Organic micropollution indices of effluents and renovated waters

Solvent-extractable organics (SEO), representing organic micropollutants, were studied in secondary and tertiary effluents using solvents of different polarity.Characterization was effected by column fractionation (including adsorption and elution with solvents of ascending polarity) and by gas-chromatographic fingerprinting.Highest recoveries of SEO were obtained with benzene followed by chloroform, and with diethyl ether as a single solvent.In secondary effluents the polar fraction accounted for about 45% and the non-polar for 32%, the remaining being of intermediate polarity. Lime treatment and detention in after-lime polishing ponds removed, respectively, about 37 and 68% of the total SEO, 63 and 75% of the (non-polar) pentane fraction, 91 and 96% of the (medium-polarity) dichloromethane fraction, and 53 and 64% of the (polar) methanol fraction.Gas chromatographic fingerprints were similar for secondary effluents with different sampling periods.Removal of the total ECD-responding organics in the overall treatment process was about 80%, (similar to the dichloromethane-fraction removal) while that of the FID-responding compounds was about 69%—very close to the total SEO removal.     

Correlation of humic substance trihalomethane formation potential and adsorption behavior to molecular weight distribution in raw and chemically treated waters

The molecular weight distributions (MWDs) of several commercially prepared humic and fulvic acids and organic matter present in natural waters were analyzed by gel chromatography. The responses of these substances to treatment by alum coagulation, lime softening, and activated carbon adsorption were also analyzed, as were their trihalomethane formation potentials before and after each treatment. The treatability characteristics and trihalomethane formation properties of the different organic substances were then related to their respective MWDs. Differences in the MWDs were found to effect differences in the behavior of lumped parameter measures of organic matter (such as TOC) with respect to the several treatment operations. The treatments in turn were observed to alter the MWDs of the organic substances as well as their phenomenological behavior in subsequent process operations.     

Modelling nitrogen transformations in waters receiving mine effluents

This paper presents a biogeochemical model developed for a clarification pond receiving ammonium nitrogen rich discharge water from the Boliden concentration plant located in northern Sweden. Present knowledge about nitrogen (N) transformations in lakes is compiled in a dynamic model that calculates concentrations of the six N species (state variables) ammonium-N (N_am), nitrate-N (N_ox), dissolved organic N in water (N_org), N in phytoplankton (N_pp), in macrophytes (N_mp) and in sediment (N_sed). It also simulates the rate of 16 N transformation processes occurring in the water column and sediment as well as water-sediment and water-atmosphere interactions. The model was programmed in the software Powersim using 2008 data, whilst validation was performed using data from 2006 to 2007. The sensitivity analysis showed that the state variables are most sensitive to changes in the coefficients related to the temperature dependence of the transformation processes. A six-year simulation of N_am showed stable behaviour over time. The calibrated model rendered coefficients of determination (R²) of 0.93, 0.79 and 0.86 for N_am, N_ox and N_org, respectively. Performance measures quantitatively expressing the deviation between modelled and measured data resulted in values close to zero, indicating a stable model structure. The simulated denitrification rate was on average five times higher than the ammonia volatilisation rate and about three times higher than the permanent burial of N_sed and, hence, the most important process for the permanent removal of N. The model can be used to simulate possible measures to reduce the nitrogen load and, after some modification and recalibration, it can be applied at other mine sites affected by N rich effluents.     

Molecular weight distributions in activated sludge effluents

Bench scale activated sludge reactors with a solids retention time of 9 days were operated at all combinations of two levels of pH, dissolved oxygen (DO) concentration and feed type (pH 6 and 8; DO 1 and 7 mgl⁻¹; simple and complex feed). Long-term composite samples were collected and adjusted to neutral pH and equal concentrations of alkalinity and ammonia nitrogen. The molecular weight distributions of the soluble organic carbon (SOC) in the samples were determined by ultrafiltration through membranes with nominal rejection values of 1000, 10,000, 25,000 and 100,000. The distributions were generally bimodal with the bulk of the SOC in the largest and smallest fractions. Following ozonation to a residual of 0.30–0.35 mg 1⁻¹ after 5 min contact, the distributions were shifted so that more of the SOC appeared in the lowest molecular weight fraction although significant amounts remained in the other fractions. When samples were breakpoint chlorinated to a residual of 5–10 mg l⁻¹ free available chlorine after 2 h contact, very little high molecular weight material remained and almost all of the SOC appeared in the low molecular weight fraction. By using ³⁶Cl during breakpoint chlorination it was also possible to evaluate the distribution of organically bound chlorine among the molecular weight fractions and this revealed that the bulk of it was associated with organics having molecular weight less than 1000.     

Toxicological and ecotoxic impact of secondary and tertiary treated sewage effluents

Secondary sewage effluents are discharged in significant quantities in aquatic environments delivering pollutants that were not removed during treatment; yet advanced treated effluents are not lacking of contaminants. In this study, biochemical biomarkers were measured in liver and kidney of rainbow trout (Oncorynchus mykiss) exposed to unchlorinated, chlorinated and tertiary treated secondary sewage effluents. In addition, organic matter, nitrogen and suspended solids were assayed, while a common bioassay, Daphnia magna 21d reproduction test was also applied in order to examine potential relation between the performed bioassay and the biomarkers. Processes using oxidative conditions, such as ozonation and chlorination, resulted in significantly increased breeding rate (up to 74%) of the organism. Biomarkers measurements incorporated the determination of total glutathione (GSH), glutathione S-transferases (GST), glutathione peroxidase (GPX), lipid peroxidation (LPO) and an innovative biomarker in such applications, haem peroxidase. In general, the response of biomarkers was dependent upon the treatment method and it was tissue specific. Secondary effluents inhibited liver GST and haem peroxidase, while GSH levels and LPO were significantly provoked in liver. Ozonation provoked hepatic peroxidation, in terms of haem peroxidase and LPO, and GST; while the protective (to Reactive Oxidant Species – ROS) GSH was depleted, suggesting extended ROS attack to the organism. Similar response of biomarkers (but to a lesser extend) was observed after exposure of trout to effluents submitted to both coagulation and ozonation, emphasizing the significance of removing the residual organic matter by other methods than oxidative ones. Ozonation also enhanced renal LPO and GPX; however the former employment of coagulation limited the peroxidation phenomena. Chlorination mainly affected the levels of total GSH in both tissues.     

Membrane filtration of two sulphonamides in tertiary effluents and subsequent adsorption on activated carbon

The adsorption behaviour of two polar organic micropollutants (N-n-butylbenzenesulphonamide and sulphmethoxazole) onto powdered activated carbon (PAC) under competitive conditions prior to and after filtration with a tight ultrafiltration membrane was examined. The sulphonamides were spiked into microfiltered tertiary municipal effluent in microg L(-1) quantities. Ultrafiltration of these effluents resulted in better adsorbability for both the micropollutants and the background organic matter in the permeates compared to the feed waters. This behaviour seems to be caused by a reduced blocking of micropores by lower concentrations of high molecular weight compounds in membrane filtrates. A combined treatment of ultrafiltration prior to adsorption can therefore reduce the carbon demand for potentially harmful micropollutants in effluents.     

Automated fluorometric method for determination of boron in waters, detergents and sewage effluents

An automated method for the determination of boron in natural waters, detergents and sewage effluents is described. The method is based on the reaction of 4'-chloro-2-hydroxy-4-methoxybenzophenone (CHMB) with boron to produce fluorescent species, in a 90% sulfuric acid medium. The method has been made specific to remove any interferences from all major and minor ions and other organic compounds normally present in water. The method is capable of measuring different chemical forms of boron such as boric acid, borax, sodium perborate and tetraphenyl boron. The method analyses 10 samples per hour, in the 5–100 μg 1⁻¹ boron range. The rate of sample analysis can be increased to 20 per hour at higher concentration ranges. The limit of detection is 1 μg 1⁻¹ boron.     

Monochloramine decay in model and distribution system waters

Chloramines have long been used to provide a disinfecting residual in distribution systems where it is difficult to maintain a free chlorine residual or where disinfection by-product (DBP) formation is of concern. While chloramines are generally considered less reactive than free chlorine, they are inherently unstable even in the absence of reactive substances. These reactions, often referred to as "auto-decomposition", always occur and hence define the maximum stability of monochloramine in water. The effect of additional reactive material must be measured relative to this basic loss process. A thorough understanding of the auto-decomposition reactions is fundamental to the development of mechanisms that account for reactions with additional substances and to the ultimate formation of DBPs. A kinetic model describing auto-decomposition was recently developed. This model is based on studies of isolated individual reactions and on observations of the reactive ammonia-chlorine system as a whole. The work presented here validates and extends this model for use in waters typical of those encountered in distribution systems and under realistic chloramination conditions. The effect of carbonate and temperature on auto-decomposition is discussed. The influence of bromide and nitrite at representative monochloramine concentrations is also examined, and additional reactions to account for their influence on monochloramine decay are presented to demonstrate the ability of the model to incorporate inorganic demand pathways that occur parallel to auto-decomposition.     

Organic pollutants in the effluents of large wastewater treatment plants in Sweden

Effluents from the three largest WWTPs in Sweden were analysed for the presence of organic pollutants by GC-MS. From a total of 137 identified compounds only 10 were priority pollutants. A broad spectrum of non-regulated organic pollutants found in the effluents included aromatic hydrocarbons, food and household related compounds, solvents, plasticisers, flame retardants, preservatives, antioxidants and washing and cleaning related compounds. The concentrations of individual compounds in effluents of all three WWTPs were in the range of 0.5–50 μg/l. Rather few point-discharged pollutants from specific industries were present in the effluents. The majority of pollutants detected in the effluents were attributable to the overall usage and discharge of chemical products in modern society. These pollutants originate from diffuse sources and represent “a background chemical pollution load” of the receiving waters through the discharge from WWTPs in large cities.     

Occurrence and implications of estrogens and xenoestrogens in sewage effluents and receiving waters from South East Queensland

We report a survey on the occurrence of estrogens (estrone, E1; 17β-estradiol, E2; 17α-ethynylestradiol, EE2) and xenoestrogens (bisphenol-A, BPA; 4-t-octylphenol, 4-t-OP; 4-nonylphenols, 4-NP; and nonylphenol mono- and di-ethoxylates, NPE1 and NPE2) in effluents from five wastewater treatment plants and their receiving waters in South East Queensland. The total xenoestrogen concentrations in effluent ranged between 2446 ng/L and 6579 ng/L, with 4-NP and NPE1-2 having much higher concentration levels than BPA and 4-t-OP. The estrogen levels in effluent varied from 9.12 to 32.22 ng/L for E1, from 1.37 ng/L to 6.35 ng/L for E2 and from 0.11 ng/L to 1.20 ng/L for EE2. No significant differences (p < 0.05) in the concentrations of the selected estrogenic compounds were found for the effluents from the five sewage treatment plants. The estrogens and xenoestrogens were also found in the receiving waters at relatively lower concentration levels due to dilution of effluents in the rivers. Based on the chemical analysis data and relative potency of the compound from in vitro and in vivo bioassays from the literature, the calculated in vitro EEQ values (estrogen equivalents) in the receiving river waters downstream of the effluent discharge points ranged from 1.32 to 11.79 ng/L, while the in vivo EEQ values (vitellogenin response in rainbow trout) ranged from 2.48 to 21.18 ng/L. The three estrogens accounted for the majority of the EEQ in the water samples. This study indicates that the rivers of South East Queensland are at potential risk.     

Characterization of soluble microbial products from anaerobic treatment by molecular weight distribution and nickel-chelating properties

Nine anaerobic chemostats fed glucose as the sole carbon and energy source were used to investigate the characteristics of soluble microbial products (SMP). These reactors were maintained at solids retention times (SRT) of 15, 25, and 40 days (3 reactors for each SRT) with organic loading rates of 0.25 or 0.50 g COD/1-d. Results showed that the concentration of SMP increased with increasing SRT (steady-state SMP for 15-, 25-, and 40-d systems were 54, 126, and 291 mg COD/1, respectively). Distribution of SMP among three molecular weight categories (MW < 1000 daltons, 1000 < MW < 10,000, and MW > 10,000) was bimodal. The fraction of SMP with MW > 10,000 was found to increase with increasing SRT (34 mg/l and 48% of total SMP for a 15-d SRT, 83 mg/l and 62% for a 25-d SRT, and 242 mg/l and 76% for a 40-d system). The stability constant (^cK) between Ni and SMP was approximately 10^3.62, a value very similar to some naturally occurring organic acids. The total SMP-ligand concentration (C_T,L) ranged from 0.07 to 1.33 mM as Ni and increased with increasing SRT. The complexation capacity ranged from 0.65 to 5.97 μmol of Ni/mg SMP, and was independent of SRT with an average of 2.49 μmol of Ni/mg SMP.     

Chelating properties and molecular weight distribution of soluble microbial products from an aerobic membrane bioreactor

This paper presents a detailed study on soluble microbial products (SMPs) in an aerobic membrane bioreactor (MBR) treating synthetic wastewater simulating municipal wastewater. The concentration of SMP in the reactor conformed to a cyclical pattern of accumulation and reduction in relation to SRT. The molecular weight (MW) distribution of accumulated SMP was determined to vary from <1kD to >100kD. Copper chelating properties of various SMP fractions in the MBR were compared before and after copper addition to the feed. The conditional stability constant (LogcK), complexation capacity (Cc), and SMP-ligand concentration (CL) were evaluated to determine the impact of copper on the chelating properties. The results indicated that accumulated SMP in the aerobic MBRs without copper addition are moderate chelators with LogcK values of 7.6-8.3 mol(-1) for the moderate ligands and 6.3-6.8 mol(-1) for the relatively weaker ligands. SMPs with MW of 1-10 kD were found to have the highest complexation capacity among all SMP fractions. The complexation capacity of accumulated SMP after feeding copper was 0.11 micromol/mg of SMP, almost half of its value prior to feeding copper. The reduction of C(c) after feeding copper was a result of an increase in large molecular weight SMP (>100 kD).     

Integrated ozone and biotreatment of pulp mill effluent and changes in biodegradability and molecular weight distribution of organic compounds

The overall effectiveness of integrating ozonation with biological treatment on the biodegradability enhancement and recalcitrant organic matter (ROM) removal from pulp mill alkaline bleach plant effluent was investigated. Ozonation was performed in a semi-batch bubble column reactor at pH of 11 and 4.5. Batch biological treatment was conducted in shake flasks. Samples obtained during the treatments were monitored for BOD₅, COD, TOC, and molecular weight distribution. At an ozone dosage of 0.7-0.8 mg O₃/mL wastewater, integrated treatment showed about 30% higher TOC mineralization compared to individual ozonation or biotreatment. Ozone treatment enhanced the biodegradability of the effluent (monitored as 21% COD reduction and 13% BOD₅ enhancement), allowing for a higher removal of pollutants. The conversion of high molecular weight (HMW) to low molecular weight (LMW) compounds was an important factor in the overall biodegradability enhancement of the alkaline effluent. The overall biodegradability of the LMW compounds did not change over the course of ozonation, but it increased from 5% to 50% (measured as COD removal) for the HMW portion. Ozonation at pH of 11 was more effective than that at pH of 4.5 in terms of generating more biodegradable compounds.     

Modelling particle size distribution dynamics in marine waters

Numerical simulations were carried out to determine the particle size distribution (PSD) in marine waters by accounting for particle influx, coagulation, sedimentation and breakage. Instead of the conventional rectilinear model and Euclidean geometry, a curvilinear collision model and fractal scaling mathematics were used in the models. A steady-state PSD can be achieved after a period of simulation regardless of the initial conditions. The cumulative PSD in the steady state follows a power-law function, which has three linear regions after log-log transformation, with different slopes corresponding to the three collision mechanisms, Brownian motion, fluid shear and differential sedimentation. The PSD slope varies from -3.5 to -1.2 as a function of the size range and the fractal dimension of the particles concerned. The environmental conditions do not significantly alter the PSD slope, although they may change the position of the PSD and related particle concentrations. The simulation demonstrates a generality in the shape of the steady-state PSD in the ocean, which is in agreement with many field observations. Breakage does not affect the size distribution of small particles, while a strong shear may cause a notable change in the PSD for larger and fractal particles only. The simplified approach of previous works using dimensional analysis still offers valuable approximations for the PSD slopes, although the previous solutions do not always agree with the simulation results. The variation in the PSD slope observed in field investigations can be reproduced numerically. It is argued that non-steady-state conditions in natural waters could be the main reason for the deviation of PSD slopes. A change in the nature of the particles, such as stickiness, and environmental variables, such as particle input and shear intensity, could force the PSD to shift from one steady state to another. During such a transition, the PSD slope may vary to some extent with the particle population dynamics.     

Determination of fluorine by micro diffusion as applied to waste waters, river samples and effluents

A method for the analysis of fluorine in waste waters, river samples and trade effluents is described. This employs a modification of the micro diffusion technique for the separation and concentration of the fluorine contained in the sample.     

Enteric virus levels in wastewater effluents and surface waters in the severn trent water authority 1979–1981

Viral surveillance of wastewater effluents and surface waters was carried out between January 1979 and July 1981. Enteric viruses were detected in 45% of 381 samples of effluent and in 48% of 533 samples of surface waters. Viral levels in effluents varied considerably with the highest recovered being 31,000 plaque forming units per litre (pfu l⁻¹). A substantial number of effluent samples gave levels lower than the practical detection limit of 100 pfu l⁻¹. Levels were markedly lower in surface waters, the highest being 647 pfu l⁻¹. River water which had received long-term bankside storage only yielded virus infrequently. The narrow range of serotypes identified probably reflects the limitations of the BGM cell system used in the assay procedure. Serotypes belonged to the polio and coxsackie B groups with only a low incidence of echovirus.     

Colloidal organic matter from wastewater treatment plant effluents: Characterization and role in metal distribution

Colloidal organic matter from wastewater treatment plants was characterized and examined with respect to its role in metal distribution by using tangential flow ultrafiltration, liquid chromatography coupled with organic carbon and UV detectors, and an asymmetrical flow field-flow fractionation (AFlFFF) multidetection platform. Results revealed that a humic-like fraction of low aromaticity with an average molar mass ranging from 1600 to 2600 Da was the main colloidal component. High molar mass fractions (HMM), with molar mass ranges between 20 and 200 kDa, were present in lower proportions. Ag, Cd, Cu, Cr, Mn and Zn were found mainly in the dissolved phase (<0.45 μm) and their distribution between colloidal and truly dissolved fractions was strongly influenced by the distribution of dissolved organic carbon. AFlFFF coupled to ICP-MS showed that Ag, Cd, Cu, Cr, Mn and Zn associate to the low molar mass fraction of the colloidal pool, whereas Al, Fe and Pb were equally bound to low and high molar mass fractions.     

Quantification and molecular characterization of enteric viruses detected in effluents from two hospital wastewater treatment plants

Hospital wastewater has been described as an important source of spreading pathogenic microorganisms in the environment. However, there are few studies reporting the presence and concentrations of gastroenteric viruses and hepatitis A viruses in these environmental matrices. The aim of this study was to assess the contamination by viruses responsible for acute gastroenteritis and hepatitis derived from hospital wastewater treatment plants (WWTPs). Rotavirus A (RV-A), human adenoviruses (HAdV), norovirus genogroup I and II (NoV GI/GII) and hepatitis A viruses (HAV) were detected and quantified in sewage samples from two WWTPs located in Rio de Janeiro (Brazil) that operates different sewage treatments. WWTP-1 uses an Upflow Anaerobic Sludge Blanket (UASB reactor) and three serial anaerobic filters while WWTP-2 uses aerobic processes, activated sludge with extended aeration and final chlorination of the effluents. Viruses’ detection was investigated by using conventional PCR/RT-PCR, quantitative real-time PCR (qPCR) and partial sequencing of the genome of the viruses detected. Rate of viruses detection ranged from 7% (NoV GI in WWTP-1) to 95% (RV-A in WWTP-2) and genome from all viruses were detected. The most prevalent genotypes were RV-A SG I, HAdV species D and F, NoV GII/4 and HAV subgenotype IA. Mean values of viral loads (genome copies (GC)/ml) obtained in filtered effluents from anaerobic process was 1.9 × 10³ (RV-A), 2.8 × 10³ (HAdV) and 2.4 × 10³ (NoV GII). For chlorinated effluents from activated sludge process, the mean values of viral loads (GC/ml) was 1.2 × 10⁵ (RV-A), 1.4 × 10³ (HAdV), 8.1 × 10² (NoV GII) and 2.8 × 10⁴ (HAV). Data on viral detection in treated effluents of hospital WWTPs confirmed the potential for environmental contamination by viruses and could be useful to establish standards for policies on wastewater management.     

Spatial and temporal distribution of pesticide residues in surface waters in northeastern Greece

A monitoring study of 147 compounds in surface river waters from northeastern Greece near Greek/Bulgarian/Turkish borders was carried out during 1999-2007. Based on agricultural use eight sampling points along the rivers Ardas, Evros and Erythropotamos were set up, covering the distance from the Greek/Bulgarian borders down to the river's discharge (river's delta) in the Greek territory. In total, 88 sampling events were carried out from 1999 to 2007. Pesticides were extracted by solid-phase extraction (SPE) and analyzed by gas chromatography-mass spectrometry (GC-EI-MS) using a multiresidue in-house analytical method including pesticides belonging to different chemical classes. Aquatic risk concerning the detected pesticides was assessed on the basis of the risk quotient (RQ = PEC/PNEC). From the 28 compounds (pesticides, metabolites and caffeine) that were detected in surface waters of northeastern Greece the soil applied pesticides were the most frequently detected. High pesticide concentrations were detected within 2 months of their application. Extreme pesticide concentrations were detected in the beginning of the irrigation season or just after high rainfall events. Generally, low levels of pesticide residues were found in the first sampling point (Greek/Bulgarian borders) of all rivers, however o′,p′ DDT, o′,p′ DDE and γ-HCH were mainly detected in this sampling point regarded as cross-boundary contamination. The most commonly encountered compounds in the river waters were atrazine, DEA, alachlor, trifluralin, prometryne, molinate, carbofuran, carbaryl and diazinon. Increased loading (primary as well as secondary peaks) seemed to be a consequence of application (timing, rate, frequency) and intense rainfall during the application period. Aquatic risk assessment revealed that from the 28 compounds that were constantly detected 12 showed non-acceptable risk when median concentrations were used as PEC and 18 when extreme concentrations were used as PEC values.