicate that, contrary to conventional thinking, sampling under low discharge conditions may underestimate septic effluent delivery to streams. The estimated contribution of septic systems to measured total phosphorus stream loads on a given sampling day varied widely (<1–36%, considering attenuation between the septic tank and stream), but typically septic system contributions to nitrate stream loads were low (<2%). The findings provide guidance on the application of this new tool for managing septic effluent contributions of nutrients and other wastewater contaminants to rural watershed streams.

Nitrate contamination of groundwater in the Lower Volta River Basin of Ghana: Sources and related human health risks.

A significant population within the Lower Volta River Basin of Ghana relies solely on untreated groundwater (GW) and surface water (SW) for various purposes. However, negative practices associated with increasing human activities pose threats to particularly GW quality in the basin. Using NO3- as a proxy, this study mainly focused on the status of GW contamination, origins of NO3- and potential human health risks through integrated hydrochemistry, correlation analysis, isotopes (15N, δ18O), Bayesian and USEPA human health risk models. Slightly acidic to alkaline GW and SW environments were observed. Electrical conductivity (EC) values above 1000μS/cm were recorded in 45% of the GW with a maximum of 19370μS/cm. NO3- in GW ranged from 0.12 to 733mg/L with average 59.6mg/L and positively correlated with K+, Ca2+, Mg2+, Cl-, Na+ and EC. In SW, a maximum of 5.3mg/L of NO3- was observed. Largely, 75% of the GW exceeded local background NO3- value of 2.1mg/L, while 35% were above the WHO recommended value of 50mg/L. Bivariate and correlation relationships elucidated human contributions to sources of NO3-, Cl-, SO42- and K+ to GW in the basin. From NO3-/Cl- ratio, 43% of the GW and 21% of SW were affected by effluents and agrochemicals. Values for δ15N-NO3- and δ18O-NO3- ranged from +4.2‰ to +27.5‰ and +4.5‰ to +19.9‰ for GW, and from +3.8‰ to +14.0‰ and +10.7‰ to +25.2‰ for SW. Manure, septic effluents and mineralized fertilizers are sources of NO3- contamination of water in the basin. The Bayesian model apportioned 80% of GW NO3- contamination to sewage/manure. Hazard index indicated 70%, 50% and 48% medium to high-risk levels for infants, children and adults respectively, with 79% high-risk of SW NO2- contamination to infants. Immediate measures for GW and SW quality protection are recommended.

Septic systems contribute artificial sweeteners to streams through groundwater

Artificial sweeteners are ubiquitous constituents of sanitary wastewater and are not completely attenuated by wastewater treatment processes. Consequently, artificial sweeteners are increasingly employed as a tool to detect wastewater and help evaluate its impact on aquatic environments. In rural areas, septic systems are known point sources of artificial sweeteners to groundwater, however the potential contribution of artificial sweeteners to streams via this pathway is unknown. We analyzed 294 samples from 173 stream sites in Southern Ontario, Canada, for acesulfame, saccharin, cyclamate, and sucralose, and found that 91% had one or more of these compounds present. The stream sites sampled did not have municipal wastewater treatment plants upstream and therefore septic system effluent was the most likely source of the artificial sweeteners. Acesulfame, which is the most recalcitrant of the four artificial sweeteners, was by far the most ubiquitous in streams, with a 91% detection frequency, compared to 27, 8, and 3% for saccharin, cyclamate, and sucralose, respectively. Stream concentrations ranged from non-detectable to maximum values of 225, 380, 204, and 291 ng/L for acesulfame, saccharin, cyclamate, and sucralose, respectively. We calculated that water from septic effluent contributed from <0.005% to 0.5% of streamflow, with a median value of 0.052%. This is the first study to use artificial sweetener concentrations to quantify the fraction of septic effluent reaching streams via groundwater flow. Using acesulfame concentrations, we calculated that approximately 13% of the septic effluent water generated in rural Southern Ontario eventually ends up in local streams, however this is likely a conservative estimate. Although much of the septic effluent water that reaches streams may be free of all but the most persistent anthropogenic compounds, our study demonstrates that domestic wastewater must be considered as a possible source of stream contaminants, even if municipal wastewater is not a factor in the watershed.

Hazard Identification and Risk Assessment-Based Water Safety Plan for Packaged Water Production Companies in Abeokuta, South West Nigeria

Provision of quality drinking water is paramount for sustaining good public health in urban residents. Packaged water produced and consumed across cities in Nigeria lacks integrity in protecting Health. Water safety plan based on hazard identification and risk assessment in each component of the water production system is essential in providing quality water by packaged water producing companies in Nigeria. This study aims at developing water safety plan for selected packaged water manufacturing companies in Abeokuta, Ogun State, Nigeria. Hazard identification and risk assessment were carried out based on site inspection studies, key informant interview, questionnaire survey and water sample analysis, and risk analysis using semi-quantitative risk matrix approach. The results revealed a total of 26 possible hazardous events which may compromise water quality such as on-site septic tanks and effluents discharged at source water and improper maintenance and hygiene practices within the system. Based on these, appropriate mitigation and monitoring plans were drawn for action. The research found that water safety plan is feasible for the packaged water systems, and therefore calls on the relevant stakeholders for urgent implementation towards ensuring clean drinking water and protecting public health as more and more people are opting for packaged waters due to uncertain public water safety.

Differentiation of Surface Water and Groundwater in a Karst System Using Anthropogenic Signatures

Surface water–groundwater interaction within a karstic system enhances contaminant transport, making karst aquifers susceptible to anthropogenic practices. Contaminated waters related to agricultural and animal husbandry in northwestern Illinois (USA) prompted this investigation. Six streams and five springs were sampled for 16 parameters to assess anthropogenic influences. Statistical analyses revealed differences in 13 of 16 parameters between the stream and spring waters. Rock–water interaction was identified as the dominant mechanism defining the chemistry for both waters, which were classified as Ca-Mg HCO3. Elevated nitrate as nitrogen (NO3-N), chloride (Cl−), sodium, and potassium concentrations indicate that human activities have influenced the quality of both water types. All streams and springs had NO3-N concentration exceeding background levels, with concentrations ranging from 2.9 to 14.5 mg/L and 2.9 to 30.1 mg/L, respectively. NO3-N/Cl relationships at individual locations showed elevated concentrations of NO3-N due to fertilizers, while the spring waters were influenced by manure, septic effluent, or mixed sources. The presence of coliform supports the likelihood of animal or human waste influences on waters. Dissimilarities within their chemical fingerprints can be traced to aid in differentiating sources within the waters.

Microplastic Contamination in Karst Groundwater Systems.

Groundwater in karst aquifers constitutes about 25% of drinking water sources globally. Karst aquifers are open systems, susceptible to contamination by surface-borne pollutants. In this study, springs and wells from two karst aquifers in Illinois, USA, were found to contain microplastics and other anthropogenic contaminants. All microplastics were fibers, with a maximum concentration of 15.2 particles/L. The presence of microplastic was consistent with other parameters, including phosphate, chloride and triclosan, suggesting septic effluent as a source. More studies are needed on microplastic sources, abundance, and impacts on karst ecosystems.

Coupled hydrogeochemical evaluation of a vulnerable karst aquifer impacted by septic effluent in a protected natural area

Karst aquifers are highly vulnerable to pollution from human activities. Among sources of these contaminants, septic tank effluent can easily pollute karst aquifers, especially concentrated inputs such as those, for example, from tourist hotels. However, the impacts of septic effluent from relatively large, concentrated inputs on karst aquifers have seldom been assessed previously and therefore provide the focus of this study. Artificial tracer tests, geochemical analysis, and dual nitrate stable isotopes were employed to evaluate the impacts of a concentrated input of septic effluent from the Jinfoshan Holiday Hotel (JHH) on the vulnerable Shuifang Spring (SFS) karst aquifer in a remote mountainous area, the Jinfoshan Karst World Heritage Site within Chongqing Municipality of southwest China. The results of artificial tracer tests showed that the underground flow mainly occurred in a primary conduit with a pooled or bifurcated flow path that connects a sinkhole input to SFS. The high tracer recovery rates suggest that the karst aquifer was characterized by high intrinsic vulnerability to contamination. Chemographs at SFS responded rapidly to the episodic release of effluent from JHH. Decreased pH and dissolved oxygen and elevated turbidity, specific conductance and NH4+ concentrations of SFS resulted from the episodic release of septic tank effluent from the JHH during high-use periods. Although the nitrate concentrations were far below the guideline value of the Standard for Groundwater Quality of China, the isotopes of δ15NNO3 and δ18ONO3 suggest that nitrate flowing from SFS was primarily derived from manure and sewage, in addition to soil organic N. Thus, episodic release of septic effluent provides a challenge to the sustainability of karst groundwater management. The results of this study may be relevant to other remote and mountainous karst environments where tourism provide otherwise scarce economic resources and particularly to protected sites throughout the world.

Impact of hotel septic effluent on the Jinfoshan Karst aquifer, SW China

The karst aquifer of Jinfoshan Karst (JFK) in UNESCO’s South China Karst World Heritage Site was investigated. An artificial tracer test, geochemistry, and oxygen and hydrogen isotopes were employed to assess the impacts of effluent from the Jinfoshan Holiday Hotel (JHH), Chongqing, on the karst aquifer and its outlet, Shuifang spring (SFS). Most of the fluorescent dye (uranine) flushed into a JHH toilet was recovered at SFS, suggesting a strong hydraulic connection between JHH and SFS. The waters of SFS were of HCO3–Ca type, whereas the effluent had more complex hydrochemical characteristics. The effluent was characterized by higher mean δD and δ18O values. The slope of the δD–δ18O evaporation line for effluent was significantly lower than that of the local meteoric water line, indicating evaporation. Concentrations of major elements at SFS were below the threshold values of the Chinese Standard for Groundwater Quality. However, hydrogen and oxygen isotopic compositions of SFS waters were influenced by the effluent and mixing with water from diffuse sources within the aquifer. Low values of d-excess at SFS corresponded well to periods of high tourism activity (weekends and holidays), suggesting that declining d-excess probably signifies an increased release of contaminants from the hotel. The contribution of effluent to the discharge of the SFS was ~18%. Because of tourism activities and their production of wastewater, the results of this study may be relevant to other karst environments and World Heritage Sites throughout the world.

Influence of septic system wastewater treatment on titanium dioxide nanoparticle subsurface transport mechanisms.

Engineered nanomaterials (ENMs) are commonly incorporated into food and consumer applications to enhance a specific product aspect (i.e., optical properties). Life cycle analyses revealed ENMs can be released from products during usage and reach wastewater treatment plants (WWTPs), with titanium dioxide (TiO2) accounting for a large fraction. As such, food grade (FG) TiO2, a more common form of TiO2 in wastewater, was used in this study. Nanomaterials in WWTPs have been well characterized, although the problematic septic system has been neglected. Elution and bioaccumulation of TiO2 ENMs from WTTPs in downriver sediments and microorganisms has been observed; however, little is known about mechanisms governing the elution of FG TiO2 from the septic drainage system. This study characterized the transport behavior and mechanisms of FG TiO2 particles in porous media conditions after septic waste treatment. FG and industrial grade (IG) TiO2 (more commonly studied) were introduced to septic tank effluent and low-ionic strength electrolyte solutions prior to column transport experiments. Results indicate that FG TiO2 aggregate size (200-400nm) remained consistent across solutions. Additionally, elution of FG and IG TiO2 was greatest in septic effluent at the higher nanoparticle concentration (100ppm). FG TiO2 was well retained at the low (2ppm) concentration in septic effluent, suggesting that particles that escape the septic system may still be retained in drainage field before reaching the groundwater system, although eluted particles are highly stabilized. Findings provide valuable insight into the significance of the solution environment at mediating differences observed between uniquely engineered nanomaterials. Graphical abstract.

Impacts of a Rural Subdivision on Groundwater Quality: Results of Long-Term Monitoring.

A rural subdivision in south central Wisconsin was instrumented with monitoring wells and lysimeters before, during, and after its construction to examine the impacts of the unsewered subdivision on groundwater quality and quantity. Prior to construction, the 78-acre (32 ha) site was farmland. Sixteen homes were constructed beginning in 2003. Initial monitoring from 2002 to 2005 showed that groundwater beneath the site had been impacted by previous agricultural use, with nitrate-N values as high as 30 mg/L and some detections of the herbicide atrazine. Our 12-year study shows that the transition from agricultural to residential land use has changed groundwater quality in both negative and positive ways. Although groundwater elevations showed typical seasonal fluctuations each year, there were no measurable changes in groundwater levels or general flow directions during the 12-year study period. Chloride values increased in many wells, possibly as a result of road salting or water softener discharge. Nitrate concentrations varied spatially and temporally over the study period, with some initial concentrations substantially above the drinking water standard. In some wells, nitrate and atrazine levels have declined substantially since agriculture ceased. However, atrazine was still present at trace concentrations throughout the site in 2014. Wastewater tracers show there are small but detectable impacts from septic effluent on groundwater quality. Particle traces based on a groundwater flow model are consistent with the hypothesis that septic leachate has impacted groundwater quality.

Temporal and spatial variation in pharmaceutical concentrations in an urban river system

Many studies have quantified pharmaceuticals in the environment, few however, have incorporated detailed temporal and spatial variability due to associated costs in terms of time and materials. Here, we target 33 physico-chemically diverse pharmaceuticals in a spatiotemporal exposure study into the occurrence of pharmaceuticals in the wastewater system and the Rivers Ouse and Foss (two diverse river systems) in the city of York, UK. Removal rates in two of the WWTPs sampled (a conventional activated sludge (CAS) and trickling filter plant) ranged from not eliminated (carbamazepine) to >99% (paracetamol). Data comparisons indicate that pharmaceutical exposures in river systems are highly variable regionally, in part due to variability in prescribing practices, hydrology, wastewater management, and urbanisation and that select annual median pharmaceutical concentrations observed in this study were higher than those previously observed in the European Union and Asia thus far. Significant spatial variability was found between all sites in both river systems, while seasonal variability was significant for 86% and 50% of compounds in the River Foss and Ouse, respectively. Seasonal variations in flow, in-stream attenuation, usage and septic effluent releases are suspected drivers behind some of the observed temporal exposure variability. When the data were used to evaluate a simple environmental exposure model for pharmaceuticals, mean ratios of predicted environmental concentrations (PECs), obtained using the model, to measured environmental concentrations (MECs) were 0.51 and 0.04 for the River Foss and River Ouse, respectively. Such PEC/MEC ratios indicate that the model underestimates actual concentrations in both river systems, but to a much greater extent in the larger River Ouse.