Total Trihalomethane Formation Potential Research Articles

Parallel factor analysis of fluorescence excitation emissions to identify seasonal and watershed differences in trihalomethane precursors

Concentration and chemical composition of dissolved organic matter (DOM) play a major role in formation and speciation of disinfection by-products, such as trihalomethanes (THMs), in water treatment plants (WTPs) during disinfection. This study characterized DOM across the process trains of WTPs using fluorescence excitation emission matrices (EEMs) together with parallel factor analysis (PARAFAC). The PARAFAC model was developed from 216 EEMs of bimonthly water samples from three WTPs in Khon Kaen, Thailand, from May 2018 to Mar 2019. Three PARAFAC components identified were humic-like DOM of terrestrial, and microbial or agricultural origin, while the one protein-like component was previously defined as tryptophan-like fluorophore. The relationships between water quality parameters, including the maximum fluorescent intensities (Fmax) of PARAFAC components and THM formation potential (THM-FP) were investigated using Spearman's rank correlation. The Fmax of PARAFAC components, UVA254, DOC, and THM-FP were greater in dry season. Chloroform was the primary THM formed at two sites using surface water as their water source, while the site using surface water with saline groundwater intrusion had higher concentration of brominated THMs. Results indicated that Fmax of humic-like components extracted by PARAFAC analysis were the most accurate THM-FP surrogate parameter assessed for the water samples tested and the correlations between Fmax and THM-FP were site specific (ρ = 0.81–0.85). The result demonstrates that fluorescence spectroscopy analysis has yielded insights into relationships between the DOM optical characteristics and their total THM-FP even at sites with different speciation of THMs.

Sorptive removal of disinfection by-product precursors from UK lowland surface waters: Impact of molecular weight and bromide

The current study compared the impact of three different unit processes, coagulation, granular activated carbon (GAC), and a novel suspended ion exchange (SIX) technology, on disinfection by-product formation potential (DBPFP) from two UK lowland water sources with medium to high bromide content. Specific attention was given to the influence of the organic molecular weight (MW) fraction on DBPFP as well as the impact of bromide concentration. Whilst few studies have investigated the impact of MW fractions from Liquid Chromatography with Organic Carbon Detection (LC-OCD) analysis on dissolved organic carbon (DOC) removal by different processes, none have studied the influence of DOC MW fractions from this analysis on DBP formation. The impact of higher bromide concentration was to decrease the total trihalomethane (THM) and haloacetic acid (HAA) mass concentration, in contrast to previously reported studies. Results indicated that for a moderate bromide concentration source (135 μg/L), the THM formation potential was reduced by 22% or 64% after coagulation or SIX treatment, respectively. For a high bromide content source (210 μg/L), the THM formation potential removal was 47% or 69% following GAC or SIX treatment, respectively. The trend was the same for HAAs, albeit with greater differences between the two processes/feedwaters with reference to overall removal. A statistical analysis indicated that organic matter of MW > 350 g/mol had a significant impact on DBPFP. A multiple linear regression of the MW fractions against DBPFP showed a strong correlation (R2 between 0.90 and 0.93), indicating that LC-OCD analysis alone could be used to predict DBP formation with reasonable accuracy, and offering the potential for rapid risk assessment of water sources.

Seasonal and spatial variation in total trihalomethane formation potential in groundwater in Tulkarm and Hebron, Palestine

Water disinfection using processes such as chlorination is required to kill bacteria and harmful biological components. During chlorination, organic components in water react with chlorine, forming harmful disinfection by-products such as trihalomethanes (THMs). These compounds are very harmful to humans, animals, and plants. Thus, the concentration of these substances in groundwater as well as the seasonal variation in this concentration are of immense interest to scientists. A headspace method was used to analyze trihalomethanes (THMs) using an Agilent 6890N GC/MS. Five-milliliter water samples were employed in this analysis. Separation was performed on a J&W-VRX column. A selected ion monitoring (SIM) mode that complied with US EPA method no. 501 was developed for the detection of four THM species. Quantification and method validation were performed using external standard calibration. The total trihalomethane formation potentials (TTHMFPs) in four groundwater wells in the summer and the winter were found to be below the maximum limits specified by environmental agencies. Seasonal variations were more pronounced for the formation of chloroform (CF), which was the dominant THM species formed. The fraction of the TTHMFP that was due to CF increased in the winter in groundwater samples from the Anabta (2), Anabta (3), and Al Rehya wells, whereas the fraction of the TTHMFP that was due to CF was almost the same in summer (43.2%) and in winter (40.3%) in the groundwater samples from the Al Fawar well. These findings are important for the appropriate regulation of THM levels and for achieving a better understanding of environmental public health and epidemiological issues concerning disinfection by-products in Palestine.

Using the entrapped bioprocess as the pretreatment method for the drinking water treatment receiving eutrophic source water

Control of organic matter, nutrients and disinfection byproduct formation is a major challenge for the drinking water treatment plants on Matsu Islands, Taiwan, receiving source water from the eutrophic reservoirs. A pilot entrapped biomass reactor (EBR) system was installed as the pretreatment process to reduce organic and nitrogen contents into the drinking water treatment plant. The effects of hydraulic retention time (HRT) and combination of preceding physical treatment (ultraviolet and ultrasound) on the treatment performance were further evaluated. The results showed that the EBR system achieved higher than 81%, 35%, 12% and 46% of reduction in chlorophyll a (Chl a), total COD (TCOD), dissolved organic carbon (DOC) and total nitrogen (TN), respectively under varied influent concentrations. The treatment performance was not significantly influenced by HRT and presence/absence of physical pretreatment and the effluent water quality was stable; however, removal efficiencies and removal rates of Chl a, TCOD and DOC showed strong correlation with their influent concentrations. Excitation–emission matrix (EEM) fluorescence spectroscopy identified fulvic-like and humic-like substances as the two major components of dissolved organic matter (DOM) in the reservoir, and decreased intensity of the major peaks in effluent EEM fluorescence spectra suggested the effective removal of DOM without production of additional amount of soluble microbial products in the EBR. Through the treatment by EBR, about 10% of reduction of total trihalomethane formation potential for the effluent could also be achieved. Therefore, the overall results of this study demonstrate that EBR can be a potential pretreatment process for drinking water treatment plants receiving eutrophic source water.

Removal of Trihalomethane Precursors by Nanofiltration in Low-SUVA Drinking Water

Trihalomethanes (THMs) are prevalent disinfection by-products. High THM formation is usually associated with natural organic matter with high molecular weight and aromatic characteristics, which is efficiently removed by nanofiltration (NF). In the Sea of Galilee and the Israeli National Water Carrier (NWC), water shows high THM formation potential, although it mainly contains low molecular weight and hydrophilic organic matter with low aromaticity. In the present study, NF removal abilities were tested on treated NWC water using three different spiral wound membranes (NF90, NF270, and DL). Rejections and fluxes were tested as a function of pressure, water recovery, and membrane type. Feed and permeate dissolved organic carbon (DOC), UVA254, total THM formation (THMF), and total THM formation potential (THMFP), as well as alkalinity, conductivity, hardness, Ca2+, Mg2+, and Cl− were measured to evaluate rejection and THM formation reduction. The results demonstrated that NF can efficiently remove natural organic matter (NOM) and reduce THM formation, even in this challenging type of water. At low water recovery, membranes showed average rejection of about 70–85% for THMFP and THM. Upon elevating recovery, average THM and THMFP rejection decreased to 55–70%, with THM content still well below regulation limits. Of the membranes tested, the higher permeability of NF270 appears to make it economically favorable for the applications tested in this work.

THMs Precursor Removal Efficiency from Different Wastewater Treatment Technologies Effluents

Treated wastewater is one of the critical practices of sustainable water management. In Palestinian authority region different wastewater technologies are used to produce variety of effluents that are potentially suitable for different purposes. In this study, these different treated wastewater effluents were characterized chemically, biologically, and physically. Results showed that some of these effluents neither comply with Palestinian nor with other global effluent discharge guidelines. Chemical reactivity of five different treated wastewater effluents with chlorine was measured by determining their chlorine demand and total trihalomethane formation potential (TTHMFP). Results showed that different wastewater effluents chemical reactivity with chlorine and TTHMFP is not only dependent on wastewater treatment technology but also is affected by original water source from which was the water emerged. In all cases, measured THMs superseded acceptable drinking water limits. This would indicate responsibility of high percentage of cancer, hepatic and renal diseases among the local people.

Suitability of Organic Matter Surrogates to Predict Trihalomethane Formation in Drinking Water Sources

Broadly applicable disinfection by-product (DBP) precursor surrogate parameters could be leveraged at drinking water treatment plants (DWTPs) to curb formation of regulated DBPs, such as trihalomethanes (THMs). In this study, dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254), fluorescence excitation/emission wavelength pairs (IEx/Em), and the maximum fluorescence intensities (FMAX) of components from parallel factor (PARAFAC) analysis were evaluated as total THM formation potential (TTHMFP) precursor surrogate parameters. A diverse set of source waters from eleven DWTPs located within watersheds underlain by six different soil orders were coagulated with alum at pH 6, 7, and 8, resulting in 44 sample waters. DOC, UV254, IEx/Em, and FMAX values were measured to characterize dissolved organic matter in raw and treated waters and THMs were quantified following formation potential tests with free chlorine. For the 44 sample waters, the linear TTHMFP correlation with UV254 was stronger (r2=0.89) than I240/562 (r2=0.81, the strongest surrogate parameter from excitation/emission matrix pair picking), FMAX from a humic/fulvic acid-like PARAFAC component (r2=0.78), and DOC (r2=0.75). Results indicate that UV254 was the most accurate TTHMFP precursor surrogate parameter assessed for a diverse group of raw and alum-coagulated waters.

Understanding effects of water characteristics on natural organic matter treatability by PACl and a novel PACl-chitosan coagulants

In this study, we investigated the relationship between water characteristics and removal of natural organic matter (NOM) using polyaluminium chloride (PACl) and a newly developed coagulant obtained by hybridising PACl with chitosan (PACl-chitosan) for two different types of water. Using UV–visible spectroscopy analysis, we showed that PACl-chitosan is more effective than PACl for treating water samples that contain higher levels of activated polyhydroxyaromatic moieties. As a result, a lower level of total trihalomethanes formation potential (THMFP) was detected for synthetic water treated with PACl-chitosan coagulant compared to water treated with PACl only. In contrast, no difference was observed for the total THMFP that were formed following coagulation with either coagulant, for water sample containing the same level of organic carbon concentration, but lower levels of polyhydroxyaromatic moieties. Our work shows how the complex characteristics and interactions of organic matter with coagulant component can affect the outcome of the treatment process, and in this case, enhance the treatment. The use of PACl-chitosan was also shown to produce larger floc for both water samples; this again, can lead to better removal.

Spectral evaluation of watershed DOM and DBP precursors

Dissolved organic matter (DOM) quantity and character from eight locations, including rivers and managed‐flow sites, within two northern Colorado Rocky Mountain watersheds were examined using fluorescence and absorbance spectroscopy to characterize changes in DOM quantity and quality. River sites exhibited strong seasonal variability, containing higher concentrations of more aromatic DOM during spring runoff. Reservoir‐influenced, managed sites had year‐round stability and were less aromatic compared with the rivers. Total trihalomethane formation potential (TTHMFP) was used as a measure of DOM chlorine reactivity. Fluorescence compositional metrics (fluorescence index [FI] and Peak C/UV340 ratios) correlated with TTHMFP yields. River sites showed increased TTHMFP concentrations during runoff but little change in TTHMFP yield. Managed sites showed little seasonal variation in both TTHMFP and TTHMFP yield. The results show that fluorescence parameters provide additional information on DOM character not available from conventional measures and may be useful in facilitating watershed management and treatment decisions.

Occurrence of THM and NDMA precursors in a watershed: Effect of seasons and anthropogenic pollution

In pristine watersheds, natural organic matter is the main source of disinfection by-product (DBP) precursors. However, the presence of point or non-point pollution sources in watersheds may lead to increased levels of DBP precursors which in turn form DBPs in the drinking water treatment plant upon chlorination or chloramination. In this study, water samples were collected from a lake used to obtain drinking water for Istanbul as well as its tributaries to investigate the presence of the precursors of two disinfection by-products, trihalomethanes (THM) and N-nitrosodimethylamine (NDMA). In addition, the effect of seasons and the possible relationships between these precursors and water quality parameters were evaluated. The concentrations of THM and NDMA precursors measured as total THM formation potential (TTHMFP) and NDMA formation potential (NDMAFP) ranged between 126 and 1523μg/L THM and <2 and 1648ng/L NDMA, respectively. Such wide ranges imply that some of the tributaries are affected by anthropogenic pollution sources, which is also supported by high DOC, Cl− and NH3 concentrations. No significant correlation was found between the water quality parameters and DBP formation potential, except for a weak correlation between NDMAFP and DOC concentrations. The effect of the sampling location was more pronounced than the seasonal variation due to anthropogenic pollution in some tributaries and no significant correlation was obtained between the seasons and water quality parameters.

The role of nitrobenzene on the yield of trihalomethane formation potential in aqueous solutions with Microcystis aeruginosa

Algae are one of the most important disinfection by-product (DBP) precursors in aquatic environments. The contents of DBP precursors in algae are influenced by not only environmental factors but also some xenobiotics. Trihalomethane formation potential (THMFP) in both the separate and interactive pollution of Microcystis aeruginosa and Nitrobenzene (NB) was investigated in batch experiment to discover the effects of xenobiotics on the yield of DBP precursors in the algal solution. The results show that in the separate NB solution, NB did not react with Cl 2 to form trihalomethane (THM), whereas in the algae solution, THMFP had a significant positive linear correlation with M. aeruginosa density in both solution and extracellular organic matter (EOM). The correlation coefficients were 0.9845 ( p = 3.567 × 10 −4) and 0.9854 ( p = 1.406 × 10 −4), respectively. According to regression results, about 77.9% of the total THMFP came from the algal cells, while the rest came from EOM. When the interactive pollution of M. aeruginosa and NB occurred, the growth of algae was inhibited by NB. The density of M. aeruginosa in a high concentration NB solution (280 μg/L) was only 71.1% of that in the solution without NB after 5 days of incubation. However, THMFP in the mixture (algae and NB) and the EOM did not change significantly, and the productivity of THMFP by the algae (THMFP/10 8cells) increased with the increase in NB concentration. There was a significant linear correlation between THMFP/10 8cell and NB concentration ( r = 0.9117, p < 0.01), which shows the contribution of the algae to THM formation was enhanced by NB. This result might be caused by the increased protein productivity and the biodegradation of NB by M. aeruginosa.

Photocatalytic oxidation of DBP precursors using UV with suspended and fixed TiO 2

French River water (Nova Scotia, Canada) was separated into six different natural organic matter (NOM) fractions, including hydrophobic acids, bases and neutrals and hydrophilic acids, bases and neutrals. The raw water, as well as each of the NOM fractions were analysed for disinfection by-product (DBP) formation potential before and after advanced oxidation with UV/TiO 2 to determine the efficacy of this treatment for the removal of DBP precursors. The UV/TiO 2 treatment was carried out with a nanostructured thin film (NSTF), coated with TiO 2 which is compared with the use of a TiO 2 suspension. For the raw river water, removals of total trihalomethane formation potential (TTHMFP) and total haloacetic acid formation potential (THAA 9FP) were found to be approximately 20% and 90%, respectively, with 50 mJ/cm 2 UV exposure and 1 mg/L TiO 2. For the fractionated samples, approximately 75% of both trihalomethane (THM) and haloacetic acid (HAA) precursors were found to be associated with the hydrophobic acid fraction. For this individual fraction the same UV/TiO 2 treatments exhibited approximately 20–25% removal of both TTHMFP and THAA 9FP, suggesting that the fractionation process may have affected the treatability of HAA precursors or may have altered the results of the oxidation processes.

Microbial Degradation of Plant Leachate Alters Lignin Phenols and Trihalomethane Precursors

Although the importance of vascular plant-derived dissolved organic carbon (DOC) in freshwater systems has been studied, the role of leached DOC as precursors of disinfection byproducts (DBPs) during drinking water treatment is not well known. Here we measured the propensity of leachates from four crops and four aquatic macrophytes to form trihalomethanes (THMs)-a regulated class of DBPs-before and after 21 d of microbial degradation. We also measured lignin phenol content and specific UV absorbance (SUVA(254)) to test the assumption that aromatic compounds from vascular plants are resistant to microbial degradation and readily form DBPs. Leaching solubilized 9 to 26% of total plant carbon, which formed 1.93 to 6.72 mmol THM mol C(-1). However, leachate DOC concentrations decreased by 85 to 92% over the 21-d incubation, with a concomitant decrease of 67 to 92% in total THM formation potential. Carbon-normalized THM yields in the residual DOC pool increased by 2.5 times on average, consistent with the preferential uptake of nonprecursor material. Lignin phenol concentrations decreased by 64 to 96% over 21 d, but a lack of correlation between lignin content and THM yields or SUVA(254) suggested that lignin-derived compounds are not the source of increased THM precursor yields in the residual DOC pool. Our results indicate that microbial carbon utilization alters THM precursors in ecosystems with direct plant leaching, but more work is needed to identify the specific dissolved organic matter components with a greater propensity to form DBPs and affect watershed management, drinking water quality, and human health.

小笠原諸島の水道原水の水質 −消毒副生成物生成能を中心として−

The formation potentials of 24 disinfection by-products, six indicators of organic matter and the number of algae were measured in raw water once a month for one year from October 2006 to September 2007 in order to investigate the quality of water in the two water purification plants on the Ogasawara Islands. It was estimated that the main source of organic matter in raw water on the Ogasawara Islands was not autochthonous organic matter but allochthonous organic matter that flows from streams into reservoirs, as determined from the correlations between the parameters of water quality, the relationship between rainfall and water quality, UV absorbance: TOC ratio and other factors. The mean annual formation potentials of disinfection by-products in filtered raw water on Chichijima Island and Hahajima Island were as follows: total haloacetic acid: 286, 194 μg·L-1, total trihalomethane: 227, 190 μg·L-1, total haloacetonitrile: 13 μg·L-1, and chloral hydrate: 13, 9 μg·L-1, respectively. The total trihalomethane formation potentials were at the maximum levels in our country and the formation potentials of other disinfection by-products were also presumed to be their maximum levels. The formation potentials of the brominated disinfection by-products in most months were higher than those of the nonbrominated disinfection by-products. The correlations of total trihalomethane formation potential (mole concentration) with color, TOC, KMnO4 consumption and UV absorbance were lower than those of the formation potentials of total haloacetic acid, total haloacetonitrile and chloral hydrate in raw water. KMnO4 consumption and UV absorbance were effective indicators of disinfection by-product formation potential for these high correlations (P<0.01).

Relating organic matter character to trihalomethanes formation potential: a data mining approach

The removal of natural organic matter (NOM) during water treatment is becoming more important for all water utilities in the UK, as a result of tightened regulatory standards for trihalomethanes (THM), disinfection by-products (DBP) formed when residual organics react with chlorine. This paper considers the spatial and temporal variability of raw and clarified water arising from 16 surface water treatment works in the Midlands region of the UK. A wide range of investigation techniques are applied in order to develop effective strategies for the treatment of NOM-rich water. For the first time, rigorous data mining techniques are applied to a major dataset in order to examine potential inter-relationships between a wide range of quality parameters including, inter alia, total organic carbon (TOC), UV254, coagulation pH, resin fractionation (hydrophilic acids (HPIA), hydrophobic acids (HPOA), hydrophilic non-acids (HPINA)) and total THM formation potential (TTHMFP). This paper focuses on the use of principal component analysis (PCA) to develop robust algorithms for the prediction of TOC removal and hence THM formation. Results show that raw water characteristics can be categorised into three main types, according to their HPOA content and specific ultraviolet absorbance (SUVA.). PCA identified possible THMFP precursors, according to raw water type verified by strong statistical relationships.

The impact of alum coagulation on the character, biodegradability and disinfection by-product formation potential of reservoir natural organic matter (NOM) fractions

Natural Organic Matter (NOM) from Myponga Reservoir, South Australia, was separated into four organic fractions based on their hydrophobic and hydrophilic properties using a sequence of non-ionic and ionic resins. NOM fractions were isolated for the purpose of determining the impact of alum coagulation on removal of these fractions in conventional water treatment, and their potential as precursors in the formation of disinfection by-products (DBP) and in supporting microbial growth. The NOM comprised VHA (very hydrophobic acids), SHA (slightly hydrophobic acids), CHA (charged hydrophilics) and NEU (neutral hydrophilics) fractions. These fractions were then jar tested with alum using low (50 mg/L), operational (100 mg/L) and very high (200 mg/L) doses to assess the removal capacities for these fractions in a conventional treatment plant. High-performance size exclusion chromatography-UV-DOC (HPSEC-UV-DOC) revealed that alum removed more of the hydrophobic and higher molecular weight components of NOM, but less of the NEU fraction and lower molecular weight components of NOM. Determination of biodegradable dissolved organic carbon (BDOC) indicated that the NEU fraction had the highest biodegradability, followed by the CHA, SHA and VHA fractions. The VHA fraction had the highest total-trihalomethane formation potential (t-THMFP), followed by NEU, SHA and CHA. The NOM not removed by alum coagulation had the potential to support microbial growth (NEU fraction), and disinfection by-product (DBP) formation (VHA and NEU fractions). To obtain treated water with lower overall residual NOM, other treatment methods would need to be applied in addition to alum coagulation in order to reduce the concentration of the neutral fraction.

Influence of the treatment process combinations on the formation of THM species in water

The objectives of this study were to investigate formation of trihalomethane (THM) species in waters treated by different methods and to determine effectiveness of using various methods for controlling disinfection by-product (DBP) precursors in drinking water. Experiments were carried out using batch experimental set-ups. Combinations of pre-ozonation, post-ozonation, enhanced coagulation, rapid sand filtration, activated carbon filtration and UV radiation were performed. Finished waters were analyzed for dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC), ultraviolet absorbance at 254 nm (UV 254), total trihalomethane formation potential (TTHMFP), bromide and bromate. The results indicated that using the sequence of pre-ozonation/enhanced coagulation/activated carbon filter is the most effective method for reducing THM precursors. It was also concluded that the formation of THM species primarily related to the characteristics of finished water before chlorination.

DBPs formation and toxicity monitoring in different origin water treated by ozone and alum/PAC coagulation

In this study, aluminium sulphate (alum) and polyaluminum chloride (PAC) coagulation were used for coagulation of different origin water (Buyukcekmece, BC and Omerli, OM in Istanbul, Turkey and Carmine, CR in Salerno, Italy) treatment. The effect of pre-ozonation alone and combined with coagulation on NOM removal which was characterized by TOC, UV254 was investigated. DBPs formation and acute toxicity on Daphnia magna of chlorinated raw and treated samples were defined in parallel. Moreover, bromide spiking was evaluated for DBPs speciation. Optimum alum dose for TOC removal was found to be 40 mg/L for OM while 80 mg/L of alum exhibited the lowest total trihalomethane formation potential (TTHMFP). Pre-ozonation enhanced the removal of TOC and reduction of TTHMFP when it was used in combination with both coagulants. In contrast, total haloacetic acid formation potential (THAAFP) increased after each coagulation, ozonation and their combination. 300 µg/L bromide spiking (around the same level with BC) in raw sample collected from CR increased the formation of brominated disinfection byproducts. Raw and treated samples displayed acute toxicity on Daphnia magna in different pattern and practically “no dose-response behavior” was observed.

Reduction of dissolved organic matter in terms of DOC, UV-254, SUVA and THMFP in industrial estate wastewater treated by stabilization ponds

The aim of this research was to monitor the influent and effluent water quality of the aeration, facultative and oxidation water treatment ponds of an industrial estate. This industrial estate, the largest in northern Thailand, has proposed to utilization of reclaimed treated wastewater in their raw water supply so as to cope with the yearly water shortage during the dry season. Water samples were collected four times from four sampling points and evaluated for their dissolved organic matter (DOM) content in terms of dissolved organic carbon (DOC), ultraviolet light absorbance at 254 nm (UV-254), specific ultraviolet absorption (SUVA), trihalomethane formation potential (THMFP) and trihalomethane (THM) species. Average values of DOC, UV-254, SUVA and THMFP in the influent wastewater of 12.9 mg L(-1), 0.165 cm(-1), 1.29 L mg(-1) m(-1) and 1.24 mg L(-1), respectively, were observed. The aeration ponds produced the best results: a 54% reduction of DOC, a 33% reduction of UV-254, and a 57% reduction of THMFP. However, SUVA in the aeration pond effluent showed a moderate increase. The facultative ponds and oxidation ponds did not take part in the reduction of DOC, UV-254, SUVA and THMFP. Average DOC, UV-254, SUVA and THMFP value of the treated wastewater were 5.8 mg L(-1), 0.107 cm(-1), 1.85 L mg(-1) m(-1) and 468 microg L(-1), respectively. Chloroform, at 72.6% of total THMFP, was found to be the predominant THM species.

Formation of hazardous by-products resulting from the irradiation of natural organic matter: Comparison between UV and VUV irradiation

The use of ultraviolet (UV) or vacuum ultraviolet (VUV) photo-oxidation followed by biological treatment for the removal of natural organic matter (NOM) in drinking water is a potential water treatment technique under investigation. This paper reports on the trihalomethane formation potential (THMFP), the haloacetic acid formation potential (HAAFP), and formation of nitrite and peroxide following both UV and VUV irradiation of NOM prior to biological treatment. The total THMFP was found to decrease with increasing UV and VUV irradiation dose, although there was a linear increase in bromoform formation. Determination of the THMFP of NOM fractions obtained after irradiation, showed that the hydrophobic fraction was dominated by chlorinated species which accounted for the majority of the total THMFP, while bromoform was observed only in the hydrophilic fraction of NOM. VUV irradiation reduced the HAAFP with increasing dose, in contrast, UV irradiation had a limited effect on the overall HAAFP. Following UV or VUV irradiation, the chlorinated species accounted for the majority of HAAFP; however, significant formation of brominated haloacetic acid (HAA) was observed. The nitrate concentration of the untreated water directly influenced the concentration of nitrite produced as a consequence of UV and VUV irradiation. Hydrogen peroxide formation was greater during VUV irradiation than during UV irradiation. Samples exposed to various doses of UV or VUV irradiation (up to 138 J cm −2) were deemed non-cytotoxic (African green monkey kidney cells) and non-mutagenic (Ames test).