Multivariate statistical relationships between routine water plant data and trihalomethane levels. Implications for studies of human health

Routine water treatment plant data were used to construct a mathematical/statistical model of trihalomethane formation during lime-soda ash softening. Chemical characteristics of the raw water, such as temperature and color, and several treatment parameters, including chlorine dose, were significant predictors for chloroform and total trihalomethanes. The pattern of prediction was notably different for the brominated species. The results of this preliminary study support the view that routine water plant data can be used to estimate retrospectively, and with accuracy, trihalomethane levels for past time periods in which only the routine plant data are available. Possible limitations of the approach and the prospects for improving epidemiologic health effects studies of trihalomethanes in drinking water are discussed.     

The Use of Bone Charcoal in the Treatment of Rural Water Supplies

As a result of the Water Act of 1989 on the quality of water intended for human consumption, a number of small spring sources in Yorkshire were the subject of legal undertakings for remedial action to reduce the concentration of trihalomethanes in the distribution system. The trihalomethanes are formed when the colour in these waters, which is made up of predominantly fulvic and humic acids, is chlorinated. Therefore, in order to solve the problem of trihalomethanes in treated water, colour removal was necessary.
The paper describes the use of bone charcoal in slow sand filters to remove colour from rural water supplies. It covers six months pilot-plant work which was undertaken at Marsett water-treatment works (near Richmond), and the implementation at other plants within Yorkshire. low-rate filtration through bone charcoal ensured that the colour and trihalomethane concentrations in filtered water complied with EC standards, and the material coped well with rapid changes in raw water quality.     

Effect of alum treatment on the trihalomethane formation and bacterial regrowth potential of natural and synthetic waters

Waters from five reservoirs and "synthetic waters", prepared using terrestrially derived dissolved organic matter (DOM) extracted from vegetation and reservoir catchment soils, were studied for their treatability with alum using a jar test procedure. DOM in drinking water is a precursor for the formation of trihalomethanes (THM) following chlorine disinfection and can also be a substrate for microbial growth in the drinking water distribution system. The trihalomethane formation potential (THMFP) represents an upper concentration limit on THMs formed by chlorination, while bacterial regrowth potential (BRP) is an indicator of the bioavailability of DOM. BRP and THMFP were measured before and after alum treatment and the results were related to the source of the DOM. It was found that freshly derived terrestrial DOM in synthetic water resulted in higher THMFP and BRP than DOM in reservoir waters. For the samples investigated, conventional alum treatment did not always reduce the THM precursor levels formed in laboratory tests below the NH&MRC (1996) guideline level of 250 microg/L nor produce microbially stable waters.     

Potential impact of chlorination of Sandy bottom swimming areas on drinking water sources

The concentrations of trihalomethanes and haloacetic acids, disinfection by‐products (DBPs) of chlorine, were measured in sandy bottom swimming areas to determine their potential impact on surface and ground water that are sources of drinking water. Total trihalomethanes and individual haloacetic acid concentrations in several swimming area samples were higher than the drinking water standards (current and proposed). Individual trihalomethanes (except bromoform) also exceeded ground and surface water release standards. No release standard exists for haloacetic acids. The DBPs, while exceeding standards, would be diluted by the ground water and microbially degraded prior to reaching the drinking water plant. So while DBPs from swimming areas contributed to groundwater concentrations, the current drinking water standards could still be met using source waters impacted by chlorinated swimming areas. It is suggested, though, that any release of chlorinated DBPs to surface and ground water be minimized to obtain the highest quality water sources for drinking water.     

Chemometric modeling and prediction of trihalomethane formation in Barcelona's water works plant

Formation and occurrence of trihalomethanes (CHCl3, CHBr3, CHCl2Br, and CHBr2Cl) are investigated in water chlorination disinfection processes in the Barcelona's water works plant (WWP). Twenty-three WWP variables were measured and investigated for correlation with trihalomethane formation. Multivariate statistical methods including principal component analysis (PCA), multilinear regression (MLR), stepwise MLR (SWR), principal component regression (PCR) and partial least squares regression (PLSR) have been used and compared to model and predict the complex behavior observed for the measured trihalomethane concentrations. The results, obtained by PCA as well as the evaluation of the statistical significance of the coefficients in the linear regression vectors, revealed that the most important WWP variables for trihalomethane formation were: water temperature, total organic carbon, added chlorine concentrations, UV absorbance and turbidity at different sites of the WWP, as well as other variables like wells supply flow levels and carbon filters age. Overall, MLR and PLSR methods performed the best and gave similar good predictive properties. Best results were obtained for the total sum of trihalomethane concentrations, TTHM, with average modeling and prediction relative errors of 12% and 16%, respectively. Among the individual trihalomethanes, the concentrations of CHBr3 were the worst predicted ones with average modeling and prediction relative errors between 21-25% and 29-31%, respectively, followed by CHCl2Br with 23-26% and 25-27%. Better predictions were obtained for the concentrations of CHBr2Cl with relative modeling and prediction errors varying between 14-17% and 21%, and for the concentrations of CHCl3 with 21-24% and 23-25% errors, respectively.     

Multi-route trihalomethane exposure in households using municipal tap water treated with chlorine or ozone-chlorine

In Korea, data for multi-route trihalomethane (THM) exposure in households using municipal tap water treated with ozone-chlorine or chlorine are unavailable or very limited. Accordingly, the present study was designed to obtain those data by measurements of the THM concentrations in the tap water and indoor and outdoor air in the two types of households, along with an estimation of THM exposure from water ingestion, showering, and the inhalation of indoor air. Chloroform was the most abundant THM in all three media, yet no bromoform was detected in any sample. Similar to previous findings, the winter chloroform concentration in tap water treated with chlorine (22.1 microg/l, median) was significantly higher than that in the tap water treated with ozone-chlorine (16.8 microg/l, median). However, the summer water chloroform concentrations and summer and winter water concentrations of the other two THMs (bromodichloromethane and dibromochloromethane) exhibited no significant difference between the chlorine and ozone-chlorine-treated water. It was suggested that the effects of the water parameters including biochemical oxygen demand of raw water entering water treatment plants should be considered when evaluating the advantage of ozone-chlorine disinfection for THM formation over chlorine disinfection. The indoor air THM concentration trend was also consistent with the water concentration trend. The indoor to outdoor air concentration ratios were comparable with previous studies. The THM exposure estimates from water ingestion, showering, and the inhalation of apartment indoor air when not in the shower suggested that, for residents living in the surveyed households, their exposure to THMs in the home was mostly associated with their household water uses. The THM exposure estimates from tap water ingestion were similar to those from showering.     

Trihalomethane exposures in indoor swimming pools: a level III fugacity model

The potential for generation of disinfection byproducts (DBPs) in swimming pools is high due to the concentrations of chlorine required to maintain adequate disinfection, and the presence of organics introduced by the swimmers. Health Canada set guidelines for trihalomethanes (THMs) in drinking water; however, no such guideline exists for swimming pool waters. Exposure occurs through ingestion, inhalation and dermal contact in swimming pools. In this research, a multimedia model is developed to evaluate exposure concentrations of THMs in the air and water of an indoor swimming pool. THM water concentration data were obtained from 15 indoor swimming pool facilities in Quebec (Canada). A level III fugacity model is used to estimate inhalation, dermal contact and ingestion exposure doses. The results of the proposed model will be useful to perform a human health risk assessment and develop risk management strategies including developing health-based guidelines for disinfection practices and the design of ventilation system for indoor swimming pools.     

Bacterial dynamics in the drinking water distribution system of Brussels

Water samples and pipe coupons were collected from the Brussel's drinking water distribution system (DS). A treated surface water and various groundwaters feed this DS. Parameters related to bacterial regrowth have been measured on these samples: temperature, concentrations of free residual chlorine, concentration of biodegradable dissolved organic carbon (BDOC), abundance of suspended bacteria, densities of fixed bacteria and levels of bacterial activity. Results showed that groundwaters were less susceptible to favor bacterial regrowth in the DS pipes. Treated surface water and mixed waters had the highest potential of bacterial regrowth in the DS dead ends. Results also showed that the potential regrowth induced by the distribution of a treated surface water could be reduced if: (1) the BDOC levels were below 0.25 mg C/l at the outlet of the surface water treatment plant; (2) a significant free chlorine residual was present within the whole DS. Second-stage biological filtration using granular activated carbon is now under construction at the surface water treatment plant feeding a part of this DS. This treatment implementation should reduce BDOC levels and chlorine demand of the treated surface water and will further reduce the slight regrowth phenomena observed in this DS.     

Trihalomethane formation in whirlpool SPAs

In a survey of 25 whirlpool spas using halogen disinfectants, the only organohalide contaminant observed in the water and in the air at concentrations in excess of 1 μg l⁻¹ (water) and 1 μg m⁻³ (air) was the trihalomethane corresponding to the disinfectant used. The levels of trihalomethane observed in the water in thermal spas were comparable to levels reported for swimming pools. We conclude that the heat, agitation and aeration of the spas do not produce higher residual levels of trihalomethanes in the water and do not promote the formation of novel volatile organohalides. The concentration of trihalomethane in the water appeared to be related to the combination of high total dissolved solids and high disinfectant levels. The trihalomethane levels in the air though dependent on the concentration of trihalomethane in the water were modified by the variety of room sizes, ventilation rates, water surface areas and aeration rates associated with each individual spa.     

双水源对置供水管网中三卤甲烷变化规律浅析

为有效控制供水管网中的三卤甲烷浓度,考察了以太湖和阳澄湖为双水源的管网水中三卤甲烷的变化趋势。采集S市分别经过A水厂(以太湖为水源)和B水厂(以阳澄湖为水源)处理后的供水管网水样,探讨三卤甲烷和余氯浓度随供水距离的变化规律,并进行了三卤甲烷-余氯和三卤甲烷-供水距离的线性回归分析。结果表明,在A、B水厂单独供水管网中,三卤甲烷随供水距离的增加而升高,余氯浓度随供水距离的增加而降低;在A、B水厂同时供水的对置供水管网中,三卤甲烷浓度由A水厂到B水厂呈现先升高后降低的变化规律,而余氯浓度则呈现先降低后增加的变化规律,对置供水管网中10 km处为水力交接点,此处余氯浓度最低,三卤甲烷浓度最高。经线性回归分析发现,三卤甲烷浓度与余氯浓度和供水距离之间存在显著的相关性,并且温度对模型的影响较大。     

Chlorine demand-based predictive modeling of THM formation in water distribution networks

The potential carcinogenicity of trihalomethanes (THMs) has led to increasingly stricter regulation of drinking water supplies. This has led to the need to manage better the chemical and microbiological risk balance in chlorinated supplies. The use of empirical equations to predict THM concentrations in water quality models is challenging and expensive due to the numerous temporally and spatially dependent uncertainties involved. In this paper, the benefits of a simple predictive method using a THM productivity parameter based on chlorine consumed by bulk free chlorine reactions are explored using extensive field data from a water distribution system in the Midlands region of the UK. It is concluded that the productivity parameter provides an appropriate, relatively robust, yet straightforward alternative to the use of an empirical equation based on regression analyses to predict THM concentrations in distribution, and that the method has the potential to help distribution system water quality model calibration.     

Spatial and temporal evolution of trihalomethanes in three water distribution systems

Spatial and seasonal changes in trihalomethane (THM) concentrations were investigated in three distribution systems of Quebec (Canada) which are supplied by different surface waters and which use a variety of physicochemical treatment strategies. The investigation was based on an intensive 25-week sampling programme, undertaken at a time of year when the temperature of southern Quebec surface waters exceeds 4 degrees C (April-November). THMs and other water quality and operational parameters were monitored at points along the distribution system--between the treatment plant and the system extremities--which represented variable residence times of water. Results showed that THM concentrations vary significantly (from 1.5 to 2 times, depending on the utility) between finished waters as they leave the plant and water at the system extremities. When water temperature exceeds 15 degrees C, spatial THM variations are particularly high (from 2 to 4 times, depending on the utility). The development of multivariate regression models showed that water temperature was a better predictor of THM seasonal variability than chlorine dose, surrogates of natural organic matter and pH. Also, initial THM formation (in finished waters leaving the plant) was a good predictor of THM levels at distribution system extremities.     

Persistence of pharmaceuticals and other organic compounds in chlorinated drinking water as a function of time

Ninety eight pharmaceuticals and other organic compounds (POOCs) that were amended to samples of chlorinated drinking-water were extracted and analyzed 1, 3, 6, 8, and 10 days after amendment to determine whether the total chlorine residual reacted with the amended POOCs in drinking water in a time frame similar to the residence time of drinking water in a water distribution system. Results indicated that if all 98 were present in the finished drinking water from a drinking-water treatment plant using free chlorine at 1.2 mg/L as the distribution system disinfectant residual, 52 POOCs would be present in the drinking water after 10 days at approximately the same concentration as in the newly finished drinking water. Concentrations of 16 POOCs would be reduced by 32% to 92%, and 22 POOCs would react completely with residual chlorine within 24 h. Thus, the presence of free chlorine residual is an effective means for transforming some POOCs during distribution.     

Volatile halogenated hydrocarbons in Belgian drinking waters

A comparative study was carried out to determine levels of volatile halogenated hydrocarbons, especially trihalomethanes (THM) in different Belgian drinking waters, prepared from both ground and surface waters. In addition to examining raw and treated water leaving the production plants, changes in haloform concentration during transport in the distribution system were also studied. Only a slight decrease of haloform concentration after decompression in water towers and reservoirs occurred and was rapidly compensated by on going chlorination by residual free chlorine.Despite of the very different conditions used for chlorination in the plants studied, a fairly clear relation was found between total THM content in the finished waters and TOC-values of the raw waters, indicating that the primary organic load was the determining factor for haloform formation.     

Epidemoilogical Studies on cancer and organic compounds in U.S. drinking waters

Two national surveys of U. S. drinking waters have been conducted todetermine the presence and concentration levels of organic compounds, particularly trihalomethanes. Most drinking water supplies from surface water sources have been shown to contain numerous organic compounds at very low levels. Chloroform is present in virtually all drinking water supplies that are treated with chlorine as a disinfectant.The health effects of organic compounds have been investigated by animal and epidemiological studies.Numerous epidemiological studies have been conducted on various geographic sections of the United States. Fourteen epidemiological studies that were hypothesis generating studies were conducted to determine if there is a positive — association between drinking water and increased cancer mortality. These studies may indicate which organ(s) might potentially be the affected organ(s). Further epidemiological studies that tested various hypotheses were conducted A summary of these studies is presented, which indicates that there is potentially an increased risk of bladder, colon, and rectum cancer from drinking waters containing trihalomethanes.     

Continuous monitoring of residual chlorine concentrations in response to controlled microbial intrusions in a laboratory-scale distribution system

The objective of this work was to evaluate the efficacy of deploying free chlorine sensors as surrogate monitors for bacterial contamination events in drinking water distribution systems. An on-line sensor integral with a laboratory-scale distribution system (LDS) was shown to respond rapidly to changes in residual free chlorine concentrations induced by injected loads of Escherichia coli suspended in a chlorine demand free buffer. The magnitude of the residual response was proportional to the injected cell concentration, the background free chlorine concentration in the LDS, and the contact time between the chlorine residual and the injected suspension, consistent with previous results in batch reactors. The magnitude of the residual response was predicted when kinetic models developed from reaction kinetics between free chlorine and E. coli determined in batch systems were evaluated at contact times determined from LDS hydraulics. This result highlights the suitability of using batch kinetics when modeling contaminant-induced chlorine decay in the distribution system. Modeling the propagation of chlorine demand signals generated by specific pathogens could aid in the assessment of distribution system vulnerability.     

Association between haloacetic acid degradation and heterotrophic bacteria in water distribution systems

The occurrences of trihalomethanes (THMs), haloacetic acids (HAAs) and heterotrophic bacteria were monitored in five small water systems over a nine-month period to investigate the association between HAA degradation and heterotrophic bacteria populations. The sampling sites were chosen to cover the entire distribution network for each system. An inverse association between heterotrophic bacteria and HAA concentrations was found at some locations where chlorine residuals were around or less than 0.3 mg L⁻¹. At other sample locations, where chlorine residuals were higher (over 0.7 mg L⁻¹), no HAA reduction was observed. A high heterotrophic bacteria count accompanied with a low chlorine residual could be used as an indicator for HAA degradation in distribution systems.     

DBP formation kinetics in a simulated distribution system

Little is known about how the growth of halogenated disinfection by-products (DBPs) in drinking water is affected by time spent in a distribution system. Experiments were performed to compare the rate of trihalomethane and haloacetic acid production in a simulated pipe environment to that observed for the same water held in glass bottles. Results showed that although the rate of chlorine consumption in the pipe was much greater than in the bottle, there was no decrease in the amount of haloacetic acids produced and that trihalomethane levels actually increased by an average of 15%. Separate tests confirmed that this increase was due to a reservoir of organic precursor material associated with deposits on the pipe wall. This work suggests that the rate of DBP production in a distribution system will not necessarily be reduced by increased chlorine consumption due to non-DBP producing reactions with deposits on the pipe wall.     

Comparison of the disinfection by-product formation potential of treated waters exposed to chlorine and monochloramine

The formation of disinfection by-products (DBPs) from chlorination and monochloramination of treated drinking waters was determined. Samples were collected after treatment at 11 water treatment works but before exposure to chlorine or monochloramine. Formation potential tests were carried out to determine the DBPs formed by chlorination and monochloramination. DBPs measured were trihalomethanes (THMs), haloacetic acids (HAAs), halonitromethanes (HNMs), haloacetonitriles (HANs), haloaldehydes (HAs), haloketones (HKs) and iodo-THMs (i-THMs). All waters had the potential to form significant levels of all the DBPs measured. Compared to chlorine, monochloramination generally resulted in lower concentrations of DBPs with the exception of 1,1-dichloropropanone. The concentrations of THMs correlated well with the HAAs formed. The impact of bromine on the speciation of the DBPs was determined. The literature findings that higher bromide levels lead to higher concentrations of brominated DBPS were confirmed.     

Analysis of selected trace organics in advanced wastewater treatment systems

Effluents through four different pilot tertiary wastewater treatment systems were monitored for selected trace organic compounds. The effects of using ozone, free and combined chlorine residuals in these systems were also studied. Advanced treatment of secondary effluent using various combinations of flocculation (alum and polymer), dual media filtration, and carbon adsorption were evaluated for production/removal of volatile halogenated organics, polynuclear aromatics, chlorinated pesticides, and polychlorinated biphenyls. Gas chromatographic methods were used for the analysis of these different classes of compounds: specific techniques and analytical parameters are described. Salient results included: drastic increases in trihalomethane production using free chlorine residuals: disinfection with combined chlorine species does not produce significant levels of trihalomethanes: approximately 90% reduction in trihalomethane levels by carbon adsorption: absence of detectable quantities of polynuclear aromatics: significant decreases in pesticide and PCB levels by carbon adsorption and chlorination. Statistical dependence of trihalomethane production on soluble COD, suspended solids and chloramine levels was evident from multiple linear regression calculations.