Uso de coagulantes e floculantes naturais no tratamento de efluentes de lavanderia hospitalar

Abstract

The importance of water for humans and species is undeniable. Her scarcity coupled with the depletion of her sources has been a cause for serious concern. On the other hand, anthropic action has caused pollution of water resources and contributed to an imminent water crisis. Hereupon, hospitals and their laundries are major consumers of water, generating an exorbitant volume of effluents of low biodegradability and high recalcitrance. In this light, scientific literature warns that hospital laundry effluents are among the most harmful when compared to other sectors. Treatment at source is a solution that avoids dumping this category of effluents directly into public sewers and fountains. However, the legislation of Brazil, Europe and the World Health Organization (WHO), in general, does not require the treatment of these discharges before launch. Oftentimes, several pollutants present in them cannot be removed in municipal sewage stations, which can cause serious damage to public and environmental health. Coagulation and flocculation are emerging as a viable alternative for the treatment of effluents. However, coagulants and flocculants based on traditional compounds such as aluminum and iron can cause secondary pollution. In this perspective, the present study used composites extracted from natural sources to promote coagulation, flocculation and sedimentation (C/F/S) and to clarify the laundry effluents of the largest hospital in the State of Tocantins, Brazil. To complete this study, samples of effluents from the study area were collected and characterized and submitted to C/F/S with a Jartest, on a bench scale. The control parameters, turbidity and apparent color, were measured to evaluate the efficiency of the clarification. The findings showed that hydroxyapatite combined with chitosan is the most suitable coagulant/flocculant. At pH 8 and dosage of 50 mg/L, such a combination reduced turbidity and apparent color by more than 62 and 49%, respectively. A surprising benefit of the treatment was at pH 6, when for this dosage the turbidity and the apparent color were reduced by more than 67 and 55%, respectively. At the same time, only at pH 6, a chitosan gel was tested, which revealed the optimal dosage of 60 mg/L, removal of almost 40% for both parameters. A comparison with traditional compounds showed that natural compounds are eight times more efficient. The materials used in this study are inexpensive and obtained from sources widely available in most countries. Besides, it is possible to obtain it from food residues, which allows the integration of treatment chains promoting the development of a circular economy.