Acta Chim. Slov. 2005, 52, 131–137 131 Scientific Paper Combination of Fenton and Biological Oxidation for TVeatment of Heavily Polluted Fermentation Waste Broth Andreja Žgajnar Gotvajn* and Jana Zagorc-Končan Faculty of Chemistij and Chemical Technology, University of Ljubljana, Aškerčeva 5, Ljubljana, Slovenia, E-mail: andreja.zgajnar@ki.si Received 22-12-2004 Abstract The aim of our work was to study the biotreatability of heavily polluted pharmaceutical fermentation broth (COD value of 124,500 mg-I/1) as well as application of Fenton oxidation for effective pretreatment. Because waste broth expressed biodegradability (BOD5/COD ratio was 0.40), biological treatment was the first choice. At the same tirne, in preliminary ready biodegradability assessment test, diluted broth degraded 65% as well it was not toxic to mixed bacterial culture of activated sludge. Further experiments in pilot laboratory biological treatment plant confirm acceptable treatment efficiency up to 0.01 vol% of the broth added (76%). However, we had considered additional pretreatment method to be able to enhance biotreatability. Fenton procedure was optimised in batch reactor using different concentrations of Fe2+, H202, temperatures (40/45 °C), as well as dif-ferent retention times (up to 30 minutes). The highest treatment efficiency reached only 44% according to COD, but ready biodegradability of the sample increased (82%). Fenton oxidation was confirmed as possible method for pretreatment of broth, because it slighth/ enhanced biodegradability, it reduced organic pollution and formed products were non-toxic. We have focused our future work into a study on optimisation of applied procedure for improving biotreatability of the investigated broth. Key words: biodegradability, biological treatment, pharmaceutical waste broth, Fenton oxidation, toxicity Introduction Up-to-date approach to management of the wastewaters is mainly based on quantity minimisation as well as “in-situ” pollution prevention. In spite of use of available BATs (Best Available Technologies), genera-tion of wastewaters in industrial processes is sometimes unavoidable and in most cases a process to reduce the organic load and other contaminants must be employed before water discharge.1 To remove majority of the organic load, biological processes are usually used, because they are more economic then chemical ones. At the same time, they are environmental friendly, using optimised natural pathways to actually destroy pollution not only transform it into another form.2 In some cases, however, due to the high organic load, toxiciry, or presence of persistent compounds, biological treatment is not feasible. In such a čase, chemical pretreatment is usually investigated, because it can adequately increase biodegradability and remove toxiciry of the wastewater prior to biological treatment.3'4 Advanced oxidation processes have been often used to reduce organic load or toxicity of different wastewaters, recently.5'6 They are defined as oxidation processes, which generate hydroxyl free radicals with a high electrochemical oxidant potential (2.8 V vs. normal hydrogen electrode) in sufficient quantiry to affect water constituents. They could be formed using classical oxidants (hydrogen peroxide, ozone, Etc.) and UV radiation or catalyst.7'8 Hydroxyl radicals than react with organics and broke them down gradually into smaller fragments with higher biodegradation potential. Sometimes organics are even completeh/ degraded mainly into C02 and water. One common feature of such systems is high demand on electrical energy for devices such as ozonizers, UV lamps, ultrasounds and this result in higher treatment costs. The only excep-tion is Fenton process, where under acidic conditions, a Fe2+/H202 mixture produces hydroxide radicals in a very cost-effective manner (Reaction 1): Fe2+ + H202 -> Fe3+ + OH" + OH" k = 76.5 morV1 (1) Formed Fe(III) can react with H2O2 in the so-called Fenton-like reactions (Reactions 2–4) regenerat-ing Fe2+ and thus supporting the Fenton process: Fe3+ + H202 -> Fe2+ + H02* + H+ k = 2xl0-3 mor1s-1 (2) Žgajnar Gotvajn and Zagorc-Končan Treatment of Fermentation Waste Broth 132 Acta Chim. Slov. 2005, 52, 131-137 Fe3+ + H02* -> Fe2+ + 02 + H+ (3) Fe3+ + R-^ Fe2+ + R+ (4) Several studies have demonstrated, that the best oxidation efficiency is achieved when neither H202 nor Fe2+ is overdosed, so that the maximum amount of OH• radicals is available for the oxidation of organics.9 Many authors suggested Fe2+ to H202 mass ratio to be optimal at 1 to 10, but it must be optimised for particular waste-water to minimize scavenging effects.9 For pharmaceuti-cal wastewaters usualh/ Fe2+/H202 mass ratio from 1/2 to 1/10 is found to be the most effective one.5 The Fenton reaction has a short reaction time among ali advanced oxidation processes and it has other important advantages. Iron and H202 are cheap and non-toxic, there is no mass transfer limitations due to its homogenous catalytic nature, there is no energy involved as catalyst and the process is easily to run and control. It has been widely used for treatment of highly polluted textile and paper mili wastewaters, as well as pharmaceutical wastewaters.5'6'9 Substantial quantities of pharmaceuticals are used in human and veterinary medicine. They are often not metabolised by the body after administration. Depend-ing upon their excretion rate, they are released into the effluent and reach sewage treatment plant. If they are not degraded, they could enter the environment, where little is known about their fate and effects. They usually have two characteristics, which declare them as environmental hostile: they are stable and biologicalh/ effective.10 For these reasons optimisation of produc-tion processes and effective end-of pipe treatment is necessary to avoid broad contamination of receiving environment due to the pharmaceutical industry. The aim of our work was to study the biotreat-ability of heavily polluted pharmaceutical fermentation broth as well as application of Fenton oxidation for effective pretreatment. Materials and Methods Wastewater The same sample of the waste fermentation broth was used for ali of the experiments. It was produced in the pharmaceutical factory, during biosynthesis of active substances for human medicine. Remained broth was random grab sampled from the effluent of the reactor and it is aftenvards mixed (0.7 vol%) with other wastewaters from the factory. Formed effluent is then released into sewerage system leading to municipal wastewater treatment plant. Due to this dilution the highest expected volumetric load of the investigated fermentation broth in biological treatment plant is 0.042 vol%. Žgajnar Gotvajn and Zagorc-Končan Physico-chemical analysis of the wastewater pH, BOD5n (Biochemical Oxygen Demand), COD12 (Chemical Oxygen Demand), DOC (Dissolved Organic Carbon), IC13 (Inorganic Carbon) (Shimadzu TOC 5000A Analyser, 1998), nitrogen as Kljeldahl nitrogen14, ammonium nitrogen15 (Kjeltec Auto Anah/ser FOSS Tecator, 1998), N02"-N and N03"-N and P043"-P16 (DIONEX 120, 2000) were determined in fresh raw sample of the broth prior to toxicity and bio-degradability testing, as well as treatment experiments. The same parameters were also determined in the in-fluent and effluent of the pilot laboratory wastewater treatment plant. COD12 measurements were used to determine removal efficiency of organics during chemi-cal oxidation in Fenton process. Toxicity testing Raw broth toxicity was determined using two dif-ferent toxicity tests. We determined the inhibition of oxygen consumption by activated sludge, using low (100 mgvss-L_1) concentration of the inoculum - activated sludge.17 Addition of toxic concentration of the waste-water (as 5, 10 and 50 vol%) results in a decrease in the oxygen consumption rate. Oxygen concentration was followed up to 180 minutes at 20+1 °C. The percentage inhibition of the oxygen consumption was estimated by comparison of oxygen consumption rate (mg-L^-min-1) in the test mixture with a control containing no test material. Finally percentage of inhibition was plotted versus logarithm of wastewaters' concentration (vol%) to determine EC (Effective Concentration) values. Above mentioned toxicity test was accomplished using non-adapted inoculum. Its source was laboratory treatment plant with 8.3 L of aeration basin, sludge re-tention time was 9-11 days, and hydraulic retention time was 6-7 hours. The plant was fed with synthetic municipal wastewater, constituted of 130 mg-L-1 of peptone, 0.9 mg-L-1 of P as KH2P04, 70 vol% of distilled water and 30 vol% of domestic sewage. The same activated sludge was also used in biodegradability assessment test. We performed additional acute toxicity test on raw fermentation broth with freeze-dried luminiscent bacte-ria Vibrio fischeri (DR. LANGE LUMIStox, 2001).18 It was also used for monitoring changes in toxicity of the sample during biological and chemical treatment. Biodegradability testing Biodegradability of the sample was determined by applying standardized method where oxygen consumption during biodegradation of diluted raw broth has been measured.19 The same method was also used for checking biodegradability of the effluent from pilot biological treatment plant, as well as after Fenton oxida-tion experiment. Treatment of Fermentation Waste Broth Acta Chim. Slov. 2005, 52, 131–137 133 Initial concentration of the raw broth in biode-gradability test (0.1 vol%) was chosen on the basis of toxicity test with measurement of inhibition of oxygen consumption. Biodegradability assessment tests with effluent from biological pilot plant as well as chemi-cally treated broth were performed with non-diluted samples. Experiments were conducted in a closed respirom-eter Micro Oxymax, Columbus Instruments, USA, 1996. As inoculum non-adapted activated sludge from a laboratory wastewater treatment plant was used. Its concentration in measuring chamber was 30 mgvss-L_1. Temperature was maintained at 20+1 °C. Ali tests were run in 250 mL duplicates. Nitrification of the sample was prevented by addition of 4 ml-L"1 of alilthiourea (1 g-L"1). Abiotic degradation of wastewater was evalu-ated under the same conditions simultaneously without inoculation. Biodegradation curves were plotted as % of degradation versus time to read out lag phase (time in days to reach 10% degradation) and maximal level of biodegradation (Dm, %) and to calculate the rate of biodegradation as rate constant kj (day-1).20 We simplify the calculations neglecting changes in biomass yield and data fit the first order kinetics. In Equation 1, c corre-sponds to the concentration of the substance (mg-L-1), which in our čase was expressed as oxygen consumption in particular time interval t (Day). In fact, we have many organics degrading according to different rates with overall (pseudo)first order kinetics.21 Table 1. Process parameters during the start-up procedure and during plant operation. dc k dt = lc In Dt^ 1— =-kt 100J eq (l) eq (2) For calculation of rate constants, Equation 1 was modified to Equation 2, to enable direct calculation of degradation rate constants (k1; day_1 or min"1) from degradation levels (Dt, %).22 Biological pilot treatment plant Biological treatment of the diluted fermentation broth was run out in laboratory aerobic wastewater treatment plant. Aeration basin of the unit had a volume of 8.3 L and the volume of the secondary clarifier was 2.2 L. The start-up influent was synthetic municipal wastewater as deseribed for the unit, used for cultiva-tion of inoculum for toxicity test. 4 days after, 0.01 vol% of the broth was added and operation of the plant was followed for 19 days. Then the broth load was inereased to 0.02 vol%, causing intensive sludge bulking within 2 days. The treatment unit collapsed due to the washout of the activated sludge. Process parameters Start-up Operation Influent flow(L-day1) 22.0 (±2.0) 27.3 (±1.3) Sample concentration in the influent (vol%) / 0.01 Hydraulic retention time (h) 9.0 (±0.7) 7.3 (±0.3) Sludge volume index(mL-g1) 88 (±13) 70 (±9) CODhfluent (mg-L ') 130 (±12) 190 (±5) Sludge concentration (gvss-L1) 3.2 3.5 (±0.3) Biomass loading rate (gcoD-gvss 1-day ') 0.10 (±0.03) 0.18 (±0.02) Volumetric loading rate (gcoD-L 1-day ') 0.34 (±0.07) 0.63 (±0.04) /.. .No sample was added. Start-up and operational parameters for the wastewater treatment plant are presented in Table 1. Temperature of the system was maintained constant (20+2 °C), diffused aeration assured at least 2 mg-L"1 of dissolved oxygen. DOC, IC and temperature of the system were checked daily, while COD, BOD5, pH, sludge volume index and concentration of activated sludge were monitored periodicalh/ during 19 days of the experiment. Toxicity of the influent and effluent was determined once during the experiment. Fenton oxidation ezperiments Experiments were performed using 500-times diluted broth sample (0.2 vol%). Wastewater samples were filtered through black ribbon to remove solids and pH was adjusted to 4.0 (±0.2) before chemical oxidation experiments. A 150 mL sample was placed into 500 mL Erlenmayer flask, which was submerged in a temperature controlled water bath to attain desired constant temperature (40/45 °C). FeS04, p.a. was added to attain selected Fe2+ concentrations (0.2/0.3/0.4 M). Finally, Fenton reaction was started with addition of H202 (30% w/v, p.a.) to achieve concentrations 2.0/2.5/3.0/3.5 M. The reaction is fast and exothermic: initial temperature was among 40 and 45 °C, so we conducted our experi-ments at 40 and 45 °C. The aqueous solution of Fenton reagent and diluted broth was stirred during the reaction period up to 35 minutes. Samples were redrawn at 5, 10, 20 and 30 minutes and COD was determined im-mediately. Prior to COD analysis 1M NaOH was added to stop the oxidation at pH = 12 (±0.2). To eliminate the excess H202, the sample was boiled for 10 minutes and then allowed to cool to room temperature. It has been filtered aftenvards to remove the formed ferric hydroxide and COD was determined. Žgajnar Gotvajn and Zagorc-Končan Treatment of Fermentation Waste Broth 134 Acta Chim. Slov. 2005, 52, 131–137 Results and Discussion Characterization of fermentation broth Main physico-chemical characteristics of the raw sample are presented in Table 2. The value of soluble COD (124,500 mg-L-1) was extremely high, but BOD5/ COD ratio was not too low (0.40) to achieve good bio-logical treatment under appropriate conditions. At the same time, sample appeared to be not very toxic. It was not toxic to mixed culture of acti-vated sludge according to measurement of inhibition of oxygen consumption up to 50 vol%, while 30minEC20, based on bioluminescence inhibition was 0.48 vol% and 30minEC50 was 1.11 vol%. Wastewater should not inhibit microorganisms at concentrations applied in biodegradability assessment test or in pilot treatment plant (0.1/0.01/0.02 vol%). Table 2. Physico-chemical analysis of the raw pharmaceutical broth. Parameter Value pH 6.9 (±0.1) COD (mg-L ') 124,500 (±11,200) DOC (mg-L ') 40,200 (±500) IC (mg-L ') 400 (±8) BODsfmg-L1) 49,400 (±2,700) N-organicfmg-L1) 3,200 (±800) N-NIL+fmg-L1) 245 (±66) N-N03 (mg-L ') 27 (±1) P-PO43 (mg-L ') 141 (±78) Cl (mg-L1) 51 (±2) Results of the ready biodegradability assessment test are presented in Figure 1. 80 60 40 _/ J 20 / f m / 10 15 20 25 t (Days) 30 Figure 1. Biodegradation of diluted raw fermentation broth (0.1 vol%) in ready biodegradability assessment test. Initial COD of the sample was 125 mg-L"1. Waste-water degraded 65%, what was higher than expected on the basis of BOD5/COD ratio (40%) due to the better conditions and longer incubation period. It also degraded rapidly, kj = 0.12 day_1 (r2 = 0.98), lag phase was 3 days. Abiotic elimination reached 2% (+ 2%) and it was neglected. We predicted good biotreatability of the diluted broth in biological pilot treatment plant. Reference compound sodium acetate degraded 65% in 14 days confirming validity of the biodegradability assessment test. Biological treatment of fermentation broth The aerobic biological pilot plant was running for 24 days. We allowed 3 days for starting-up, then 0.01 vol% of the wastewater has been added for the next 19 days to achieve constant operational param-eters. Then 0.02 vol% of the wastewater was added, resulting in immediate increase of SVI (990 mL/L"1) and washout of activated sludge. After 2 days sludge concentration dropped to 0.5 g'L_1 and experiment has been terminated. Average DOC, IC and COD values during the constant operation of the treatment unit are presented for the influent and the effluent in Table 3. Average treatment efficiency according to COD was 82% and 76% according to DOC. Degradation rate constants based on COD measurements were 5.63 day_1 and 4.69 day_1 according to DOC measurements (Equation 2), re-spectively. They were much higher as measured in ready biodegradability assessment test (0.12 day_1). Reduction of inorganic carbon (IC) indicated nitrification of the nitrogen components, what has also been confirmed by nitrogen mass balance (Table 4). Table 3. Average COD, DOC and IC values of the influent (0.01 vol% of the sample) and the effluent of the pilot biological treat-ment plant during constant operation period (19 days). Value Influent Effluent COD (mg-L ') 190 (±5) 34 (±6) DOC (mg-L ') 95.1 (±13.6) 22.4 (±5.4) IC (mg-L ') 69.6 (±14.3) 23.9 (±5.9) DOC removal in % versus time is presented in Figure 2. DOC removal showed slight decrease from initial 86% to final 74%, indicating minor impact of the wastewater to the activated sludge system. In spite of the fact, that raw fermentation broth was non-toxic to Vibrio fischeri up to 0.48 vol% (30minEC20), diluted broth (0.01 vol%) at the influent of the pilot plant expressed high toxicity: 30minEC20 was 0.86 vol% and 30minEC50 was 4.43 vol%. Increased toxicity was probabh/ a consequence of synergistic effect among the sample and dilution medium (municipal sewage and nutrient solution). o 5 Žgajnar Gotvajn and Zagorc-Končan Treatment of Fermentation Waste Broth Acta Chim. Slov. 2005, 52, 131–137 135 100 80 60 40 20 ^-^-^r^-^-^V-H 50 0 5 10 15 20 t (Days) Figure 2. Treatment efficiency according to DOC removal of diluted sample (0.01 vol%) in biological pilot treatment plant. This could be one of the reasons for decreasing treatment performance of the unit. After biological treatment, wastewater effluent had no toxic impact to luminiscent bacteria. Table 4. Concentration of nitrogen components in the influent and effluent of biological pilot plant during constant operation (19 days). Parameter Influent Effluent N-organic (mg-L ') (±4.5) 0.1 N-NH^mg-L1) 52.0 (±19.4) 1.5 N-N02 (mg-L ') / 1.0 N-N03 (mg-L ') 1.8 (±0.2) 36.1 /...Analysis was not accomplished. Concentration of organic and ammonium nitrogen decreased (99%/97%) during biological treatment, while concentration of nitrate N increased significantly, confirming nitrification processes. Chemical treatment of fermentation broth COD removal rate in Fenton oxidation experi-ments under different conditions is presented in Figure 3 (the first set of experiments) and Figure 4 (the second set of experiments). In ali the cases more than 90% of final COD removal was achieved in first 10 minutes of reaction, what has also been reported by other authors.5 That is important for the pretreatment of an industrial wastewater, because it can be accomplished quickly vvithout a need for large treatment reactors. Degrada-tion rate constants (Equation 2) were comparable in the first set of four experiments, where Fe2+ and peroxide concentrations were varied in the mass ratio Fe2/H202 from 1/5 to 1/6. This range has been selected for our investigation on the basis of literature data for comparable pharmaceutical broth.5 kj varied from 0.019 to 0.030 min"1 and they were not depended upon concentrations of H202 or Fe2+ and their mass ratio. As could be seen from Figure 3, the highest COD removal efficiency (as COD removal in %) in the first set of experiments was achieved after the highest ad- 40 30 20 10 2.5 M H202; 0.3 M Fe2+; T = 45 °C 3.0 M H202; 0.3 M Fe2+; T = 40 °C 3.5 M H202; 0.4 M Fe2+; T = 40 °C 2.0 M H202; 0.2 M Fe2+; T = 40 °C 10 15 20 t (min) 25 30 35 Figure 3. Treatment efficiency according to COD removal of diluted sample (0.2 vol%) in Fenton oxidation experiments (the first set of experiments). dition of reagents (0.4 M Fe2+ and 3.5 M H202, with mass ratio Fe2+/H202 was 1/5): 26%. It was only 2% higher than in oxidation experiment with 0.3 M Fe2+ and 3.0 M H202 (mass ratio Fe2+/H202 was 1/6), so we assumed that higher concentrations of both reagents would not improve treatment efficiency enough to be economicalh/ acceptable. Selected Fe2+/H202 mass ratios (1/5 or 1/6) seemed to be not effective enough for tested fermentation broth. At the same time, addi-tion of hydrogen peroxide could not be increased over 3.5 M due to a violent reaction with a quick boiling of the sample. Water bath was unable to maintain required temperature and the system overheated up to 65 °C. Although some different strategies to add the hydrogen peroxide carefully were tested, no reliable results could be obtained from these experiments. This experiment, although not conducted under controlled circumstances, confirmed low impact of the temperature to oxidation of the sample. Temperature showed no positive effect on the final COD removal efficiency (18% COD removal at 45 °C in comparable experiments with 2 M and 2.5 M H202 at 40 °C), but the reaction rate was the highest at 45 °C: kx = 0.030 min"1 (Equation 2). 50 40 30 20 10 10 15 20 25 30 35 t (min) Figure 4. Treatment efficiency according to COD removal of diluted sample (0.2 vol%) in Fenton oxidation experiments (the second set of experiments). 0 0 5 0 0 5 Žgajnar Gotvajn and Zagorc-Končan Treatment of Fermentation Waste Broth 136 Acta Chim. Slov. 2005, 52, 131–137 The second set of experiments was conducted at the mass ratio Fe2+/H202 of 1/11 at the same tem-peratures: 40 and 45 °C (Figure 4). Final levels of degradation were comparable (42%/44%) and much higher than in the first set of experiments (Figure 3). Degradation rate constants kj were also higher (0.049 min"1 at 40 °C and 0.058 at 45 °C), confirming impact of the temperature on the reaction rate but not to final removal rate. Due to the fast oxidation of the sample (final DOC removal was achieved practicalh/ within the first 10 minutes of experiments), we assumed that reaction at higher temperature is unnecessarv and economicallv unacceptable. We investigated the sample, which has showed the highest, 44% COD removal efficiencv (0.2 M Fe2+ and 3.5 M H202; Fe2+/H202 mass ratio was 1/11, Figure 4), determining its toxicity to Vibrio fischeri as well as its biodegradabilitv. After chemical treatment diluted broth (0.2 vol%) was not toxic to luminiscent bacteria, as raw broth was non-toxic prior to chemical oxidation. At the same time, Fenton process enhanced biodegradabilitv of the sample. Its maximal level of biodegrada-tion reached 82% (65% in the čase of untreated broth) and it also degraded more rapidlv (kj = 0.17 day_1) in comparison with untreated broth (kx = 0.12 day_1), with negligible abiotic elimination. Conclusions A study on selection of appropriate treatment techniques of complex fermentation pharmaceutical broth has been conducted. Fermentation broth was highly polluted (COD value of 124,500 mg-L"1), with BOD5/COD ratio 0.4. Biological treatment was the first choice for broth treatment due to its cost-effectiveness and environmental acceptability. At the same time, in preliminary ready biodegradability assessment test, diluted broth degraded 65% as well it was not toxic to mixed bacterial culture of activated sludge. Effective-ness of biological treatment was studied in pilot plant, where satisfactory average 76% of COD removal was obtained, as well as effective nitrification up to 0.01 vol% of broth in municipal wastewater. At higher broth load (0.02 vol%) pilot plant has collapsed due to the vvashout of bulked activated sludge. Additional pre-treatment using Fenton oxidation has been considered to enhance biotreatability. Fenton process has been optimised using different concentrations of Fe2+ and H202. The highest removal of organics reached 44% (0.2 M Fe2+ and 3.5 M H202 at 40 °C). Broth toxic-ity was not affected at investigated conditions, while increased biodegradability of the diluted broth up to 82% has been detected. A further investigation will be focused on biological treatment of the produced pre-treated broth to design a complete treatment for the waste broth under study. Acknowledgements This work was supported by the Ministry of Educa-tion, Science and Technology of Republic of Slovenia. References 1. M. Richardson, Environmental Xenobiotics, Taylor and Francis Publishers, London, 1996, pp. 17-31. 2. W.W. Eckenfelder, P. Grau, Activated Sludge Process Design and Control -Theorj and Practice, Technomic Publishing AG, Basel, 1992, pp. 57-112. 3. G. M. Masters, Introduction to Environmental Engineering and Science, Prentice Hali, Upper Saddle River, New Yersey, 1996, pp. 163-264. 4. R. A. Conway, R. D. Ross, Handbook oflndustrial Waste Disposal, Van Nostrand Reinhold Company, New York, 1980, pp. 71-147. 5. N. San Sebastian, J. F. Fernandez, X. F. Segura, A. S. Ferrer, /. Hazard. Mater. 2003, 101, 315-322. 6. A. Lopez, M. Pagano, A. Volpe, A. C. Di Pinto, Chemosphere 2004, 54, 1005-1010. 7. X.-R. Xu, H.-B. Li, W.-H. Wang, J.-D. Gu, Chemosphere 2004, 57, 595-600. 8. R. Maciel, G. L. Sant'Anna, M. Dezoti, Chemosphere 2004, 57, 717-719. 9. F. Torrades, M. Perez, H. D. Mansilla, J. Peral, Chemospere 2003, 53, 1211-1220. 10. M. Carballa, F. Omil, J. M. Lema, M. Llompart, C. Garcia-Jares, I. Rodriguez, M. Gomez, T. Ternes, Water Res. 2004, 38, 2918-2926. 11. ISO, International Standard ISO 5815, Geneva, 1989. 12. ISO, International Standard ISO 6060, Geneva, 1989. 13. ISO, International Standard ISO 8245, Geneva, 1987. 14. ISO, International Standard ISO 5663, Geneva, 1984. 15. ISO, International Standard ISO 5664, Geneva, 1984. 16. ISO, International Standard ISO 10304-1, Geneva, 1992. 17. ISO, International Standard ISO 8192, Geneva, 1986. 18. ISO, International Standard ISO 11348-21, Geneva, 1998. 19. ISO, International Standard ISO 9408, Geneva, 1999. 20. H. Painter, Detailed Review Paper on Biodegradability Testing, OECD Guidelines for the Testing of Chemicals, OECD, Pariš, 1995, pp. 57-134. 21. C. C. Lee, S. Dar Lin, Handbook of Environmental Engineering Calculations, McGraw Hill, New York, 2000, pp. 1463-1737. 22. N. S. Battersby, Chemosphere 1990, 21, 1243-1284. Žgajnar Gotvajn and Zagorc-Končan Treatment of Fermentation Waste Broth Acta Chim. Slov. 2005, 52, 131–137 137 Povzetek Namen našega dela je bil preučiti možnost biološkega čiščenja fermentacijske odpadne brozge in ugotoviti smiselnost uporabe Fentonovega oksidacijskega procesa kot ene izmed možnosti (pred)čiščenja te močno obremenjene brozge. Odpadno farmacevtsko brozgo smo najprej želeli čistiti v biološki čistilni napravi, saj je bila kljub visoki obremenitvi z organskim onesnaženjem (KPK = 124.500 mg·L–1), dobro biološko razgradljiva. V izbirnem testu za določanje lahke biorazgradljivosti se je znatno razredčena odpadna brozga razgradila 65%, obenem pa tudi ni bila znatno strupena niti na mikroorganizme aktivnega blata niti ne na luminiscenčne bakterije Vibrio fischeri. Simulacija biološkega čiščenja odpadne fermentacijske brozge v pilotni biološki čistilni napravi je bila uspešna le pri nizkih obremenitvah reaktorja z odpadno brozgo (0,01 vol%, 76% čiščenje glede na DOC), medtem ko se je pri višjih obremenitvah sistem porušil zaradi izplavljanja napihnjenega aktivnega blata. Zato smo surovo odpadno brozgo obdelali po Fentonovem postopku v šaržnem reaktorju. Postopek smo optimirali z različnimi koncentracijami Fe2+ soli, vodikovega peroksida, pri različnih temperaturah (40 in 45 °C) ter zadrževalnih časih (do 30 min). Dosegli smo 44% učinek čiščenja glede na KPK, obenem pa se je povečala lahka biorazgradljivost tako obdelane fermentacijske brozge. Fentonova oksidacija preiskovane brozge se je izkazala kot dovolj učinkovita metoda (pred)čiščenja, zato smo nadaljnje raziskave usmerili v študij sposobnosti biološkega čiščenja tako obdelane fermentacijske brozge. Žgajnar Gotvajn and Zagorc-Končan Treatment of Fermentation Waste Broth