Caracterização mineralógica, morfológica e físico-química de lodo de estação de tratamento de água de indústria de alimentos

Abstract

The vast majority of industrial sectors require a significant amount of water. The food and beverage industries are among the sectors with the greatest need of water to carry out their production processes. The water used in these processes must be adequate to the quality standards required by the legislation. To guarantee the water quality, physicochemical treatments are carried out at Water Treatment Stations (ETA). The objective of this study was to perform the mineralogical, morphological and physicochemical characterization of ETA centrifuged sludge from a food industry located in the city of Dois Vizinhos - Paraná. This ETA uses conventional treatment processes, i.e., the water passes through the steps of flocculation, where aluminum polychloride (PAC) is used as flocculating agent, coagulation, decantation and filtration. Chlorine gas is also used for disinfection and, when necessary, sodium carbonate for pH correction. The sludge goes through centrifugal processes focused on volume reduction, where the sludge is dehydrated and left for disposal. In this work, in order to identify the mineral compounds present in the sludge, X-ray diffraction (XRD) analysis was performed, the morphological characterization was performed through the Scanning Electron Microscopy (SEM) ,while the physicochemical characteristics were performed through the analyzes of Zero Load Point (pHPCZ), Chemical Oxygen Demand (COD), Fourier Transform Infrared Spectrometry (FITR), and Atomic Absorption Spectrometry (AAS). In the literature, it is possible to identify several forms of reuse for ETA sludge, mentioning the use in ceramic industry, civil construction, as adsorbent of heavy metals, for correction and fertilization of the soil and for waterproofing of the soil. The characteristics found in this study were compared with data from the literature, being possible to identify the possible forms of reuse for the sludge. As results it was possible to identify that Quartz, Calcite and Hematite were the main found mineral compounds, and that the average size of crystalline is 10.40 nm. The surface of the sludge has acidic characteristics, with pHPCZ of approximately 4 and a COD of 6150 mgO2/L. As for the morphology, it was possible to identify that the sludge consists of granules with irregular shapes and sizes, large particle distribution and irregular surface topography. The functional groups found were hydroxyl (-OH), carboxyl (C = O), aliphatic amines (C - N), esters, ethers, alcohols and carboxylic acid represented by the C - O group, validating the presence of the mineral Calcite found in the XRD analysis. Comparing the obtained results with literature, it was possible to observe the potential of application of this ETA sludge in the ceramics industry, civil construction and adsorbent of heavy metals.