Otimização do sistema de tratamento do efluente para remoção de chumbo por precipitação química: estudo de caso em uma indústria de baterias automotivas

Abstract

Water is the main resource for life and human activities maintenance. The United Nations (UN) establishes at its Sustainable Development Goal (SDG) 6, for the 2030 Agenda, the promotion of sustainable water management, increasing water-use efficiency. In lead-acid batteries industry, lead is the main raw material for manufacturing, being a risk for occupational contamination and environmental damage. Thus, aiming on the reduction of the contamination, water is used for equipment cleaning, floors and products, generating effluents that are sent to the Effluent Treatment Plant (ETP) for subsequent reuse. However, monitoring identified the presence of residual lead in the treated effluent stored in reuse tanks. Thus, this study aimed to optimize the treatment process at the ETP to improve lead removal efficiency. The methodology was based on Kaizen philosophy, combined with the PDCA cycle and the use of the 5G method and the Ishikawa diagram. Jar test prototyping revealed limitations such as an agitation speed restricted to 30 RPM, lack of standardization in flocculant preparation, and an inadequate operating pH of 6. To address these issues, an action plan was implemented: the addition of a rapid mixing stage at 200 RPM, standardization of flocculant dilution at a 1:100 ratio with increased dosage and adjustment of the operating pH to 8, favoring the formation of insoluble lead hydroxide in alkaline water. As a result, lead removal was effective, with no detectable presence of the metal in the reuse effluent from February to August of 2025.