Biodegradability prediction

Abstract: In many cases, treatment of wastewaters requires a combination of processes that very often includes biological treatment. Wet oxidation (WO) in combination with biotreatment has been successfully used for the treatment of refractory wastes. Therefore, information about the biodegradability of wastewater solutes and particulates after wet oxidation is very important. The present work proposes a model that can describe the oxidation process via organic concentration characteristics such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), and immediately available BOD (IA BOD) and so can allow the prediction of biodegradability (i.e., BOD/COD ratio). The reaction mechanism includes the destruction of nonbiodegradable substances bytwo pathways: oxidation to carbon dioxide and water and oxidation to larger biodegradable compounds with their further degradation to smaller ones measured via IA BOD. The destruction of small biodegradable compounds to end products is also included in the model. The experiments were performed at different temperatures (170-200 degrees C) and partial oxygen pressures (0.5-1.5 MPa) in a batch stainless steel high-pressure autoclave. The model of concentrated thermomechanical pulp circulation water was selected for the experiments. The proposed model correlates with the experimental data well and it is compared with other WO models in the literature.

Abstract: With the pending implementation of REACH, both old and new chemicals will have to be registered and chemical safety reports will have to be compiled. Depending on the yearly tonnages produced or imported, (eco-) toxicological and chemical fate data of varying degrees of detail will have to be produced. It has been forecast that these new requirements will result in higher costs for registration and an increased need for animal testing. Some of this additional workload could be avoided by making use of in vitro or in silico prediction methods. At Eawag (Swiss Federal Institute of Aquatic Science and Technology) several research groups are working on the development and validation of quantitative structure-activity relationships (QSARs) and related methods to predict ecotoxicological and fate endpoints, such as reactivities in or partitioning between different environmental media, based on chemical structure or easily measurable physico-chemical properties. When developing such tools, special attention has to be paid to use only descriptors whose mechanistic significance for the modelled endpoint is well understood on a molecular level. In this article four examples of our work in the field of compound fate and effect predictions will be presented: i) the measurement of compound descriptors for use in linear-free-energy relationships to predict partition coefficients between environmental media; ii) the development of free-energy relationships for the prediction of indirect photolysis; iii) the evaluation of existing structure-biodegradability models to predict soil biodegradation half-lives; and iv) the application of mode-of-action-based test batteries to develop quantitative structure-activity relationships to classify chemicals according to their modes of toxic action.

Abstract: Biodegradation of organic compounds would reveal important information on the final fate of a chemical in the environment. However, establishing biodegradability and fate of a chemical is cumbersome. In this scenario, the use of multimedia models help in predicting the fate and half-life of any compound to establish biodegradability. The study commenced with collection of wastewater samples, after primary and secondary treatment, from a Common Effluent Treatment Plant (CETP) treating tannery wastewater. The samples were subjected to gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS analysis identified that polyphenolic compounds were detected after biological treatment. The identified compounds emanated from tanning, dyeing, and fatliquoring process of leather making. Estimation Program Interface (EPI) Suite BIOWIN 3 and BIOWIN 4 model prediction revealed that while the primary biodegradation time-frame ranged from days to weeks, the ultimate biodegradation took weeks in the case of all the detected compounds. This study established that BIOWIN model could be used as a screening tool to determine biodegradability of complex chemicals used in tanneries and help to design better treatment facility with enhanced efficiency for removal of polyphenolic compounds. This methodology can also be applied to other industrial wastewaters containing recalcitrant chemicals, and with the help of BIOWIN model, information on biodegradability of chemicals present in the wastewater can be obtained.

Abstract: Biodegradability is a key property in the development of safer fragrances. In this work we present a green methodology for its preliminary assessment. The structure of various fragrant molecules is characterized by computing a large set of topological indices. Those relevant to biodegradability are selected by means of a hybrid stepwise selection method to build a linear classifier. This model is compared with a more complex artificial neural network trained with the indices previously found. After validation, the models show promise for time and cost reduction in the development of new, safer fragrances. The methodology presented could easily be adapted to many quasi-big data problems in R&D environments.