This study evaluated the use of nanofiltration (NF) membranes to reduce trihalomethane formation potential (THMFP) in drinking water sources along a hydric system. Ten NF membranes were tested on pre-chlorinated water and showed high rejection of THM precursors, though permeability varied. NF270, ESNA1LF2 and TFC-SR100 membranes were selected for further study based on conductivity rejection capabilities. Water reservoirs significantly increased THM precursor levels. Smaller conductivity rejection by ESNA1LF2 resulted in lower THMFP reduction, demonstrating the relationship between conductivity rejection and disinfection byproduct reduction by NF membranes.

1. Trihalomethane formation potential along an
hydric system:
Nanofiltration in drinking water treatment
G. 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
INTRODUCTION
Membrane technology in drinking water treatment has been considered to be variety of DBPs depending on the conditions as water quality or chlorine dose.
effective removing turbidity, organics, microorganisms and disinfection by-products Trihalomethanes (THMs) and haloacetic acids (HAAs) are the most known and
(DBPs) precursors (Van der Bruggen et al. 2003). Concerns regarding the potential relatively easy characterised DBPs. Some studies have related different organic
health effects of DBP prompted industrialized countries to develop more stringent fractions to their formation potential of DBP, typically THMFP (Chow et al. 2005).
regulations which implies new technologies as nanofiltration (NF) to treat fresh
water. 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
Chlorination has been the main procedure to disinfect municipal drinking waters. la Rubia et al. 2008). At the same time, medium conditions and operational parameters
Reactions between chlorine and natural organic matter (NOM) produce a wide were studied to improve NF process knowledge.
METHODOLOGY
An automated lab-scale experimental setup equipped with a cross-flow module • Organic matter was monitored with a high sensivity
1
(SEPA-CFII Osmonics) was used to evaluate THMFP reduction and productivity of combustion total organic carbon (TOC) instrument
10 commercial NF membranes with pre-chlorinated feed water from a drinking Reservoir 1 (Anallytik-Jena).
water treatment plant (WTP) at transmembrane pressures (TMP) ranging from 2 to (100 Hm3)
15 bar (APHA 1998, Chen et al. 2008). • Major ions concentration in the feed and permeate
2
samples were analyzed by ion chromatography
Three membranes were selected to evaluate its capacity to decrease THM (Dionex 2100).
Formation Potential (THMFP) in waters from River Llobregat source to Manresa 3
drinking WTP (Figure 1). Previously to the NF experiments, water samples were 4
• THM quantification by Gas Chromatography with
filtered through glass-fiber filters. Apart from conductivity and pH measurements Static Head Space injector coupled to an Electronic
Reservoir 2
on-line, the following analytical methods were carried out to evaluate the NF 5
(0.2 Hm3) Capture Detector (Agilent) to evaluate THMFP
performance of the membranes: 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
RESULTS AND DISCUSSION
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.
Fig.3. TMP front permeate flux Fig.4. Conductivity rejection front permeate
Fig. 2. THMFP reduction by ten NF membranes tested
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 Fig.5. Evaluation of THMFP through an hydric system and their reduction by NF
reservoirs 1 and 2, indicating the enormous effect of eutrophication to the THM monitoring changes in water conductivity.
precursor material.
CONCLUSIONS
• 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.
REFERENCES
• 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.
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)”.