Nevenka Adler

Recent developments in the coupling of photoassisted and aerobic biological processes for the treatment of biorecalcitrant compounds

A general strategy to develop combined photochemical and biological system for biorecalcitrant wastewater treatment is proposed. For the development of this strategy, the following points were taken into account: the biodegradability of initial solutions, the operation mode of the coupled reactor, the chemical and biological characteristics of the phototreated solutions, the evaluation of different photoassisted advanced oxidation processes, the optimal conditions of both photochemical and biological processes, and the efficiency of the coupled reactor. The strategy to couple photochemical and biological processes is illustrated by case studies of four different biorecalcitrant pollutants. Three kinds of combined systems were developed using either photo-Fenton, Fe3+/UV, or TiO2 supported on glass rings for the photocatalytic pretreatment and in all cases immobilized biomass for the biological step. The advantages of the each coupled system are discussed and beneficial effects of such two-step treatments were found. However this strategy is not a universal solution. Chemical, biological, and kinetic studies must be always carried out to ensure that the photochemical pretreatment increase the biocompatibility of the treated wastewater. Some field experiments using solar reactor indicated that a coupled photochemical–biological treatment system at pilot scale is a possible way to achieve the complete mineralization of the biorecalcitrant pollutants.

Electrochemical detoxification of a 1,4-benzoquinone solution in wastewater treatment

The electro-oxidn. of 1,4-benzoquinone in water soln. was investigated. The benzoquinone concn., intermediate products, dissolved org. C (DOC), COD, and toxicity of the oxidized soln. was monitored during oxidn. with Ti/IrO2 and Ti/SnO2 anodes (in the following text: IrO2 and SnO2 anodes). It was found that the most important parameter is the nature of the anode. With the IrO2 anode, primary oxidn. was attained, i.e. benzene ring rupture occurred, resulting in an accumulation of carboxylic acids formation as final non-toxic products. With the SnO2 anode, carboxylic acids are formed in a much faster reaction and then oxidized, giving only CO2 as the final product. Detoxification of benzoquinone soln. using both electrodes was detd. in the course of the reaction by the Microtox test, activated sludge respirometric test, and were also predicted using a developed formula. Calcd. av. toxicity, knowing the chem. compn. of the oxidized soln., DOC, and individual EC50 of the components were in agreement with obsd. values. The biodegradability of compds. in the soln. at the end of electrolysis with the IrO2 anode was demonstrated. [on SciFinder (R)]

Volumetric oxygen mass transfer coefficient in an upflow cocurrent packed-bed bioreactor

Reference LBE-ARTICLE-1998-005doi:10.1016/S0009-2509(98)00003-7View record in Web of Science Record created on 2005-03-02, modified on 2016-09-29

A procedure for production of adapted bacteria to degrade chlorinated aromatics

Production of biomass adapted to the degradation of a mixture of chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) was investigated in a batch culture with substrates supplied by pulses. CB and o-DCB concentrations which gave the best adapted biomass productivity were determined and found to be 150 and 30 microl l(-1), respectively. The biomass productivity was 51 mg l(-1) h(-1). The biomass yield was 0.38 g of biomass dry weight per gram of substrate. The pulses of 200 microl CB and 40 microl o-DCB, were inhibitory to the bacterial culture. Among the metabolites, muconic acid was found in large quantities in the medium and in the cells. At a time between two pulses of 60 min, adding 150 microl CB and 30 microl o-DCB per each pulse, 7.6g l(-1) of biomass was obtained. The produced biomass served as an inoculum for the biotrickling filter which treated industrial waste gases contaminated by CBs. The method of adapted biomass production was described using CBs, but the degradation of any other toxic volatile pollutant can be improved using this technique.

Biomass growth monitoring using pressure drop in a cocurrent biofilter

The possibility of following the biomass growth by pressure drop measurement was investigated in an aerated cocurrent upflow fixed-bed bioreactor continuously fed with wastewater containing industrial organic pollutants. The experiments were carried out in a biological filtration oxygenated reactor (Biofor) pilot plant packed with expanded clay balls (Biolite) of 2.7-mm diameter, which served as biomass carriers. The column was equipped for on-line pressure drop measurements. Correlation between pressure drop measurements and Reynolds numbers of air and water were determined in experiments carried out without biomass. Under operating conditions with biomass, it was demonstrated that column clogging and the operating time between washing cycles can be predicted depending on the volumetric organic load for a given total organic carbon inlet concentration. The biological activity of the fixed biomass was estimated from the oxygen consumption rate per unit time and carrier area. The oxygen consumption rate measurements demonstrated that the biological activity depends on the inlet substrate concentration, and that the Biofor column was most efficient between 75 and 100 g m-3 of total organic carbon inlet concentration. In the course of the wastewater treatment, using pressure drop measurements, the equivalent diameter of the Biolite particles, the reduced column macroporosity, and the biofilm thickness were calculated. An expression correlating biofilm density and biofilm thickness, as determined from the pressure drop measurements, was proposed. Good agreement was found between the fixed biomass in the reactor, determined as volatile suspended solids, and the biologically active biomass, estimated by respirometry. Copyright 1998 John Wiley & Sons, Inc.

Aerobic and anaerobic biodegradability of 1-Anthraquinone sulphonate

Abstract The present work investigates 1-anthraquinone sulphonate (1-AS) biodegradation under (i) aerobic conditions using domestic activated sludge as inoculum, (ii) anaerobic conditions using sludge from an anaerobic domestic wastewater treatment digestor in a sulphate-containing or methanogenic environment, (iii) a combination of anaerobic followed by aerobic conditions. The process was evaluated in terms of primary degradation, i.e. 1-AS elimination and ultimate degradation, as total dissolved organic carbon removal. It was shown that aerobic conditions lead to the complete primary and ultimate degradation, of 1-AS. By contrast, neither under sulphato-reductive nor methanogenic conditions does anaerobic digestion lead to the significant degradation of 1-AS. The use of anaerobic treatment followed by aerobic treatment did not improve degradation. Indeed aerobic post-treatment resulted in the re-appearance of pollutant in the medium even though this had been partly degraded under anaerobic conditions.

Inoculum standardization for biodegradability tests

To obtain standardized inoculum with constant characteristics for biodegradability test, Actizym powder was used instead of sludge. A predigestion and stabilization step were introduced to prepare “activated Actizym”, before inoculation and addition of test chemical. The inoculum obtained is similar to activated sludge in its microbiological and physical aspects. The reproducibility of the method was prooved and several controls were made using chemicals with different biodegradation rates.

Wastewater treatment with biofilms: Estimation of biokinetic parameters using a segmented column

Reference LBE-ARTICLE-1998-013View record in Web of Science Record created on 2005-03-02, modified on 2016-10-02

Dynamic liquid holdup and oxygen mass transfer in a cocurrent upflow bioreactor with small packing at low Reynolds numbers

Abstract An experimental investigation of dynamic liquid holdup and oxygen absorption mass transfer was carried out in a laboratory bioreactor packed with expanded clay balls. The column was operated with a cocurrent upflow of air and water at low Reynolds numbers. The data obtained for dynamic liquid holdup have been represented by a modified Stiegel-Shah relation with a relative mean error of 0.7%. For prediction of the oxygen mass transfer coefficient, an empirical correlation based on air and water mass superficial velocities has been proposed. It reproduced our experimental results with a relative mean error of 9%. Both correlations proposed in this study are valid for small packing spheres around 2.7 mm in diameter and Reynolds numbers varying for gas and liquid from 0.197 to 0.593 and from 3.875 to 9.315 respectively.

Degradation of sodium anthraquinone sulphonate by free and immobilized bacterial cultures

Aerobic biodegradation of a xenobiotic recalcitrant compound sodium anthraquinone-2-sulphonate (SAS), was investigated using as an inoculum a mixed microbial culture, which was activated sludge from industrial and domestic waste-water treatment plants. The difference in SAS degradation was examined using two main systems: (1) suspended cells and (2) immobilized cells, both in batch and in continuous culture. In the suspended cell system, under continuous culture conditions using SAS as a unique source of carbon and energy, it was possible to degrade about 95% of this substrate after 6 days. Maximal SAS removal rates in the suspended-cell system were 593 mg SAS l−1 h−1 and 88.7 mg SAS l−1 h−1 for dilution rates (D) of 0.05 h−1 and 0.075 h−1, respectively. In the immobilized-cell system, almost all SAS was degraded in 6 days and the maximal removal rate reached 88.7 mg SAS l−1 h−1 at D=0.05 h−1. Application of a continuous-flow enrichment procedure resulted in selection of several kinds of micro-organisms and led to a progressive elimination of some species of Aeromonas. A stable microbial community of 11 strains has been established and characterized at D=0.075 h−1. Most of them were Gram-negative and belonged to the genus Pseudomonas.