Tratamento de águas residuais em uma indústria de envase de refrigerante e água mineral utilizando sulfato de alumínio com sistema de homogeneização adaptado

Abstract

It is well known that with the increased consumption of beverages such as soft drinks, juices, among others, there is an increase in the production of effluents. The lack of treatment of these effluents generates major environmental, social and economic impacts. The effluents generated by soft drinks, predominantly made up of sugars, juices, colorants, extracts and organic acids, have a high organic load, which increases the values of biological oxygen demand (BOD) and chemical oxygen demand (COD), which are potential polluters of receiving bodies such as rivers and lakes. The aim of this work was to improve the conditions of effluents treated by acti-vated sludge, aligning biological and physical-chemical treatment, in a soft drink and mineral water industry, using aluminium sulphate (Al2(SO4)3) as a coagulant and a system adapted for homogenization and pH correction. In wastewater treatment plants (WWTPs) that only use activated sludge as a form of treatment, (Al2(SO4)3) can be an ally in improving the conditions of effluent that has already undergone activated sludge treatment. However, the use of aluminium sulphate requires a homogenization system to mix it with the effluent and to correct the pH. The methodology of this work is based on using this coagulant to improve the final effluent, adapting a recirculation system that homogenizes the inorganic coagu-lant with sodium hydroxide to correct the pH. The system works by sucking the effluent from the bottom of the decanter and discharging it over itself, ensuring a complete mixture between the coagulant, the sodium hydroxide and the effluent. Laboratory tests were carried out to determine the correct concentration of the coagulant, using turbidity and COD analyses. The BOD5 analysis, which is the analysis of BOD over a period of five days, was only carried out at the time of the field test, taking a sample before and after the coagulation process in the decanter tank. The results obtained using 10mL of coagulant (20g/L) for each liter of effluent showed a good reduction in the COD turbidity of the effluent already treated by activated sludge. With the addition of the coagulant to the samples, followed by correction of the pH to 7, there was a reduction in turbidity from 362 turbidity units (UT) to 41UT. In the COD analysis, there was a reduction from 326mg/L ofdissolved O2 to 81mg/L. There was also a significant reduction in the results of the BOD analysis of the effluent treated in the decanter itself, from 354.6mg/L ofO2 to 183.6mg/L. These results showed that both the addition of the coagulant and the adapted homogenization system were effective in reducing the parameters analyzed (turbidity, COD and BOD). The volume of sludge decanted by coagulation in 10 minutes also proved to be very low and this results in faster disposal, making the whole process more agile and ruling out the need to use a flocculant.