Water Research 37 (2003) 2813–2820 Removal of resin acids and sterols from pulp mill effluents by activated sludge treatment A. Kostamo, J.V.K. Kukkonen* Laboratory of Aquatic Ecology and Ecotoxicology, Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland Received 18 January 2002; accepted 6 February 2003 Abstract The wastewater treatment plant of an elemental chlorine free bleachingkraft pulp mill located in eastern Finland was sampled in order to study the fate of wood extractives and the toxicity to luminescence bacteria (Vibrio fischeri)in different parts of the plant. Resin acids and sterols were analyzed from water, particles and sludge samples during three different runs. Waters before biotreatment and primary sludge were found to be toxic; but in the activated sludge treatment toxicity was removed. Duringwastewater treatment, concentrations of wood extractives were reduced over 97%. In activated sludge treatment, over 94% of the resin acids and over 41% of the sterols were degraded or transformed to other compounds. Furthermore, in general, less than 5% of the resin acids and over 31% of the sterols were removed in biosludge to the sludge thickener. Most of the extractives were discharged attached to particles. Although some disturbing factors increased the load of wood extractives during samplings, these factors did not affect the operational efficiency of the secondary treatment system. r 2003 Elsevier Science Ltd. All rights reserved. Keywords: Wood extractives; Resin acids; Sterols; Activated sludge treatment; Flash test; Kraft pulp mill 1. Introduction have also reduced the load: modified cooking, oxygen delignification, more effective washing of pulp and more After changes in the bleaching processes, research on closed water circulation [1,3,5]. pulp mill effluents has expanded from chlorinated Secondary treatment of pulp mill effluents reduces, in compounds to wood extractives such as resin acids and addition to BOD and COD, the toxicity of effluents sterols [1]. These extractives cause foamingproblems [4,6]. Many studies have found resin acids and and are impurities in the products and on the equipment unsaturated fatty acids toxic to aquatic organisms, and of pulp and paper mills [2]. Since the early 1990s, the use various methods have been used to test toxicity [7–9]. of ECF bleachingtechniques has become common, Recently, bacterial testinghas become popular because replacingthe use of chlorine gas [3]. Moreover, in the it is sensitive and relatively quick and easy to perform 1980s, the introduction of activated sludge wastewater [6,10,11]. treatment has reduced BOD in effluents by 85–95% and Quite recently, it has been shown that plant sterols COD by 40–80% [4]. Other improvements in the process (phytosterols) may act as disrupters of the hormonal and biochemical systems of aquatic organisms. The structure *Correspondingauthor. Tel.: +358-13-2513575; fax: +358- of phytosterols is similar to that of the steroid hormones 13-2513590. of vertebrates. Transformation products of sterols, in E-mail address: jussi.kukkonen@joensuu.fi particular, can have adverse endocrine effects, andro- (J.V.K. Kukkonen). genic effects, on fish [12–14]. In addition, studies on the 0043-1354/03/$ - see front matter r 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0043-1354(03)00108-8 2814 A. Kostamo, J.V.K. Kukkonen / Water Research 37 (2003) 2813–2820 impacts of pulp mill effluents have been reported, for the hydraulic retention. Background information on the instance, stimulated growth and enzymatic induction samplings is presented in Table 1. [15–17], and decrease in levels of sex hormones and in Before the analyses, the wastewaters were filtered on reproductive capacity [12,18–20]. Transformation pro- Whatman GF-C filters. Solids in the water and dry ducts of sterols and resin acids can be formed during weights of the sludges were determined. Water and biological treatment of wastewater [13,14,17]. Possible particle samples were stored at À20C until analyzed. In transformation reactions are hydrogenation, hydroxyla- addition, the sludge samples were freeze-dried with a tion, decarboxylation and aromatization. Up to 40% of HETOSICC freeze-drier. Filtered water, solid matter the discharged compounds can be in the form of with the filter, and freeze-dried sludge samples were transformation products [13]. extracted accordingto Kaplin et al. [21]. Briefly, the The objective of this study was to analyze removal of water samples were extracted with hexane/EtOH (v/v: resin acids and plant sterols from effluent of an ECF 4/1) as solvent. The solid matter with filter and the kraft pulp mill by an activated sludge treatment plant. sludge samples were hydrolyzed with 0.5 M KOH in To get an overview of the performance of the treatment 90% EtOH and were then further extracted with diethyl plant, the samples were collected at different points in ether. Derivatized samples were analyzed semiquantita- the treatment process and duringdifferent runs of the tively with a Hewlett-Packard GC-MSD accompanied pulp mill. In addition to chemical analysis, the overall with an HP-1 column (25 m, i.d. 0.32 mm, film thickness bacterial toxicity of the samples was tested. 0.17 mm). The analyzed compounds are shown in Table 2. Of these compounds, levopimaric acid and palustric acid, as well as 7-prenol and 24-methylene cycloartenol 2. Materials and methods overlapped. The internal standards used were heneico- sanoic acid (21:0) and cholesterol. Later in this article, Wastewater treatment plant of an ECF (O-Do-EOP- triterpenyl alcohols and squalene are included in the D-D) kraft pulp mill located in eastern Finland was sterol group. sampled in order to study the fate of extractives and Dissolved organic carbon (DOC) was determined luminescence bacterial (V. fischeri) toxicity in different from the filtered water samples with a Shimadzu total parts of the plant (Fig. 1). In 1998, the pulp production organic carbon analyzer 5000A (Shimadzu, Kyoto, in this mill was 586 000 ADt/a; and the discharged loads Japan). In addition, total carbon contents of solid of COD, AOX, P and N were 7 640, 90, 2, and 39 t/a, matter and sludges were analyzed with a CHN- respectively. The pulp mill uses ca. 40 m3 water per ton analyzer (Carlo Erba Elemental Analyzer, Milano, of pulp produced. The samples were taken duringthree Italy). Bacterial (V. fischeri) toxicity and the EC50 different runs, twice in each. The runs were: (1) both values of the non-filtered effluents and sludges were fibrelines producingbirch pulp (Birch), (2) one line determined with a Flash-test [22] by Bio-Nobile Oy, producingbirch pulp and the other producingconifer Turku, Finland. The Flash-test is a kinetic direct- pulp (Norm), and (3) one line producingbirch and the contact luminescent bacterial test. The test is compar- other producing conifer pulp with a higher percentage of able to other bacterial tests (i.e. Microtox) and it is spruce (Reinf). Samplings were performed considering recommended for colored samples [22] because each Debarking Activated sludge treatment Ecological pond Primary clarifier Secondary clarifiers 1 5 2 3 4 7 6 Sludge thickener 1 = mill inflow 2 = total effluent 3 = before activated sludge treatment 4 = secondary clarified water 5 = discharge 6 = primary sludge 7 = biosludge Fig. 1. Sampling points. A. Kostamo, J.V.K. Kukkonen / Water Research 37 (2003) 2813–2820 2815 Table 1 Production, proportion of birch and conifer pulp production, average wastewater flow, adsorbable organic carbon (AOX), chemical (CODCr) and biological oxygen demand (BOD7), organic carbon (OC), dissolved organic carbon (DOC), and pH before (in) and after (out) the activated sludge treatment, total concentrations of nitrogen and phosphorous (totN and totP), and the amount of water solids at different samplingpoints Birch/spruce Birch/conifer Reinf1 Reinf2 Norm1 Norm2 Birch1 Birch2 Production, ADt/d 1945 1727 1986 1856 1638 1978 Birch/conifer, ADt/d 1315/630 1147/580 1363/623 1351/505 1638/0 1978/0 Average flow, m3/d 71 400 67 800 63 400 63 300 65 500 65 800 AOX, kg/d 258 230 240 240 230 230 CODCr in, mg/l 1658 2080 1602 1964 1492 2064 CODCr out, mg/l 364 308 323 342 272 302 BOD7 in, mg/l 459 675 569 621 496 599 BOD7 out, mg/l 7 7 6 7 6 8 DOC in, mg/l 282 430 388 486 483 361 DOC out, mg/l 143 168 142 130 304 123 OC in, mg/l 34.9 38.4 44.0 44.8 42.7 37.6 OC out, mg/l 14.3 14.6 13.9 14.9 13.6 14.9 totP out, mg/l 0.08 0.07 0.06 0.05 0.07 0.04 totN out, mg/l 1.37 1.23 1.61 0.84 2.2 1.46 pH in 6.1 6.0 7.6 6.2 6.5 6.9 pH out 8.0 8.2 8.0 8.0 8.0 8.0 Solids 2a, mg/l 219 244 265 267 590 690 Solids 3a, mg/l 81 129 85 129 112 84 Solids 5a, mg/l 5.4 6.8 5.0 1.2 4.0 4.8 Solids 6a, mg/l 7320 46 330 14 490 30 250 6950 33 850 Solids 7a, mg/l 5880 5720 4900 3800 6870 5440 a Number of a samplingpoint; see Fig. 1. Table 2 Analyzed compounds Resin acids Sterols Triterpenyl alcohols Hydrocarbon and prenol Pimaranes Campesterol Lupeol Squalene Pimaric acid Campestanol Methylbetulinate 7-prenol Sandaracopimaric acid b-sitosterol Betulinol Isopimaric acid Stigmastanol Abietanes Cycloartenol Palustric acid Citrostadienol Levopimaric acid 24-methylene cycloartenol Dehydroabietic acid Neoabietic acid Abietic acid sample acts as its own reference, and no correction for 3. Results color or turbidity is needed.