Presentation on theme: "Trihalomethanes formation after chlorination process Kovacs Melinda Haydee1, Dumitru Ristoiu1, Iovanca Haiduc1, Sidonia Vancea2 1Babes Bolyai University."— Presentation transcript:
Trihalomethanes formation after chlorination process Kovacs Melinda Haydee1, Dumitru Ristoiu1, Iovanca Haiduc1, Sidonia Vancea2 1Babes Bolyai University of Cluj-Napoca, Faculty of Environmental Science, Str. P-ta Stefan cel Mare, no.4, , Cluj-Napoca, Kovacs Melinda Haydee1, Dumitru Ristoiu1, Iovanca Haiduc1, Sidonia Vancea2 1Babes Bolyai University of Cluj-Napoca, Faculty of Environmental Science, Str. P-ta Stefan cel Mare, no.4, , Cluj-Napoca, 2Garda de mediu, Comisariatul judetean Cluj, str. G-ral T. Mosoiu, nr. 49, Cluj-Napoca, Romania. 2Garda de mediu, Comisariatul judetean Cluj, str. G-ral T. Mosoiu, nr. 49, Cluj-Napoca, Romania.
Chlorination Chlorine and its compounds are the most commonly used disinfectants for water treatment in Romania. AdvantagesDisadvantages Provides a strong residual in the distribution system Formation of disinfection by- products (DBPs) especially trihalomethanes (THMs) Easily applied, controlled, and monitored Provides poor Cryptosporidium* and Giardia ** control Relatively inexpensive Effective at low concentration Highly effective against most pathogens * Cryptosporidium parasite is the cause of gastrointestinal diseases (USEPA, 1997) ** Giardia Lamblia is the cause of gastrointestinal illness (e.g. diarrhea, vomiting, cramps) (USEPA, 1997) Tabel 1: Advantages and disadvantages of chlorine (Rook, 1976; El-Shafy and Grunwald, 2000; Clark, 1998)
What happened with chlorine in water ? Chlorine dissolved in water: Cl 2 + H 2 O HOCl + H + + Cl - HOCl generally reacts with the various components that make up chlorine demand as follows: HOCl + Cl demand products Reaction of chlorine in water Oxidation of bromide: DBPs Reaction with NOM: DBPs
Trihalomethanes THMs ? (THMs) Trihalomethanes (THMs) are organohalogen compounds. are formed They are formed after reaction of chlorine with natural organic matter (NOM) present in all water. Natural organic matter in water (Precursors) Chlorinated organic intermediates Complex reaction pathway + HOCl THMs HOCl Fig. 1: THMs formation pathway Cl2 + H2O → + H+ + Cl- HOCl + Br- → + Cl- HOCl + I- → + Cl2 HOCl HOBr HOI HOX THMs include: - Chloroform - Chloroform (CHCl 3 ) (CHCl 3 ) - Dibromochloromethane (CHBr 2 Cl) (CHBr 2 Cl) - Bromodichloromethane (CHBrCl 2 ) (CHBrCl 2 ) - Bromoform (CHBr 3 ) (CHBr 3 )
Possible Health effects of THMs WHY THMs ? THMs appear to be the most prevalent halogenated by-products of chlorination. THMs appear to be the most prevalent halogenated by-products of chlorination. DBPsCompoundRating* Possible detrimental effects THMs CHCl 3 B2 Cancer, liver, kidney, and reproductive effects CHCl 2 BrC Nervous system, liver, kidney and reproductive effects CHClBr 2 B2 Cancer, liver, kidney and reproductive effects CHBr 3 B2 Cancer, nervous system, liver and kidney effects Toxicological information for THMs (modified after USEPA, 1999b) B2 - Probable human carcinogen (sufficient laboratory evidence) C - Possible human carcinogen
CompoundWHO (1993) USEPA (2001) Canada (2001) Aus-NZ (2000) UK (2000) Romania Total THMs0.100 g/l g/l g/l g/l g/l g/l Standards / Guidelines related to THMs (mg/l) in various jurisdictions of the World Tabel 2: Standards/Guidelines related to THMs (mg/l) in different countries of the world. * Maximum Contaminant Level Goals (MCLG)
Location of the sampling points Location of the sampling points WTP Gilau Experiments were carried out with five town from judetul Cluj: Cluj-Napoca, Dej, Beclean, Jibou and Gherla
THMs monitoring by GC THMs were analyzed using headspace technique gas chromatography with an electron capture detector. The GC was fitted with a 30 m TR-5V capillary column - Cyanopropylphenyl Polysiloxane, the internal diameter was 53 mm and the film thickness was 3 m (Thermo Finningan, USA) Fig.: Static headspace technique Fig.: Laboratory instrument – GC - ECD Fig.: THM chromatograms obtained after water analysis Relativ standard deviation for 20 µg/l and 80 µg/l is between % Recovery for 1 µg/l, 20 µg/l and 80 µg/l µg/l are in range 93 – 120 % Limit of detectuion for THMs is: CHCl3 is 0.3 µg/l ; CHCl2Br is 0.2 µg/l; CHClBr2 is 0.3 µg/l; CHBr3 is 0.6 µg/l
Table: CHCl 3 g/l measured in Water Treatment Plant and distribution system CHCl 3 concentration measured in WTP Gilau in 2006 Sampling placeAugustSeptemberOctoberNovemberDecember Raw wateru.l.d 1.02u.l.d Filtrated wateru.l.d. u.l.du.l.d. Exit reservoir Sapca Verde Beer factory Faculty of Chemistry Faculty of Environmental Science Institute of public health Month 2007 Sampling placeJanuaryFebruaryMarchAprilMayJuneJulyAugust Raw wateru.l.d Filtrated wateru.l.d. Exit reservoir Sapca Verde Beer factory Fac.of Chemistry Fac. of Environ Inst. publ health
Factors affecting THM formationMONTH Chlorine dose 2006 (mg/l) Chlorine dose 2007 (mg/l) 2007 (mg/l) January1.1 February1.0 March11.1 April11.2 May June11.4 Julie August September1.6 October1.4 November1.3 December1.1 There are several factors affecting the formation potential of THMs. The major variables that affect THM formation are: Chlorine dose and residual; Concentration and nature of NOM (mainly humic substances); Contact time; pH; Water temperature; Presence of inorganic ions like bromide; Type of raw water also affects the THM levels. Higher THMs concentrations are expected at higher levels of the above mentioned parameters. The effect of disinfectant concentration on THM formation have shown as the disinfectant concentration increases also THM formation increase. Fig.: With increases of chlorine dose it is observed also the CHCl 3 increases.
THMs measurements in Water Treatment Plant and distribution system in Cluj-Romania in different month
Fig.: With increases of filtrated water temperature it is observed also the CHCl 3 increases.
General presentation of chloroform evolution in the WTP Gilau and distribution system ( )
Chlorine and THM kinetics Base line conditions Seasonally variable conditionsThe experiments were conducted under two conditions: Base line conditions (pH 7, 21 C°, 2.5 mg/l Cl2) to gain information about the change of the organic matter in the raw water and Seasonally variable conditions to simulate the actual process at the treatment plant. Experiments under seasonally variable conditions were carried out with pH and temperature and chlorine dose as measured in the pretreated water on the sampling day.
CHCl 3 concentration measured in sampling point from WTP Gilau and CHCl 3 concentration obtained in laboratory experiment in different month in 2006 S.P.AugustSeptemberOctoberNovemberDecember MEMEMEMEME
CHCl 3 concentration measured in sampling point from WTP Gilau and CHCl 3 concentration obtained in laboratory experiment in different month in 2007 S.P.JanuaryFebruaryMarchApril MEMEMEME CHCl 3 concentration measured in sampling point from WTP Gilau and CHCl 3 concentration obtained in laboratory experiment in different month in 2007 S.P.MayJuneJulyAugust MEMEMEME
Relationship between chlorine consumption and CHCl 3 formation under seasonally variable condition. NH 2 Cl concentration were subtracted from the chlorine consumption. We found a good corelation between the residence time and THM and chloroform consumption – r2 was The first order rate constant was determine – M-1s-1
CONCLUSIONS Static headspace sample preparation can be used for quantitative analysis of THMs in environmental samples. Chloroform was the dominant THM species observed after the chlorination. THM concentration depended on the applied initial chlorine demand of the water samples, as the chlorine dose was increased, more THM formed. For a given initial chlorine dose, the formation of THMs and consumption of chlorine were both completed at the same reaction time, however, the time, period required for the completion of THM formation varied with the chlorine dose and season. At high chlorine dose, THM formation was complete earlier then the low doses due to the fact that the initial chlorine concentration is an important factor affecting the time of completion of the reaction as well as the amount and rate of THM formation (higher values of initial chlorine results in higher reaction rates).
The THM formation rates in the distribution system of Cluj- Napoca have a high seasonal variability. The main parameters causing variances in the THM formation rate were the concentration and composition of the organic substances in the raw water. Residual chlorine concentration during the completion of THM formation, the overall yield values (total THM formed/total chlorine consumed during the entire reaction periods) as well as the average yield values ( g TTHM formed/mg Chlorine consumed between two reaction times) differ through sampled months that may be attributed to the variations in the nature of organic matter. In all months, the formation yields were highest during the first hours of reaction time.