Aerobic and anaerobic biodegradation of polyethylene glycols using sludge microbes

Enhancing the High-Solid Anaerobic Digestion of Horticultural Waste by Adding Surfactants

The influence of adding surfactants on the performance of high-solid anaerobic digestion of horticultural waste was extensively investigated in batch systems. Adding Tween series and polyethylene glycol series non-ionic surfactants had positive effects on biogas production, resulting in 370.1 mL/g VS and 256.6 mL/g VS with Tween 60 and polyethylene glycol 300 at a surfactant-to-grass mass ratio of 0.20, while the biogas production of anaerobic digestion without surfactants was 107.54 mL/g VS. The optimal and economically feasible choice was adding Tween 20 at a ratio of 0.08 g/g grass in high-solid anaerobic digestion. A kinetics model reliably represented the relationship between surfactant concentration and biogas production. The mechanism of surfactants working on lignocellulose was investigated. The improvement in high-solid anaerobic digestion by adding surfactants was attributed to the interaction between lignocelluloses and surfactants and the extraction of biodegradable fractions from the porous structure. An economic analysis showed that adding Tween 20 was likely to make a profit and be more feasible than adding Tween 60 and polyethylene glycol 300. This study confirms the enhancement in biogas production from horticultural waste by adding non-ionic surfactants.

ToF-SIMS evaluation of PEG-related mass peaks and applications in PEG detection in cosmetic products

Polyethylene glycols (PEGs) are used in industrial, medical, health care, and personal care applications. The cycling and disposal of synthetic polymers like PEGs pose significant environmental concerns. Detecting and monitoring PEGs in the real world calls for immediate attention. This study unveils the efficacy of time-of-flight secondary ion mass spectrometry (ToF-SIMS) as a reliable approach for precise analysis and identification of reference PEGs and PEGs used in cosmetic products. By comparing SIMS spectra, we show remarkable sensitivity in pinpointing distinctive ion peaks inherent to various PEG compounds. Moreover, the employment of principal component analysis effectively discriminates compositions among different samples. Notably, the application of SIMS two-dimensional image analysis visually portrays the spatial distribution of various PEGs as reference materials. The same is observed in authentic cosmetic products. The application of ToF-SIMS underscores its potential in distinguishing PEGs within intricate environmental context. ToF-SIMS provides an effective solution to studying emerging environmental challenges, offering straightforward sample preparation and superior detection of synthetic organics in mass spectral analysis. These features show that SIMS can serve as a promising alternative for evaluation and assessment of PEGs in terms of the source, emission, and transport of anthropogenic organics.

Impact of Polyethylene-Glycol-Induced Water Potential on Methane Yield and Microbial Consortium Dynamics in the Anaerobic Degradation of Glucose

This study investigated the relationship between water potential (Ψ) and the cation-induced inhibition of methane production in anaerobic digesters. The Ψ around methanogens was manipulated using polyethylene glycol (PEG) in a batch anaerobic reactor, ranging from -0.92 to -5.10 MPa. The ultimate methane potential (Bu) decreased significantly from 0.293 to 0.002 Nm3 kg-1-VSadded as Ψ decreased. When Ψ lowered from -0.92 MPa to -1.48 MPa, the community distribution of acetoclastic Methanosarcina decreased from 59.62% to 40.44%, while those of hydrogenotrophic Methanoculleus and Methanobacterium increased from 17.70% and 1.30% to 36.30% and 18.07%, respectively. These results mirrored changes observed in methanogenic communities affected by cation inhibition with KCl. Our findings strongly indicate that the inhibitory effect of cations on methane production may stem more from the water stress induced by cations than from their direct toxic effects. This study highlights the importance of considering Ψ dynamics in understanding cation-mediated inhibition in anaerobic digesters, providing insights into optimizing microbial processes for enhanced methane production from organic substrates.

Metagenomic investigations into the microbial consortia, degradation pathways, and enzyme systems involved in the biodegradation of plastics in a tropical lentic pond sediment

The exploitation of exciting features of plastics for diverse applications has resulted in significant plastic waste generation, which negatively impacts environmental compartments, metabolic processes, and the well-being of aquatic ecosystems biota. A shotgun metagenomic approach was deployed to investigate the microbial consortia, degradation pathways, and enzyme systems involved in the degradation of plastics in a tropical lentic pond sediment (APS). Functional annotation of the APS proteome (ORFs) using the PlasticDB database revealed annotation of 1015 proteins of enzymes such as depolymerase, esterase, lipase, hydrolase, nitrobenzylesterase, chitinase, carboxylesterase, polyesterase, oxidoreductase, polyamidase, PETase, MHETase, laccase, alkane monooxygenase, among others involved in the depolymerization of the plastic polymers. It also revealed that polyethylene glycol (PEG), polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), polyethylene terephthalate (PET), and nylon have the highest number of annotated enzymes. Further annotation using the KEGG GhostKOALA revealed that except for terephthalate, all the other degradation products of the plastic polymers depolymerization such as glyoxylate, adipate, succinate, 1,4-butanediol, ethylene glycol, lactate, and acetaldehyde were further metabolized to intermediates of the tricarboxylic acid cycle. Taxonomic characterization of the annotated proteins using the AAI Profiler and BLASTP revealed that Pseudomonadota members dominate most plastic types, followed by Actinomycetota and Acidobacteriota. The study reveals novel plastic degraders from diverse phyla hitherto not reported to be involved in plastic degradation. This suggests that plastic pollution in aquatic environments is prevalent with well-adapted degrading communities and could be the silver lining in mitigating the impacts of plastic pollution in aquatic environments.

Water-soluble polymers: Emerging contaminants detected, separated and quantified by a novel GPC/MALDI-TOF method

Water-soluble polymers (WSPs) are additives used as thickeners, stabilisers and flocculants in industry and in household products, including personal care products. Given their widespread use, it is likely WSPs enter the environment, particularly through wastewaters. This is of concern as there is little ecotoxicological research on their fate and behaviour once in the environment, which means their risk to aquatic life is not understood. The lack of suitable analytical techniques to detect, characterise and quantify WSPs hinders research on the potential impact of these polymers. A novel method has been developed that identifies polymers within a sample and separates them using gel-permeation chromatography (GPC). This is coupled with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), to quantify the polymer fractions using molecular weight information. This process has been carried out on a range of aqueous media. Polyethylene glycol (PEG) ingredients were successfully separated from non-polymeric material in a commercial shaving gel personal care product (PCP), before being quantified at 1.62 wt%. This method was applied to a spiked wastewater influent sample to demonstrate the extraction and separation of PEG from organic constituents such as dissolved organic matter (DOM). This highlighted the additional challenges of analysing WSPs in the environment, as factors such as sorption and biodegradation affected the total recovery of PEG, with an extraction efficiency of 53%. Overall, this method was applied for the extraction of PEG from a PCP with accurate quantification, before a proof-of-concept extraction from wastewater demonstrated the difficulties associated with WSP analysis in environmental samples. This method provides opportunities to use tandem GPC/MALDI-TOF MS to quantify WSPs in a broad array of environmental samples. Additional studies could include its application to wastewater or freshwater monitoring.

Biodegradation of polymers in managing plastic waste - A review

The modern economy that is fast-moving and convenience centric has led to excessive consumption of plastic. This has unwittingly led to egregious accumulation of plastic waste polluting the environment. Unfortunately, present means of plastic waste management have all been proven as less than adequate; namely recycling, landfill and incineration. Recent focus on plastic waste management has seen the confluence of the developments in biodegradable polymers and microbial engineering strategy for more expedient decomposition of plastic waste at composting facilities. This review paper is an assimilation of current developments in the areas of biodegradable polymer as well as microbial strategy towards management of polymer waste. Advents in biodegradable polymers have been promising, especially with aliphatic polyesters and starch in blends or co-polymers of these. Microbial strategies have been pursued for the identification of microbial strains and understanding of their enzymatic degradation process on polymers. New insights in these two areas have been focused in improving the rate of degradation of plastic waste at composting facilities. Recent alignment of testing and certification standards is outlined to give intimate insights into the mechanisms and factors influencing biodegradation. Despite recent milestones, economic viability of composting plastic waste in mainstream waste facilities is still a distance away. As it remains that a polymer that is biodegradable is functionally inferior to conventional polymers. Rather, it requires a shift in consumer behaviour to accept less durable biodegradable plastic products, this will then lower the threshold for biodegradable polymers to become a commercial reality.

Removal of polyethylene glycols from wastewater: A comparison of different approaches

Physicochemical methods such as adsorption on activated carbon, oxidation with either ozone or Fenton reagent, and chemical precipitation (coagulation), were assessed for the removal of polyethylene glycol (PEG) from wastewater. This contaminant is rarely investigated due to its low toxicity, although its presence limits the use of large water resources. The experimental tests showed that adsorption on activated carbon is well approximated by a Langmuir isotherm, and influenced by contact time, PEG molecular weight, pH, temperature, and initial PEG concentration. Ozonation allowed fragmenting the polymeric chains but was unable to remove completely the PEG, while about 85% of the total organic carbon (TOC) was removed by Fenton oxidation reaction by using a ratio between H₂O₂ and Fe^II close to 4. Coagulation did not produce results worthy of note, most likely because the uncharged PEG molecule does not interact with the iron hydroxide flocs. However, when performed after the Fenton oxidation (i.e., by simply raising the pH to values > 8), it allowed a further reduction of the residual TOC, up to 96% of the total, in the best case. Based on the resources used by each process studied and in consideration of the effectiveness of each of them, a semi-quantitative comparison on the sustainability of the different approaches is proposed.

Aerobic biological degradation of organic matter and fracturing fluid additives in high salinity hydraulic fracturing wastewaters

Reuse of hydraulic fracturing wastewaters depends on effective tailored treatment to prepare the water for the intended end use. Aerobic biological treatment of hydraulic fracturing produced water was examined to degrade dissolved organic carbon (DOC) and polyethylene glycols (PEGs). Biological treatment experiments of three produced water samples with DOC concentrations ranging from 22 to 420 mg/L and total dissolved solids (TDS) levels ranging from 26 to 157 g/L were conducted in 48-240 h batches. Samples were not pretreated to remove suspended solids and were inoculated with activated sludge and acclimated over several weeks. Results show that between 50% and 80% of DOC was removed in 12-24 h but a sizeable portion, on a mass basis, remained in the samples with higher DOC concentrations. PEGs were also shown to readily biodegrade into singly- and doubly-carboxylated metabolites, but were not shown to degrade past that point, leading to accumulation of PEG-dicarboxylates (PEG-diCs) in the batch reactors. Possible explanations include residence times that were too long, resulting in starved microbial populations (and thus, a stopping of PEG degradation) or the presence of other ethoxylated additives that degraded into PEGs and PEG-diCs and fed this accumulation. This work demonstrates that a well-acclimated microbial culture is capable of degrading a large portion of DOC in hydraulic fracturing wastewaters across a wide spectrum of TDS concentrations, indicating that biological treatment is a viable option for enabling reuse of produced water.

Occurrence and potential environmental risk of surfactants and their transformation products discharged by wastewater treatment plants

Seven-day composite effluent samples from a German monitoring campaign including 33 conventional wastewater treatment plants (WWTP) were analyzed for linear alkylbenzene sulfonates (LAS) and alkyl ethoxysulfates (AES) and were screened by wide-scope suspect screening for 1564 surfactants and their transformation products (TPs) by UHPLC-ESI-QTOF-MS. Corresponding seven-day composite influent samples of selected WWTPs showed high influent concentrations as well as very high removal rates for LAS and AES. However, average total LAS and AES effluent concentrations were still 14.4 μg/L and 0.57 μg/L, respectively. The LAS-byproducts di-alkyl tetralin sulfonates (DATSs), the TPs sulfophenyl alkyl carboxylic acids (SPACs) and sulfo-tetralin alkyl carboxylic acids (STACs) reached maximum effluent concentrations of 19 μg/L, 17 μg/L and 5.3 μg/L, respectively. In many cases the sum of the concentration of all LAS-related byproducts and TPs surpassed the concentration of the precursors. High concentrations of up to 7.4 μg/L were found for 41 polyethylenoglycol homologs. Quantified surfactants and their TPs and by-products together accounted for concentrations up to 82 μg/L in WWTP effluents. To determine the risk of individual surfactants and their mixtures, single homologs were grouped by a "weighted carbon number approach" to derive normalized Predicted No-Effect Concentrations (PNEC), based on experimental ecotoxicity data from existing risk assessments, complemented by suitable Quantitative Structure-Activity Relationships (QSAR) predictions. Predicted Environmental Concentrations (PEC) were derived by dividing effluent concentrations of surfactants by local dilution factors. Risks for all analyzed surfactants were below the commonly accepted PEC/PNEC ratio of 1 for single compounds, while contributions to mixture toxicity effects from background levels of LAS and DATS cannot be excluded. Maximum LAS concentrations exceeded half of its PNEC, which may trigger country-wide screening to investigate potential environmental risks.

Degradation of polyethylene glycols and polypropylene glycols in microcosms simulating a spill of produced water in shallow groundwater

Polyethylene glycols (PEGs) and polypropylene glycols (PPGs) are frequently used in hydraulic fracturing fluids and have been detected in water returning to the surface from hydraulically fractured oil and gas wells in multiple basins. We identified degradation pathways and kinetics for PEGs and PPGs under conditions simulating a spill of produced water to shallow groundwater. Sediment-groundwater microcosm experiments were conducted using four produced water samples from two Denver-Julesburg Basin wells at early and late production. High-resolution mass spectrometry was used to identify the formation of mono- and di-carboxylated PEGs and mono-carboxylated PPGs, which are products of PEG and PPG biodegradation, respectively. Under oxic conditions, first-order half-lives were more rapid for PEGs (<0.4-1.1 d) compared to PPGs (2.5-14 d). PEG and PPG degradation corresponded to increased relative abundance of primary alcohol dehydrogenase genes predicted from metagenome analysis of the 16S rRNA gene. Further degradation was not observed under anoxic conditions. Our results provide insight into the differences between the degradation rates and pathways of PEGs and PPGs, which may be utilized to better characterize shallow groundwater contamination following a release of produced water.

Distribution and diagenetic fate of synthetic surfactants and their metabolites in sewage-impacted estuarine sediments

Surfactants are high production volume chemicals used in numerous domestic and industrial applications and, after use, the most abundant organic contaminants in wastewater. Their discharge might jeopardize the receiving aquatic ecosystems, including sediments, where they tend to accumulate. This is the first comprehensive study on their distribution and fate in this environmental compartment as we performed simultaneous analysis of the three main classes of surfactants (anionic: LAS; nonionic: NPEO and AEO; cationic: DTDMAC, DADMAC, BAC, and ATMAC) and some of their transformation products (SPC, NP, NPEC, and PEG). To account for spatial and time trends, surface sediments and dated cores were collected from Jamaica Bay, a heavily sewage-impacted estuary in New York City. The concentrations of surfactants in surface sediments were between 18 and > 200 μg g^-1 and showed slight variation (<10%) over different sampling years (1998, 2003 and 2008). Cationic surfactants were found at the highest concentrations, with DTDMAC accounting for between 52 and 90% of the total sum of target compounds. Vertical concentration profiles in dated cores from the most contaminated station, in the vicinity of the biggest local sewage treatment plant (STP), indicated two sub-surface surfactant peaks in the mid-1960s (469 μg g^-1) and late 1980s (572 μg g^-1) coinciding with known STP upgrades. This trend was observed for most target compounds, except for DADMAC, C22ATMAC, and PEG, which showed a continuous increase towards the top of the cores. In-situ degradation was studied by comparing sediment core samples taken 12 years apart (1996 and 2008) and revealed a net decrease in PEG and specific surfactants (BAC, ATMAC, NPEO, and AEO) accompanied by growing concentrations of metabolites (SPC, NP, and NPEC). DTDMAC, DADMAC, and LAS, however, remained stable over this period, suggesting recalcitrant behavior under the anaerobic conditions in Jamaica Bay sediments.

MAIN FINDING

Chronology of major synthetic surfactants are illustrated in the dated sediment cores, as well as their different diagenetic fates.

New approaches to enhance pollutant removal in artificially aerated wastewater treatment systems

Freshwater ecosystems sustain human society through the provision of a range of services. However, the status of these ecosystems is threatened by a multitude of pressures, including point sources of wastewater. Future treatment of wastewater will increasingly require new forms of decentralised infrastructure. The research reported here sought to enhance pollutant removal within a novel wastewater treatment technology, based on un-planted, artificially aerated, horizontal subsurface flow constructed wetlands. The potential for these systems to treat de-icer contaminated runoff from airports, a source of wastewater that is likely to grow in importance alongside the expansion of air travel and under future climate scenarios, was evaluated. A new configuration for the delivery of air to aerated treatment systems was developed and tested, based on a phased-aeration approach. This new aeration approach significantly improved pollutant removal efficiency compared to alternative aeration configurations, achieving >90% removal of influent load for COD, BOD₅ and TOC. Optimised operating conditions under phased aeration were also determined. Based on a hydraulic retention time of 1.5 d and a pollutant mass loading rate of 0.10 kg d^-1 m^-2 BOD₅, >95% BOD₅ removal, alongside final effluent BOD₅ concentrations <21 mg L^-1, could be achieved from an influent characterised by a BOD₅ concentration > 800 mg L^-1. Key controls on oxygen transfer efficiency within the aerated treatment system were also determined, revealing that standard oxygen transfer efficiency was inversely related to aeration rate between 1 L and 3 L min^-1 and positively related to bed media depth between 1500 mm and 3000 mm. The research reported here highlights the potential for optimisation and subsequent widespread application of the aerated wetland technology, in order to protect and restore freshwater ecosystems and the services that they provide to human society.

Enzymes as Enhancers for the Biodegradation of Synthetic Polymers in Wastewater

Synthetic polyesters are today the second-largest class of ingredients in household products and are entering wastewater treatment plants (WWTPs) after product utilization. One approach to improve polymer biodegradation in wastewater would be to complement current processes with polyester-hydrolyzing enzymes and their microbial producers. In this study, the hydrolysis of poly(oxyethylene terephthalate) polymer by hydrolases from wastewater microorganisms was investigated in vitro and under realistic WWTP conditions. An esterase and a cutinase from Pseudomonas pseudoalcaligenes and a lipase from Pseudomonas pelagia were heterologously expressed in Escherichia coli BL21-Gold(DE3) and were purified by a C-terminal His₆ tag. The hydrolases were proven to hydrolyze the polymer effectively, which is a prerequisite for further biodegradation. The hydrolases maintained high activity up to 50 % upon lowering the temperature from 28 to 15 °C to mimic WWTP conditions. The hydrolases were also not inhibited by the wastewater matrix. Polyester-hydrolyzing enzymes active under WWTP conditions and their microbial producers thus have the potential to improve biological treatment of wastewater rich in synthetic polymers.

Characterization of the chemicals used in hydraulic fracturing fluids for wells located in the Marcellus Shale Play

Hydraulic fracturing, coupled with the advances in horizontal drilling, has been used for recovering oil and natural gas from shale formations and has aided in increasing the production of these energy resources. The large volumes of hydraulic fracturing fluids used in this technology contain chemical additives, which may be toxic organics or produce toxic degradation byproducts. This paper investigated the chemicals introduced into the hydraulic fracturing fluids for completed wells located in Pennsylvania and West Virginia from data provided by the well operators. The results showed a total of 5071 wells, with average water volumes of 5,383,743 ± 2,789,077 gal (mean ± standard deviation). A total of 517 chemicals was introduced into the formulated hydraulic fracturing fluids. Of the 517 chemicals listed by the operators, 96 were inorganic compounds, 358 chemicals were organic species, and the remaining 63 cannot be identified. Many toxic organics were used in the hydraulic fracturing fluids. Some of them are carcinogenic, including formaldehyde, naphthalene, and acrylamide. The degradation of alkylphenol ethoxylates would produce more toxic, persistent, and estrogenic intermediates. Acrylamide monomer as a primary degradation intermediate of polyacrylamides is carcinogenic. Most of the chemicals appearing in the hydraulic fracturing fluids can be removed when adopting the appropriate treatments.

Model framework for integrating multiple exposure pathways to chemicals in household cleaning products

We present a screening-level exposure-assessment method which integrates exposure from all plausible exposure pathways as a result of indoor residential use of cleaning products. The exposure pathways we considered are (i) exposure to a user during product use via inhalation and dermal, (ii) exposure to chemical residues left on clothing, (iii) exposure to all occupants from the portion released indoors during use via inhalation and dermal, and (iv) exposure to the general population due to down-the-drain disposal via inhalation and ingestion. We use consumer product volatilization models to account for the chemical fractions volatilized to air (f_volatilized ) and disposed down the drain (f_{down-the-drain} ) during product use. For each exposure pathway, we use a fate and exposure model to estimate intake rates (iR) in mg/kg/d. Overall, the contribution of the four exposure pathways to the total exposure varies by the type of cleaning activities and with chemical properties. By providing a more comprehensive exposure model and by capturing additional exposures from often-overlooked exposure pathways, our method allows us to compare the relative contribution of various exposure routes and could improve high-throughput exposure assessment for chemicals in cleaning products.

Hydrolysis of Ionic Phthalic Acid Based Polyesters by Wastewater Microorganisms and Their Enzymes

Water-soluble polyesters are used in a range of applications today and enter wastewater treatment plants after product utilization. However, little is known about extracellular enzymes and aquatic microorganisms involved in polyester biodegradation and mineralization. In this study, structurally different ionic phthalic acid based polyesters (the number-average molecular weights (M_n) 1770 to 10 000 g/mol and semi crystalline with crystallinity below 1%) were synthesized in various combinations. Typical wastewater microorganisms like Pseudomonas sp. were chosen for in-silico screening toward polyester hydrolyzing enzymes. Based on the in-silico search, a cutinase from Pseudomonas pseudoalcaligenes (PpCutA) and a putative lipase from Pseudomonas pelagia (PpelaLip) were identified. The enzymes PpCutA and PpelaLip were demonstrated to hydrolyze all structurally different polyesters. Activities on all the polyesters were also confirmed with the strains P. pseudoalcaligenes and P. pelagia. Parameters identified to enhance hydrolysis included increased water solubility and polyester hydrophilicity as well as shorter diol chain lengths. For example, polyesters containing 1,2-ethanediol were hydrolyzed faster than polyesters containing 1,8-octanediol. Interestingly, the same trend was observed in biodegradation experiments. This information is important to gain a better mechanistic understanding of biodegradation processes of polyesters in WWTPs where the extracellular enzymatic hydrolysis seems to be the limiting step.

A new arylesterase from Pseudomonas pseudoalcaligenes can hydrolyze ionic phthalic polyesters

Extracellular enzymes are assumed to be responsible for the initial and rate limiting step in biodegradation of polymers. Mainly enzymes with aliphatic esters as their natural substrates (e.g. lipase, cutinases) have until now been evaluated for polyester hydrolysis studies. However, the potential of enzymes with aromatic esters as their natural substrates (e.g. arylesterases) have been neglected although many types of polyester today contain aromatic moieties. Consequently, in order to elucidate biodegradation of phthalic polyesters in aquatic systems, a novel arylesterase (PpEst) was investigated related to hydrolysis of ionic phthalic polyesters. The hydrolysis of various ionic phthalic polyesters by PpEst was mechanistically studied. The polyester building blocks (terephthalic acid (TA), 5-sulfoisophthalic acid (NaSIP) and alkyl or ether diols) were systematically varied to investigate the impact on hydrolysis. PpEst effectively hydrolyzed all 14 synthetized ionic phthalic polyesters as indicated by released TA. However, no NaSIP was detected indicating that PpEst has a limited capacity to cleave bonds in close vicinity to the ionic monomer NaSIP. The systematic study indicated that increasing water solubility and hydrophilicity significantly enhanced hydrolysis. A higher release of TA was seen with increasing NaSIP ratio while up to 20 times more TA was released when alkyl diols were replaced by ether diol analogues. In contrast, cyclic and branched diols had a negative effect on hydrolysis when compared to linear diols. PpEst also revealed a linear release of TA over seven days for ether containing polyesters, indicating a very stable enzyme.

Anaerobic degradation of alcohol ethoxylates and polyethylene glycols in marine sediments

This research is focused on alcohol polyethoxylates (AEOs), nonionic surfactants used in a wide variety of products such as household cleaners and detergents. Our main objective in this work was to study the anaerobic degradation of these compounds and their main aerobic degradation products and precursors (polyethylene glycols, PEGs, which are also used for many other applications) in marine sediments, providing the first data available on this topic. First, we observed that average AEO sediment-water partition coefficients (Kd) increased towards those homologs having longer alkyl chains (from 257 L/kg for C12 to 5772 L/kg for C18),which were less susceptible to undergo biodegradation. Overall, AEO and PEG removal percentages reached up to 99.7 and 93%, respectively, after 169 days of incubation using anaerobic conditions in sediments ([O2] = 0 ppm, Eh = -170 to -380 mV and T = 30 °C). Average half-life was estimated to be in a range from 10 to 15 days for AEO homologs (C12AEO8-C18AEO8), and 18 days for PEGEO8.Methanogenic activity proved to be intense during the experiment, confirming the occurrence of anaerobic conditions. This is the first study showing that AEOs and PEGs can be degraded in absence of oxygen in marine sediments, so this new information should be taken into account for future environmental risk assessments on these chemicals.

Bioaugmentation treatment of PV wafer manufacturing wastewater by microbial culture

The wastewater of silicon photovoltaic (PV) battery manufacturing contained polyethylene glycol (PEG) and detergents, which possessed the characteristics of high content of organics and low bioavailability, and then resulted in high treatment costs. To address the difficulties of existing treatment facilities in stably meeting discharge standards, eight tons of microbial culture (consisting of Bacillus sp. and Rhodococcus sp.) were added into the aerobic treatment unit. Subsequently, the effectiveness of the microbial culture in small-scale biological wastewater treatment was evaluated, and the operating conditions for engineering applications were optimized. The application study showed that the average chemical oxygen demand (COD) removal efficiency reached 95.0% when the pH value was 7, the gas-water ratio was 28:1, the reflux ratio was 50%, which indicated an increase of 51.2% contrasting with the situation without bioaugmentation. The volume load of the treatment facilities after augmentation increased by 127.9% and could tolerate the COD shock load reached 2,340 mg·L(-1). At last, the effluence met the class I standard of the Integrated Wastewater Discharge Standard (GB8978-1996).

Occurrence, distribution and partitioning of nonionic surfactants and pharmaceuticals in the urbanized Long Island Sound Estuary (NY)

This work deals with the environmental distribution of nonionic surfactants (nonylphenol and alcohol ethoxylates), their metabolites (NP, nonylphenol; NPEC, nonylphenol ethoxycarboxylates; and PEG, polyethylene glycols) and a selection of 64 pharmaceuticals in the Long Island Sound (LIS) Estuary which receives important sewage discharges from New York City (NYC). Most target compounds were efficiently removed (>95%) in one wastewater treatment plant monitored, with the exception of NPEC and some specific drugs (e.g., hydrochlorothiazide). Concentrations of surfactants (1.4-4.5 μg L(-1)) and pharmaceuticals (0.1-0.3 μg L(-1)) in seawater were influenced by tides and sampling depth, consistent with salinity differences. Surfactants levels in suspended solids samples were higher than 1 μg g(-1), whereas only most hydrophobic or positively charged pharmaceuticals could be found (e.g., tamoxifen, clarithromycin). Maximum levels of target compounds in LIS sediments (PEG at highest concentrations, 2.8 μg g(-1)) were measured nearest NYC, sharply decreasing with distance from major sewage inputs.

Partitioning of alcohol ethoxylates and polyethylene glycols in the marine environment: field samplings vs laboratory experiments

Nowadays, alcohol ethoxylates (AEOs) constitute the most important group of non-ionic surfactants, used in a wide range of applications such as household cleaners and detergents. Significant amounts of these compounds and their degradation products (polyethylene glycols, PEGs, which are also used for many other applications) reach aquatic environments, and are eliminated from the water column by degradation and sorption processes. This work deals with the environmental distribution of AEOs and PEGs in the Long Island Sound Estuary, a setting impacted by sewage discharges from New York City (NYC). The distribution of target compounds in seawater was influenced by tides, consistent with salinity differences, and concentrations in suspended solid samples ranged from 1.5 to 20.5 μg/g. The more hydrophobic AEOs were mostly attached to the particulate matter whereas the more polar PEGs were predominant in the dissolved form. Later, the sorption of these chemicals was characterized in the laboratory. Experimental and environmental sorption coefficients for AEOs and PEGs showed average values from 3607 to 164,994 L/kg and from 74 to 32,862 L/kg, respectively. The sorption data were fitted to a Freundlich isotherm model with parameters n and log KF between 0.8-1.2 and 1.46-4.39 L/kg, respectively. AEO and PEG sorptions on marine sediment were also found to be mostly not affected by changes in salinity.

Aerobic biodegradation of polyethylene glycols of different molecular weights in wastewater and seawater

In order to distinguish between aerobic biodegradation of synthetic polymers in fresh and seawater, polyethylene glycols (PEGs) were systematically and comparatively investigated in inocula from municipal wastewater and seawater aquarium filters for the first time. The molecular weight (MW) of the PEGs, (HO(CH(2)CH(2)O)(n)H, n=3-1350) as representatives of water-soluble polymers, ranged from 250 to 57,800Da. The biodegradation was observed by removal of dissolved organic carbon and carbon dioxide production by applying standardized ISO and OECD test methods. Specific analyses using liquid chromatography mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were performed. All PEGs selected were completely biodegradable in freshwater media within 65d. PEGs with an MW up to 14,600Da have a similar degradation pathway which is characterized by gradual splitting of C(2)-units off the chain resulting in formation of short-chain PEGs. In artificial seawater media, full biodegradation of PEGs up to 7400Da required more time than in freshwater. PEGs with MW 10,300 and 14,600Da were only partially degraded whereas PEGs with MW 26,600 and 57,800Da were not degraded for a period of 135d. The biodegradation pathway of PEG 250 and PEG 970 in seawater is similar to that for freshwater. For PEGs having an MW from 2000 to 10,300Da, the degradation pathway in seawater differs from the pathway of the shorter PEGs.