Kim Y.J. (Ed.) Advanced Environmental Monitoring

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20 Differentiating Effluent Organic Matter from Natural Organic Matter 263

reference, FIs of the Suwannee River humic and fulvic acids, and pure EfOM

(which was generated from a laboratory bench-scale bioreactor and isolated by an

electrodialysis/reverse osmosis desalting process) were determined to be 0.864,

0.969, and 1.459, respectively. The FIs of EfOM were higher than those of NOM,

which means that the properties of EfOM that distinguish it from NOM are mainly

microbial—in origin. The same trends of FIs were also observed in other wastewa-

ters in this study (results not shown).

Fluorescence EEM measurements for upstream water, wastewater, and down-

stream of WWTP (influent of drinking water treatment plant) clearly showed dif-

ferent peaks between NOM and EfOM (Fig. 20.1). Previous researchers working

with fluorescence spectroscopy identified tryptophan-like, protein-like peaks at

Ex/Em = 275/340 nm and humic-like peaks at 260/380–460 nm and 350/420–

480 nm (Coble 1996; Coble et al. 1998; Stedmon et al. 2003). EEMs of wastewater

and wastewater-impacted water exhibit the presence of protein-like substances

at the range of excitation wavelength 260–290 nm and emission wavelength

320–370 nm, which were at a similar location observed in other studies, and this

protein-like peak may have originated from soluble microbial products (SMPs)

present in biologically treated wastewater.

In general, the SEC–DOC of surface waters and wastewaters is separated into

three main peaks according to their molecular weight distributions, as shown in Fig.

20.2: the zone 1 peak represents large molecules, such as polysaccharides, proteins,

and organic colloids, the zone 2 peak is attributed to humic substances, and the

zone 3 peak corresponds to low molecular weight organic acids. Corresponding

UVA

254

chromatograms showed low absorbance in the zone 1 peak, and greatly

increased absorbancy in zone 2, with intermediate absorbance in the zone 3 peak,

which indicates that macromolecular constituents in the zone 1 peak do not consist

of aromatic rings or conjugated bonds, but saturated structures or linear ring systems

that may be more labile and hydrophilic, although they are macromolecules. On the

other hand, components (humic substances) in the zone 2 peak are likely to be

Fig. 20.1 EEM contour maps of samples (February 2004) collected upstream of WWTP (left),

wastewater effluent (middle), and downstream of WWTP (right) from a Northeast USA water-

shed. (x-axis: emission [Em] wavelengths of 290–500 nm, y-axis: excitation [Ex] wavelengths of

240–450 nm) (Nam, 2007)

264 S.-N. Nam et al.

hydrophobic and microbially resistant in spite of somewhat smaller molecules

(relative to zone 1).

The SEC–DOC fractions for each peak from the SEC are summarized in

Table 20.3. The percentage for each peak was determined by the ratio of inte-

grated peak area to total peak area, and each percentage was then converted to

DOC (relative to the bulk water DOC). As can be seen in Table 20.3, EfOM had

a higher DOC content of polysaccharides, indicating a higher contribution to

the DOC of the EfOM by microbial sources. In addition, the EfOM also showed

a higher DOC content of both humic substances and low molecular weight

organic acids relative to the NOM; given that humic substances are predomi-

nately derived from drinking water NOM, this higher EfOM humic substance

content may reflect a diverse drinking water source encompassing more than

the upstream sample.

Figure 20.3 shows the results of total dissolved carbohydrates measurements

using the phenol–sulfuric acid method. Higher levels of polysaccharides were

present in EfOM, which was consistent with SEC–DOC data. Polysaccharides are

one of the components of bacterial cell walls and are released during the

Fig. 20.2 SEC of DOC fractions (upper) and UVA

254

fractions (lower) for upstream water, waste-

water, and downstream water samples (February 2004) from a Northeast USA watershed, and

their molecular weight (MW) distributions (WWTP sample diluted approximately threefold rela-

tive to upstream and downstream samples) (Nam, 2007)

20 Differentiating Effluent Organic Matter from Natural Organic Matter 265

endogenous cell decay. Therefore, the primary characteristics of EfOM mostly

reflect microbial sources.

20.3.2 Treatability of EfOM-Impacted or -Dominated

Water by Coagulation

Figure 20.4 shows the DOC removal efficiencies of NOM/EfOM mixtures by

coagulation. Here, EfOM-dominated waters are defined as waters mixed with 50/50

or 25/75 or 0/100 (NOM %/EfOM %) ratios, and EfOM-impacted water will be the

75/25 mixture. As shown, the DOC removals from adding 40 mg/L of coagulant

ferric chloride were 54 and 57% in the upstream sample and the EfOM-impacted

water, respectively, whereas the DOC in the EfOM-dominated waters was removed

by 38–46%.

Based on previous researchers’ studies related to coagulation of NOM, it is

known that the coagulation process preferentially removes hydrophobic organic

matter over hydrophilic organic matter. The fluorescence EEM spectra of samples

through the coagulation process support this trend (Fig. 20.5). As the NOM water

was increasingly mixed with more of the EfOM, the protein-like peak became

Table 20.3 Characterization results of upstream water, wastewater, and downstream water from

a Northeast USA watershed (SEC–DOC data from samples taken in February 2004) (Nam, 2007)

DOC (mg/L)

Samples DOC (mg/L) PS HS LMA

UPST (Upstream water) 2.58 0.27 1.19 1.12

WWTP (WW effluent) 7.61 0.58 4.39 2.63

INFL (Downstream water) 3.10 0.22 1.21 1.67

PS, HS, and LMA denote polysaccharides, humic substances, low molecular weight organic acids

Fig. 20.3 Total dissolved carbohydrates (polysaccharides) for upstream water (UPST), wastewater

(WWTP), and downstream water (INFL) (n = 3) (Nam, 2007)

266 S.-N. Nam et al.

clearer and its fluorescence intensity increased as well (upper Figures in Fig. 20.5).

From the coagulation process, humic-like materials were significantly removed, but

the protein-like materials showed lower removals.

Considering that EfOM is more hydrophilic than NOM according to previously

presented characteristics of EfOM, these results are reasonable. In addition, as the

upstream water was mixed with more of the EfOM, the bulk concentration of DOC

increased (Table 20.1). So when 40 mg/L of coagulant was added, the coagulant to

DOC ratio was 13 mg/mg for the upstream (100/0) sample, whereas the ratio was

only 6.5 mg/mg for the EfOM (0/100) sample. So the presence of EfOM can also

increase the coagulant demand. On a constant coagulant/DOC ratio (e.g., ∼6.5 mg/mg),

Fig. 20.4 Removal of DOC in NOM/EfOM mixtures by coagulation (Nam, 2007)

Fig. 20.5 EEM contour maps before coagulation (upper) and after coagulation with 40 mg/L

dose (lower) (x-axis: emission wavelength of 290–500 nm, y-axis: excitation wavelength of

240–450 nm) (Nam, 2007)

20 Differentiating Effluent Organic Matter from Natural Organic Matter 267

coagulant doses of 20 and 40 mg/L would be needed for the upstream and EfOM

samples, respectively. The use of 20 mg/L of coagulant on the upstream sample or

40 mg/L of coagulant on the EfOM sample both resulted in similar DOC removal

efficiencies (∼40%, Fig. 20.4).

These results mean that the presence of EfOM in a drinking water source may

have an impact on the efficiency of the drinking water treatment process due to the

different properties of EfOM with respect to NOM, especially in terms of DOC

(DBP precursor) removal and/or coagulant demand.

Coagulation resulted in increased FIs of the NOM/EfOM mixtures. Allochthonous

materials, which are sources of humic-like materials, were preferentially removed

over autochthonous organic matter, which caused an increase in the relative portion

of organic matter from autochthonous sources (Fig. 20.6).

20.3.3 Biodegradation of EfOM

Figures 20.7 and 20.8 shows the EEM contour plots and SEC–DOC of EfOM

through aerobic BDOC tests. Fig. 20.7 portrays a WWTP sample from the

Northeast USA watershed while Fig. 20.8 corresponds to a sample taken from a

wastewater-dominated stream in a Southwest USA watershed. In contrast to the

coagulation process, biodegradation preferentially removed protein-like substances.

In Fig. 20.8, degradation of organic carbon in the polysaccharide peak was more

complete and faster, whereas humic substances were slowly and incompletely

biodegraded.

Fig. 20.6 Changes in FIs of the NOM/EfOM mixtures by the coagulation process (Nam, 2007)

268 S.-N. Nam et al.

After a 21-day BDOC test, the polysaccharide peak almost completely disap-

peared. Because large-sized components of the polysaccharide peak are saturated

or linear structures, with fewer double bonds, bacteria were more easily able to

assimilate these structures compared to humic substances with unsaturated,

branched or ring structures.

Through this research project, aerobic BDOC

showed a linear relation with

DOC, the hydrophilic organic matter fraction, the amount of polysaccharides of

raw waters, as well as the concentration of dissolved organic nitrogen (DON).

However, it was inversely related to the SUVA values of samples (results not

shown).

Fig. 20.7 Changes in EEM contour maps by aerobic BDOC

test of EfOM (data from wastewater

sample taken from a Northeast USA WWTP in August 2005) (x-axis: emission wavelength of

290–500 nm, y-axis: excitation wavelength of 240–450 nm) (Nam, 2007)

Fig. 20.8 SEC-DOC of aerobic BDOC test of EfOM for 5 and 21 days (data used here were for

a sample collected from a Southwest USA watershed in February 2005, which was EfOM-

dominated) (Nam, 2007)

20 Differentiating Effluent Organic Matter from Natural Organic Matter 269

20.4 Conclusions

NOM and EfOM collected from a WWTP and river sites upstream and downstream

of the WWTP were characterized with analytical techniques. Also, treatability of

various NOM/EfOM mixtures was evaluated with the coagulation process as a rep-

resentative drinking water treatment process. The experimental results from this

work are as follows:

●

EfOM exhibited lower SUVA, higher fractions of hydrophilic organic matter,

and higher FIs compared to NOM, indicating that the EfOM source is from

autochthonous and microbially derived sources.

●

A distinct difference in EEMs between NOM and EfOM was the presence of a

clear protein-like peak, which was in EfOM, but not in NOM.

●

In SEC–DOC results, EfOM contained a higher DOC content polysaccharide (or

protein) groups, and those constituents exhibited nonaromatic and hydrophilic

characters.

●

Total dissolved polysaccharide measurements were also higher in EfOM.

●

DOC removals of EfOM with the same coagulant dose were less efficient than

with NOM, and these results were attributed to higher hydrophilic character of

EfOM (where the coagulation process removed hydrophobic organic matter

more favorably) and due to an increase in coagulant demand.

●

In contrast with coagulation, biodegradation of EfOM preferentially (and faster)

removed hydrophilic substances (protein-like and polysaccharide groups).

Through these results, it is elucidated that EfOM has distinguishable properties that

are different from NOM and which may have a negative impact on drinking water

treatment plants using conventional (coagulation) processes. Therefore, when

EfOM-impacted waters are used as a potable source, other additional treatment proc-

esses or environmental buffers (e.g., biological filtration, river bank filtration, soil

aquifer treatment, etc.) may need to be considered in order to remove hydrophilic

components (proteins and polysaccharides).

Acknowledgements This study has been performed through funding from the American Water

Works Association (Awwa) Research Foundation (project # 2948). The authors gratefully

acknowledge that the Awwa Research Foundation is the joint owner of the technical information

upon which this publication is based. The authors thank the Foundation and the U.S. government,

through the Environmental Protection Agency (USEPA) for its financial, technical, and adminis-

trative assistance in funding and managing the project through which this information was discov-

ered. The comments and views detailed herein may not necessarily reflect the views of the Awwa

Research Foundation, its officers, directors, affiliates or agents, or the views of the U.S. Federal

Government. The project manager is Alice Fulmer.

The authors also acknowledge our coinvestigators at Arizona State University (Paul Westerhoff

and Baiyang Chen) who provided the DON data for this study. Finally, the participating utilities

and agencies and their staff are acknowledged for their invaluable assistance and financial

support.

270 S.-N. Nam et al.

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Chapter 21

An Advanced Monitoring and Control System

for Optimization of the Ozone-AOP (Advanced

Oxidation Process) for the Treatment

of Drinking Water

Joon-Wun Kang

, Byung Soo Oh

, Sang Yeon Park

, Tae-Mun Hwang

Hyun Je Oh

, and Youn Kyoo Choung

Abstract This study was conducted to illustrate an innovative method for the

optimization and control of the ozone-AOP (advanced oxidation process) to

achieve the target oxidation objective for the removal of hazardous micropollut-

ants, while minimizing the formation of harmful by-products, bromate (BrO

The control method was based on a specifically conceived analytical setup with

FIA (flow injection analysis), which can accurately isolate and measure an

individual oxidant in the presence of other oxidants (ozone, hydrogen peroxide,

free chlorine, etc). Three auto-analyzing units (Ozone Kinetic Analyzing Unit,

Hydrogen Peroxide Analyzing Unit and Bromate Analyzer) were specially

devised for this study, which were successfully tested on both in lab- and demo-

scales for in-plant operation.

Keywords: Bromate, ozone, ozone/hydrogen peroxide, hydroxyl radical (OH•),

optimization

21.1 Introduction

Ozone has been continuously used in the treatment of drinking water for close to

100 years. Recently, the number of ozone installations has rapidly grown world

wide for the effective removal of toxic chemicals and inactivation of pathogenic

microorganisms. On ozonation, pollutants can be oxidized by molecular ozone or

Department of Environmental Engineering, YIEST, Yonsei University at Wonju, 234, Maeji,

Wonju, KOREA (220–710)

Korea Institute of Construction Technology, 2311 Daehwa-Dong, Ilsan-gu, Kyonggi-do,

KOREA (411–712)

School of Civil & Environmental Engineering, Yonsei University, Seoul, KOREA

271

Y.J. Kim and U. Platt (eds.), Advanced Environmental Monitoring,

271–281.

272 J.-W. Kang et al.

the hydroxyl radical (OH•), from the decomposition of molecular ozone in water

(Staehelin and Hoigné 1982). For efficient disinfection, the minimization of ozone

decomposition is desirable, but for the oxidation of micropollutants, a process

modification to increase the proportion of OH• is much favored since OH• is more

reactive than ozone molecule. Ozonation alone does not appear to generate a

sufficiently high concentration of OH•. Therefore, many attempts have been made

to explore AOPs (advanced oxidation processes) to enhance the production of

OH•. Of the ozone-based AOPs, the ozone/hydrogen peroxide (peroxone) process

is one of the most effective processes for the production OH• (Duguet

et al. 1985).

However, in ozone-related processes, i.e. ozone alone or the peroxone process,

the formation and control of bromate has been regarded as the most important issue

since it was first implicated as a potential carcinogen (Buffel et al. 2004). The

maximum permissible level of bromate in drinking water has been set at 10 µg/L in

both the U.S. and the European Union (Fed. Resist. 1994; Amtsblatt der

Euopäischen Gemeinschaften L 330 1998). During oxidation, it has been found that

two mechanisms are responsible for bromate formation: molecular ozone and OH•.

The contribution to bromate formation via these two oxidants is affected by water

quality variables and operational conditions, such as pH, temperature, bromide

level, ozone dosage and contact time, as well as other matrix conditions. In the per-

oxone process, the ratio of hydrogen peroxide to ozone could also affect bromate

formation, as the molecular ozone concentration, residual hydrogen peroxide and

OH• are sensitive to fluctuations in the water quality. Therefore, the aim of this

study was to propose an automated real-time control system for optimization of the

ozone-AOP process in relation to bromate formation.

21.2 Methods

21.2.1 Ozone Analysis System

Figure 21.1 is the schematic diagram of an ozone analysis system (O

-k

device)

designed for the continuous monitoring of residual ozone, as well as the decompo-

sition rate, using a highly sensitive detective analytical method employing an FIA

technique. The design of this measuring system, incorporating several peristaltic

pumps, solenoid valves and a UV/Vis detector, was based on the indigo method

(Hoigné and Bader 1981). The device was designed to be controlled by an ICU

equipped with a data acquisition system (data acquisition interval was less than

0.05 s) (Park et al. 2000). Figure 21.1(b) shows a typical decomposition pattern of

ozone in raw water. Two apparent ozone decay phases, which consists with the

instantaneous ozone demanded phase (IOD) followed by a rather slower decay rate

with the first order (k

) in [O

], were successfully measured with this online moni-

toring setup.