Combinação de processos físico-químicos para o tratamento de efluente da indústria de bebidas com obtenção de água de reúso

Abstract

The search for new sources of drinking water has been growing. Seeking to optimize the treatment and reuse of liquids from unusual sources, such as effluents, a line of research known as zero discharge (DLZ) has emerged. The most difficult techniques to achieve DLZ are through thermal concentration and crystallization processes, processes that are efficient for recovering water for use, but require large amounts of energy, increase costs and even make DLZ unfeasible. Due to the high energy demand, the use of the membrane separation process (MSP) has been gaining ground, as well as the integration of these with appropriate pretreatment techniques. The beer industry is of great economic importance. The beer production process involves several steps and inputs that generate different characteristics to the product and, consequently, to the effluent, which may still contain chemicals used in the equipment cleaning process, such as sodium hydroxide. Due to the need to maintain the food safety of the product, the cleaning stage is essential, and on average, for each liter of beer produced, 3 to 10 liters of drinking water are used for the process. In this context, this work aims to study the treatment of brewery effluent for the recovery of water for reuse, seeking the DLZ. In this work, a mapping of the components contained in the effluent was carried out for the sequence of its treatment with different techniques. The techniques that comprised the scope of treatment were peroxy-electrocoagulation with aluminum electrodes followed by electrodialysis, processes used as pretreatment of the reverse osmosis membrane. The remaining concentrated effluent from the osmosis membrane was used in an evaporator to obtain the greatest possible water recovery, being eliminated and classified for appropriate disposal. The characterization of the raw effluent indicated that it has a high organic load, with more than 42 g O2/L of COD, as well as turbidity, reaching 7100 NTU, and total solids reaching 67 g/L. The use of electrocoagulation as pretreatment of the effluent showed effectiveness in the reduction of substances, highlighting that with the addition of 3 ml H2O2/L the process presents greater efficiency, obtaining a reduction of 32.96% of COD, compared to the reduction of 21.76% of electrocoagulation without peroxide. The electrocoagulation process increases the ionic concentration of the effluent, and the use of electrodialysis membranes proved effective in the removal of controlled compounds. The process was able to reduce the post-electrocoagulation conductivity by 90.55% with 60 minutes of operation, highlighting the removal of 98.79% of the chloride concentration and 93.22% of sodium. The osmosis membrane proved to be efficient in water recovery, being able to recover 50% of the volume of pretreated effluent supplied, presenting a 40.78% reduction in the initial permeate flow. The water recovered by the osmosis process meets the configurations pertinent to the current legislation on effluent treatment, being only above the aluminum concentration referred to GM/MS Nº 888:2021. The use of an evaporator proved to be efficient in increasing water recovery from the osmosis concentration stream, maintaining the high quality standards of the recovered water. With the proposed combination of methods, it was possible to recover 79.57% of the initial effluent volume as water for reuse, coming close, but not achieving the initial objective of obtaining DLZ. 4.19% of the effluent was not reused, and according to ABNT NBR 10004:2004, this elimination is classified as class IIA - noninert. The proposed process was able to treat the effluent with water recovery for use, minimizing the volume of waste that will have to be discarded into nature, reducing water consumption and positioning the brewing industry in the circular process of resources. [resumo fornecido pelo autor]