Fate and effect of xenobiotics on biodegradation processes: basis for respirometric appraisal

Abstract

The paper mainly focused on illustrating the merit of respirometric analysis in assessing the inhibitory/toxic impact of xenobiotics on substrate biodegradation. It also evaluated biodegradation characteristics of these chemicals at continuous exposure through acclimation ofthe microbial culture. The nature and role ofoxygen uptake rate (OUR) profiles were discussed in conjunction with appropriate modelling, which should incorporate dissolved oxygen as an indispensable component for respirometric evaluation. Emphasis was placed upon differentiating acute effects from chronic impact, which may be totally different as it involves biodegradation of the chemical due biomass acclimation. Three case studies, each involving OUR measurements and process modelling, were presented for this purpose. The first one related to the inhibitory action of pharmaceutical effluent when mixed with plain-settled tannery wastewater. The second investigated the fate of H-acid, a commercially important naphthalene sulfonate, which exerted no adverse effect on substrate biodegradation, while remaining intact before and after a long acclimation period. The third one involved 2,6-dihydroxybenzoic acid, a naturally occurring organic compound in olive oil wastewater, which became biodegradable after acclimation by the development ofa specific microbial biomass fraction, while it heavily inhibited substrate biodegradation at first exposure. Model evaluation of the experimental data could provide related information on process stoichiometry and kinetics in all studies.

Modeling acute impact of sulfamethoxazole on the utilization of simple and complex substrates by fast growing microbial culture

“…The OUR level exhibited an initial peak value, due to the utilization of the readily biodegradable COD fraction; this level was 80 mgO 2 L ‐1 h ‐1 for the control reactor and it was slightly reduced to around 60 mgO 2 L ‐1 h ‐1 with SMX dosing. It should be noted that the observed effect should not be interpreted at first as an inhibitory effect as the initial OUR peak directly relates to and becomes primarily affected by the selected F/M ( S 0 / X H ) ratio . After the initial peak, shapes of all OUR profiles include two distinctly different slopes related to slowly biodegradable (hydrolysable) components in the peptone mixture.…”

Particle size distribution analysis of chemically enhanced two‐phase membrane filtration for olive mill effluents

“…It is interesting to note that environmental scientists are also deeply attracted to the olive oil industry, mainly because it generates one of the most complex and problematic wastewaters associated with industrial activities. In fact, olive mill effluent is quite strong with a chemical oxygen demand (COD) concentration usually exceeding 100 g L −1 ; it contains high levels of recalcitrant compounds responsible for its characteristic dark color, and also a significant part of its COD content is composed of fatty acids and phenolic compounds exerting toxic effects on microorganisms …”

Pentachlorophenol aerobic removal in a sequential reactor: start-up procedure and kinetic study

“…The VSS concentration was also monitored but at longer time intervals (hours) due to its very low variation with respect to the typical concentrations utilized in the bioreactor. The OUR was continuously monitored during I 1a 10 2980 I 1b 10 2820 II 2a 15 2540 II 2b 15 2460 III 3a 20 2720 III 3b 20 2250 the reaction phase to evaluate the PCP-specific biodegradation rate, as suggested by Orhon and Sozen [17] and Lepik and Tenno. [18] In order to verify data reproducibility, the biodegradation tests were performed in duplicates under the same operating conditions.…”