0048-9697(85)90338-9] F. Fiessinger; J.J. Rook; J.P. Duguet -- Alternative Methods for Chlorination

8/16/2019 0048-9697(85)90338-9] F. Fiessinger; J.J. Rook; J.P. Duguet -- Alternative Methods for Chlorination

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The Science of the Total Enuironment, 47 (1985) 299-315

Elsevier Science Publishers B.V., Amsterdam -Printed in The Netherlands

299

ALTERNATIVE METHOOS FOR CHLORINATION

F. Fiessinger, J.J. R ook and J.P. Ouguet

Laboratoire Central Lyonnaise des Eaux, 78230 Le Pecq (France)

ABSTRACT

Existing disinfectants are oxidative agents which all present negative

effects on subsequent treatment processes. None of them has decisive advantages

over chlorine, althouq h chlorine-dioxide and chloramines migh t at times be

preferable. Optim um treatment practices wil l improve the removal of organic

orecursors before final disinfection which could then consist in a liqh t chlorine

addition. A

philosophy of radical change

in water treatment- technology

encompassing physical treatment without chemicals such as memb rane filtration ,

solid disinfectants is presented.

INTRODUCTION

Since its introduction into water treatment in the begin ning of this century,

chlorine has held a predom inant position as reliab le disinfectant because of its

broad range biocid al effectiveness,

its reasonable persistence in treated waters,

its ease of applica tion and control and its cost effectiveness.

In addition

chlorine is the only chemical agent that is able to oxidize ammonia readily.

Chlorine is also used for controlling the proliferation of algae during the warm

periods in uncovered coagula tion and sedim entation basins. Unfortunately, when

organic m atter is present chlorination results in the formatio n of undesirable

halogenated compounds ; i.e.

total haloge nated compounds (TOX) and more

particularly the Trihalom ethanes (THM).

The use of modern analytical techniques

has led to the identific ation of a large part of them (Christman et al., 1983,

Bruchet et a1.1984, Coleman et al. 1984, Ouguet et al. 1984b) as illustrated in

Figure 1. Som e of these compounds like dichloroaceton itrile, several chlorinated

ketones, chloroform are known to be mutagenic or toxic (Sim mon et al. 1977, Bul l

1980).

The effects of water chlorinatio n on mutagen ic activity have been studied.

Many authors, (Kool, 1984) , conclude that chlorinatio n increases mutagenicity

(see Fig.2) but the nature of organics and chlorinatio n conditions have a great

influence. Thus Cognet (1984) found that during chlorinatio n of treated Sei ne

water, variation of mutagenicity during one year was not statistically

significative.

0048-9697/8 5/$03.30 0 1985 Elsevier Science Publishers B.V.


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300

[ 78.8 7. MWc1000 1

\

1

- VOLATILE5

I NON VOLATILES

Fig. 1.

Diagram of molecular weigh t distribution of TOX after prech lorination

of a reservoir water (C halet, France) and speciation of the volatile fraction.

I

2 3 4

VOLUME OF WATER

i Ilterl

Fig. 2. Comparison of mutagenic activity on Salmo nella thyphimurium strain

TA'98(-'S9) , before (xl and after prechlorination/Dissoved air flotatio n A

of a surface water (Moul le, France)


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301

Another risk is related to the direct toxicity of chlorine gas during its

road transport and its storage as liqu id chlorine, in plants located near densely

populat ed areas. This risk can be avoided by using sodium hypochlorite instead

of liqu id chlorine, though at a 20 to 25 % increase in costs (Gomella,198 0). In

situ generation of chlorine, through electrolysis migh t also be appli ed.

ALTERNATIVE DISINFECTANTS

Altho ugh chlorine is a good disinfectant,

the potenti al health risks of

halogen ated by-products formation have caused the entire subject of drinking

water disinfection to be reconsidered. The mai n alternative disinfectants in use

are ozone, chlorine dioxide, chloramines and to a less extend ultraviolet light,

hydrogen peroxide, permanga nate, other halogens an d silver ions. Gom ella (1980)

and Fiessinger (1981) summarized the properties of several disinfectants with

respect to their possible reactivities with water constituents. An extended

summary of oxidant properties based on these surveys is shown in table 1.

TABLE 1

Comparis on of Various Disinfectants

cl2 c102 03 KMn04 NH2C1 H2°2

Iron and manganes e

Ammonia

THM formation

THM precursors

removal

Formation of mutagens

or toxic substances

Enhanced biodegrada-

bility

Taste removal

Disinfection

+

it+

ttt

t

+

t

t

it

+

t-

t-

++

+

tt

ttt

tt

t-

t-

++

tt

ttt

+ t

+

? ?

?

t ?

t

t

t- t-

+

- no effect

+ littl e effect

tt

effect

ttt very effectiv e

For the evalu ation of the different properties and effects of an alternative

disinfectant it must be distinguished where it is applied in the treatment

process,(see Fig.31 either in preoxidation,

as an interm ediate step or in post-

disinfection, i.e. before or after the bulk of the organic matter, especially the

trihalomethane formation potential (THMFP) has been removed.


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Fig. 3. Influence of iight on residual Cl02 and chlorite concentration

Fig. 4. Possible positions of oxidation treatments in surface water treatment

process


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303

Preoxidation

Traditionall y preoxidation is performed,

at the beginning of the treatment

process, to ensure good

hygienic conditions throughout the treatment and to

control alga l growth in flocculation basins. Thus growth can be lim ited by

covering the basins p:‘ovitled

that ammon ia would be removed in subsequent

treatment steps.

Perman ganate. The applica tion of perman ganate in pretreatment oxidizes iron,

manganes e and destroys taste and odor causing substances. It can reduce THMFP but

at the pretreatment dosage usually appl ied the reduction of chloroform formation

is relatively modest (Singer et a1.,1980).

Perman ganate is not a very effective

disinfectant and a possible residual of

manganese precipitation in the

distribution system are two reasons why permang anate is rarely used in water

treatment.

Chlorin e dioxide. The great advantages of the use of chlorine dioxide in

pretreatment are algicidal effect and negligible formation of halogenated by-

products (Stevens 1 982). However, chlorine dioxide produces polar compounds such

as aldehydes,

ketones and acids (Rav Acha, 1984). The mai n inorganic by-products

is chlorite which is reported to be toxic.

Using mouse skin initi ation promoti on essays , amon g mice w hen concentrates

of water disinfected with chlorine dioxide were appli ed, no effect was

observed. However, short term toxicity of chlorine dioxide and more specifically

its inorganic reaction products may present a higher risk than chlorine or ozone

(Bull 19801.

Chlorite (C102-) and chlorate (C103-) in high concentrations (100 mg/l) have

been found to produce methemoglo binemia in animals (Komorita, 1985).

These

uncertainties have made health authorities reluctant to allow the applica tion of

chlorine dioxide in many countries. In some countries standards as low as 0.1

mg/l chlorites have been edicted. In order to main tain these inorganic by-

products at such a low level, the reagents and the by-products concentrations

have to be constantly monitor ed which cause. Many analytical problems are not yet

solved (Masschelein, 1984). The disinfective efficiency of chlorine dioxi de is

reported to be superior to that of chlorine (Hoff, 1981, Longley ,198l). On the

other hand when Cl02 is applied in open basins the photodecomposition of Cl02

necessitates the applica tion of an excessive dose (Fiessinger, 1981) (see Fig.4).

The costs for applying chlorine dioxide are 3 to 4 times than those for

chlorine (Gomella, 1980).


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Ozone. The preozonation of natural organic matter does not lead to its direct

removal as is reflected by nearly unchanged TOC values. The primary effect is to

modify the chemical nature of the molecules towards increase of polarity. The

increased polarity wil l in turn favor adsorbability in subsequent coagulati on

filtration and adsorption processes (Kuehn, 1981). A clear exampl e of improved

turbidity removal induced by oxidative pretreatment was found for preozonated

Sein e water (Fiessinger, 1981) (see Fig. 5). The same improvem ent however, could

be achieved by a slighty increased alum dose, such that in this case prcozonation

was an expensive means for saving on flocculant costs.

Reckhow and Singer (1984) have shown that preozonation of certain lake waters

reduced the formation potentials of THM and TOX significantly (see fig.6). Doses

exceeding 1.2 mg 03 per mg TOC per liter hampere d the removal of THM and TOX

precursors in alum coagulatio n,. Jekel however reported improved removal of

turbidity caused by humic acid coated miner al particles along with improved

particle agglomeration, when preozonation was applied in ratio's below 0.8 mg 03

per mg TOC (Jekel, 1983). Increase of that ratio had no further effect.

The polymerizing effect of ozone on smal l sized micropollutan ts may present

more interesting possibilities. Duguet and a1.(1985a)) using a dichlorop henol

synthetic organic compounds found that ozonation induced polymerizatio n to

hexamers and insoluble polymers, which will improve removal in coagulation

filtration.

As with other oxidants, ozonation also leads to formatio n of organic by-

products mostly aldehydes, ketones and carboxylic acids (Mal leviall e, 1980)

Especially aldehydes have been quantif ied (Van Hoof et al., 1985) .

Ozonation by-products may also induce mutagenicity in the treated water which

can be effectively removed by activated carbon (Van Hoof,1983). It is also

possible to dimi nish the production of mutagens duri ng ozonation by prolonged

contact time or dosage (Duguet et a1.,1984a) (see Fig.7). Ozonation of organic

matter will naturally increase biodegradability,(Peel and Benedek, 1983) which

can be considered (see Fig. 8) as an advantage as wel l as an disadvantage. This

mater ial must be removed biologic ally before the water leaves the treatment

plant since it may interfere with post disinfection. A principle disadvantage of

the biodegr adation taking place in biologi cally operated carbon filters is that a

complete ecology of higher plankton wil l develop and foul the filters. Practical

experience has shown that the filtered waters may contain heavy loads of

zooplankton during summer periods (Rook, 1983).


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306

1000

I

‘A

I

TA 98 - S9

.”

<

3

z

>

:

400

\

/

I ‘\

\

\

?, /

\

\I

\

d

200

t

‘h lOOmI

H20

Fig. 7. Effect of ozonation conditions on mutagenic activity of a ground

water at three sample volumes (Le Pecq, France)

30-

20-

lo-

0-

m..:A+-

.:.

. --

J/.-;”

,’

MAY JUL S EPT OCl

Fig. 8. Effects of ozone dose (00) and contact time (TC) on the biodegra dability

of a filtered water (SFW)


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In our view the full advantage of preoxidation can only be obtaine d when used

in combi nation with an effective means of removing biodeg radable subtances, such

as slow sand filtration . Walker observed in a comparative study (1984) of

preozonated slow sand filters a doubl ed removal of TOC, 35 % of the init ial 3.7

mg/l TOC versus 16 % in the non-ozonated control filter.

Post Disinfection

The reason for the use of disinfectants after the complete water treatment is

to kill or inactivate microorganisms still present to protect the distribution

system from regrowth and safeguard hygienic quality. This necessity is even more

pronounced if prechlorination is abandone d. In this case post-disinfection may be

the only hygienic barrier. The choice of disinfectant must be made on the basis

of germic idal activity and persistence for main taini ng a residual in the network

to prevent any further contam ination.

Experimental data show the following order

of decreasing germic idal efficiency 03 'Cl02 'HOC1 >OCl- > NHC12" NH2C l. Ozone

is the best disinfectant but its half life is not sufficient to mai ntain a

residual (see Fig. 9).

Moreover the applica tion of ozone may produce some

biodeg radable matter resulting in regrowth.

For chlorine dioxide this proble m exists to a less extent. Besides it has the

advantage of its long half life ensuring a residual throughout the network. At

the final point of the treatment

organic matter is at minim um. The formation of

chlorite by the organic matter reduction of Cl02 is than lim ited such that the

acute toxicity may be considered to be less significant.

Som e combinatio ns of oxidants like chloramin e + hydrogen peroxide have been

shown to improve control of bacterial regrowth in a treated surface water for

which chlorine disinfection was insufficient (Germonpre, 1985).

More studies

should be done to verify the efficencies of such combination s (H20,

03 + H202 +

UV, 03 t UV). Disinfection using UV involves different mechanisms such as direct

UV action and formation of high energetic radicals which have short half lifes,

but the problem of persistence remains.

This short survey shows that replacement

of chlorine by another disinfectant is not quite an easy task.

The ideal

disinfectant may have four mai n properties :

- germic idal effect

- persistent residual

- no precursor of toxic by-products

- low cost.


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DECR EASE IN RESIDUAL OZONE WITH TIME - SEINE WATER

o.51

.4-

;;i

E

\

; 0.3-

z

::

0

< 02

2

z

: O.l-

0

0 5

10 15

T (mid

Fig. 9. Decrease in residual ozone with time (Seine water, France)

Fig. 10. Chloroform formation during conventinal breakpoint chlorinatio n curve

0

TOC : 12mg/I

l- l

NH

4

:2gmg/l

”

\

2

-1000

2

%

E

h

T

RATIO Cl/N


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Chlorin e still remains the best availa ble means of disinfection. However

optimal

conditions for its applica tion must be determi ned with respect to a

min imiz ing by-product formation to ensure hygienic safeguard.

It is still

preferable to reduce the amm onia content by biolo gical treatment in order to

avoid high chlorine demands.

ALTERNATIVE STRATEGIES FOR A BETTER USE OF CHLORINE

With the objective to reduce haloge nated compounds such as THM's,

two

treatment strategies can be follow ed :

the chloramination and the use of chlorine

after a maxi mal reduction of organics and specifically mainly the precursors of

chlorinated compounds. The developm ent of new adsorbents such as activated

alum ina and resins may further improve the removal of precursors

Chloramination

As illustrated in figure 10 in natural water containing ammonia, the

trihalome thanes are formed at a chlorine dose corresponding to the destruction of

chloramines of free appearance of free chlorine.

Althou gh the chloramines are weak disinfectants they have alga l inhib iting

properties. With the objective to reduce haloge nated compounds, the pretreatment

may be realized with chloramines. In this case, the chlorine dose must be

adjusted to the maximum of chloramine with or without addition of ammonia. On

line measurem ent of chloramines is not easy and the process control is difficult

to realize.

The mai n problems related to chloramines are tastes and odors a nd some health

effects.

Although monochloramine is the predominant form at a pH of 8, the

correlated traces of di an trichloramines have offensive odors as found by

Krasner (1984) (Table 2).

TABLE 2

Sensory Threshold Values

Compou nds Threshold (mg/l as Cl21

Aroma Flavor

Hypochlorous acid 0.28 0.24

Hypochlorite ion 0.36 0.30

Monochloramine 0.65 0.48

Dichlor amine 0.15 0.13 (from : Krasner 1984)


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The health effects of chloramines and the knowledge of by-products formed

(organic chloramines . ..) need more research,

thus chloramines have recently

been found to cause hemolytic anem ia in patients undergo ing kidney dialysis

(Komorita, 1985).

To solve the problems of taste, odors and health effects

chloram ination may be follow ed by a chloram ine removal from water by reduction on

activated carbon which should be carefully monitor ed to produce a water of

desired quality. This alternative chlorination has a promisin g developm ent; thus

one of the largest water utiliti es

in the USA has changed from chlorine to

chloramines for the control of THM formation.

This control may be also realized by the use of chlorine after the reduction

of organics to a great extent.

OPTIMIZATION OF ORGANICS REMOVA L BEFORE CHLORINATION

As illustrated by figure 11 the use of chlorine only at the end of the water

treatment permits a great reduction of THM formation.

A low THM level may be

obtaine d by the optim ization of each treatment step. Coagulants such as A13+ and

Fe3+ remove significant concentrations of TOC and THM precursors which, in actual

practice tends to range from about 40 % to 70 %. Singer (1983 ) found that the

removals of THMFP concentrations tend to be higher than the corresponding

reduction in TOC. Some improvements in the utilization of metal coagulants can

result in a better reduction of precursors but the comb ination of ozone with an

ddsorbant like activated carbon can retain a large part of

organics from

clarified water. This unil operation is already used routinely in drinking water

production in Europe. However, activated carbon is a rather non specific

adsorbant which whil e a good principle, frequently leaves a fraction of organics

in the water which may give rise to haloge nated compounds during post-

chlorination . Improvements of the yield of the adsorption wil l be feasible by a

research of new adsorbants of different nature combine d with an optimiz ed

oxidation like e.g. ozone coupled with

hydrogen

peroxide (Ouguet et al,

1985b) (see Fig. 12). Ozonation in all cases produces polar products which are

less adsorbable by activated carbon. This is illustrated by shifts in the

adsorption isotherms shown in Figure 13. In a study reported by Duguet et al.

(1985b 1 the k-value of the Freundlich isotherm (TOC) was dimin ished by a factor

3 after preozonation. With activated alum ina, however, an increased adsorption

was observed, enhanced by the combine d action of 03 and H202. This case is an

examp le of an optim ization of organics removal which can lead to more effective

reduction of the formation of toxic compounds during final chlorinatio n.


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S

E

O

I

M

E

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T

T

G

N

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1

2

I

o

S

A

N

D

F

T

R

A

T

O

N

/

I

1

\

O

Z

O

N

A

T

O

N

\

\ -

o

G

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C

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14/17

312

100

75

3 5c

E

2

2:

(

I 1

I’ o

n_.:_ ChP

I I

/ I

Ce(mg/l)

Fig. 13. Effect of ozonation on the isotherms for adsorption of a lake water

(Chalet) on alum ina and activated carbon.

An addi tiona l advantage of having rem oved organic matter as far as possible

is the reduction of chlorine consumption in the distribution system resulting in

lower doses needed for maintaining a desired residual. Depending on the state of

network mul tiple injections of low doses of chlorine at several crucial points

may be necessary.

CONCLUSIONS

- There is no satisfactory alternative for chlorinatio n:

. Prechlorination should be abandoned

. Alg al growth may be controlled with chloramines, or coverage of open

. sedime ntation basins

. Amm onia can be removed biologically

. Chlori ne dioxide and chloramines may constitute satisfactory interim

alternatives


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313

. Ozone should be used as a comple ment not for a replacement.

- Com binati on of oxidants migh t present interesting synergistic effects in

particular for oxidation 03 + UV.

- Chlorin e can be main tained as a final disinfectant if organic precursors are

sufficiently removed. Process sequences of oxidation, adsorption and

biodegr adation should be carefully designed.

- Disinfection practices should be revised in the light of new germs, Giardia,

Legionella, . . .

- Disinfection mechanisms should be further investigated.

- Megatrends

. New disinfectants

Immunological applications

Imm obilize d disinfectants, Ag . . .

nascent chlorine, electrical treatment

. Improved removal techniques

micro and ultrafiltratio n

improved coagulants

REFERENCES

Bruchet, A., Tsutsumi, Y.; Duguet, J.P. and Mall evia lle, J., 1984.

Characterization of total haloge nated compounds along various water

treatment processes. Presented to the Fifth Conference on Water

Chlorination.

Environmental Impact and Health

Effects. Williamsburg,

Virginia.

Bull, R.J., 1980.

Health effects of alternate disinfectants and their reaction

products. J. Awwa , 5: 299-303.

Christman, R.F., Norvood, D.L., Mill ingto n, D.S., Johnson J.D. and Stevens, AA

1983. Identificati on and yields of major haloge nated products of aquatic

fulvic acid chlorination . Env. Sci. tech., 17 : 625-628.'

Cognet, L., Duguet, J.P., Courtois, Y., Bordet, J.P. and Mall evial le, J., 1984.

Use of MRR for Ames test in a practical operating system. Congress of the

Division of Environmental Chemistry. ACS. Philadelphia , 26-31.

Colem an. W.E., Munc h. J.W.. Kavlor, W.H.. Streicher, R.P., Rinoha nd, H.P. and

Meier,

J.R. 1984:Gas chromatography/mass spectroscopy analysis of-mutagenic

extracts of aqueous chlorinated humic acid.

A comparison of the by-products

to drinking water contaminants. Env. Sci. Techn., 18: 674-681.

Duguet, J.P., Ellul, A., Brodard, E. and Mallevialle J., 1984a. Evolution de la

mutagenese au tours d'un treitement d'ozonation, IOA Congress, Brussels.


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Van Hoof, F., 1983. Remov al and formatio n of mutagenic activity by ozone. Proc.

ICA Symposiu m, "Environm ental Impact and benefit", Brussels, 410-423.

Van Hoof, F., Wittocx, A., Van Bruggenh out, E. and Janssens, J., 1985.

Determ ination of aliphati c aldehydes in water by high pressure liqu id

chroma tography . (in press).

0048-9697(85)90338-9] F. Fiessinger; J.J. Rook; J.P. Duguet -- Alternative Methods for Chlorination

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Transcript of 0048-9697(85)90338-9] F. Fiessinger; J.J. Rook; J.P. Duguet -- Alternative Methods for Chlorination