Trihalomethane formation potential along an

hydric system:

Nanofiltration in drinking water treatmentG. Ribera*. L. Llenas*. X. Martínez-Lladó*. M. Rovira*.**. J. De Pablo*.**

* CTM Centre Tecnològic; Av. Bases de Manresa 1. 08242 Manresa. Spain

(E-mail: gemma.ribera@ctm.com.es. xavier.martinez@ctm.com.es)

**Department of Chemical Engineering. Polytechnic University of Catalonia; Av. Diagonal 647. 08028

Barcelona. Spain

Membrane technology in drinking water treatment has been considered to be

effective removing turbidity, organics, microorganisms and disinfection by-products

(DBPs) precursors (Van der Bruggen et al. 2003). Concerns regarding the potential

health effects of DBP prompted industrialized countries to develop more stringent

regulations which implies new technologies as nanofiltration (NF) to treat fresh

water.

Chlorination has been the main procedure to disinfect municipal drinking waters.

Reactions between chlorine and natural organic matter (NOM) produce a wide

INTRODUCTION

An automated lab-scale experimental setup equipped with a cross-flow module

(SEPA-CFII Osmonics) was used to evaluate THMFP reduction and productivity of

10 commercial NF membranes with pre-chlorinated feed water from a drinking

water treatment plant (WTP) at transmembrane pressures (TMP) ranging from 2 to

15 bar (APHA 1998, Chen et al. 2008).

Three membranes were selected to evaluate its capacity to decrease THM

Formation Potential (THMFP) in waters from River Llobregat source to Manresa

drinking WTP (Figure 1). Previously to the NF experiments, water samples were

filtered through glass-fiber filters. Apart from conductivity and pH measurements

on-line, the following analytical methods were carried out to evaluate the NF

performance of the membranes:

• This study has demonstrated NF as a suitable technology to reduce DBPs in drinking water treatment, in spite of the great influence of water reservoirs over THM precursors.

• Membrane selection can play an important role in terms to water productivity, in this study NF270 results the best one, considering TFC-SR2 is not available on the market.

• The smaller conductivity rejection, the lower THMFP reduction. ESNA1LF2 has the lowest salt rejection, allowing salt passage and reducing scaling in spiral wounds.

METHODOLOGY

RESULTS AND DISCUSSION

CONCLUSIONS

• Van der Bruggen B., Vandecasteele C. (2003) Removal of pollutants from surface water and groundwater by nanofiltration: overview of possible applications in the drinking water industry.

Environ pollut 122, (3) 435-445.

•Chow A.T:, Gao S., Dahlgren R.A., (2005). Physical and chemical fractionation of dissolved organic matter and trihalomethane precursors: A review, J water supply: Res and Technol AQUA/IWA

Publishing 54 (8), 475-507.

• De la Rubia A., Rodríguez M., León V., Prats D., (2008). Removal of natural organic matter and THM formation potential by ultra- and nanofiltration of surface wáter, Water Res 42, 714-722.

• APHA, AWWA, WPCF (1998). 5710 Trihalomethane Formation Potential (THMFP) Standard methods for the examinations of water and wastewater, 19 th ed. Washington D.C.

• Chen Ch., Zhang X., Zhu L., Liu J., He W., Han H., (2008). Disinfection by-products and their precursors in a water treatment plant in North China: Seasonal changes and fraction analysis, Sci Tot

Environ 397, 140-147.

• Pérez J.P., Herrero S.M., García C.P., Moreno B.C., (2008). Determintaion of trihalomethanes in wáter samples: A review, Anal Chim Act 629, 6-23.

REFERENCES

variety of DBPs depending on the conditions as water quality or chlorine dose.

Trihalomethanes (THMs) and haloacetic acids (HAAs) are the most known and

relatively easy characterised DBPs. Some studies have related different organic

fractions to their formation potential of DBP, typically THMFP (Chow et al. 2005).

The objective of this work was evaluate commercial NF membranes to reduce

effectively THM formed during the chlorination of fresh water from an hydric system (De

la Rubia et al. 2008). At the same time, medium conditions and operational parameters

were studied to improve NF process knowledge.

This study was financially supported by Aigües de Manresa S.A. (AMSA) within the scope of CDTI project “Desarrollos tecnológicos hacia un ciclo del agua urbano auto-

sostenible (NAIGMA)”.

THMFP reduction and permeability were studied with ten NF membranes using

prechlorinated water samples from Manresa’s drinking WTP (sampling point number

5). As can be seen in Figure 2, even with the high THMFP of the raw water, all

membranes showed high rejections of THM precursors.

1

3

Reservoir 1

(100 Hm3)

Reservoir 2

(0.2 Hm3)

2

4

5

• Organic matter was monitored with a high sensivity

combustion total organic carbon (TOC) instrument

(Anallytik-Jena).

• Major ions concentration in the feed and permeate

samples were analyzed by ion chromatography

(Dionex 2100).

• THM quantification by Gas Chromatography with

Static Head Space injector coupled to an Electronic

Capture Detector (Agilent) to evaluate THMFP

reduction (Pérez et al. 2008).

Fig. 1. Sampling points in the hydric system selected: 1) Pobla de Lillet (Llobregat Source); 2) Gironella; 3) Balsareny; 4) Parc de l’Agulla; 5) Drinking WTP in Manresa

Fig.3. TMP front permeate flux

Fig. 2. THMFP reduction by ten NF membranes tested

Fig.5. Evaluation of THMFP through an hydric system and their reduction by NF

monitoring changes in water conductivity.

However, a wide range of permeability and conductivity rejection values were

observed using different commercial NF membranes (Figures 3 and 4). NF270

(DOW), ESNA1LF2 (Hydranautics) and TFC-SR100 (Koch) were the membranes

selected due to their different capabilities to reject conductivity.

As can be seen in Figure 5 water reservoirs are the main responsible for the

increasing THMFP. The total THM concentration was nearly doubled after water

reservoirs 1 and 2, indicating the enormous effect of eutrophication to the THM

precursor material.

Fig.4. Conductivity rejection front permeate