Health risk assessment of phthalate esters (PAEs) in drinking water sources of China

Phthalate esters (PAEs) with endocrine disruption effects and carcinogenicity are widely detected in water environment. Occurrences of PAEs in source water and removal efficiencies of PAEs by drinking water treatment plants (DWTPs) in China were surveyed from publications in the last 10 years. Concentration of diethylhexyl phthalate (DEHP) in source water with median value of 1.3 μg/L was higher than that of dimethyl phthalate (DMP), diethyl phthalate (DEP), and di-n-butyl phthalate (DnBP). If the removal efficiencies of DEHP and DnBP reached 60 and 90 %, respectively, the calculated PAE concentration in drinking water can generally meet Standards for Drinking Water Quality in China. The health risks of PAEs, including non-carcinogenic and carcinogenic risks via the "water source-DWTP-oral ingestion/dermal permeation" pathway, were evaluated with Monte Carlo simulation and sensitivity analysis under certain removal efficiencies from 0 to 95 %. The carcinogenic risk of DEHP was lower than the upper acceptable carcinogenic risk level (10(-4)), while the probability of DEHP's carcinogenic risk between lower (10(-6)) and upper (10(-4)) acceptable carcinogenic risk level decreased from about 21.2 to 0.4 % through increasing DEHP removal efficiency from 0 to 95 %. The non-carcinogenic risk of DEHP was higher than that of DEP and DnBP. In all cases, the total non-carcinogenic risk of DEP, DnBP, and DEHP was lower than 1, indicating that there would be unlikely incremental non-carcinogenic risk to humans. Both carcinogenic risk and non-carcinogenic risk of PAEs in drinking water to female were a little higher than those to male.

A fingerprint analysis method for characterization of dissolved organic matter in secondary effluents of municipal wastewater treatment plant

Dissolved organic matter (DOM) in wastewater and reclaimed water is related to water quality, safety, and treatability. In this study, DOM was characterized through a fingerprint analysis method for DOM characterization using resin fractionation followed by size exclusion chromatography (SEC). Resin fractionation was used in the first step to divide the DOM in water samples into six resin fractions, namely, hydrophobic acids (HOA), hydrophobic bases (HOB), hydrophobic neutrals (HON), hydrophilic acids (HIA), hydrophilic bases (HIB), and hydrophilic neutrals (HIN). SEC analysis was then performed to separate each resin fraction into several (n) subfractions with different molecular weights (MW). Thus, the total DOM in the water sample was fractionated into 6n subfractions. After quantification of each subfraction by dissolved organic carbon (DOC), a fingerprint graph was constructed to express the distribution of DOM in the subfractions. The fingerprint analysis method was applied to a secondary effluent sample during ozonation. Ozonation (dose of 10 mg L(-1)) removed the DOC only by 8 % and reduced UV254 of the sample by 36 %. Fingerprint graphs also revealed that the resin fractions changed quite limitedly but transformation of subfractions occurred notably.

Antiestrogenic activity and related disinfection by-product formation induced by bromide during chlorine disinfection of sewage secondary effluent

Chlorine disinfection, widely used in wastewater reclamation, can form toxic and harmful disinfection by-products (DBPs), some of which are associated with endocrine disruption. In this study, the presence of bromide was found to promote an increase in antiestrogenic activity using a yeast two-hybrid assay in the sewage secondary effluent during chlorine disinfection. Among the dissolved organic matters in the secondary effluent, hydrophobic acids and hydrophilic substance fractions were determined as potential precursors associated with increase in antiestrogenic activity in the secondary effluent induced by bromide. Further antiestrogenic activity evaluation and mass spectrum characterization following the semipreparative liquid chromatography fractionation of a natural organic matter precursor, tyrosine, after chlorination under the presence of bromide revealed, for the first time, that 2-(bromo-4-hydroxyphenyl) acetonitrile (Br-HPAN) and 2-(dibromo-4-hydroxyphenyl) acetonitrile (DBr-HPAN) exhibited antiestrogenic activity. Br-HPAN and DBr-HPAN were the DBPs involved in the increase in antiestrogenic activity in the tyrosine solution. Bromide was shown to induce the formation of Br-HPAN and DBr-HPAN in the secondary effluent during chlorine disinfection.

[Health risk induced by estrogens during unplanned indirect potable reuse of reclaimed water from domestic wastewater]

The estrogenic endocrine disruptors in reclaimed water from domestic wastewater may induce health risks to human being, when reclaimed water is used for augmentation of drinking water unplannedly and indirectly. This study investigated changes in concentrations of estrone, estradiol, 17alpha-ethinyl estradiol, bisphenol A, nonylphenol and octylphenol in reclaimed water during the reuse of reclaimed water for augmentation to water source such as lakes and reservoir via river. Thereafter, health risk induced by estrogens during the resue of reclaimed water was evaluated. The concentration of estrogen in secondary effluent ranged 0.1-100 ng x L(-1). The highest concentrations of bisphenol A and nonylphenol reached up to 1-10 microg x L(-1). During the indirect reuse of reclaimed water as potable water, the dilution and degradation in river and lake, and the removal by drinking water treatment process could change the concentrations of estrogen. The non-carcinogenic risks of estrone, estradiol, bisphenol A, nonylphenol and octylphenol were lower than 1. When the hydraulic retention time of 17alpha-ethinyl estradiol (EE2) in lakes and reservoir was higher than 30 days, the non-carcinogenic risk of EE2 was lower than 1 in most cases. When the hydraulic retention time of EE2 in lakes and reservoir was less than 30 days and the percentages of reclaimed water in drinking water were higher than 50%, the non-carcinogenic risk induced by EE2 was higher than 1 in 20%-50% samples. This indicated that the risks of EE2 should be concerned.

Transformation of anti-estrogenic-activity related dissolved organic matter in secondary effluents during ozonation

Anti-estrogenic activity of dissolved organic matter (DOM) in reclaimed water is gaining increasing attention. In this study, anti-estrogenic activity removal efficiency by ozonation in the tertiary treatment process of domestic wastewater was investigated. The anti-estrogenic activity in the secondary effluents used in this study ranged between 0.95 and 2.00 mg-TAM L(-1) and decreased significantly after ozonation. The removal efficiency of anti-estrogenic activity at a dose of 10 mg-O3 L(-1) was 65-87%. The removal of the anti-estrogenic activity was highly correlated with the removal of UV254, suggesting that UV254 can be used as a surrogate for anti-estrogenic activity during ozonation. The results of size exclusion chromatography of the wastewater samples during ozonation showed that the UV254 absorbance of the DOM fraction with large apparent molecular weight (MW) around 7.6 k Da dropped significantly, and the DOM fraction was suspected to be humic substances which have been previously identified as anti-estrogenic constituents in secondary effluents. The excitation emission matrix fluorescence spectra of the wastewater samples proved that humic substances existed in the DOM and indeed reacted with the ozone. With the help of two-dimensional correlation of Fourier transform infrared, it was confirmed that the aromatic structures in the DOM were largely destroyed by ozonation. Therefore, it was suggested that the destruction of the aromatic structures in the DOM was related to the removal of the anti-estrogenic activity.

Clinical analysis of diagnosis and treatment of 13 cases with cesarean scar pregnancy

OBJECTIVE

To explore effective methods in diagnosing and treating cesarean scar pregnancy (CSP) after cesarean section.

MATERIALS AND METHODS

The clinical data of 13 cases with CSP who were admitted to the present hospital from October 2009 to February 2012 were retrospectively analyzed.

RESULTS

The agreement diagnostic rate was 92.3% (12/13). On the basis of transvaginal color Doppler ultrasonography 12 patients had medical therapy combined with uterine artery embolization (UAE) and curettage was successfully performed. One patient was diagnosed through an emergency setting due to symptomatology.

CONCLUSION

Early accurate diagnosis of CSP is the key to perform proper and successful treatment.

Enhanced decomposition of 1,4-dioxane in water by ozonation under alkaline condition

1,4-Dioxane is a probable human carcinogenic and refractory substance that is widely detected in aquatic environments. Traditional wastewater treatment processes, including activated sludge, cannot remove 1,4-dioxane. Removing 1,4-dioxane with a reaction kinetic constant of 0.32 L/(mol·s) by using ozone, a strong oxidant, is difficult. However, under alkaline environment, ozone generates a hydroxyl radical (•OH) that exhibits strong oxidative potential. Thus, the ozonation of 1,4-dioxane in water under different pH conditions was investigated in this study. In neutral solution, with an inlet ozone feed rate of 0.19 mmol/(L·min), the removal efficiency of 1,4-dioxane was 7.6% at 0.5 h, whereas that in alkaline solution was higher (16.3-94.5%) within a pH range of 9-12. However, the removal efficiency of dissolved organic carbon was considerably lower than that of 1,4-dioxane. This result indicates that several persistent intermediates were generated during 1,4-dioxane ozonation. The pseudo first-order reaction further depicted the reaction of 1,4-dioxane. The obvious kinetic constants (kobs) at pH 9, 10, 11 and 12 were 0.94, 2.41, 24.88 and 2610 L/(mol·s), respectively. Scavenger experiments on radical species indicated that •OH played a key role in removing 1,4-dioxane during ozonation under alkaline condition.

Removal potential of anti-estrogenic activity in secondary effluents by coagulation

Anti-estrogenic activity in wastewater is gaining increased attention because of its endocrine-disrupting function. In this study, the level and removal efficiency by coagulation of anti-estrogenic activity in secondary effluents of domestic wastewater treatment plants were studied. Anti-estrogenic activity was detected in secondary effluent samples at a tamoxifen (TAM) equivalent concentration level of 0.38-0.94 mg-TAML(-1). Dissolved organic matters (DOM) with the molecular weight (MW) less than 3000 Da in hydrophobic acids (HOA) and hydrophobic neutrals (HON) fractions of the secondary effluent were the key fractions related to anti-estrogenic activity. Coagulation with FeCl(3) and polyaluminium chloride (PAC) can remove the anti-estrogenic activity of the secondary effluents, but the removal efficiency was limited. The removal efficiency using FeCl(3) coagulant was higher than that induced by PAC. Dissolved organic carbon was continuously removed with increased coagulant dose (0-120 mg L(-1) FeCl(3) or 0-60 mg L(-1) PAC). However, the removal of anti-estrogenic activity was not enhanced further when the coagulant concentration was beyond a critical value (30 mg L(-1) FeCl(3) or 10 mg L(-1) PAC). The highest removal of anti-estrogenic activity was about 36% by FeCl(3) and 20% by PAC. Size exclusion chromatography results indicated difficulty in removing DOM with MW less than 3000 Da in the secondary effluent during coagulation even at a high coagulant concentration, which led to low removal efficiency of anti-estrogenic activity.

Effects of chemical agent injections on genotoxicity of wastewater in a microfiltration-reverse osmosis membrane process for wastewater reuse

With combined microfiltration (MF)/ultrafiltration (UF) and reverse osmosis (RO) process being widely used in municipal wastewater reclamation, RO concentrate with high level genotoxicity is becoming a potential risk to water environment. In this study, wastewater genotoxicity in a MF-RO process for municipal wastewater reclamation and also the effects of chemical agent injections were evaluated by SOS/umu genotoxicity test. The genotoxicity of RO concentrate ranged 500-559 μg 4-NQO (4-nitroquinoline-1-oxide)/L and 12-22 μg 4-NQO/mg DOC, was much higher than that of RO influent. Further research suggested that Kathon biocide was a key chemical agent associated with the genotoxicity increase. Kathon biocide used in RO system was highly genotoxic in vitro and Kathon biocide retained in RO system could contribute to a higher genotoxicity of RO concentrate. Hence, treatments for biocides before discharging are necessary. Chlorination of secondary effluent could significantly decrease the genotoxicity and increasing chlorine dosage could be an efficacious method to decrease the genotoxicity of RO concentrate. According to the result of the experiment, the dosage of chlorine in dual-membrane process could be set to about 2.5 mg Cl₂/L. The effect of antiscalant (2-phosphomobutane-1,2,4-tricarboxylic acid) was also investigated; it turned out to have no effect on genotoxicity.

Formation of haloacetonitriles and haloacetamides during chlorination of pure culture bacteria

The increasing reuse of organic nitrogen-rich wastewater raises concerns regarding the formation of nitrogenous disinfection by-products (N-DBPs), such as haloacetonitriles and haloacetamides. Previous research mainly focused on N-DBPs formation from dissolved organic matter in wastewater. In this study, dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) formation from particles in the secondary effluents of a domestic wastewater treatment plant during chlorination was assessed to account for 26-46% of the total formation. As part of particles in wastewater, bacterial cells enriched in organic nitrogen are considered a potential source for the formation of N-DBPs during chlorination. The formation of DCAN, DCAcAm and trichloroacetamide (TCAcAm) during the chlorination of a Gram-negative bacterium of Escherichia coli (E. coli) and a Gram-positive bacterium of Enterococcus faecalis (E. faecalis) were then evaluated. Compared with dissolved organic matter in the secondary effluent, bacterial cells formed more DCAN, DCAcAm and TCAcAm during chlorination. E. faecalis formed more DCAN, but less DCAcAm and TCAcAm than E. coli did under most chlorination conditions. Moreover, the effects of contact time, chlorine dose, pH value and ammonia nitrogen concentration on the N-DBPs formation from the two bacterial suspensions were investigated. Under the chlorination conditions in this study, DCAN formation from the bacterial suspensions initially increased and then decreased, while TCAcAm formation increased with increasing contact time and chlorine dose. DCAcAm formation from the bacterial suspensions increased with the prolonged contact time, and increased and then decreased with increasing chlorine dose. DCAN, DCAcAm and TCAcAm formation was favored under neutral pH condition, but was reduced with the addition of ammonia during the chlorination of the two bacterial suspensions.

Dichloroacetonitrile and dichloroacetamide can form independently during chlorination and chloramination of drinking waters, model organic matters, and wastewater effluents

The increasing usage of organic nitrogen-rich wastewater- or algal-impacted waters, and chloramines for secondary disinfection, raises concerns regarding the formation of haloacetonitriles, haloacetamides and other nitrogenous disinfection byproducts (N-DBPs). Previous research obtained contradictory results regarding the relative importance of chlorination or chloramination for promoting these byproducts, but applied chlorine and chloramines at different doses and exposure periods. Additionally, mechanistic work, mostly using model precursors, suggested that haloacetonitrile and haloacetamide formation should be correlated because hydrolysis of haloacetonitriles forms haloacetamides. In this work, the formation of dichloroacetonitrile (DCAN) and dichloroacetamide (DCAcAm) were compared across a range of chlorine and chloramine exposures for drinking waters, wastewater effluents, algal extracellular polymeric substances (EPS), NOM isolates and model precursors. While chlorination favored formation of DCAN over DCAcAm, chloramination nearly always formed more DCAcAm than DCAN, suggesting the existence of haloacetamide formation pathways that are independent of the hydrolysis of haloacetonitriles. Experiments with asparagine as a model precursor also suggested DCAcAm formation without a DCAN intermediate. Application of (15)N-labeled monochloramine indicated initial rapid formation of both DCAN and DCAcAm by pathways where the nitrogen originated from organic nitrogen precursors. However, slower formation occurred by pathways involving chloramine incorporation into organic precursors. While wastewater effluents and algal EPS tended to be more potent precursors for DCAN during chlorination, humic materials were more potent precursors for DCAcAm during chlorination and for both DCAN and DCAcAm during chloramination. These results suggest that, rather than considering haloacetamides as haloacetonitrile hydrolysis products, they should be treated as a separate N-DBP class associated with chloramination. While use of impaired waters may promote DCAN formation during chlorination, use of chloramines may promote haloacetamide formation for a wider array of waters.

Removal of genotoxicity in chlorinated secondary effluent of a domestic wastewater treatment plant during dechlorination

PURPOSE

Dechlorination with tetravalent sulfur is widely used in wastewater treatment processes after chlorination. Dechlorination can remove certain genotoxic disinfection by-products (DBPs). However, the reactions occurring during dechlorination of chlorinated secondary effluent and their genotoxic chemicals are still very complex, and the related genotoxicity changes remain unknown. Therefore, the effects of dechlorination on genotoxicity in secondary effluent and its fractions and typical genotoxic chemical after chlorination were evaluated.

METHODS

The dissolved organic matter in the secondary effluent sample was separated into four fractions with XAD-8 resin. Genotoxicity of secondary effluent and its fractions was evaluated by SOS/umu test, an ISO standard method. The concentration of typical genotoxic chemical named ofloxacin was determined by liquid chromatography with a mass spectrometer and a fluorescence detector.

RESULTS

Dechlorination with the addition of Na(2)SO(3) notably decreased the genotoxicity in the chlorinated secondary effluent, especially in the presence of high ammonia nitrogen concentration in the sample before chlorination. The Na(2)SO(3) addition significantly decreased the genotoxicity of the secondary effluent and its genotoxic ofloxacin prior to chlorination. The genotoxicity in the fractions containing hydrophobic acids (HOA) increased after chlorination, while addition of Na(2)SO(3) decreased the genotoxicity induced by chlorination. Tryptophan found in HOA exhibited genotoxicity after chlorination, while dechlorination decreased the genotoxicity in chlorinated tryptophan induced by DBPs.

CONCLUSIONS

Dechlorination was found to decrease the genotoxicity of chlorinated secondary effluent. The decrease was associated with the reduction of genotoxicity in genotoxic chemicals in secondary effluent prior to chlorination and DBPs.

Effect of chlorination on endotoxin activities in secondary sewage effluent and typical Gram-negative bacteria

Wastewater reuse is a viable and attractive method to address water shortage problems. However, wastewater can have high endotoxin activity. Endotoxins are toxic inflammatory agents and are considered a risk factor for wastewater reuse. In this study, the effect of chlorination on endotoxin activity in secondary sewage effluent was evaluated by Limulus (Tachypleus tridentatus) Amebocyte Lysate assay. It was found that chlorination could not decrease endotoxin activity of secondary effluent effectively under the conditions employed in this study. Chlorination of a pure cultured Gram-negative bacterium (Escherichia coli), and a Gram-negative bacterium isolated from secondary sewage effluent, resulted in a significant increase in endotoxin activity, suggesting that the presence of Gram-negative bacteria contributed substantially to endotoxin activity, masking any potential reduction that may be attributable to chlorination. Furthermore, the activities of both free and cell-bound endotoxins in pure culture increased significantly during chlorination due to cell wall damage induced by chlorination.

Effects of chlorination on the properties of dissolved organic matter and its genotoxicity in secondary sewage effluent under two different ammonium concentrations

Recently, NH(4)(+) has been reported to induce potential risks during wastewater chlorination. Thus, the effects of chlorination on genotoxicity and fluorescence spectra of secondary sewage effluents, were investigated in this study before and after adding a high NH(4)(+) quantity. Chlorination decreased the genotoxicity of secondary sewage effluent, while the presence of a high level of NH(4)(+) inhibited this decrease. By further ultrafiltration following XAD-8 resin fractionation, it was found that, with a high NH(4)(+) concentration, the genotoxicity in the fraction of hydrophobic acids (HOA) increased after chlorination and a sub-fraction of HOA with molecular weight less than 1 kDa was the key fraction resulting in this increase. Similar to genotoxicity changes, NH(4)(+) was also found to influence the changes in fluorescence spectra during chlorination. After chlorination, the fluorescence intensity of the dissolved organic matter (DOM) notably decreased, and the emission band of DOM fluorescence spectra shifted to a lower wavelength. However, the presence of NH(4)(+) inhibited both the decrease in intensity and shift. The changes in fluorescence spectra suggested that the fluorescent structure of secondary effluent may decompose during chlorination, but NH(4)(+) could inhibit this decomposition.

Reduced effect of bromide on the genotoxicity in secondary effluent of a municipal wastewater treatment plant during chlorination

Chlorination of wastewater can form genotoxic, mutagenic, and/or carcinogenic disinfection byproduct (DBPs). In this study, the effect of bromide on genotoxicity in secondary effluent of a municipal wastewater treatment plant during chlorination was evaluated by the SOS/umu test. The presence of bromide notably decreased the genotoxicity in secondary effluent during chlorination, especially under conditions of high ammonia concentration. Bromide significantly decreased the concentration of ofloxacin, a genotoxic chemical in secondary effluent, during chlorination with high concentration of ammonia, while genotoxic DBPs formation of humic acid and aromatic amino acids associated with bromide limitedly contributed to the changes of genotoxicity in secondary effluent under the conditions of this study. By fractionating dissolved organic matter (DOM) in the secondary effluent into different fractions, the fractions containing hydrophilic substances (HIS) and hydrophobic acids (HOA) contributed to the decrease in genotoxicity induced by bromide. Chlorination of HOA without bromide increased genotoxicity, while the addition of bromide decreased genotoxicity.

Characterization and identification of antiestrogenic products of phenylalanine chlorination

Recent studies have reported that chlorination increased the antiestrogenic activity of wastewater, suggesting that disinfection by-products (DBPs) formed during chlorination is a potential and important source of endocrine-disruptor. However, antiestrogenic DBPs have not been identified. In this study, the antiestrogenic activity after aqueous chlorination of phenylalanine solution was evaluated by yeast two-hybrid assay and antiestrogenic DBPs were also identified and characterized. For the first time, aqueous chlorination of phenylalanine was found to form antiestrogenic DBPs when the antiestrogenic activity of chlorinated phenylalanine solution (0.5 mmol L(-1)) increased from undetectable to 57 mumol-tamoxifen (TAM) L(-1) with the increase in chlorine doses from 0 to 0.5 mmol-Cl2 L(-1). This level decreased sharply when chlorine addition went over 0.5 mmol-Cl2 L(-1). By fractionating DBPs of chlorinated phenylalanine solution into different fractions via semipreparative liquid chromatography, a key fraction with high antiestrogenic activity was discovered and collected. Based on analyses of mass spectrometry (MS) and nuclear magnetic resonance (NMR), the compound involved in this fraction (21 mg) was determined to be 2,4-diphenylcrotonaldehyde, which is newly identified as a relatively high antiestrogenic chemical.

Monitoring and evaluation of removal of pathogens at municipal wastewater treatment plants

The concentrations and removal of Cryptosporidium, Giardia, and microbial indicators, including somatic coliphages and fecal coliforms were investigated through the wastewater treatment processes at three municipal wastewater treatment plants in Beijing, China. The experimental results showed that the concentrations of Cryptosporidium in untreated wastewater, primary treatment effluent, secondary treatment effluent, tertiary treatment effluent were 33-600, 67-333, 0-9 and 0-0.4 oocysts L(-1), and that of Giardia were 130-3,600, 533-2,033, 0-32 and 0-2.1 cysts L(-1), respectively. The reduction ratios of Cryptosporidium and Giardia by the primary treatment process were 0.12 log and 0.18 log, respectively. Oxidation ditch process had higher reduction efficiency to Cryptosporidium and Giardia than anaerobic-anoxic-oxic process and conventional activated sludge process, probably because of longer retention time and higher sludge concentration. Membrane ultrafiltration had a notably better efficiency to reduce microorganisms, especially Cryptosporidium and Giardia, than conventional flocculation sedimentation and sand filtration process, as the tertiary treatment. Comparing with total coliforms, fecal coliforms and heterotrophic bacteria, concentration of somatic coliphages was correlated better with that of Cryptosporidium and Giardia in untreated wastewater and secondary treatment effluent.

Effects of operating conditions on THMs and HAAs formation during wastewater chlorination

Disinfection is the last barrier of wastewater reclamation process to protect ecosystem safety and human health. However, the chlorination process results in the formation of mutagenic/carcinogenic disinfection by-products (DBPs) deriving from the reaction of the chlorine with organic compounds in wastewater. The effects of operating conditions (chlorine dose, contact time, reaction temperature and pH value) of chlorination on the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) in biologically treated wastewater samples were investigated in this study. The results indicated that the total THMs (TTHM) and total HAAs (THAA) increased exponentially with increasing chlorine dose, but there are discrepancies between the formation rates of TTHM and THAA. The THAA reached a peak at contact time of 2h and thereafter decreased with extended time. The formation time of THMs depends on the wastewater content of quick or slow formers. The yields of bromated HAAs (as MBAA, BCAA, and BDCAA) would decrease markedly after the contact time over 2h during wastewater chlorination, and were favored in low pH values of 4 and high pH values of 9 under certain contact time. In addition, the formation of MBAA, BCAA, BDCAA decreased gradually as reaction temperature increased from 4 to 30 degrees C in the chlorination of wastewater containing a certain concentration of bromide. The effects of operating conditions on THMs and HAAs formation during wastewater chlorination were completely different from those of surface water disinfection.

Effect of ammonia on the formation of THMs and HAAs in secondary effluent chlorination

Recent studies have reported that genotoxicity is increased significantly in wastewater with a high ammonia concentration after chlorination. Thus, this paper studied the effect of ammonia on the formation and speciation of trihalomethanes (THMs) and haloacetic acids (HAAs) during the chlorination of two different biologically-treated wastewater samples from different sources. The formation of THM species was suppressed with increasing ammonia concentration in both samples, but the effect of ammonia concentration on the formation of HAA species (as dichloroacetic, bromochloroacetic, and bromodichloroacetic acid) was quite different. The yields of dihalogenated species occupied the greatest fractions of the total HAAs (over 46%) in both wastewater samples under the experiment scope. However, regarding the distribution of mono-, di-, and trihalogenated species in HAAs, there were discrepancies between the wastewater samples from different sources. The bromine incorporation factors n(Br) and n'(Br), as a function of ammonia concentration, were influenced by the Br(-)/N mass ratio in wastewater chlorination, and were constant when the Br(-)/N mass ratio was lower than 0.003 (or 0.53 microMmM(-1)) due to the low concentrations of bromide ions.

Effect of chlorination on the estrogenic/antiestrogenic activities of biologically treated wastewater

Chlorination is widely used in wastewater reclamation, however harmful disinfection byproducts (DBPs) may be formed during disinfection. These DBPs are considered as a potential and important source of endocrine-disruption. In this study, the effects of chlorination on estrogenic and antiestrogenic activities in biologically treated wastewater were evaluated by yeast two-hybrid assay. For the first time, chlorination was found to increase the antiestrogenic activity of wastewater notably and decrease the estrogenic activity. By fractionating dissolved organic matter (DOM) in wastewater into different fractions, it was found that the polar compounds (PC) fraction of DOM was the key fraction involved in increasing antiestrogenic activity during chlorination of wastewater. Furthermore, fluorescence spectroscopy analysis on different fractions of soluble organic compounds in wastewater suggested that the PC fraction contained most of the aromatic amino acids and humic/fulvic acid, which were then demonstrated as the precursors of antiestrogenic DBPs through chlorination experiments of tryptophan, humic acid, and tannic acid.

Effect of bromide on the formation of disinfection by-products during wastewater chlorination

The effect of bromide ion on the formation and speciation of trihalomethanes (THMs) and haloacetic acids (HAAs) during the chlorination of biologically treated wastewaters was investigated. The experimental results showed that the formation of total THMs and total HAAs during chlorine disinfection increased with increasing bromide levels in wastewater. The formation of CHBr(3) increased nearly linearly with increasing bromide ion levels, while CHCl(2)Br and CHClBr(2) increased with increasing bromide concentration from 0 to 3.2 mg L(-1) and thereafter remained constant or slightly decreased. Increasing initial bromide levels up to 12.8mgL(-1) resulted in sharp decrease of the concentration of CHCl(3) and chloro- HAAs. The mixed bromochloro- HAAs and bromo-only species replaced chloro- HAAs as the dominated species of HAA with increasing bromide levels. The distribution of monohalogenated, dihalogenated and trihalogenated species of HAAs in chlorinated wastewater at high concentration of bromide (>2 mg L(-1)) is different from that of drinking/natural water. The values of the bromine incorporation factors, n (Br) and n' (Br), increased with increasing bromide concentration and remained constant or slightly decreased with increasing contact time under the studied range of bromide ion concentrations during chlorination. Moreover, the bromine incorporation into THMs was higher than that of HAAs with bromide levels ranging from 1.0 to 12.8 mg L(-1), indicating the dissimilar formation mechanisms of THMs and HAAs involving bromide.

[Effect of reaction conditions on the removal of pathogenic protozoan from secondary effluent in flocculation process]

Cryptosporidium and Giardia in reclaimed water are endangering the health of human beings by direct and indirect ways. Compared with traditional disinfection measures, flocculation, clarification and filtration can remove the pathogenic protozoan from wastewater more effectively. The factors affecting the removal of pathogenic protozoan from secondary effluent in flocculation process, including type and dosage of flocculant, pH, temperature and other reaction conditions were studied. The experimental results showed that the effectiveness of pathogenic protozoan removal appeared to be good at pH 6 - 8 and bad at low temperature. The effectiveness increased with the increase of ferric chloride dosage. Aluminium sulphate and poly aluminium chloride gave better performance in removal of pathogenic protozoan at the dosage of 70 mg/L and 20 mg/L respectively.

Influence of ultraviolet-C on structure and function of Synechococcus sp. PCC 7942 photolyase

In this work, an over-expressed cyclobutane pyrimidine dimer (CPD) photolyase of Synechococcus sp. PCC 7942 was used to investigate UV-C (ultraviolet irradiation of C-region) influence on photoreactivation. In vivo photoreactivation experiments indicated that the survival rate decreased from 100 to 2.6% when the UV-C flux was increased from 1.1 to 68.5 muW/cm2. It seemed that the photolyase was easily inactivated at UV-C intensities >or=25.5 muW/cm2. Spectrometric analysis indicated that tertiary structure of the photolyase changed evidently when the UV-C fluxes were >or=25.5 muW/cm2, while the secondary structure was almost unchanged even at 170 muW/cm2. Band shift assay indicated that catalytic activity of the photolyase was impaired at fluxes >or=25.5 muW/cm2, but no significant influence on DNA-binding activity was observed. These results suggest that photoreactivation is efficient at UV-C fluxes <or=25.5 muW/cm2, but would be impaired by intense UV-C irradiation due to structure changes of the photolyase.

[Isolation of a bacterial strain capable of nitrobenzene-degradation at low temperature and the biodegradation characteristics]

Seven bacterial strains that can degrade nitrobenzene at low temperature were isolated from the sediments of a nitrobenzene polluted river. One of the strains, NB1, can mineralize 20 mg/L nitrobenzene completely under the temperature range from 2.5 degrees C to 35 degrees C with an optimum temperature of 25 degrees C. At 5 degrees C, the strain can grow and degrade 20 mg/L nitrobenzene under pH 6 - 9. As long as the concentration of nitrobenzene was not higher than 100 mg/L, it can be degraded by the strain successfully. The strain was identified as Pseudomonas putida according to its morphology, biochemical properties and 16S rDNA sequence analysis. The growth and nitrobenzene degradation character of the strain at different temperature, especially at low temperature, showsthe potential for the bioremediation of nitrobenzene contaminated environment.