Biodegradability of the Anti-tumour Agents 5-Fluorouracil,Cytarabine, and Gemcitabine: Impact of the Chemical Structure and Synergistic Toxicity with Hospital Effluent

Most anti-tumour agents are known to be carcinogenic, mutagenic, teratogenic, embryotoxic or fetotoxic. Only little is known about the environmental impact of pharmaceuticals. Unmetabolized active substances are excreted and will show up in municipal wastewater. Therefore, we examined the biodegradability of the widely used anti-tumour agent 5-fluorouracil (5-FU), also as an example for assessing the impact of hospital effluent on the biodegradation of a test compound. The biodegradability of the structurally similar anti-tumour agents cytarabine and gemcitabine was also examined. Test systems used were the closed bottle test (OECD 301 D) and the modified Zahn-Wellens test (OECD 302 B). 5-FU was not biodegradable in the closed bottle test (CBT) nor in the Zahn-Wellens test (ZWT). At the highest concentration of 5-FU, with hospital effluent an inhibition of the degradation of substances present in hospital effluent was observed, probably as a result of a synergistic effect by 5-FU with antibiotics present in hospital sewage. Gemcitabine was biodegraded 42% in the CBT. The prolongation of the test period to 40 days only improved the result to 45%. In the ZWT, the biodegradation of gemcitabine was 50%. Cytarabine was partially biodegraded in the CBT (50%), but only after an adaptation period of 20 days. After a test prolongation to 40 days, the degree of biodegradation was 80%. In the ZWT, the biodegradability was > 95% after only a few days.     

Oil refinery wastewater treatment using coupled electrocoagulation and fixed film biological processes

Oil refinery wastewater was treated using a coupled treatment process including electrocoagulation (EC) and a fixed film aerobic bioreactor. Different variables were tested to identify the best conditions using this procedure. After EC, the effluent was treated in an aerobic biofilter. EC was capable to remove over 88% of the overall chemical oxygen demand (COD) in the wastewater under the best working conditions (6.5 V, 0.1 M NaCl, 4 electrodes without initial pH adjustment) with total petroleum hydrocarbon (TPH) removal slightly higher than 80%. Aluminum release from the electrodes to the wastewater was found an important factor for the EC efficiency and closely related with several operational factors. Application of EC allowed to increase the biodegradability of the sample from 0.015, rated as non-biodegradable, up to 0.5 widely considered as biodegradable. The effluent was further treated using an aerobic biofilter inoculated with a bacterial consortium including gram positive and gram negative strains and tested for COD and TPH removal from the EC treated effluent during 30 days. Cell count showed the typical bacteria growth starting at day three and increasing up to a maximum after eight days. After day eight, cell growth showed a plateau which agreed with the highest decrease on contaminant concentration. Final TPHs concentration was found about 600 mgL⁻¹ after 30 days whereas COD concentration after biological treatment was as low as 933 mgL⁻¹. The coupled EC-aerobic biofilter was capable to remove up to 98% of the total TPH amount and over 95% of the COD load in the oil refinery wastewater.     

Biodegradability of dispersed crude oil at two different temperatures

Laboratory experiments were initiated to study the biodegradability of oil after dispersants were applied. Two experiments were conducted, one at 20 degrees C and the other at 5 degrees C. In both experiments, only the dispersed oil fraction was investigated. Each experiment required treatment flasks containing 3.5% artificial seawater and crude oil previously dispersed by either Corexit 9500 or JD2000 at a dispersant-to-oil ratio of 1:25. Two different concentrations of dispersed oil were prepared, the dispersed oil then transferred to shake flasks, which were inoculated with a bacterial culture and shaken on a rotary shaker at 200 rpm for several weeks. Periodically, triplicate flasks were removed and sacrificed to determine the residual oil concentration remaining at that time. Oil compositional analysis was performed by gas chromatography/mass spectrometry (GC/MS) to quantify the biodegradability. Dispersed oil biodegraded rapidly at 20 degrees C and less rapidly at 5 degrees C, in line with the hypothesis that the ultimate fate of dispersed oil in the sea is rapid loss by biodegradation.     

Biodegradability of Photographic Developers and Ingredients of Photographic Developers,especially of Hydroquinone and Isoascorbic Acid

The biodegradability of 5 different commercially available common photographic developers and their ingredients hydroquinone, isoascorbic acid, and its sodium salt was determined in parallel using the OECD-screening-test (OECD 301E). The results obtained from the degradation test on hydroquinone were compared with the results of other laboratories. Biodegradability of developers containing isoascorbic acid was in the same range as of comparable products containing hydroquinone.     

Biodegradability Assessment and Treatability of High Strength Complex Industrial Park Wastewater

Industrial park wastewater (IPWW) includes complex non‐biodegradable organic compounds. A wastewater treatability study using biodegradability assessment approach was carried out for an industrial park housing mainly textile and machinery sectors. Biodegradable and inert chemical oxygen demand (COD) fractions with soluble and particulate counterparts were experimentally estimated by implementing respirometric methods. Aerobic batch test methods and oxygen uptake rate profiles were used to map kinetic parameters and COD fractions. Denitrification potential was also determined by application of anoxic batch tests. Relevant kinetic constants, stoichiometric, and design parameters were determined for biological processes. Tests were carried out for raw and physico‐chemically pre‐treated IPWW. Hence, it was aimed to assess the effects and necessity of pre‐treatment on biological processes. Biological mineralization, nitrification, and denitrification processes were also designed and tested using a bench scale continuous treatment model for pre‐treated IPWW. The sum of initial inert soluble COD fraction and production of soluble microbial products decreased about 25% for the case of pre‐treated IPWW as compared to raw IPWW. Eighty‐three percent total COD and 89% total Kjeldahl nitrogen removal efficiencies were attained for the modeling experiments of pre‐treated IPWW. Results showed the significance of pre‐treatment if complex strength industrial wastewaters are to be biologically treated.     

Investigations on the Biodegradability of Chlorinated Fulvic Acids Untersuchungen zur mikrobiellen Verwertbarkeit gechlorter Fulvinsäuren

Microbial biodegradation of organic substances takes place during drinking water treatment, but also in the distribution net, if the drinking water still contains biodegradable organic substances. This phenomenon is called regrowth. The regrowth potential of a drinking water is high, when for instance ozonation is used as the last step of treatment. It was proved before, that ozonation increases the biodegradability of humic substances, which are the main fraction of organic carbon in drinking water. In this work the objective was to check, if chlorination has a similar effect on humic substances. Using the method developed by Werner of measuring the regrowth potential of a water it could be shown by dilution series with chlorinated and unchlorinated humic substances that the substrate quality of these organics is increased by chlorination. The better substrate quality is seen in the chlorinated solutions, which might contain also low molecular weight organic compounds, but also in the fulvic acid fraction after XAD-enrichment, which removes most of the low molecular weight organic compounds. The chlorination creates in the fulvic acid solutions a shift of molecular size to smaller molecules and higher polar substances, which might be the reasons for the better biodegradability. From these results it can be concluded, that chlorination produces substances, which are more easily biodegradable. But this will not produce regrowth problems as long as there is free chlorine present as a disinfectant. In contrast, when the chlorine demand is very high and no free chlorine is left, this might produce high colony counts in the distribution net.