Caracterização das águas de lavagem provenientes da etapa de purificação da produção de biodiesel de óleo de tilápia

Abstract

Biodiesel is a fuel derived from renewable energy and considered environmentally friendly for being clean-burning. It means that it does not release into the atmosphere gases that contribute to the increasing of greenhouse effect. It is in fact, an option to replace petroleum fuels. The raw materials used to produce biodiesel may be either of vegetable or animal origins. Facing the dilemma of using vegetable raw materials for other purposes, such as food, the raw materials derived from animal fats, such as the oil extracted from fish viscera, appears as an interesting source of research for the use in biodiesel production. In the state of Ceará, the Castanhão dam has one of the largest farming areas of tilapia, a fish species that resists even in very polluted waters and therefore, is reproduced easily serving as food mainly in inner towns. Parallel to such advantage, there is the disadvantage of the fish viscera disposal. It is a fraction that has no use in soils and surface waters, causing serious environmental problems. Aiming to minimize the aforementioned problem, the association of the Castanhão dam fish farmers, in partnership with the Center for Industrial Technology Foundation of Ceará (NUTEC) started a research on the utilization of such visceral material in the biodiesel production. The research was carried out at the NUTEC and the production of biodiesel from viscera of tilapia has shown to have viability. However, during the process of biodiesel production, effluents are generated from high pollution loads due to the reagents used and the very composition of the raw material. Such effluents, called washing water originate from the step of purification of the biodiesel, the aqueous washing. The biodiesel obtained by a chemical reaction of transesterification, ie, fat (oil extracted from the viscera of tilapia), was transformed into an ester (biodiesel) in the presence of an alcohol (methanol) and a catalyst (sodium hydroxide). Then, the washing water from this step was characterized by physical-chemical analysis of parameters: pH, total ammonia, oxygen chemical demand (OCD), total phosphorus and methanol content, following the procedures in (APHA , 1998 and 2005) and (European Standard EN-14110/2001 - VARIAN). Comparing the results with the standards for effluent discharge of CONAMA Resolution nº 430, March 22nd, 2011, it was observed that the concentrations of the analyzed parameters were not in accordance with the aforementioned Federal Environmental Legislation. Therefore, we concluded that the washing water from the purification step of biodiesel is an effluent that cannot be rejected before an appropriate treatment to be fit in the established standards.