Trace Organic Micropollutants Research Articles

Exploring organic micropollutant biodegradation under dynamic substrate loading in rapid sand filters

Microbial removal of trace organic micropollutants (OMPs) from drinking water sources remains challenging. Nitrifying and heterotrophic bacteria in rapid sand filters (RSFs) are capable of biodegrading OMPs while growing on ammonia and dissolved organic matter (DOM). The loading patterns of ammonia and DOM may therefore affect microbial activities as well as OMP biodegradation. So far, there is very limited information on the effect of substrate loading on OMP biodegradation at environmentally relevant concentrations (∼ 1 µg/L) in RSFs. We investigated the biodegradation rates of 16 OMPs at various substrate loading rates and/or empty bed contact times (EBCT). The presence of DOM improved the biodegradation of paracetamol (41.8%) by functioning as supplementary carbon source for the heterotrophic degrader, while hindering the biodegradation of 2,4-D, mecoprop and benzotriazole due to substrate competition. Lower loading ratios of DOM/benzotriazole benefited benzotriazole biodegradation by reducing substrate competition. Higher ammonia loading rates enhanced benzotriazole removal by stimulating nitrification-based co-metabolism. However, stimulating nitrification inhibited heterotrophic activity, which in turn inhibited the biodegradation of paracetamol, 2,4-D and mecoprop. A longer EBCT promoted metformin biodegradation as it is a slowly biodegradable compound, but suppressed the biodegradation of paracetamol and benzotriazole due to limited substrate supply. Therefore, the optimal substrate loading pattern is contingent on the type of OMP, which can be chosen based on the priority compounds in practice. The overall results contribute to understanding OMP biodegradation mechanisms at trace concentrations and offer a step towards enhancing microbial removal of OMPs from drinking water by optimally using RSFs.

Adsorption property and mechanism of polyacrylate-divinylbenzene microspheres for removal of trace organic micropollutants from water

In this study, polyacrylate-divinylbenzene (PADVB) microspheres were facilely prepared via the precipitation polymerization method, and the microspheres were used as an efficient adsorbent for the removal of trace level organic micropollutants (OMPs) from environmental waters. Preparation conditions of PADVB microspheres were optimized, and the characterizations of the microspheres were performed using a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption/desorption isotherms. The microspheres had broad-spectrum adsorption ability for various organic micropollutants containing hydroxy, amidogen, aromatic or heteroaromatic ring in their chemical structure, such as atrazine, 2,4 dichlorophenol, 2,4 dibromophenol, 2,6 dichlorophenol, sulfamethoxazole, estradiol, and bisphenol A. Besides, the effects of initial concentration, initial pH value, adsorption time, and the type of adsorbates on the adsorption performance were investigated systematically. PADVB microspheres could be used for removing trace OMPs from environmental water. Monolayer and homogeneous sorption process occurred on the surface of PADVB microspheres through chemisorption mechanisms. The X-ray photoelectron spectroscopy (XPS) and FT-IR spectrum of PADVB microspheres before and after adsorption proved that the OMPs adsorption onto PADVB microspheres was mainly due to the formation of the hydrogen bond and π-π electron-donor-acceptor (EDA) interactions. Besides, PADVB microspheres can be recovered for reuse via (low-pressure) microfiltration and could be regenerated sufficiently by using 80% (v/v) ethanol.

Hydrogen bonding-induced hydrophobic assembly yields strong affinity of an adsorptive membrane for ultrafast removal of trace organic micropollutants from water

Hydrogen bonding-induced hydrophobic assembly yields strong affinity of an adsorptive membrane for ultrafast removal of trace organic micropollutants from water.

Temperature-dependent redox zonation, nitrate removal and attenuation of organic micropollutants during bank filtration

River bank filtration (RBF) is considered to efficiently remove nitrate and trace organic micropollutants (OMP) from polluted surface waters. This is essential for maintaining good groundwater quality and providing high quality drinking water. Predicting the fate of OMP during RBF is difficult as the biogeochemical factors controlling the removal efficiency are not fully understood. To determine in-situ removal efficiency and degradation rates of nitrate and OMP indicator substances we conducted a field study in a RBF system during a period of one and a half years incorporating temporally and spatially varying redox conditions and temperature changes typically occurring in temperate climates. RBF was analyzed by means of mixing ratios between infiltrated river water and groundwater as well as average residence times of surface water towards the individual groundwater observation wells. These results were used to calculate temperature dependent first order degradation rates of redox sensitive species and several OMP. Five out of ten investigated OMP were completely removed along RBF pathways. We demonstrate that degradation rates of several OMP during bank filtration were controlled by redox conditions and temperature whereby temperature itself also had a significant influence on the extent of the most reactive oxic zone. The seasonal variations in temperature alone could explain a considerable percentage of the variance in dissolved oxygen (34%), nitrate (81%) as well as the OMPs diclofenac (44%) and sulfamethoxazole (76%). Estimated in-situ degradation rates roughly varied within one order of magnitude for temperature changes between 5 °C and 20 °C. This study highlights that temporal variability in temperature and redox zonation is a significant factor for migration and degradation of nitrate and several OMPs.

Fate and removal of trace pollutants from an anion exchange spent brine during the recovery process of natural organic matter and salts

The results of this sampling campaign on pilot scale processes aim to evaluate the occurrence and behavior of trace organic micro-pollutants and metal elements during anion exchange treatment of surface water and the subsequent treatment of generated spent brine with two types of electrodialysis membrane pairs. This knowledge is relevant to assess the quality and reusability of secondary products created during brine treatment; specifically the excess of sodium chloride to be recycled onsite and the natural organic matter, mostly consisting of humic substances, which find multiple applications in the agricultural industry. This study highlights that (1) the attachment mechanism of organic micro-pollutants to anion exchange resin occurs through electrostatic interaction and the subsequent transfer through ion exchange membranes is restricted by size exclusion; and (2) the complexation of trace metals compounds with the natural organic matter partly explains their removal by anion exchange. Complexes remain stable during treatment of the brine with electrodialysis.

Influences of multi influent matrices on the retention of PPCPs by nanofiltration membranes

Nanofiltration (NF) has great potential in removing trace organic micropollutants in wastewater, especially pharmaceuticals and personal care products (PPCPs). However, little information is available on PPCPs rejections under complex feed water matrices, which better represent real wastewater treatment conditions. In this paper, the PPCPs rejection behaviors and the dominating mechanisms by NF membranes were studied under multi mixed influent matrices which contained various inorganic ions, humic acids and sodium alginate. The results showed that the DF30 membrane had the highest rejection of negatively charged indomethacin (95.4%) and diclofenac sodium (94.1%) in pure water. Our study also showed that electrostatic effect and steric hindrance were the primary rejection mechanisms of PPCPs by DF30 membrane in pure water. The predominant fouling of DF30 membrane could be explained by the complete blocking model in the filtration of mixed influent matrices containing both inorganic ions and organic matters. The components in membrane bioreactor (MBR) effluent was beneficial to retention of positively and neutrally charged PPCPs, but had no significant effects on retention of negatively charged PPCPs. Risk quotients of the six target PPCPs in NF effluent were all lower than 0.1, likely indicating low risk to aquatic organisms. This work has potential implications for a deeper understanding of PPCPs rejections by NF in wastewater treatment.

Application of bar adsorptive microextraction to determine trace organic micro-pollutants in environmental water matrices

ABSTRACTThe present work proposes the application of bar adsorptive micro-extraction (BAµE) coated with an N-vinylpyrrolidone polymer (NVP) combined with micro-liquid desorption (200 µL) followed by high-performance liquid chromatography with diode array detection (BAµE(NVP)-µLD/HPLC-DAD) for the determination of trace levels of emerging organic micro-pollutants in environmental water matrices. The model compounds selected include an antibacterial/antifungal agent (triclosan), two pharmaceuticals (carbamazepine and diclofenac) and two steroid hormones (17α-ethinylestradiol and 17β-estradiol), in which the latter three were recently included in the European Union watch list of substances to be monitored in the field of water policy. Assays performed on 25 mL of ultrapure water samples spiked at the 8.0 µg L−1 level yielded average recoveries ranging from 81.9 to 102.4% for the compounds studied using optimised experimental conditions. The proposed analytical methodology demonstrated suitable detection limits (0.02–0.10 µg L−1) and good linear dynamic ranges (0.1–20.0 µg L−1) with determination coefficients higher than 0.9909. Using the standard addition method (SAM), the present analytical approach was applied on environmental water matrices, including surface, sea, river and groundwaters. The proposed method proved to be a suitable and alternative sorption-based static micro-extraction technique for monitoring trace levels of organic micro-pollutants in environmental water matrices.

Screening of 1300 organic micro-pollutants in groundwater from Beijing and Tianjin, North China

Groundwater contamination in China has become a growing public concern because of the country's rapid economic development and dramatically increasing fresh water demand. However, there is little information available on groundwater quality, particularly with respect to trace organic micro-pollutants contamination. This study was undertaken to investigate the occurrence of 1300 pollutants at 27 groundwater sites in Beijing and Tianjin, North China. Seventy-eight chemicals (6% of the targeted compounds) were detected in at least one sampling point; observed chemicals included polycyclic aromatic hydrocarbons (PAHs), pesticides, plasticizers, antioxidants, pharmaceuticals and other emerging compounds. Chemicals with a frequency of detection over 70% were 2-ethyl-1-hexanol (median concentration 152 ng L−1), benzyl alcohol (582 ng L−1), 2-phenoxy-ethanol (129 ng L−1), acetophenone (74 ng L−1), pentamethylbenzene (51 ng L−1), nitrobenzene (40 ng L−1) and dimethyl phthalate (64 ng L−1). Pesticides with concentrations exceeding the EU maximum residual limits (MRL) of 0.1 μg L−1 were 1,4-dichlorobenzene, oxadixyl, diflubenzuron, carbendazim, diuron, and the E and Z isomers of dimethomorph. Naphthalene and its 7 alkylated derivatives were widely observed at maximum concentration up to 30 μg L−1, which, although high, is still below the Australian drinking water guidelines of 70 μg L−1. The risk assessment indicated there is no human health risk through the oral consumption from most wells, although there were four wells in which total seven compounds were found at the concentrations with a potential adverse health effects. This work provides a wide reconnaissance on broad spectrum of organic micro-contaminants in groundwater in North China.

Drinking water treatment by in situ generated ferrate(VI)

The present study aims to investigate the efficiency of on-site produced ferrate(VI) for drinking water treatment as well as for the removal of micro pollutants. The study examined and validated the laboratory electrochemical production of ferrate(VI) and tested water treatment efficiency of the resulting ferrate(VI) in comparison with that of FeClSO4 and poly-aluminium chloride (PACl). The performance of water treatment was compared by the removal efficiency of turbidity, dissolved organic carbon, microbial count and trace organic micro pollutants. Major observations were that 0.5 mg/L of ferrate(VI) as Fe was sufficient to remove most of the contaminants and achieve complete disinfection irrespective of the original microbial counts. Ferrate(VI) has considerable oxidation potential to degrade commonly occurring trace organic micropollutants (other than melamine) in the Danube River water. In contrast, FeClSO4 or PACl cannot remove any trace micro pollutants.

Removal of Trace Organic Micropollutants by Drinking Water Biological Filters

The long-term removal of 34 trace organic micropollutants (<1 μg L(-1)) was evaluated and modeled in drinking water biological filters with sand media from a full-scale plant. The micropollutants included pesticides, pharmaceuticals, and personal care products, some of which are endocrine disrupting chemicals, and represent a wide range of uses, chemical structures, adsorbabilities, and biodegradabilities. Micropollutant removal ranged from no measurable removal (<15%) for 13 compounds to removal below the detection limit and followed one of four trends over the one year study period: steady state removal throughout, increasing removal to steady state (acclimation), decreasing removal, or no removal (recalcitrant). Removals for all 19 nonrecalcitrant compounds followed first-order kinetics when at steady state with increased removal at longer empty bed contact times (EBCT). Rate constants were calculated, 0.02-0.37 min(-1), and used in a pseudo-first-order rate model with the EBCT to predict removals in laboratory biofilters at a different EBCT and influent conditions. Drinking water biofiltration has the potential to be an effective process for the control of many trace organic contaminants and a pseudo-first-order model can serve as an appropriate method for approximating performance.

Determination and occurrence of organic micropollutants in reverse osmosis treatment for advanced water reuse

The growing demand on water resources has increased the interest in wastewater reclamation for multiple end-use applications such as indirect and direct potable reuse. In these applications, the removal of organic micropollutants is of a greater concern than in conventional wastewater treatment. This article presents a collection of data of trace organic micropollutants in an urban wastewater treatment plant (WWTP) in North East Spain using reverse osmosis (RO) membrane treatment. The RO rejection values of the organic molecules studied with a wide range of solute size and hydrophobicity were determined. Several chromatographic methods monitoring different endocrine disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs) were used. Results indicated that secondary effluents from this Spanish WWTP contained most of the studied organic compounds indicating incomplete removal of organics in the conventional treatment of the plant. However, the rejection of most micropollutants was high for all three RO membrane types (low energy, high rejection, fouling resistant) tested. It was observed that some selected micropollutants were less efficiently removed (e.g. the small and polar and the more hydrophobic) and the molecular weight and membrane material influenced removal efficiencies.

Immobilization of Iron Tetrasulfophthalocyanine on MCF-NH2 and MCM-41 Mesoporous Silicas

Trace organic micropollutants have adverse effects on human health and ecosystem at low concentrations. In this study, feasibility of new catalysts for oxidation of organic micropollutants was investigated. Iron tetrasulfophthalocyanine (FeTsPc) has been immobilized on the surface of functionalized MCF (mesocellular silica form)-NH2 and MCM-41 mesoporous silicas by means of chemical bonding to ammosilane groups. MCF, prepared by precipitation from a micellar solution, consisted of unit cells which had internal void (~20 nm) and pores (~11 nm). NH2-functional groups were added to the surface of MCF and MCM-41 using (3-aminopropyl)triethoxysilane (APTES). 1-ethyl-3-(3’dimethylaminopropyl)carbodiimide (WSC) was used as a coupling agent. N-hydroxysuccinimide (NHS) was added during the reaction to improve the efficiency of amination. The prepared materials, FeTsPc/NH2-MCF and FeTsPc/NH2-MCM-41, were characterized by UV-DRS (diffuse reflectance UV-vis spectroscopy) and FT-IR. Bisphenol-A (BPA) was chosen as a model micropollutant. The catalytic activities of the supported Fe-TsPc were examined by the oxidation of BPA in the presence of hydroperoxide. The amount of immobilized FeTsPc and the specific reactivity were also analyzed to provide quantitative evaluation of the catalysts. The results indicated that the FeTsPc/NH2-MCM-41 showed higher activity and durability in the liquid-phase oxidation of BPA under mild condition compared with the FeTsPc/NH2-MCF and unsupported catalyst.

Comparing microfiltration-reverse osmosis and soil-aquifer treatment for indirect potable reuse of water

Microfiltration (MF) followed by reverse osmosis (RO) and soil-aquifer treatment (SAT) are the two principal technologies considered for indirect potable reuse of wastewater. This study, conducted at the Northwest Water Reclamation Plant, Mesa (Arizona), evaluated MF/RO and SAT (>6 months residence time) treated tertiary effluent with respect to organics removal. Effluent organic matter was characterized as total organic carbon (TOC), by UV absorbance (UVA), solid-state carbon-13 nuclear magnetic resonance spectroscopy, and size exclusion chromatography. Several trace organic micropollutants, including EDTA, NTA, and alkylphenolethoxylate residues, were analyzed by GC/MS. The study revealed that final TOC concentrations of MF/RO and SAT are 0.3 and 1.0 mg l −1, respectively. Based on the characterization techniques used, the character of bulk organics present in final SAT water resembles the character of natural organic matter present in drinking water. Depending on the molecular weight cut-off, RO membranes can efficiently reject high molecular weight organic matter (characterized as humic and fulvic acids). However, approximately 40–50 percent of the remaining TOC in permeates consists of low molecular weight acids and neutrals representing a molecular weight range of ∼500 Da and less. In the SAT treated effluent, EDTA and APECs were removed to approximately 4.3 and 0.54 μg/l, respectively, but were below the detection limit in the MF/RO treated effluent.

Determination of trace organic micropollutants in atmospheric deposition

An analytical procedure has been developed and demonstrated for the isomer specific determination of 41 polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in wet and dry atmospheric deposition. A combination of solid phase and liquid extraction was used to produce a concentrated crude extract, which was purified and fractionated using open column liquid chromatography before analysis using gas chromatography — mass spectrometry with stable isotope dilution calibration. Analysis of preliminary atmospheric deposition samples collected over a 30-day period gave measurements in the following ranges: PCDDs and PCDFs — 15–1420 pg; PCBs — 0.3–109 ng; and PAHs — 0.02–2.72 μg.