effect of biological treatment on halogenated organics in bleached kraft pulp mill effluents studied...

Environ. Sci. Technol. 1003, 27, 547-557

(37) Dodd, J. A.; Ondov, J. M.; Tuncel, G.; Dzubay, T. G.; Stevens, R. K. Environ. Sei. Technol. 1991,25, 890-903.

(38) Evans, M.; Vithanaduage, I.; Williams, A. J . Inst. Energy 1981, 179-186.

(39) Lahaye, J. Carbon 1992,30,309-314. (40) Ogren, J. A.; Charlson, R. S. Tellus 1984, 36B, 262-271. (41) Smith, D. M.; Akhter, M. S.; Jassim, J. A.; Sergides, C. A.;

Welch, W. F.; Chughtai, A. R. Aerosol Sci. Technol. 1989,

Received for review June 29,1992. Revised manuscript received

10, 311-325.

November 5,1992. Accepted November 10,1992, This work was supported in part by NSF Grant ATM-9007796, and also by Grant CIR-D519 from Arizona State University. Microscopy was done at the Facility for High-Resolution Electron Microscopy in the Center for Solid State Science and in the Materials Science Electron Microscope Laboratory, both at ASU. The Facility for High-Resolution Microscopy was established with support from the National Science Foundation (Grant DMR-86-11609) and also ASU. The Materials Science Electron Microscopy Labo- ratory was established with aid from a grant from the United States Department of Education.

Effect of Biological Treatment on Halogenated Organics in Bleached Kraft Pulp Mill Effluents Studied by Molecular Weight Distribution Analysis

Jounl K. Jokela, s t Mlnna Lahe,$ Mats Ek,s and Mirja Salklnoja-Salonent

Department of Applied Chemistry and Microbiology, University of Helsinki, Viikki, SF-007 10 Helsinki, Finland, Department of Biochemistry, University of Turku, SF-20500 Turku, Finland, and IVL, Swedish Environmental Research Institute, Box 21060, S-10031 Stockholm, Sweden

The removal potential of different biological treatments of organohalogen compounds in kraft pulping and bleaching effluents was studied by nonaqueous size-exclusion chromatography and grouping the compounds by solubility and adsorption characteristics. Organohalogen compounds of waste waters from five pulp mills with different processes exhibited similar molecular weight distributions, ranging from 100 to 4000. The anaerobic/ aerobic lagoon system removed 58-6690 of the organochlorine compounds from the water phase and the full- scale activated sludge plants removed 19-55%. Both biotreatments removed all size classes of organochlorine molecules and slightly changed the relative size distribution of the compounds remaining in the water phase toward the larger molecular weights. The organic chlorine compounds were divided into three categories on the basis of extractability to organic solvent and adsorption to activated carbon, one of the categories being recalcitrant to the biotreatments studied.

Introduction The wood pulping and bleaching industry discharges

large quantities of mainly lignin-related chlorinated compounds to the receiving waters. These effluents have a negative impact on plant and animal communities in receiving areas (1). Two different possibilities to handle this problem are to make internal changes to the pulping and bleaching processes to lower the level of the discharged compounds or to improve the waste water treatment technologies.

The adsorbable organic halogen (AOX) discharge from pulp mills in Finland decreased from 2.7 kg of AOX/ ton of pulp in 1989 to 1.7 kg/ton in 1991 (average of soft- and hardwoods) (2). This favorable development is to an important part based on the operation of biological treatment plants that are now operative at 13 of the 15 mills (3). Also, process changes have already resulted in substantially

* Correspondence: Department of Applied Chemistry and Mi- crobiology, University of Helsinki, Faculty of Agriculture and For- estry, Viikki, SF-00710 Helsinki, Finland.

University of Helsinki.

Swedish Environmental Research Institute. *University of Turku.

decreased formation of chlorinated organic compounds (4). The biological treatment methods for industrial waste

waters most widely used are activated sludge and aerated lagoon processes. These methods effectively remove oxygen-consuming substances and suspended solids. An important group of compounds in pulping and bleaching waste waters are the chlorinated compounds, some of which are known to be toxic, mutagenic, and even carci- nogenic (5,6). However, the concentrations of these compounds in bleached kraft pulp mill effluent (BKME) are so low that the waste waters are not acutely toxic. The removal of several individual organochlorine compounds during biological waste water treatment has been described (7-13), but understanding of the removal process is poor.

The results reported for bioremoval of organic halogen compounds, measured as AOX, during waste water treatment in the wood pulping industry varied between 25 and 65% (14,15), indicating that these compounds are relatively resistant to biological treatment. Also, the fact that AOX has accumulated downstream of pulp mills (16) indicates incomplete degradation of organochlorine compounds under environmental conditions.

It is commonly thought that the major reason for the recalcitrance is the large molecular size of the organic halogen compounds, termed chlorolignins, said to account for up to 80% of the AOX (15,17). It is also thought that chlorinated organic matter is more recalcitrant to biodegradation than are nonchlorinated compounds. We recently showed that the apparent large size of chlorolignin is more related to the tendency to form intermolecular associations than actual covalent bonds (18). When diluted to concentrations that are likely to occur in recipient water, 65% of the AOX behaved as molecules of' sizes ranging from MW 100 to 1000 (18). It is therefore important to evaluate the effects of treatment systems on this molecular size range with particular emphasis on the aquatic phase which is discharged into the environment.

The biodegradability and uptake of xenobiotic compounds by microbial biomass very likely depend on their absorption and solubility properties. The least polar compounds will migrate from the water phase into sludge, also independent of active uptake by biomass. Therefore study of the adsorption and solvent solubility properties of waste water organochlorines may give important clues

0013-936X193/0927-0547$04.00/0 0 1993 Amerlcan Chemical Society Environ. Sci. Technol., Vol. 27, No. 3, 1993 547

to understanding biodegradability. In this study we measured the changes of molecular

weight distribution (MWD), solubility, and adsorptivity of the organochlorine compounds found in the aqueous phase of the BKME during the course of biotreatment. Our report shows that the recalcitrant organochlorine compounds do not represent any specific size class, that no enrichment of highly chlorinated matter to the water phase occurred as a result of biotreatment, and that organic chlorine compounds could be separated into categories having different recalcitrance toward biotreatment by a simple extraction protocol.

Experimental Methods Sampling. Waste waters from mills A, C, and D were

sampled during 1991 and bleaching effluents from mill E during 1990.

Waste water from mill A was sampled before and after the equalization basin (25 000 m3) and also after activated sludge treatment, before discharge into the receiving basin (recipient). Volumes of the aeration and postclarification basins of the full-scale activated sludge plant were 25 000 m3 each.

An aerobic/anaerobic pilot-scale treatment plant for bleached kraft pulp and paper mill effluents was run at mill B in 1988/1989. Samples were taken at this plant from the influent and the effluent during 1989. The hy- draulic retention time was 2 d during the first sampling period (Pl) and 4 d during the second period (P2). The aeration basin (five compartments of 5 m3, total volume 25 m3) was divided into three sections aerated differently: full aeration (first section, 10 m3), anoxic (second section, 5 m3), full aeration during sampling period P1 and low aeration (0.5-0.8 mg of O,/L) during sampling period P2 (third section, 10 m3). During the second period, another aeration basin (25 m3) was connected in series after the first aeration basin and was used for postaeration and clarification.

Mill C had anaerobic/aerobic lagoon treatment after clarification. Municipal waste water was also treated in this plant, joining the system after the first sampling point and accounting for 0.5% of the total BOD in the waste water. Waste water was sampled before and after the anaerobic lagoon used for equalization (150000 m3) and also after aerobic lagoon treatment (400000 m3) at the exit to the recipient.

The total volume of the treatment basins of the full-scale activated sludge plant of mill D was 9OOOO m3 and the flow 97 500 m3/d. Waste water was sampled after neutralizing and nitrogen addition stages and then after secondary clarification before discharge.

Bleaching effluent streams from mill E were biotreated both in pilot and in laboratory reactors. The pilot reactors (Pl, 3.8 m3; P3,4.4 m3) were fed with ultrafilter permeate of the EOP stage spent liquor, mixed with spent liquors from the (D+C), D,, and Ez stages (E, alkali; 0, oxygen; P, peroxide; D, chlorine dioxide; C, chlorine). The laboratory reactors L1 and L2 were fed with spent EOP plus (D+C) stage liquors. Ultrafiltration was performed by a full-scale test plant consisting of four ultrafiltration modules having polyether sulfcne membranes with a nominal molecular weight cutoff of 25000 and a total membrane area of 50 m2. Flow schemes of the pilot reactors and ultrafiltration test plant and their modes of operation are described elsewhere (19). The pilot and laboratory reactors were sampled before and after anaerobic and aerobic treatment (Pl, L1) or aerobic treatment only (P3, L2).

Samples were stored at +4 "C (short period) or frozen.

548 Environ. Sci. Technol., Vol. 27, No. 3, 1993

Fractionation of the Waste Water. A tetrahydrofuran (THF) extract was prepared by freeze-drying a BKME sample and then extracting the residue with THF as described earlier (18). BKME samples were not acid- ified prior to freeze-drying.

The organic halogen compounds contained in the BKME were divided into the three following groups: carbon adsorbable organic halogen nonextractable into THF (AOX,,), carbon adsorbable organic halogen extractable into THF (AOX,), and carbon nonadsorbable organic halogen extractable into THF (NOX,). Equations 1-3 show that this grouping builds upon the measurements of the AOX of the BKME (AOXBKME), the AOX of the THF extract (AOXTHF), and the total halogen measurement from the THF extract (EXTHF; EX, extractable halogen),

AOX,, = AOXBKME - AOXTHF (1)

AOX, = AOXTHF (2)

NOX, = EXTHF - AOXTHF (3)

Analytical Procedures. Total organic carbon (TOC) was analyzed by the TOC-5000 total organic carbon analyzer (Shimadzu).

Chemical oxygen demand (CODc,) was measured according to standard SFS-5504 (20), which is consistent with the corresponding Danish, Norwegian and Swedish standards.

Halogen was measured by using the Euroglas halogen analyzer ECS 1000 (Euroglas BV, Delft, The Netherlands). Active carbon adsorbable organic halogen (AOX) was analyzed according to standard SCAN-W 9:89 (21). Solvent (THF) extractable halogen was quantitated after an aliquot of the extract was evaporated in a porcelain cup under a flow of Nz. The contents was then combusted in the oven (1000 "C) of the Euroglas equipment, and the hydrogen halide formed was microcoulometrically titrated according to the manufacturer's manual. To measure the AOX content of the THF extract, THF was evaporated in a flow of Nz, the residue was dissolved into water, and AOX was measured from this water solution.

THF extracts were used for the analysis of MWDs by high-performance size-exclusion chromatography (HPSEC). Analysis of molecular weight distribution was performed as described earlier (18) using polystyrene standards of narrow MWD and three lignin model compounds for calibration.

Statistical Analysis. A total of 34 MWDs of the chlorinated compounds of the waste waters were analyzed statistically by principal component analysis (PCA). For this purpose, original MWD data were transformed so that 143 uniformly distributed chlorine concentrations (mg/L) between 63 and 44 000 could be used as variables. In order to compare the relative proportions of the chlorinated compounds of different chromatograms, each MWD was area-normalized. MWD data were centered before computing the PCA vectors. PCA was performed by data analysis software for MATLAB using a PC computer. More details of the software are reported elsewhere (22).

Results Waste water and treatment plant operation of five

bleached kraft pulp mills (designated as A-E) were studied. Table I summarizes the essential process features, characteristics of treatment facilities, and waste waters. Table I1 presents the data on the absolute and relative (%) re- duction of organic carbon and adsorbable organic halogen, respectively, during the treatment of waste water. It shows

4 R a

i3 f s s

Q

R 2 08 R B 08

E "a

RE 2 0

Envlron. Scl. Technol., Vol. 27, No. 3, 1093 540

h r

@ 1,w

E 1,w

3

2s

In

1 3

1,M 4

0,74

10 100 1000 10000 Molecular welght (g/mol)

:k 3 ,,,.. ,/ ,,!! ..... .... ............ -:\

0 10 100 1000 loo00

Molecular weight (g/ml)

z 0

6 -

5 -

4 -

3 -

2 -

1

E" p/ ,.i c'

:.., 0- ~ :#I-

10 100 1000 10000 Molecular weight (g/ml)

prior to treatment ------- after equalization basin I to the recipient

.................. After activated sludge, 1 - Fkure 1. Changes of molecular welsht dlstrlbutlons of UV-absorbing materlal (UV) and organic halogen compounds (GI) of BKME during full-scale activated sludge treatment on mills A and D: AS, activated sludge.

that full-scale biotreatment removed 50% of TOC and 53% of AOX on average. The removal of CODc, and AOX from the water phase by the pilot-scale biotreatments averaged 56% and 5370, respectively. These results indicate that the removability of organic halogens (AOX) in BKME was at least as good as the overall removability of organic compounds (TOC, CODc,) in the five different treatment units. Aerobic treatment removed TOC more efficiently than sole anaerobic treatment, averaging 49% (mills A, D, and E) and 19% (mills C and E), respectively, but AOX removal was equal, 50% and 49%, respectively. Combined anaerobic/aerobic removals for TOC and AOX (mills C and E) averaged 52% and 61%, respectively. Thus, combining anaerobic and aerobic treatments clearly improved total AOX removal.

Since the biotreatment removed only approximately 50% of the AOX and TOC, we next investigated the question of whether the recalcitrant fraction differed from the removed fraction in molecular size. Molecular size

distribution analysis of BKME was carried out by nonaqueous HPSEC. Results of MWDs measured as UV/ visible-absorbing (225-445 nm) and halogen-containing molecules are shown in Figures 1-3. The UV/visible- absorbing and halogen-containing material was in all cases located between 100 and 10000, irrespective of wood species, bleaching sequence, and waste water treatment protocols. Ninety percent (84-97 %) of the chlorinated compounds in untreated waste waters studied and 87% (77-97%) in biotreated waste waters were smaller than 1000.

Significant removal of BKME components was observed in all size classes of molecules, from 100 to 3000. It is actually surprising that the MWDs of organic halogens of BKMEs having undergone different biotreatment were so similar. Removal of organic halogen compounds at different stages of the biotreatment, determined as MWDs of the tetrahydrofuran-soluble halogen (Figures 1-3), correlated by a factor of 0.88 (see Figure 4) with the overall

550 Envlron. Scl. Technol., Voi. 27, No. 3, 1993

-.__ 0-

10 100 1000 lo000 Molecular weloht lo/moll

- Prior to treatment -.-.-.-. After equalization basin + anaerobic lagoon

I\ CI

Molecular weight (glmol)

Figurr 2. Changes of molecular weight dlstrlbutlons of UV-absorblng material (UV) and organlc halogen compounds (Ci) of BKME during full-scale anaeroblc + aerobic lagoon treatment (mlll C) and plbt-scale aerobic/anaeroblc treatment (mill B): P, pllot scale, AL, anaerobic -I- aeroblc lagoon.

AOX removal efficiencies presented in Table 11. The level of removal was over 10% units higher when calculated from MWD results. Correlation between the removal of the UV/visible-absorbing compounds and that of the organic carbon compounds measured as TOC (Table 11) was less clearcut. The level of removal was over 10% units lower when calculated from UV/visible absorption results. This may indicate that biotreatment increased the light absorptivity of the organic compounds. This increment in the specific absorptivity may originate from the oxidation of the waste water compounds.

Aerobic treatment of the mill E bleach plant effluent increased the absolute amount of organic halogen compounds having molecular weights over 500 (Figure 3). This was seen in the case of the pilot reactor (P3) and also in the case of the laboratory reactor (L2), thus independent of the ultrafiltration pretreatment of the bleaching liquor. This polymerization phenomenon was not seen in the waste waters of the other mills, where total mill effluent

was being treated. The photometric quantitation, though uncertain as pointed out above, also indicated polymerization of the bleach plant effluent a t mill E. The data in this investigation are not enough to conclude whether the different waste waters caused polymerization in one case and not in the others.

When replicate THF extracts were prepared from four sets of BKME samples from mill A (AS1-3) and mill C (AL2), the average coefficient of variation (CV) for chlorine content was <4% for replicate extracts and <3% for the replicate chlorine measurements of these extracts. Thus, the variability of extraction was similar to the chlorine measurement error. The repeatability of MWDs was dso analyzed, and it was found that the average coefficient of variation for the chromatographic fractions above the noise level (2% from the chlorine sum of all the fractions col- lected) was <lo%. The repeated MWDs for one BKME (mill A, AS3), shown in Figure 5, prove that the analytical variation was far less than the changes induced in the

Envlron. Sci. Technol., Vol. 27, No. 3, 1993 551

Mill E, Pilot p.. < > ; :

i i

. . . .

............ Mer maeroblc + aerobic reactor (Pl)

I \ .........

o t o 100 1000 lWW Malaular wight (glmol)

Flpum 3. Changes of molecular welght dimbutbns of UVabsorbing material (UV) and organic h a w n cornpards (CL) of spent bhdricg llqm from mill E during different blologicai treatments. Effluents from bleaching stages (D+C) + EOP (ulirafiiler permeate) + D, + E, were mixed for treating in pilot reactors (Pilot; P1 and P3) and effluents (D+C) + EOP were mlxed for treating in laboratory reactors (Lab: L t and L2).

...........

......... ..........

...

.... u 1 ,A 0 ' , I 0 20 40 60 80

AOX r e m o d (%I npun 4. Cwreletion between removal of aganic k w n wmparnds during the different stages ( I , 11, I+II) of biotreatment analyzed by AOX measurement of the waste water (Table 11) and cumulative sum from MWD analysis of the THF extracts (Figures 1-3): SolM Ilne, proportional correlation; dashed Ilne. ObSeNed unrelation curve (r = 0.88).

MWDs of BKME by the waste water biotreatment. This validates the conclusion that the biotreatment removed all size classes of organic halogens in waste waters.

Figures 1-3 showed that all sizes of BKME Components were removed during biotreatment, but they are not il- lustrative on the removal efficiencies of the different sizes of BKME components. Figure 6 illustrated the percent removal efficiencies for the molecular weight region of 5(t2000. The results show that the treatment methods fall in two categories. Aerobic methods (mills A and D and reactors L2 and P3 from mill E) resulted in less efficient removal of larger (>300) organic halogen molecules. Combined anaerobic/aerobic methods (mills B and C and reactor L1 and P1 from mill E) resulted in similar removal efficiencies across the whole molecular weight range analyzed.

We analyzed the changes in the relative amounts of the different sizes of organic halogen compounds contained in BKME in the course of biotreatment, by normalizing the chlorine MWDs of Figures 1-3 to equal areas and then analyzing the normalized MWDs by a statistical principal component analysis. The purpose of using this method

552 Environ. Scl. Technol., VoI. 27, No. 3, 1993

I h

prlw to treatment

Molecubr weigM (glml) F p m 5. Exbenms of variation of the triplicate molecular wei@t distribution analysis of the UVabsorbing matter (UV), and organic chlorine wmpounds (GI).

was to simplify MWDs so that all MWDs could be presented simultaneously in a twcdimensional plot expressing the interrelationships of these MWDs. Without any mathematical treatment of the normalized MWD data it is inconvenient to draw conclusions concerning the effects of biotreatment to the relative amounts of organic halogens in the BKME.

Table 11. Removal of Organic Carbon and Halogen from Bleached Kraft Pulp Mill Effluents by Different Biological Treatments

I ',I 80

40-

20-

waste water analysis"

sampling mill month symbol

~~~ ~

organic carbon contents (TOC) before removal upon treat. treat. stage stage stages (mg of I* IIc I + I1 C/L) ("Io) (%I (70)

organic halogen contents (AOX)

before treat. stage stage stages (mg of Ib 11' Cl/L) ( % I (70)

removal upon treat

I and I1 (%)

PH after after

before stage stage treat. I I1

A A A B B C C C C D E E E E

May May Sept June July April May Dec Oct March July July Sept Sept

AS1 830 12 52 58 100 23 38 52 5.7 5.5 7.6 AS2 780 4 50 52 58 26 40 55 6.4 5.4 7.6 AS3 750 2 41 42 73 11 43 49 4.4 6.9 7.6 P1 d 70 21 47 7.6 P2 d 59 16 51 7.4 8.0 AL1 540 13 45 52 52 50 27 63 4.1 7.4 7.5 AL2 640 34 33 56 61 57 19 66 5.7 7.2 7.2 AL3 480 14 44 52 34 53 25 65 6.2 7.3 7.5 AL4 510 15 36 46 43 42 28 58 6.7 7.0 7.7 AS1 380 43 32 30-50' 19' 7.6 6.7 P1 d 30 29 50 51 51' 16' 59' 59 2.9 6.3 7.0

L1 530 19 42 53 72 38' 24e 53e 4 d 3.0 6.9 7.3 L2 640 50 72 44' 40 3.0 6.9

P3 d 48 51 51' 29' 2.9 7.3

a Inorganic cations were analyzed (mg/L) from the waste water of two mills: mill A, Na 880, Ca 100, Fe 0.5, mill C, Na 650, Ca 130, Fe 1.4. For mills A, B, and D stage I means equalization, for mill C equalization and anaerobic lagoon, and for mill E pH adjustment and anaerobic

treatment. Full-scale (mills A and D) and modified pilot-scale (mill B) activated sludge treatment, aerobic lagoon (mill C), and aerobic treatment (mill E). dTOC results were not available but CODcr values (mg/L) were as follows: mill B, 720 (Pl) and 900 (P2); mill E, 920 (both P1 and P3). 'Long time average percent removal relevant to the period of sampling. 'Atypical value.

AS 2 'm

AS 1 ' \

o ! ; / ; / I 50 100 300 loo0 2000

IMill B /

/ AL 3

201

0~ / : I : / I 50 100 300 1000 2000

Molecular weight (g/mol)

401 20

- \-.

-100 -\ ,

50 100 300 1000 2000 Molecular weight (g/ml)

- Full scale activated sludge treatment

-.-I Pilot scale aemblclanaerobic treatment

-..- Full scale anaerobic + aerobic lagoon

--- Aerobic reactor treatment

Anaerobic + aeroblo reactor treatment . . . . . . .

Figure 6. Percent removal of the chlorinated molecules of MW 50-2000 from different kraft pulp mill (A-E) effluents during different secondary effluent treatments: AS, acttvated sludge; P, pilot scale; AL, anaerobic + aerobic lagoon; L, laboratory reactor.

The first two principal components explained 82% and drawn with the aid of these two first principal components the first three explained 88% of the variance of the MWD describes rather well the interrelationships among this data from the untreated and totally biotreated waste MWD group. waters. Thus, the principal component biplot (Figure 7A) Figure 7A shows that the MWDs segregated into two

Environ. Scl. Technol., Vol. 27, No. 3, 1993 559

6

I

-3 -2 -1 0 1 2 3 4 5 6 First principal component (scores and loadings)

Rgur 7. Principal component biplols of aremumallzed MWDs 01 chlorinated molecules from untreated and bbtreated BKNE and bleach plant effluents. Data were centered befcfe computing PCA vectcws. Panel A shows the analysis of both unveated and blotreated effluents together, and panel B shows tha analysls of different untreated effluents

families (shaded areas) so that one contained those from untreated waste waters and the other thoae from biotreated waste waters. This means that the biotreatments changed the relative proportions of the chlorinated compounds in the waste waster. Comparing the directions of the data points describing MWDs of the molecular weights with respect to the origin in Figure 7, it can be seen which molecular weights separate the MWDs from each other. The relative proportion of the molecular weights situated in the direction of a MWD data point are higher in this MWD. The principal component biplot in Figure 7A shows that the relative proportion of chlorinated molecules between 500 and 4000 was higher in biotreated than in nontreated waste waters. Four MWD pairs in Figure 7 did not position in the shaded areas. The MWD pair coded as mill C, AL3 behaved similarly to the bulk of the M W D s hut was situated in a different position. Biotreatment on mill B shifted MWDs toward smaller molecular weights

554 Envlron. Scl. Tedmol., Vol. 27, No. 3, 1993

which also was the case for the anomalous behavior of the MWD pair coded as mill A, AS1.

When MWDs of the untreated waste waters alone were statistically treated, MWDs of the waste waters from different mills did not form separate families on the principal component biplot (Figure 7B). This means that the variation between the area-normalized MWDs within one mill was higher than the variation between the different mills that it would not be possible to identify untreated waste waters originating from different mills. The first two principal components explained 86% of the variance of the MWD data from the untreated waste waters.

The MWDs shown in Figures 1-3 represent the THF- soluble fraction of the BKME. Not all the organic halogens of the BKME were soluble in T H F 90 (raw)-45% (biotreated) of the organic halogens adsorbed to active carbon appeared soluble in THF. Also, not all organic

AS; A S 1 AS 2 A S 1 AL,

Flgum 8. Changes of concantrations (upper panel) and relative prc- portions (lower panel) of tb three categorles of organlc chlorine mpanai. AOX, (cahn a&rbsble organic belogen mxbactable into THF; dark bars). AOX. (carbon adsorbable organic halogen ex- kaclable Into THF; grey bars), and NOX. (carbon nonadsorbable or- gank h a w n extractable into THF: open bars), in bleached kran pulp mill waste water during biotreatment: AS, actbated sludge; AL. anaerobic + aeroblc lagoon. halogen, extractable from BKME into THF, was adsorbed to active carbon.

We found that the oreanic haloeens of BKME could be separated into three categories: Erst, the THF insoluble but adsorbable to carbon (AOGJ, second, THF extractable (NOX,) but nonadsorbable to active carbon, and fi- nally the third and largest categov, that responsive toward both carbon and THF (AOX,). Figure 8 shows the absolute amounts (top panel) and the relative proportions (bottom panel) of these three categories of organic halogens in the different BKMEs. It is seen that the relative amounts (bottom panel) did not vary greatly from mill to mill despite the great variation in the strength of the waste water because of different water usage in the mills (top panel).

Figures 1-3 illustrate the response of combined NOX. and AOX, (THF extract) to biotreatment. Figure 8 shows the fate of the three types of organic halogens during biotreatment. The top panel shows that NOX, was readily removed by biotreatment. AOX. appeared removable to 50% and higher. AOX,, appeared recalcitrant toward biotreatment. As a result of poor bioremoval, the relative proportion of AOX, in BKME increased from 10% to almost 50% during biotreatment (bottom panel). The volatile organic halqens were lost during the experimental protocol (vacuum evaporation) and were not quantitated.

The molar ratio of C to CI (calculated from TOC and AOX) for waste water organics did not change significantly in the treatment plants, being Z(t401 in the raw BKME and 151-501 in the treated BKME (Figure 9). These ratios remained a t the same level when calculated from all the available data from mills A and C-E. The lower panel in Figure 9 (solid line) shows that an anaerobic treatment step (with pH adjustment) increased the CCl ratio, indicating that the components were being dehalo- genated. It is also seen that the THF-soluble compounds of BKME were richer in halogen than the average BKME compounds while the THF-insoluble compounds were less

....................................... E., 7 ........ . ,T

2o ........................................... ... -1%

Me,.PWize?a"* M * U I D m b b + tama .nmm*c lag"" m b r w o n to

ms m * m - Flgur. 9. Effect of aerobic (mill A) and anaerobk + aeroblc (mlll C) Mokeatment on the average CCI ratios of tb total, THF-sobble, and THF-lnsoluble EKME wganic matter. Veltlcal bars show i 1 stamlard deviation.

halogenated. The THF-insoluble fraction (AOX.,) of BKME waa the mast recalcitrant to biodegradation (Figure 8) but the least chlorinated according to Figure 9. Therefore, a high degree of chlorination did not explain the incomplete removal of organic halogen compounds during biotreatment. CCI ratios were not changed substantially if AOX values were replaced with AOX, + NOX, values in the case of THF-soluble compounds and AOX, + AOX, + NOX. values in the case of total BKME.

Discussion Full-scale activated sludge treatment plants have been

reported to remove 30435% of the AOX (14,15,23,24) and aerated lagoons 2560% of the AOX (23, 25-29). Table I1 shows that an activated sludge treatment plant could remove an average of 50% of the AOX and that an aerated lagoon could remove up to 65% of the AOX on average. The high AOX removal in the lagoon treatment was explained by the anaerobic lagoon which specifically removed AOX. Also, earlier work had shown that combined anaerobic/aerobic treatment of bleaching effluents effectively removed AOX and individual chlorinated compounds (7,9-11.13). TOC removal was 50% on the average in this study while in the literature TOC removals of 25-45% have been reported (27,28, 30).

Our previous work and this study showed that BKME organic halogens consist predominantly of small molecules; 90% of the tetrahydrofuran solubles chromatographed as <lo00 (ref 18 and this paper) and less than 10% of the AOX was retained on a loo00 MW filter (18). Transport into the cell of oligopeptides and -saccharides (31) or man-made molecules, such as polyacrylate (32), was observed to be poor above the molecular size of 1oo0. The present study showed that all sizes of solvent-soluble molecules were removed during the different biotreatments (Figures 1-3).

When molecular weight specific removal percent efficiencies (Figure 6) and area-normalized MWDs were analyzed (Figure 7). slightly better removal was observed at the lower end of the MWD. It thus seems that size somewhat restricted removability of the BKME halogens. Also, other workers have observed, using different methods for estimation of molecular weight, that biotreatment removed low molecular weight material more efficiently than

Envlron. Scl. Technol., Vol. 27, No. 3, lSg3 555

high molecular weight material (27, 28, 30, 33-35). Our results indicate that molecular size is not the main

factor limiting removal in the waste water treatment. BKME organic halogens are likely to contain molecular structures alien to the biosphere. It is unknown whether biological active transport, known as the uptake mecha- nism for biomolecules such as oligopeptides and -saccharides, operates for these molecules. Their migration from waste water into the microbial cell may rather depend on passive diffusion, which is known to depend on the functionality of the molecules.

Solubility and adsorption characteristics of the molecules can be used to group compounds on the basis of functionality. Nonpolar solvents such as diethyl ether and hexane, which have polarity indexes below 3 (36), have been shown to extract only a minor part of BKME organic halogens (37-39). To increase the extraction efficiency, we used THF because of its higher polarity (polarity index 4.2) and good solvent characteristics for lignin-type molecules (40). THF is also an optimal eluent for the polystyrene type of SEC gels used in this study (41).

We found that an average of 82% of the raw waste water AOX was soluble in THF, but interestingly, the solubility of AOX of biotreated waste waters was much lower. On closer study it was observed that the THF-insoluble fraction of AOX, termed AOX,, was virtually recalcitrant to biotreatment (Figure 8). The present study gave no information on the molecular size of the AOX,, fraction, but the aqueous SEC analysis done in our earlier study showed that the THF-insoluble part of the BKME did not have significantly a higher molecular weight than the THF-soluble part (18).

Untreated BKME also contained THF-soluble organic halogen nonadsorbable to active carbon, 5-40 mg of Cl/L, termed NOX,. The AOX assay thus underestimates the total amount of organic halogens in BKME. A low yield in the AOX assay has been observed for several individual BKME constituents (42,43). This fact does not necesaarily diminish the value of AOX for monitoring of BKME discharges because it was found that the active carbon nonadsorbable halogenated matter was efficiently removed from waste water during biotreatment (Figure 8) and is therefore unlikely to enter the aqueous ecosystem from mills provided with waste water biotreatment.

Removal efficiencies of the three categories of chlorinated compounds (AOX,,, AOX,, and NOX,) in biotreatment were different, which was explained neither by the differences in molecular weights nor by the degree of chlorination. The recalcitrant THF-insoluble BKME fraction exhibited a higher C:C1 ratio than the removable THF-soluble BKME fraction (Figure 9). The C:C1 ratio remained constant within fl standard deviation during aerobic biotreatment but increased during anaerobic lagoon treatment, where dehalogenation took place in both the THF-soluble and THF-insoluble fractions of the BKME. In other reports the change of C:C1 ratios of unfractionated BKME during the aerated lagoon treatment resulted in constant C:C1 ratios (28, 30, 44) or in decreasing ratios (45).

It was interesting that the recalcitrant class of halogenated BKME organics (AOX,,) could be separated from the bulk by simple extraction. It is possible that the AOX,, fraction is biologically so inert that it will not affect the environment, but it may also be found to have a possible environmental impact. In that case, process modifications or other treatment methods will be needed. This result, if found more generally valid to BKMEs (three different mills studied here), opens the possibility for the

chemical and environmental characterization of this fraction.

Acknowledgments

We thank Maarit Herranen (Metsasellu Oy, Aanekoski Mills), Esa Simpura and Ilkka Westergren (Kymmene Oy, Lappeenranta Mills), Carl Kurten (Oy Metsa-Botnia Ab, Kastinen Mills), and Harri Jussila (Kymin Paperiteollisuus Oy, Kuusankoski Mills) for arranging sampling at the mills; Juhani Anhava from Jaakko Poyry Oy for cooperation in the pilot project; Heikki Haario for the statistical com- putations; Eija Saski for analysis of inorganic cations; Jukka Pellinen for critical reading of the manusqript; Riitta Boeck for skilled technical assistance; Erkki Aijo for in- strument maintenance; and Eila Kerminen for many kinds of help in various situations.

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26 ( l ) , 101-117.

Received for review July I, 1992. Revised manuscript received October 27, 1992. Accepted October 28, 1992. This work was supported by the Maj and Tor Nessling Foundation and by Nordic Industry Fund Environmental Biotechnology Program A.2.1, with the industrial partners Alko Oy, Cultor Ltd., and Ekokem Oy.

Mass Spectrometric Evidence for the Formation of Bromochloramine and N-Bromo-N-chloromethylamine in Aqueous Solution

Mlchael Gatda, Llndy E. DeJarme, Tarun K. Choudhury, R. Graham Cooks,* and Dale W. Margerum"

Department of Chemistry, Purdue University, West Lafayette, Indiana 47907

Membrane introduction mass spectrometry (MIMS) is used to confirm the existence of bromochloramine and N-bromo-N-chloromethylamine in aqueous solution, which have been proposed previously from UV-visible spectra. Bromochloramine is detected by mass spectrometry and UV-visible spectroscopy as a product of monochloramine reactions with bromide ion and with hypobromous acid. The reaction of HOBr with NH2Cl is a t least 3 orders of magnitude faster than the reaction of Br- with NH2C1 at pH 6.5. UV-visible studies also confirm NHBrCl as a product in the following reactions: NH2Cl + NH2Br, NH2Cl + NHBr,, and NH2Br + HOC1. N-Bromo-N- chloromethylamine is detected by mass spectrometry and UV-visible spectroscopy in the reaction of N-chloromethylamine with hypobromous acid.

Introduction Hypochlorous acid and chloramines are commonly used

in water disinfection. Identification of reaction products in the chlorination process is essential in (a) determining water quality and (b) isolating potential health and environmental hazards. Bromide ion is commonly found in water systems, and the reaction of hypochlorous acid with bromide yields hypobromous acid as a product (1). Thus, the reactions of chloramines with bromide and hypobromous acid are of vital importance in the water treatment process. The chemistry, however, is complicated due

to the formation of a number of reactive hdoamine species. The reactions between NH2Cl and Br- have been exam-

ined in several studies (2-4). Trofe, Inman, and Johnson (2) first proposed a mixed haloamine as one of the products of this reaction. Bromochloramine was proposed on the basis of a UV-visible absorption maximum observed at a wavelength that lies between the absorption maxima for NHCl, (206 nm) and NHBr2 (232 nm). They reported a A,, of 220 nm with t = 2100 M-' cm-' in aqueous solution and a A,,, of 218 nm in ether. They observed the absorption maximum associated with this product in ether extracts of the reaction mixtures shown in eqs 1-4.

NH2C1 + Br- - products (1)

"$21 + HOBr - products (2)

NH,Br + HOC1 - products (3)

NH2Cl + NHBr, - products (4) Other workers (3 ,4) , who examined the NHzCl + Br-

reaction, concurred that NHBrCl is the probable product. However, the compound has not been isolated and its chemical composition has not been proven.

Valentine (5) examined the oxidation of N,N-diethyl- p-phenylenediamine by a mixture of NH2Cl and NHBrCl and reported that the bromine atom in NHBrCl is very labile. This author proposed molar absorptivities in water

0013-936X/93/0927-0557$04.00/0 0 1993 American Chemlcal Soclety Environ. Scl. Technol., Vol. 27, No. 3, 1993 557

effect of biological treatment on halogenated organics in bleached kraft pulp mill effluents studied...

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