Assessment of biological degradation of microcystin in laboratory conditions: the influence of temperature, light and media support

• Grant number: 16/04715-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2016
• End date: July 31, 2017
• Field of knowledge: Engineering - Sanitary Engineering - Water Supply and Wastewater Treatment
• Principal Investigator: Davi Gasparini Fernandes Cunha
• Grantee: Julia Sobottka Vendruscolo
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

The negative consequences of eutrophication in reservoirs have been increasing as human activities such as urbanization and agriculture are accelerating this phenomenon. The cyanobacteria, some of which are potentially toxic, can cause health problems in humans and animals, as well as other adverse effects to the aquatic ecosystems. In addition to the mitigation measures to reduce nutrient inputs to water bodies, the study of advanced techniques for drinking water treatment for removing cyanotoxins becomes a priority. The conventional methods for water treatment may be unable or inefficient to remove such toxins and ensure the compliance with the drinking water guidelines established by the Ministry of Health in Brazil. Some treatment processes such as chlorination, ozonation, filtration membranes and activated carbon have been evaluated for removing cyanotoxins, both intra and extracellular. However, these processes have some drawbacks, such as significant dependence of the raw water quality, the possible disruption of cyanobacterial cell, or even the generation of toxic byproducts. In this context, the biological degradation for removing cyanotoxins has shown great potential, although there are few studies on the subject, especially in Brazil. The objective of this project is to evaluate the removal of microcystin in laboratory scale through its biological degradation. Therefore, in addition to analysis of different bacterial inoculum, various conditions of light and temperature will be compared to assess the influence of these factors on the effectiveness of biodegradation. We will also compare the treatment with media support for biofilm growth (fixed bed) versus dispersed bacteria to verify whether the existence of the support for the microbial community enhances the removal of the target pollutant. This research will consist of three stages (A-selection of the most efficient inoculum; B- evaluation of light and temperature factors; C- evaluation of support media). The experiments for microcystin removal will be performed from an initial concentration of 20 µg/L or 100 µg/L of the cyanotoxin, which are often observed in more or less extensive blooms of toxic cyanobacteria. Throughout the tests, the concentrations of microcystin will be monitored (measured by the enzyme-linked immunosorbent assay - ELISA) before and after the exposure to the inoculum, as well as dissolved oxygen, total organic carbon and total suspended solids. Throughout the project, further microbiological analysis might be added to identify (at least preliminarily) the microorganisms involved in the biodegradation. It is expected that the results obtained by the research will aid in the application of such advanced treatment technique in actual full-scale water treatment plants. The schedule includes, among other activities, participation in scientific events and the possible submission of a scientific paper for a Brazilian journal, which will contribute to the formation of the candidate, who is an undergraduate student in Environmental Engineering at EESC/USP.