Evaluation of the infectivity,gene and antigenicity persistence of rotaviruses by free chlorine disinfection

The effects of free chlorine disinfection of tap water and wastewater effluents on the infectivity, gene integrity and surface antigens of rotaviruses were evaluated by a bench-scale chlorine disinfection experiments. Plaque assays, integrated cell culture-quantitative RT- PCR （ICC-RT-qPCR）, RT-qPCR, and enzyme-linked immunosorbent assays （ELISA）, respectively, were used to assess the influence of the disinfectant on virus infectivity as well as genetic and antigenic integrity of simian rotavirus SA11 as a surrogate for human rotaviruses. The ICC-RT-qPCR was able to detect rotaviruses survival from chlorine disinfection at chlorine dose up to 20 mg/L （60 min contact）, which suggested a required chlorine dose of 5 folds （from 1 to 5 mg/L） higher than that indicated by the plaque assay to achieve 1.8 log10 reductions in tap water with 60 rain exposing. The VP7 gene was more resistant than the infectivity and existed at chlorine dose up to 20 mg/L （60 min contact）, while the antigencity was undetectable with chlorine dose more than 5 mg/L （60 min contact）. The water quality also impacted the inactivation efficiencies, and rotaviruses have a relatively higher resistant in secondary effluents than in the tap water under the same chlorine disinfection treatments. This study indicated that rotaviruses have a higher infectivity, gene and antigencity resistance to chlorine than that previously indicated by plaque assay only, which seemed to underestimate the resistance of rotaviruses to chlorine and the risk of rotaviruses in environments. Present results also suggested that re-evaluation of resistance of other waterborne viruses after disinfections by more sensitive infectivity detection method （such as ICC-RT-qPCR） may be necessary, to determine the adequate disinfectant doses required for the inactivation of waterborne viruses.

Change in genotoxicity of wastewater during chlorine dioxide and chlorine disinfections and the influence of ammonia nitrogen

The effects of chlorine dioxide and chlorine disinfections on the genotoxicity of different biologically treated sewage wastewater samples were studied by umu-test.The experiment results showed that when chlorine dioxide dosage was increased from 0 to 30 mg/L,the genotoxicity of wastewater first decreased rapidly and then tended to be stable,while when the chlorine dosage was increased from 0 to 30 mg/L,the genotoxicity of wastewater changed diver sely for different samples.It was then found that ammonia nitro-gen did not affect the change of genotoxicity during chlorine dioxide disinfection of wastewater,while it greatly affected the change of genotoxicity during chlorine disin fection of wastewater.When the concentration of ammonia nitrogen was low(<10-20 mg/L),the genotoxicity of wastewater decreased after chlorine disinfection,and when the con-centration of ammonia nitrogen was high(>10-20 mg/L),the genotoxicity of wastewater increased after chlorine disinfection.

Prescreening teratogenic potential of chlorinated drinking water disinfection by-products by using Hydra regeneration assay

Practicability of method for the Hydra regeneration assay on the prescreening teratogenic potential of chlorinated drinking water disinfection by products was studied through both the assays of toxicity of adult Hydra (T) and inhibition of the growth of regeneration Hydra (I) by using chloroform, dichloromethane and chloroacetic acid. The results showed that T 50 / I 50 ratios of chloroform and chloroacetic acid were 2 77 and 6 16 respectively, with teratogenic potential. T 50 / I 50 ratio of dichloromethane was 1.69, with weaker teratogenic potential. These experimental results indicated preliminarily that the Hydra regeneration assay has certainly applied value as a prescreening assay for developmental toxicity.

Sequential use of ultraviolet light and chlorine for reclaimed water disinfection

Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity formation. The UV inactivation of the tested pathogenic bacteria was not affected by the quality of water. It was found that the inactivated bacteria were obviously reactivated after one day in dark. Fluorescent light irradiation increased the bacteria repair. The increase of UV dosage could cause more damage to bacteria to inhibit bacteria self-repair. No photoreactivation was detected when the UV dose was up to 80 mJ/cm2 for E. coli DH5ct, and 23 mJ/cm2 for S. dysenteriae. Nevertheless, sequential use of 8 mJ/cm2 of UV and low concentration of chlorine （1.5 mg/L） could effectively inhibit the photoreactivation and inactivate E. coli below the detection limits within seven days. Compared to chlorination alone, the sequential disinfection decreased the genotoxicity of treated wastewater, especially for the sample with high NH3-N concentration.

Enhanced formation of trihalomethane disinfection byproducts from halobenzoquinones under combined UV/chlorine conditions

Halobenzoquinones(HBQs)are highly toxic disinfection byproducts(DBPs)and are also precursors of other DBPs such as trihalomethanes(THMs).The formation of THMs from HBQs during chlorine-only and UV/chlorine processes with or without bromide was investigated experimentally.Density functional theory(DFT)reactivity descriptors were also applied to predict the nucleophilic/electrophilic reactive sites on HBQs and intermediates.The results were combined to explain the different behaviors of 2,6-dichloro-1,4-benzoquinone(2,6-DCBQ)and tetrachloro-1,4-benzoquinone(TCBQ)and to propose mechanism for the promoting roles of UV and hydroxylation of HBQs in THMs formation.Under UV/chlorine,UV significantly enhanced THMs formation from 2,6-DCBQ compared to chlorine-only,mainly due to the production of OH-DCBQ^(*).Excited 2,6-DCBQ^(*)by UV benefited nucleophilic hydrolysis to produce OH-DCBQ^(*),which favored electrophilic attack by chlorine,thereby inducing more THMs formation.UV/chlorine modestly promoted THMs formation from TCBQ compared to chlorine-only.Hydroxylation of TCBQ and UV irradiation were both important in promoting THMs formation due to the high electrophilic property of OH-TCBQ and TCBQ^(*).Meanwhile,hydroxylation of HBQs and CHCl3 formation were enhanced at higher pH.This work suggested that enhanced formation of THMs from HBQs should be considered in the application of combined UV and chlorine processes.

Synergistic effects of sodium hypochlorite disinfection and iron-oxidizing bacteria on early corrosion in cast iron pipes

Corrosion in drinking water distribution systems(DWDSs)may lead to pipe failures and water quality deterioration;biocorrosion is the most common type.Chlorine disinfectants are widely used in DWDSs to inhibit microorganism growth,but these also promote electrochemical corrosion to a certain extent.This study explored the independent and synergistic effects of chlorine and microorganisms on pipeline corrosion.Sodium hypochlorite(NaOCl)at different concentrations(0,0.25,0.50,and 0.75 mg/L)and iron-oxidizing bacteria(IOB)were added to the reaction system,and a biofilm annular reactor(BAR)was employed to simulate operational water supply pipes and explain the composite effects.The degree of corrosion became severe with increasing NaOCl dosage.IOB accelerated the corrosion rate at an early stage,after which the reaction system gradually stabilized.When NaOCl and IOB existed together in the BAR,both synergistic and antagonistic effects occurred during the corrosion process.The AOC content increased due to the addition of NaOCl,which is conducive to bacterial regrowth.However,biofilm on cast iron coupons was greatly influenced by the disinfectant,leading to a decrease in microbial biomass over time.More research is needed to provide guidelines for pipeline corrosion control.

Impact of combining chlorine dioxide and chlorine on DBP formation in simulated indoor swimming pools

The main objective of this study was to assess the combined use of chlorine dioxide（ClO_2）and chlorine（Cl_2） on the speciation and kinetics of disinfection by-product（DBP） formation in swimming pools using synthetic pool waters prepared with a body fluid analog（BFA）and/or fresh natural water. At 1：25（mass ratio） of ClO_2 to Cl_2, there was no significant reduction in the formation of trihalomethanes（THMs） and haloacetic acids（HAAs） for both BFA solution and natural water compared to the application of Cl_2 alone. When the mass ratio of ClO_2 to Cl_2increased to 1：1, substantial decreases in both THMs and HAAs were observed in the natural water, while there was almost no change of DBP formations in the BFA solution. Haloacetonitriles and halonitromethanes levels in both water matrices remained similar. In the presence of bromide, the overall DBP formation increased in both BFA solution and natural water. For the DBP formation kinetics, after 72 hr of contact time,very low formation of THMs and HAAs was observed for the use of ClO_2 only. Compared to Cl_2 control, however, applying the 1：1 mixture of ClO_2/Cl_2 reduced THMs by 〉 60% and HAAs by 〉 50%. Chlorite was maintained below 1.0 mg/L, while the formation of chlorate significantly increased over the reaction time. Finally, in a bench-scale indoor pool experiment, applying ClO_2 and Cl_2simultaneously produced less THMs compared to Cl_2 control and kept chlorite at 〈 0.4 mg/L, while HAAs and chlorate accumulated over 4-week operation period.

Formation and control of disinfection byproducts and toxicity during reclaimed water chlorination： A review

Chlorination is essential to the safety of reclaimed water; however, this process leads to concern regarding the formation of disinfection byproducts（DBPs） and toxicity. This study reviewed the formation and control strategies for DBPs and toxicity in reclaimed water during chlorination.Both regulated and emerging DBPs have been frequently detected in reclaimed water during chlorination at a higher level than those in drinking water, indicating they pose a greater risk to humans. Luminescent bacteria and Daphnia magna acute toxicity, anti-estrogenic activity and cytotoxicity generally increased after chlorination because of the formation of DBPs. Genotoxicity by umu-test and estrogenic activity were decreased after chlorination because of destruction of toxic chemicals. During chlorination, water quality significantly impacted changes in toxicity.Ammonium tended to attenuate toxicity changes by reacting with chlorine to form chloramine,while bromide tended to aggravate toxicity changes by forming hypobromous acid. During pretreatment by ozonation and coagulation, disinfection byproduct formation potential（DBPFP）and toxicity formation potential（TFP） occasionally increase, which is accompanied by DOC removal; thus, the decrease of DOC was limited to indicate the decrease of DBPFP and TFP. It is more important to eliminate the key fraction of precursors such as hydrophobic acid and hydrophilic neutrals. During chlorination, toxicities can increase with the increasing chlorine dose and contact time. To control the excessive toxicity formation, a relatively low chlorine dose and short contact time were required. Quenching chlorine residual with reductive reagents also effectively abated the formation of toxic compounds.

Acute toxicity variation of hydroxyl benzophenone UV filters during photoinduction–chlorination disinfection processes

Benzophenones（BPs）, a group of widely used UV filters, exert multiple, significant toxicity effects. The 11 BPs were selected as target compounds, and the photobacterium acute toxicity test and an index for acute toxicity formation potential（ATFP） were used to evaluate the toxicity variation of BPs before and after a photoinduction–chlorination disinfection process.Orthogonal experiments were performed at different pH values and chlorine dosages. The characteristics of ATFP values for 11 BPs after a photoinduction–chlorination process can be summarized as follows：（1） The ATFPs decreased as the hydroxyl group number increased in BPs molecules.（2） For those BPs with the same hydroxyl group number, the ATFPs were higher when the hydroxyl groups were located at the 3-or 4-position than those at the 2-position; the BPs with hydroxyl groups distributed on two benzene rings had higher ATFPs than those on one ring.（3） Introducing a methoxyl group and sulfonic acid group into BP molecules increased the ATFP values.（4） The ATFPs were p H-dependent, the values of which were lowest at the neutral condition and highest at the acid condition.（5） The ATFPs increased and then decreased as the chlorine dosage increased. The results can be used as a reference to scientifically evaluate the environmental fate and potential risk of BPs in photoinduction–chlorination disinfection processes.

DBP formation from degradation of DEET and ibuprofen by UV/chlorine process and subsequent post-chlorination

The formation of disinfection by-products（DBPs） from the degradation of N,N-diethyl-3-methyl benzoyl amide（DEET） and ibuprofen（IBP） by the ultraviolet irradiation（UV）/chlorine process and subsequent post-chlorination was investigated and compared with the UV/H_2O_2 process.The pseudo first-order rate constants of the degradation of DEET and IBP by the UV/chlorine process were 2 and 3.1 times higher than those by the UV/H_2O_2 process, respectively, under the tested conditions. This was due to the significant contributions of both reactive chlorine species U（RCS） and hydroxyl radicals（HO） in the UV/chlorine process. Trichloromethane, 1,1,1-trichloro-2-propanone and dichloroacetic acid were the major known DBPs formed after 90% of both DEET and IBP that were degraded by the UV/chlorine process. Their yields increased by over 50%after subsequent 1-day post-chlorination. The detected DBPs after the degradation of DEET and IBP comprised 13.5% and 19.8% of total organic chlorine（TOCl）, respectively, and the proportions increased to 19.8% and 33.9% after subsequent chlorination, respectively. In comparison to the UV/H_2O_2 process accompanied with post-chlorination, the formation of DBPs and TOCl in the UV/chlorine process together with post-chlorination was 5%–63% higher,Ulikely due to the generation of more DBP precursors from the attack of RCS, in addition to HO.

Formation of disinfection byproducts from accumulated soluble products of oleaginous microalga after chlorination

When microalgae are simultaneously applied for wastewater treatment and lipid production, soluble algal products （SAP） should be paid much attention, as they are important precursors for formation of disinfection byproducts （DBPs）, which have potential risks for human health. Chlorella sp. HQ is an oleaginous microalga that can generate SAP during growth, especially in the exponential phase. This study investigated the contribution of SAP from Chlorella sp. HQ to DBP formation after chlorination.The predominant DBP precursors from SAP were identified with the 3D excitation-emission matrix fluorescence. After chlorination, a significant reduction was observed in the fluorescence intensity of five specific fluorescence regions, particularly aromatic proteins and soluble microbial by-product-like regions, accompanied with slight shifting of the peak. The produced DBPs were demonstrated to include trihalomethanes and haloacetic acids. As the algal cultivation time was extended in wastewater, the accumulated SAP strengthened the formation of DBPs. The trend for DBP formation was as follows： chloroform〉dichloroacetic acid〉trichloroacetic acid.

Comparative mammalian cell cytotoxicity of wastewater with elevated bromide and iodide after chlorination,chloramination, or ozonation

Recycling wastewater is becoming more common as communities around the world try to better control their water resources against an increased frequency of either prolonged droughts or intense flooding. For communities in coastal areas, wastewaters may contain elevated levels of bromide（Br^-） and iodide（I^-） from seawater intrusion or high mineral content of source waters. Disinfection of such wastewater is mandatory to prevent the spread of pathogens, however little is known about the toxicity of wastewater after disinfection in the presence of Br^-and I^-. In this study we compared the induction of chronic cytotoxicity in mammalian cells in samples of municipal secondary wastewater effluent amended with elevated levels of Br^-/I^-after disinfection by chlorine, chloramines or ozone to identify which disinfection process generated wastewater with the lowest level of adverse biological response. Chlorination increased mammalian cell cytotoxicity by 5times as compared to non-disinfected controls. Chloramination produced disinfected wastewater that expressed 6.3 times more cytotoxicity than the non-disinfected controls and was 1.3 times more cytotoxic than the chlorinated samples. Ozonation produced wastewater with cytotoxicity comparable to the non-disinfected controls and was at least 4times less cytotoxic than the chlorine disinfected wastewaters. These results indicate that compared to chlorination and chloramination, ozonation of wastewater with high Br^-/Ilevels yielded the lowest mammalian cell cytotoxicity, suggesting its potential as a more favorable method to disinfect wastewater with minimizing the biological toxicity in mind.

Formation of iodo-trihalomethanes, iodo-haloacetic acids, and haloacetaldehydes during chlorination and chloramination of iodine containing waters in laboratory controlled reactions

Iodine containing disinfection by-products（I-DBPs） and haloacetaldehydes（HALs） are emerging disinfection by-product（DBP） classes of concern. The former due to its increased potential toxicity and the latter because it was found to be the third most relevant DBP class in mass in a U.S. nationwide drinking water study. These DBP classes have been scarcely investigated, and this work was performed to further explore their formation in drinking water under chlorination and chloramination scenarios. In order to do this, iodo-trihalomethanes（I-THMs）,iodo-haloacetic acids（I-HAAs） and selected HALs（mono-HALs and di-HALs species, including iodoacetaldehyde） were investigated in DBP mixtures generated after chlorination and chloramination of different water matrices containing different levels of bromide and iodide in laboratory controlled reactions. Results confirmed the enhancement of I-DBP formation in the presence of monochloramine. While I-THMs and I-HAAs contributed almost equally to total I-DBP concentrations in chlorinated water, I-THMs contributed the most to total I-DBP levels in the case of chloraminated water. The most abundant and common I-THM species generated were bromochloroiodomethane, dichloroiodomethane, and chlorodiiodomethane. Iodoacetic acid and chloroiodoacetic acid contributed the most to the total I-HAA concentrations measured in the investigated disinfected water. As for the studied HALs, dihalogenated species were the compounds that predominantly formed under both investigated treatments.

The chlorination transformation characteristics of benzophenone-4 in the presence of iodide ions

Benzophenone-type UV filters are a group of compounds widely used to protect human skin from damage of UV irradiation. Benzophenone-4（BP-4） was targeted to explore its transformation behaviors during chlorination disinfection treatment in the presence of iodide ions. With the help of ultra performance liquid phase chromatograph and high-resolution quadrupole time-of-flight mass spectrometer, totally fifteen halogenated products were identified, and five out of them were iodinated products. The transformation mechanisms of BP-4 involved electrophilic substitution generating mono-or di-halogenated products,which would be oxidized into esters and further hydrolyzed into phenolic derivatives. The desulfonation and decarboxylation were observed in chlorination system either. Obeying the transformation pathways, five iodinated products formed. The p H conditions of chlorination system determined the reaction types of transformation and corresponding species of products. The more important was that, the acute toxicity had significant increase after chlorination treatment on BP-4, especially in the presence of iodide ions. When the chlorination treatment was performed on ambient water spiked with BP-4 and iodide ions,iodinated by-products could be detected.

Total organic halogen(TOX) in human urine: A halogen-specific method for human exposure studies

Disinfection by-products（DBPs） are a complex mixture of compounds unintentionally formed as a result of disinfection processes used to treat drinking water. Effects of long-term exposure to DBPs are mostly unknown and were the subject of recent epidemiological studies. However,most bioanalytical methods focus on a select few DBPs. In this study, a new comprehensive bioanalytical method has been developed that can quantify mixtures of organic halogenated compounds, including DBPs, in human urine as total organic chlorine（TOCl）, total organic bromine（TOBr）, and total organic iodine（TOI）. The optimized method consists of urine dilution, adsorption to activated carbon, pyrolysis of activated carbon, absorption of gases in an aqueous solution, and halide analysis with ion chromatography and inductively coupled plasma-mass spectrometry. Spike recoveries for TOCl, TOBr, and TOI measurements ranged between 78% and 99%. Average TOCl, TOBr, and TOI concentrations in five urine samples from volunteers who consumed tap water were 1850, 82, and 21.0 μg/L as X^-, respectively.Volunteers who consumed spring water（control） had TOCl, TOBr, and TOI average concentrations in urine of 1090, 88, and 10.3 μg/L as X^-, respectively. TOCl and TOI in the urine samples from tap water consumers were higher than the control. However, TOBr was slightly lower in tap water urine samples compared to mineral water urine samples, indicating other sources of environmental exposure other than drinking water. A larger sample population that consumes tap water from different cities and mineral water is needed to determine TOCl, TOBr, and TOI exposure from drinking water.