análisis y remosión de contaminantes en aguas

7/25/2019 anlisis y remosin de contaminantes en aguas

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Analysis and removal of emergingcontaminants in wastewater anddrinking waterMira Petrovic , Susana Gonzalez, Damia` Barcelo

The occurrence of trace organic contaminants in wastewaters, their

behavior during wastewater treatment and production of drinking water

are key issues in the re-use of water resources. Elimination of different

classes of emerging contaminants, such as surfactant degradates, phar-

maceuticals and polar pesticides in wastewater-treatment plants (WWTPs)was found to be rather low, so sewage effluents are one of the main

sources of these compounds and their treatment-resistant metabolites.

This article reviews the state-of-the-art in the analysis of several groups of

emerging contaminants (acidic pharmaceuticals, antibacterial agents,

acidic pesticides and surfactant metabolites) in wastewaters. It also dis-

cusses the elimination of emerging contaminants in WWTPs applying

conventional activated sludge treatment (AST) and advanced treatment

processes, such as membrane bioreactors (MBRs) and advanced oxidation

processes (AOPs), as well as during production of drinking water.

# 2003 Published by Elsevier B.V.

Keywords:Acidic pesticides; Acidic pharmaceuticals; Advanced treatment; Emerging

contaminants; Surfactant degradates; Wastewater treatment

1. Introduction

Until the beginning of the 1990s, non-

polar hazardous compounds (i.e. persis-

tent organic pollutants (POPs) and heavy

metals) were a focus of interest and

awareness as priority pollutants, so were

part of intensive monitoring programs.

Today, these compounds are less relevant

for the industrialized countries, since adramatic reduction of emissions has been

achieved through the adoption of appro-

priate measures and the elimination of

the dominant sources of pollution.

However, the emission of so-called

emerging or new unregulated con-

taminants has become an environmental

problem, and there is widespread con-

sensus that this kind of contamination

may require legislative intervention. This

group mainly comprises products used in

large quantities in everyday life, such as

human and veterinary pharmaceuticals,

personal care products, surfactants and

surfactant residues, plasticizers and var-

ious industrial additives. The character-istic of these contaminants is that they do

not need to be persistent in the environ-

ment to cause negative eects, since their

high transformation and removal rates

can be oset by their continuous intro-

duction into the environment. One of the

main sources of emerging contaminants

are untreated urban wastewaters and

WWTP euents (Fig. 1). Most current

WWTPs are not designed to treat these

types of substance and a high portion of

emerging compounds and their metabo-

lites can escape elimination in WWTPs

and enter the aquatic environment via

sewage euents.

The partial or complete closure of water

cycles is an essential part of sustainable

water-resource management, and the

increasing scarcity of pristine waters for

drinking water supply and the growing

consumption of water by industry and

agriculture should be countered by the

ecient, rational utilization of water

resources. One of the options is to

increase the re-use of euents for variouspurposes, especially in industrial and

agro/food production. However, because

of the high cost of the end-of-pipe

approach (i.e. drinking water treatment),

indirect potable re-use requires ecient

treatment of wastewaters prior to their

discharge. Thus, the occurrence of trace

organic contaminants in wastewaters,

their behavior during wastewater treat-

ment and production of drinking water

are key issues that require further study.

Mira Petrovic *,

Susana Gonzalez,

Damia` Barcelo

Department of Environmental

Chemistry, IIQAB-CSIC,

c/Jordi Girona 18-26, E-08034

Barcelona, Spain

*Corresponding author.

Tel.: +34 93 400 6172;

Fax: +34 93 204 5904;

E-mail: [email protected]

Trends in Analytical Chemistry, Vol. 22, No. 10, 2003 Trends

0165-9936/$ - see front matter # 2003 Published by Elsevier B.V. doi:10.1016/S0165-9936(03)01105-1 685
http://-/?-


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Many believe that, of all emerging contaminants,

antibiotics are of greatest concern, since their emission

in the environment can increase the occurrence of

resistant bacteria in the environment [1]. However,

other emerging compounds, especially polar ones, such

as acidic pharmaceuticals, acidic pesticides and acidic

metabolites of non-ionic surfactants, also deserve parti-

cular attention. Because of their physico-chemical

properties (high water solubility and often poor degrad-

ability), they are able to penetrate through all natural

ltration steps and man-made treatments, thus pre-

senting a potential risk in drinking water supply [2,3].

Dierent classes of emerging contaminants, mainly

surfactant degradates, pharmaceuticals and personal

care products (PPCPs) and polar pesticides were found

to have rather low elimination rates and have been

detected in WWTP euents and in the receiving surfacewaters. However, for most emerging contaminants,

occurrence, risk assessment and ecotoxicological data

are not available, and it is dicult to predict their fate in

the aquatic environment. Partly, the reason for this is a

lack of analytical methods for their determination at

trace concentrations. Analysis of emerging con-

taminants is a real analytical challenge, not only

because of the diversity of chemical properties of these

compounds, but also because of generally low con-

centrations (usually at part per billion (ppb) or part per

trillion (ppt) levels) and the complexity of matrices.

This article reviews the state-of-the-art in the analy-

sis of several groups of emerging contaminants (acidic

pharmaceuticals, antibacterial agents, acidic pesticides

and surfactant metabolites) in wastewaters. It discusses

various aspects of current liquid chromatography (LC)

mass spectrometry (MS)-(MS) [LC-MS-(MS)] and gas

chromatography(GC)-MS [GC-MS] methodology, includ-

ing sample preparation. It also surveys the elimination

of emerging contaminants in WWTPs by AST and

applying advanced treatment processes, such as MBRs

and AOPs. In addition, it discusses the elimination in

treatmentprocessesatplantsfortreatingdrinkingwater.

2. Analysis of emerging contaminants in

wastewater

One of the major limitations in the analysis of emerging

contaminants remains the lack of methods for quanti-

cation of low concentrations. The prerequisite for

proper risk assessment and monitoring of the quality of

waste, surface and drinking waters is the availability of

multiresidual methods that permit measurement at the

low ng/l level (or even below that). However, these

compounds have received little attention because they

are not on regulatory lists as environmental pollutants.

However, today analytical methodology for dierent

groups of emerging contaminants is being developed

Figure 1. Components of a (partially) closed water cycle with indirect potable re-use.

Trends Trends in Analytical Chemistry, Vol. 22, No. 10, 2003

686 http://www.elsevier.com/locate/trac


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and an increasing number of methods is reported in the

literature. Still, analysis of this group of contaminants

requires further improvement in terms of sensitivity

and selectivity, especially for very complex matrices,

such as wastewater.

2.1. Acidic pharmaceuticals

Dierent methods, mainly based on LC-MS and GC-MS,

in combination with either polymer or C18-based solid-

phase extraction (SPE), are being developed for the ana-

lysis of pharmaceutical compounds. However, most

methods are tailored for neutral compounds (e.g. anti-

biotics) and less complex matrices (surface and ground-

water), while only a limited number of papers describe

procedures applicable to the analysis of polar drugs in

wastewater. A survey of analytical methods for the

quantication of regularly used polar pharmaceuticals

in wastewater matrices is given in Table 1.

A typical analytical method includes the use of octa-

decylsilica, polymeric, or hydrophilic-lipophilic balanced(HBL) supports for o-line SPE of water samples, with

either disks or, most frequently, cartridges at low pH

(typically pH=2).

Separation techniques include GC and LC, while, for

detection, MS is the technique most widely employed.

Because of the low volatility of polar pharmaceuticals,

GC-MS analysis requires an additional derivatization,

which makes sample preparation laborious and time

consuming, and also increases the possibility of con-

tamination and errors. Moreover, some compounds are

thermolabile and decompose during GC analysis (e.g.

carbamazepine forms iminostilben as degradation pro-

duct) [4].

As a result, use of LC-MS and LC-MS-MS is increasing.

When reviewing the principal methods for the analysis

of pharmaceuticals in aqueous environmental samples,

Ternes[4]indicated that LC-MS-MS is the technique of

choice for assaying polar pharmaceuticals and their

metabolites. However, he pointed out the diculty in

the enrichment step, as well as the low resolution and

signal suppression in the electrospray (ESI) interface

because of matrix impurities.

Farre et al. [5] compared LC-(ESI)-MS and GC-MS

(after derivatization with BF3-MeOH) for monitoring

some acidic and very polar analgesics (salicylic acid,ketoprofen, naproxen, diclofenac, ibuprofen and gem-

brozil) in surface water and wastewater. Results

showed a good correlation between methods, except for

gembrozil, for which derivatization was not com-

pletely achieved in some samples.

In general, the limits of detection (LODs) achieved

with LC-MS-(MS) methods were slightly higher than

those obtained with GC-MS methods (see Table 1); how-

ever, LC-MS methodology showed advantages in terms

of versatility and sample preparation being less compli-

cated (i.e., derivatization was not needed). Table1.

Metho

ds

fortheana

lysiso

faci

dicp

harmaceutica

lsinwastewaters

Compounds

Extraction

Derivatization

Chromatographic

method

Detection

LOD

(n

g/l)

Reference

Beza

fibrate,

diclofenac,

ibupro

fen,

gem

fibrozil,

carbamezapine

Sequentia

lSPE

(C18+po

lymericsorbent)

LC

MS

2

[48]

Sa

licy

licacid,

ibupro

fen,

ketopro

fen,

naproxen,

beza

fibrate,

diclofenac

SPE(po

lymericsorbent)

LC

MS

5

56

[5]

Beza

fibrate,

clofibricacid,

diclofenac,

fenopro

fen,

gem

fibrozil,

ibupro

fen,

inomethacin,ketopro

fen,

naproxen

SPE(C18)

LC

MS

MS

5

20

[49]

Beza

fibrate,

clofibricacid,

ibupro

fen

SPE(MCXorpo

lymericso

rbent)

LC

MS

MS

0.0

16

2.1

8

[50]

Ibupro

fen,

clofibricacid,

ketopro

fen,

naproxen,

diclofenac

SPE(HLB)

Diazomethane

GC

MS

0.3

4.5

[51]

Clofibricacid,

diclofenac,

ibupro

fen,p

henazone,

propyp

henazone

SPE(C18)

Pentafloro

benzy

lbromide

GC

MS

0.6

20

[52]

Clofibricacid,

naproxen,

ibupro

fen

SPE(po

larEmpore

disk)

BSTFA

(bis(trimethy

lsily

l)-tri

fluoroacetam

ide

)

GC

MS

0.4

2.6

[53]

Ibupro

fen,

naproxen,

ketopro

fen,

tolf

enamicacid,

diclofenac,

mec

lofenamicacid

SPE(HLB)

MTBSTFA

(N-methy

l-N-(

tert-butyldimethylsily

l)

trifluoroacetamide

)

GC

MS

20

[54]


http://www.elsevier.com/locate/trac 687


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Table 2 summarizes the quantitation and qualier

ions used by the various authors for the determination

of polar drugs in wastewaters using selected ion mon-

itoring (SIM) or multiple reaction monitoring (MRM).

The use of triple-quadrupole MS in LC analysis has sub-

stantially increased the selectivity and the sensitivity of

the determination, resulting in LODs better than those

in single-quadrupole LC-MS. Acidic drugs were usually

detected using an ESI interface under negative ioni-

zation conditions and deprotonated molecules were

chosen as precursor ions. Typical fragmentation pat-

terns obtained with LC-MS-(MS) showed a loss of CO2(or loss of the acidic moiety), with a limited number of

other fragments. For example, for diclofenac, ibuprofen

and ketoprofen, the product ions generated by loss of

CO2 were the only fragment ions formed.

2.2. Acidic pesticides

Chlorinated phenoxy acid herbicides account for the

majority of pesticides used worldwide, and their pre-

sence in environmental waters is well documented.

However, their behavior during wastewater treatment

has rarely been studied. This group includes, for exam-

ple, mecoprop (MCPP), MCPA, 2,4-D, 2,4-DP 2,4,5-T,

2,4-DB. These compounds are characterized by high

polarity and thermal lability. For these reasons, LC is

generally more suitable for their analysis. However, the

methods used to determine chlorinated phenoxy acid

Table 2. Quantitation and diagnostic ions (m/z) used for the LC-MS and GC-MS, and base peaks of precursor and product ions used for LC-MS-MS analysisof acidic pharmaceuticals in wastewaters. Data compiled from references listed inTable 1

Compound Analytical method Ionization mode MS MS-MS

SIM ions Precursor (m/z) Product 1 (m/z) Product 2 (m/z)

Ibuprofen LC-MS NI 205, 161LC-MS-MS NI 205M-H 161M-H-CO2

GC-MS Positive EI 177, 220a

161, 343, 386b

263, 278, 234c

Diclofenac LC-MS NI 294, 250, 232LC-MS-MS NI 294M-H 205M-H-CO2


214, 216, 475b

352/354/356d

Clofibric acid LC-MS NI 213, 127LC-MS-MS NI 213M-H 127M-H-CO2

85C4H5O2


128, 130, 394b

128, 143, 286c

Benzafibrate LC-MS NI 360, 274LC-MS-MS NI 360M-H 274M-H-C4H6O2

154M-H-C12H14O3


128, 130, 394b

Gemfibrozil LC-MS NI 249, 121LC-MS-MS NI 249M-H 121M-H-C7H12O2

Ketoprofen LC-MS NI 253, 209, 197

LC-MS-MS NI 253M-H 209M-H-CO2GC-MS Positive EI 209,268a

311d

Naproxen LC-MS NI 229, 185, 173, 170LC-MS-MS NI 229M-H 185M-H-CO2

170M-H-C2H3O2


243,302, 185c

287d

aDiazomethane derivative.bPentafluorobenzyl derivative.cTrimethylsilyl derivative.dTert-butyldimethylsilyl derivative.




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herbicides are still dominated by GC with either elec-

tron capture detection (ECD) or MS detection. The main

disadvantage of GC analysis is that it requires prior deri-

vatization step, usually using highly toxic and carcino-

genic diazomethane or, less frequently used, acid

anhydrides, benzyl halides and alkylchloroformates.

The injection-port derivatization with an ion-pair

reagent has been successfully applied[6], as well as in

situderivatization prior to solid-phase microextraction

(SPME) [7].

Alternative methods based on LC-ESI-MS have been

proposed. When using LC-MS-(MS), phenoxy acid her-

bicides are detected under negative ionization condi-

tions, typically yielding [M-H]- ion and one abundant

fragment formed by the loss of the acidic moiety[8,9],

as shown in Fig. 2 for MCPP, 2,4DP and2,4,5T.

Recently, in-tube SPME followed by LC-MS was

applied for the determination of six chlorinated phen-

oxy acid herbicides[10]. With river water, LODs were

5^30 ng/l, but wastewater was not tested.

Figure 2. MS-MS spectra and the proposed fragmentation pattern of: (a) MCPP (precursor ion m/z 213); (b) Dichlorprop (2,4-DP) (precursor ion m/z 233);

and, (c) 2,4,5-T (precursor ion m/z 253).




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2.3. Antiseptics

Several methods have been proposed for the determina-

tion of triclosan (5-chloro-2-[2,4-dichlorophenoxy]

phenol), which is used as an antiseptic agent in a vast

array of personal care (e.g. toothpaste, acne cream,

deodorant, shampoo, toilet soap) and consumer pro-

ducts (childrens toys, footwear, kitchen cutting

boards).

A method based on diazomethane derivatization and

GC-ECD was applied for quantication of triclosan in

the wastewater of a slaughterhouse [11].

Lindstro m et al. [12] detected triclosan and methyl

triclosan in lakes and in a river in Switzerland applying

either SPE (macroporous polymeric adsorbent), dia-

zoethane derivatization, silica clean-up and GC-MS

analysis or passive sampling with semi-permeable

membrane devices (SPMDs). LODs varied with the

sample matrix and were


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2.4. Alkylphenolic compounds

The trace analysis of alkylphenol ethoxylates (APEOs)

and their acidic metabolites by LC-MS or LC-MS-MS

using atmospheric pressure chemical ionization (APCI)

and ESI was recently reviewed by Petrovic et al. [15,16]

and the analytical performances for oligomeric mix-

tures of APEOs discussed. Generally, an ESI interface is

used for the analysis of alkylphenolic compounds

because of its higher sensitivity, especially for alkyl-

phenols and carboxylated compounds.

Alkylphenoxy carboxylates (APECs) were detected in

both NI and PI modes. In the NI mode, using ESI, APECs

give two types of ions:

one corresponds to the deprotonated molecule

[MH] (m/z 277, 321, 263 and 307, corre-

sponding to nonylphenol carboxylate (NPE1C),

nonylphenol ethoxycarboxylate (NPE2C), octyl-

phenol carboxylate (OPE1C), and octylphenol

ethoxycarboxylate (OPE2C), respectively); and, the other corresponds to deprotonated alkyl-

phenols[17].

The relative abundance of these two ions depends on

the extraction voltage. In the presence of ammonium

acetate and when using an APCI under PI conditions,

NPE1C gave [M+NH4]+ ions at m/z 296, while NPE2C

gave [M+NH4]+ ion atm/z 340 [18].

LC-ESI-MS was also applied for the analysis of the

dicarboxylated breakdown products [carboxylated

alkylphenoxy carboxylates (CAPECs)] in wastewaters

[19,20]. However, the identication of these com-

pounds using LC-MS, under conditions giving only

molecular ions, is dicult, since CAnPEmCs have the

same molecular mass as APECs but have one ethoxy

unit less and a shorter alkyl chain (An1PEm1C).

Moreover, since some compounds partly co-elute, the

unequivocal assignment of the individual fragments

can be accomplished only by using LC-MS-MS. Typical

fragmentation patterns obtained with LC-ESI-MS-MS

showed the formation of the carboxy-alkylphenoxy

fragment, with the additionally loss of CO2or an acetic

acid group, in the case of CA5PE12C leading tom/z149

and 133 fragments [19].

MS-MS spectra of APECs [19,21,22] show intensesignals at m/z 219 (for NPECs) andm/z 205 (for OPECs),

which are produced after the loss of the carboxylated

(ethoxy) moiety, while sequential fragmentation of the

alkyl chain resulted in ions with m/z 133 and 147.

To overcome the problem of low volatility of acidic

alkylphenolic compounds, various o-line and on-line

derivatization protocols have been developed. O-line

derivatization to corresponding triemethylsilyl ethers,

methyl ethers, acetyl esters, pentauorobenzoyl or hep-

tauorobutyl esters, respectively, was applied as a

common approach in GC-MS.

On-line direct GC injection-port derivatization using

ion-pair reagents (tetraalkylammonium salts), has

been also reported [23]. The most signicant ions in

GC-(EI)-MS of methylated NPECs were fragments pro-

duced by rupture of the benzylic bond in the branched

nonyl side-chain [23^25]. GC-CI-MS spectra of the

NPECs with isobutane as reagent gas showed char-

acteristic hydride ion-abstracted fragment ions shifted

by 1 Da from those in the corresponding EI mass spectra

[22]. When using ammonia as reagent gas, intense

ammonia-molecular ion adducts of the methyl esters,

with little or no secondary fragmentation, were repor-

ted for NPECs[26]. The ions selected were as follows:

m/z 246, 310, 354 and 398 for NPE1C, NPE2C,

NPE3C and NPE4C, respectively.

3. Elimination by AST

The present state-of-the-art of wastewater treatmentinvolves the AST process preceded by conventional

physico-chemical pre-treatment steps. Table 3 sum-

marizes data on the elimination of emerging con-

taminants in WWTPs.

3.1. PPCPs

Daughton and Ternes [1] reviewed the occurrence of

over 50 individual PPCPs (metabolites from more than

10 broad classes of therapeutic agents or personal care

products in environmental samples) mainly in WWTP

euents, surface and ground water and much less fre-

quently in drinking water. Acidic drugs comprised the

major group of PPCPs detected in municipal WWTPs

and, among them, bezabrate, naproxen, and ibupro-

fen were most abundant (concentrations up to 4.6 mg/l

in German municipal WWTPs).

Tixier et al.[27]found that carbamezapine presented

the highest daily load from the WWTP into Lake Grei-

fensee (Switzerland), followed by diclofenac and

naproxen. Their elimination during passage through a

municipal sewage treatment in most cases was found to

be quite low (see Table 3), in the range 35^90%, and

some compounds, such as carbamazepine, exhibited an

extremely low removal (only 7%) [28]. Consequently,

through sewage euents, PPCPs can enter receivingsurface waters and thus present a risk in the production

of drinking water. For example, clobric acid, a metabo-

lite of three lipid regulating agents (clobrate, etobrate

and fenobrate), has been identied in river and ground

water and even in drinking water at concentrations up

to 165 ng/l [29,30].

3.2. Acidic pesticides

Chlorinated phenoxy acids are widely used in agri-

culture, but also as herbicides on lawns, algicides in

paints and coatings and roof-protection agents in




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at-roof sealants. As a result, residues of these sub-

stances are introduced into the aquatic system through

dierent pathways.For example, inthe catchmentareaof

Lake Greifensee, 65% of MCPP originated from WWTPs

andtheremaining35%fromdiusesources[31].

Degradation of acidic pesticides under laboratory

conditions is well studied, but there are few publica-

tions dealing with their behavior in real WWTPs. Gen-

erally, AST was found to be ineective in removing

chlorinated phenoxy acid herbicides from settled sew-

age. However, under laboratory conditions MCPP

proved to be biodegradable (nearly 100%); however,

this requires a long adaptation time (lag-phase) of acti-

vated sludge[32]. In real WWTPs, this presents a majordiculty since, like the majority of herbicides, MCPP is

applied only during a short growth period of plants,

which means that WWTPs that contain a non-adapted

activated sludge, receive shock-loads of herbicides,

which will not be eliminated.

A long acclimatization period (about 4 months) was

also observed in a bench-scale study using sequencing

batch reactors before 2,4-D biodegradation was estab-

lished [33]. Subsequently, at steady-state operation,

all reactors achieved practically complete removal

(>99%) of 2,4-D.

3.3. Alkylphenolic surfactants

Although their environmental acceptability is strongly

disputed, APEOs are still among the most widely used

non-ionic surfactants. Currently, under optimized con-

ditions, more than 90^95% of these surfactants are

eliminated by conventional biological wastewater

treatment (normally AST). Even if such high elimina-

tion rates are achieved, the principal problem is the for-

mation of treatment-resistant metabolites out of the

parent surfactants. The widespread incidence of APEO-

derived compounds in treated wastewaters and the sub-

sequent disposal of euents into aquatic system raise

concerns about the impact of these compounds on the

environment. Studies have shown that their neutral(alkylphenols and short ethoxy chain ethoxylates) and

acidic treatment-resistant metabolites (APECs) possess

the ability to mimic natural hormones by interacting

with the estrogen receptor.

It was estimated that 60^65% of all nonylphenolic

compounds introduced into WWTPs are discharged

into the environment 19% as carboxylated deriva-

tives, 11% as lipophilic nonylphenol ethoxylate

(NP1EO) and nonylphenol diethoxylate (NP2EO), 25%

as nonylphenol (NP) and 8% as non-transformed

nonylphenol ethoxylates (NPEOs) [34].

Table 3. Elimination at WWTPs (AST). Data complied from references [12,28,36,51,5457]

Compound Averageelimination (%)a

Effluentconcentrations(g/l)

Main degradationproducts

Observation

Non-ionic surfactantsAlkylphenol ethoxylates 9099


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However, contrary to the general belief that NPECs

are the refractory metabolites, Di Corcia et al. [35]

found that CAPECs are the dominant products of NPEO

biotransformation. By averaging data relative to the

treated euents of ve major activated sludge WWTPs

of Rome (Italy) over 4 months, relative abundances of

NPEOs (nEO =1 and 2), NPECs and CAPECs were found

to be respectively 102%, 245%and667%.

The concentrations of the acidic metabolites, NPECs

and CAPECs typically are in the low mg/l range. How-

ever, high values (up to several hundred mg/l) are detec-

ted in euents of WWTPs receiving industrial

wastewaters, especially from tannery, textile, pulp and

paper industries [36].

4. Elimination by modern WWTPs

Although adopted as the best available technology; bio-

logical treatment eects only partial removal of a widerange of emerging contaminants, especially polar ones,

which are discharged into the nal euent. Thus, it has

become evident that the application of more enhanced

technologies may be crucial to fulll the requirements

to recycle municipal and industrial wastewaters as

drinking water. In recent years, there have been studies

of new technologies for not only wastewater treatment

but also production of drinking water. Among them

membrane treatment, using both biological (MBRs) and

non-biological processes (reversed osmosis, ultraltra-

tion, nanoltration), and AOPs are most frequently

considered as they may be appropriate for removing

trace concentrations of emerging polar contaminants.

4.1. Membrane processes

MBR technology is considered the most promising

development in microbiological wastewater treatment.

Now, when economic reasons no longer limit the appli-

cation of MBRsin industrialand municipal WWTPs [37],

andnew requirements arebeingset forwastewatertreat-

ment, MBRs may be key in direct or indirect recycling of

wastewaters, because of two of their characteristics:

(a) the low sludge load in terms of BOD, so that the

bacteria are forced to mineralize poorly degrad-able organic compounds; and

(b) the long life of the sludge gives the bacteria time

to adapt to the treatment-resistant substances

[38,39].

However, although many articles have reported on

the application of MBRs to the treatment of urban and

industrial wastewaters, there are few papers reporting

on the behavior of emerging contaminants during MBR

treatment, and all of those deal with nonylphenolic

compounds.

Using an MBR unit that comprises three bioreactors

and an external ultraltration unit followed by gran-

ular activated carbon (GAC) adsorption, Witgens et al.

[40]reported the removal of more than 90% of NP in

wastewater from a waste-dump leachate plant. The use

of a set of laboratory nanoltration membranes resul-

ted in the retention of more than 70% of NP and this

process was regarded as an alternative for the nal

treatment of MBR euents.

Li et al.[41]used GC-MS and LC-MS-MS to assess the

elimination eciency in a membrane-assisted biologi-

cal WWTP. The results showed that, compared to con-

ventional WWTPs, membrane-assisted biological

treatment with biomass concentrations of about 20 g/l

could improve the eciency of eliminating NPEOs (and

other ionic and non-ionic surfactants), but could not

entirely stop the dischargewith the permeates.

4.2. Treatment by AOPs

There have been studies of AOPs, which use a combi-nation of ozone with other oxidation agents (UV radia-

tion, hydrogen peroxide, TiO2) to enhance the

degradation of polar pharmaceuticals [42^44] and

NPEO metabolites [45].

Ternes et al.[44]used a pilot plant for ozonation and

UV disinfection of euents from a German municipal

WWTP containing antibiotics, beta blockers, anti-

phlogistics, lipid-regulator metabolites, musk frag-

rances and iodinated X-ray contrast media. When

10^15 mg/l ozone was used (contact time, 18 min), no

pharmaceuticals were detected. However, the ionic

iodinated X-ray contrast compounds exhibited removal

eciencies no higher than 14%.

In another study [43], ozonation was demon-

strated to be a suitable tool for carbamazepine abate-

ment, even under the process conditions usually

adopted in drinking water facilities. However, despite

good primary elimination, a low degree of mineraliza-

tion was observed and there was no proper total carbon

balance, even after prolonged ozonation, which

indicated the presence of unidentied degradation

products.

However, the degradation eciency of an AOP is lim-

ited by the radical scavenging capacity of the matrix of

the treated water. Thus, for sucient degradation of thepharmaceuticals (>90%) from wastewater, the ozone

concentration has to be equal to the dissolved organic

carbon (DOC) value[42],which means that economic

considerations have to underpin the feasibility of the

process for wastewater treatment.

Recently, using a laboratory-scale reactor, Ike et al.

[45] determined that the eectiveness of ozone treat-

ment in the degradation of NPEO metabolites follows

the order: NPE1C>>NP>NP1EO. Acidic metabolites

were completely degraded within 4^6 min (initial con-

centration, 0.4^1.0 mg/l), the NP concentrations were




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reduced by 75^80% in 6 min, while only 25^50% of

NP1EOwas eliminatedin thesame time.

5. Elimination in drinking water-treatment

plants

The occurrence of organic micro-contaminants in raw

water and their removal in the course of production of

drinking water and possible formation of disinfection

by-products are key issues in relation to the quality of

drinking water. Although, compounds discussed in this

review are currently not regulated in drinking water

directives, precautionary principles should be

employed, and the removal of all organic micro-con-

taminants should be as high as possible. However, sev-

eral studies have shown that the removal of emerging

polar contaminants during drinking water treatment is

incomplete.

The elimination of selected pharmaceuticals (clobric

acid, diclofenac, carbamezapine, bezabrate) during

drinking water treatment was investigated in the

laboratory, at the pilot-plant scale and in real water-

works in Germany[46].Sand ltration under aerobic

and anoxic conditions, as well as occulation using

iron(III) chloride, did not signicantly eliminate the

target pharmaceuticals, while ozonation was quite

eective in eliminating these polar compounds. Diclofe-

nac and carbamezapine were reduced by more than

90%, bezabrate was eliminated by 50%, while clobric

acid was stable even at high ozone doze. Filtration with

granular activated carbon (GAC) under waterworks con-

ditions was very eective in removing pharmaceuticals,

apart from clobric acid,less of which was adsorbed.

Figure 4. Fate of nonylphenolic compounds during production of drinking water. (a) Total concentration of nonylphenolic compounds and their elimination

during different treatment steps at waterworks Sant Joan Despi` (Barcelona, Spain); (b) Average composition (calculated on a molar basis) of nonylphenolic

compounds in raw water; and, (c) Average composition (calculated on a molar basis) of nonylphenolic compounds in pre-chlorinated water.




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The behavior of polar alkylphenolic compounds dur-

ing processing of contaminated water in waterworks

and their possible occurrence in treated water was

rarely considered to be of interest and there are hardly

any data available for drinking water.

The elimination of neutral and acidic nonylphenolic

compounds and their brominated and chlorinated deri-

vatives during drinking water-treatment processes at

the waterworks that supply drinking water to Barce-

lona (Spain) was investigated utilizing a very sensitive

LC-MS-MS method [47]. The concentration of total

nonylphenolic compounds NPECs (nEO=0^1), NPEOs

(nEO=0^1) and NP in raw water from the Llobregat

river entering the waterworks was in the range

8.3^21.6 mg/l, with NPE2C being the most abundant

compound. Pre-chlorination reduced the concen-

tration of short-ethoxy chain NPECs and NPEOs by

25^35%, and of NP by almost 90%. However, this

reduction was partly because of their transformation

to halogenated derivatives. After pre-chlorination,halogenated nonylphenolic compounds represented

approximately 13% of the total metabolite pool, of

which 97% were in the form of brominated acidic

metabolites. The eciency of further treatment steps to

eliminate nonylphenolic compounds (calculated for the

sum of all short-ethoxy chain metabolites, including

halogenated derivatives) was as follows:

settling and occulation followed by rapid sand

ltration (7%);

ozonation (87%);

GAC ltration (73%); and,

nal disinfection with chlorine (43%), resulting

in overall elimination in the range 96^99%

(mean 98% for four sampling dates), as shown in

Fig. 4.

6. Conclusions

The application of advanced LC-MS and GC-MS tech-

nologies to environmental analysis has allowed the

determination of a broader range of compounds and

thus permitted more comprehensive assessment ofenvironmental contaminants. Among the various com-

pounds considered as emerging pollutants, acidic phar-

maceuticals, surfactant degradates and acidic

pesticides are of particular concern, because of both

their ubiquity in the aquatic environment and health

concerns.

Elimination of these emerging contaminants during

wastewater and drinking water treatment is not satis-

factory, so control of improved treatment has to be

strict to ensure that the proportion of these micro-con-

taminants removed is as high as possible. Thus, in view

of the possible re-use of WWTP euents, more research

is needed to evaluate the fate of emerging contaminants

and their eects in the aquatic environment. Moreover,

as disinfection processes (either chlorination or ozona-

tion) potentially shift the assessment of the risk of

human consumption of the parent compound to its

degradation products, generic analytical protocols will

have to be developed for the simultaneous determina-

tion of parent compounds and their metabolites.

Acknowledgements

The work described in this article was supported by the

EU Project P-THREE (EVK1-CT-2002-00116) and by

the Spanish Ministerio de Ciencia y Tecnologia

(PPQ2002-10945-E). M. Petrovic acknowledges the

Ramon y Cajal contract from the Spanish MCyT. S.

Gonzalez acknowledges the grant from the Spanish

MCyT (PPQ2001-1805-CO3-01).

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