Comprehensive assessment of organic contaminant removal from on-site sewage treatment facility effluent by char-fortified filter beds.

To remove organic contaminants from wastewater using cost-efficient and currently existing methods, our study investigated char-fortified filter beds for on-site sewage treatment facilities (OSSFs) in a long-term field setting. OSSFs are commonly used in rural and semi-urban areas worldwide to treat wastewater when municipal wastewater treatment is not economically feasible. First, we screened for organic contaminants with gas chromatography and liquid chromatography mass spectrometry-based targeted and untargeted analysis and then we developed quantitative structure-property relationship models to search for key molecular features responsible for the removal of organic contaminants. We identified 74 compounds (24 confirmed by reference standards) including plasticizers, UV stabilizers, fragrances, pesticides, surfactant and polymer impurities, pharmaceuticals and their metabolites, and many biogenic compounds. Sand filters that are used as a secondary step after the septic tank in OSSFs could remove hydrophobic contaminants. The addition of biochar significantly increased the removal of these and a few hydrophilic compounds (Wilcoxon signed-rank test, α = 0.05). Besides hydrophobicity-driven sorption, biodegradation was suggested to be the most important removal pathway in this long-term field application. However, further improvements are necessary to remove very hydrophilic contaminants as they were not removed with sand and biochar-fortified sand.

Impact of on-site wastewater infiltration systems on organic contaminants in groundwater and recipient waters.

On-site sewage treatment facilities, particularly septic systems combined with soil infiltration, can be an important source of emerging organic contaminants in groundwater and surface water and thus represent a significant source of environmental and human exposure. Two infiltration systems in Åre municipality, Sweden, were examined to assess the occurrence of contaminants in groundwater and their fate and transport during infiltration. Groundwater samples, recipient surface water samples, and wastewater samples from septic tanks were collected from 2016 to 2017 covering all climatological seasons. These samples were analysed for a total of 103 contaminants, including pharmaceuticals, personal care products, organic phosphorus flame-retardants, plasticisers, perfluoroalkyl substances, and food additives. Fourteen of 103 contaminants showed 100% detection frequency in groundwater at concentrations in the low ng L-1 to low µg L-1 range. Of the compounds analysed, tris(2­butoxyethyl) phosphate, sucralose, caffeine, and benzophenone showed high abundancy with maximum concentrations in the µg L-1 range. The data were normalised for dilution using chloride and sucralose as commonly applied tracers; however, the level of sucralose decreased significantly during infiltration and it is thus suboptimal as a sewage water tracer. Large differences between the two infiltration sites were observed in detection frequencies and concentrations in groundwater, which could be attributed to the system design and the contaminant's migration time from release to sampling point. Seasonal variation was observed for selected chemicals, and the more hydrophobic chemicals showed a higher tendency for attenuation, indicating sorption as a major retention mechanism. A moderate environmental risk to aquatic organisms was estimated in adjacent surface water for galaxolide, tris(1­chloro­2­propyl) phosphate, and tris(2­butoxyethyl) phosphate. Due to this site-dependency and potential environmental risks, further studies are needed on infiltration systems in different settings and on alternative treatment techniques to reduce the contaminant discharge from on-site sewage treatment facilities.

Persistence, mobility and bioavailability of emerging organic contaminants discharged from sewage treatment plants.

Little is known about the impact of emissions of micropollutants from small and large-scale sewage treatment plants (STPs) on drinking water source areas. We investigated a populated catchment that drains into Lake Mälaren, which is the drinking water source for around 2 million people including the inhabitants of Stockholm, Sweden. To assess the persistence, mobility, bioavailability and bioaccumulation of 32 structurally diverse emerging organic contaminants, sediment, integrated passive and grab water samples were collected along the catchment of the River Fyris, Sweden. The samples were complemented with STP effluent and fish samples from one sampling event. Contaminants identified as persistent, mobile, and bioavailable were 4,6,6,7,8,8-hexamethyl-1,3,4,7-tetrahydrocyclopenta[g]isochromene (galaxolide), 2,4,7,9-tetramethyl-5-decyn-4,7-diol, tris(2-chloro-ethyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, and tris(1-chloro-2-propyl) phosphate. Galaxolide and 2,4,7,9-tetramethyl-5-decyn-4,7-diol were additionally found to be bioaccumulative, whereas n-butylbenzenesulfonamide was found to be only persistent and mobile. The total median mass flux of the persistent and mobile target analytes from Lake Ekoln into the drinking water source area of Lake Mälaren was estimated to be 27kg per year. Additionally, 10 contaminants were tentatively identified by non-target screening using NIST library searches and manual review. Two of those were confirmed by reference standards and further two contaminants, propylene glycol and rose acetate, were discharged from STPs and travelled far from the source. Attenuation of mass fluxes was highest in the summer and autumn seasons, suggesting the importance of biological degradation and photodegradation for the persistence of the studied compounds.

Mass fluxes per capita of organic contaminants from on-site sewage treatment facilities.

This study is the first attempt to quantify environmental fluxes per capita of organic contaminants discharged from on-site sewage treatment facilities (OSSFs) in affected recipients. Five sites were monitored around the River Fyris in Sweden: three mainly affected by OSSFs and two mainly affected by municipal sewage treatment plants (STPs). Gas chromatography-mass spectrometry was used to determine environmental concentrations of 30 anthropogenic contaminants, including organophosphorus compounds, rubber and plastic additives, UV stabilizers, fragrances, surfactant ingredients and polycyclic aromatic hydrocarbons. Uni- and multivariate statistical analysis of the most frequently detected contaminants showed that median fluxes per capita of tris(1,3-dichloro-2-propyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(2-chloroethyl) phosphate, and n-butylbenzene sulfonamide were similar at OSSF and STP sites, but the mass fluxes per capita of tris-(2-butoxyethyl) phosphate, 2-(methylthio)benzothiazole, and galaxolide, were significantly lower (∼2-3-fold) at OSSF sites than at STP sites (Mann-Whitney, α = 0.05). Differences between these sites were larger in samples collected in summer and autumn than in samples collected in winter. Deviations likely originated from differences in fate processes and distances between source and sampling sites. Further studies are needed to characterize mass fluxes per capita of contaminants in waters that directly receive discharges from OSSFs.

Non-target screening and prioritization of potentially persistent, bioaccumulating and toxic domestic wastewater contaminants and their removal in on-site and large-scale sewage treatment plants.

On-site sewage treatment facilities (OSSFs), which are used to reduce nutrient emissions in rural areas, were screened for anthropogenic compounds with two-dimensional gas chromatography-mass spectrometry (GC×GC-MS). The detected compounds were prioritized based on their persistence, bioaccumulation, ecotoxicity, removal efficiency, and concentrations. This comprehensive prioritization strategy, which was used for the first time on OSSF samples, ranked galaxolide, α-tocopheryl acetate, octocrylene, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, several chlorinated organophosphorus flame retardants and linear alkyl benzenes as the most relevant compounds being emitted from OSSFs. Twenty-six target analytes were then selected for further removal efficiency analysis, including compounds from the priority list along with substances from the same chemical classes, and a few reference compounds. We found significantly better removal of two polar contaminants 2,4,7,9-tetramethyl-5-decyn-4,7-diol (p=0.0003) and tris(2-butoxyethyl) phosphate (p=0.005) in soil beds, a common type of OSSF in Sweden, compared with conventional sewage treatment plants. We also report median removal efficiencies in OSSFs for compounds not studied in this context before, viz. α-tocopheryl acetate (96%), benzophenone (83%), 2-(methylthio)benzothiazole (64%), 2,4,7,9-tetramethyl-5-decyn-4,7-diol (33%), and a range of organophosphorus flame retardants (19% to 98%). The environmental load of the top prioritized compounds in soil bed effluents were in the thousands of nanogram per liter range, viz. 2,4,7,9-tetramethyl-5-decyn-4,7-diol (3000ngL-1), galaxolide (1400ngL-1), octocrylene (1200ngL-1), and α-tocopheryl acetate (660ngL-1).

Removal of 30 active pharmaceutical ingredients in surface water under long-term artificial UV irradiation.

This study investigated the i) kinetics, and ii) proportion of photolysis of 30 relatively stable active pharmaceutical ingredients (APIs) during artificial UV irradiation for 28 d in ammonium acetate buffer, filtered and unfiltered river water. Buffer was included to control removal kinetics under stable pH conditions and without particulate matter. Dark controls were used to determine removal due to other processes than photolysis and calculate the proportion of photolysis of the total removal. The removal of each API in each matrix was determined using online solid phase extraction/liquid chromatography tandem mass spectrometry (online SPE/LC-MS/MS). Most APIs transformed during the 28 d of UV irradiation and the dark controls showed that photolysis was the major removal process for the majority of the APIs studied. The half-lives ranged from 6 h (amitriptyline) in unfiltered river water to 884 h (37 d, carbamazepine) in buffer. In unfiltered river water, the proportion of APIs with short half-lives (<48 h) was much higher (29%) than in the other matrices (4%), probably due to additional organic carbon, which could have promoted indirect photolysis. Furthermore, two APIs, memantine and fluconazole, were stable in all three matrices, while alprazolam was stable in buffer and unfiltered river water and four additional APIs were stable in buffer. Considering the relatively long-term UV-exposure, this study enabled the investigation of environmentally relevant half-lives in natural waters. Many APIs showed high persistence, which is environmentally concerning and emphasizes the importance of further studies on their environmental fate and effects.

Screening and prioritization of micropollutants in wastewaters from on-site sewage treatment facilities.

A comprehensive screening of micropollutants was performed in wastewaters from on-site sewage treatment facilities (OSSFs) and urban wastewater treatment plants (WWTPs) in Sweden. A suspect screening approach, using high resolution mass spectrometry, was developed and used in combination with target analysis. With this strategy, a total number of 79 micropollutants were successfully identified, which belong to the groups of per- and polyfluoroalkyl substances (PFASs), pesticides, phosphorus-containing flame retardants (PFRs) and pharmaceuticals and personal care products (PPCPs). Results from this screening indicate that concentrations of micropollutants are similar in influents and effluents of OSSFs and WWTPs, respectively. Removal efficiencies of micropollutants were assessed in the OSSFs and compared with those observed in WWTPs. In general, removal of PFASs and PFRs was higher in package treatment OSSFs, which are based on biological treatments, while removal of PPCPs was more efficient in soil bed OSSFs. A novel comprehensive prioritization strategy was then developed to identify OSSF specific chemicals of environmental relevance. The strategy was based on the compound concentrations in the wastewater, removal efficiency, frequency of detection in OSSFs and on in silico based data for toxicity, persistency and bioaccumulation potential.

Online solid phase extraction liquid chromatography using bonded zwitterionic stationary phases and tandem mass spectrometry for rapid environmental trace analysis of highly polar hydrophilic compounds - Application for the antiviral drug Zanamivir.

Zanamivir (Za) is a highly polar and hydrophilic antiviral drug used for the treatment of influenza A viruses. Za has been detected in rivers of Japan and it's environmental occurrence has the risk of inducing antiviral resistant avian influenza viruses. In this study, a rapid automated online solid phase extraction liquid chromatography method using bonded zwitterionic stationary phases and tandem mass spectrometry (SPE/LC-MS/MS) for trace analysis of Za was developed. Furthermore, an internal standard (IS) calibration method capable of quantifying Za in Milli-Q, surface water, sewage effluent and sewage influent was evaluated. Optimum pre-extraction sample composition was found to be 95/5 v/v acetonitrile/water sample and 1% formic acid. The developed method showed acceptable linearities (r(2)≥0.994), filtration recovery (≥91%), and intra-day precisions (RSD≤16%), and acceptable and environmentally relevant LOQs (≤20ngL(-1)). Storage tests showed no significant losses of Za during 20 days and +4/-20°C (≤12%) with the exception of influent samples, which should be kept at -20°C to avoid significant Za losses. The applicability of the method was demonstrated in a study on phototransformation of Za in unfiltered and filtered surface water during 28 days of artificial UV irradiation exposure. No significant (≤12%) phototransformation was found in surface water after 28 days suggesting a relatively high photostability of Za and that Za should be of environmental concern.