TREATMENT OF WATER WASHING OF SUGAR CANE BY COAGULATION, FLOCCULATION AND SEDIMENTATION

Abstract

The manufacturing of sugar and alcohol consume and generate significant volumes of wastewater, being the largest share to the washing of sugar cane, which aims to withdraw earthenware nad straw that accumulate along the cane during the harvest. The water wash of sugar cane (WWSC) is usually recirculated and over time loses quality, requiring large volumes of replacement. Currently, the treatments applied to the WWSC to recycle is the correction of pH and natural sedimentation, without the aid of chemical coagulants, which has low efficiency and high retention time, thus the process of chemically assisted primary sedimentation (CAPS) can be an alternative for the treatment of the WWSC in recycle. The aim of this study was to promote improvement in the quality of the WWSC in a production unit of sugar and alcohol. A sample of WWSC was collected at the plant and transported to the laboratory where tests were performed in static reactors (jar-test) with commercial coagulants, ferric chloride and ferrous sulfate chloride (floculan) for the optimization of the stages of coagulation, flocculation and sedimentation. During the period of the survey was carried out monitoring of WWSC in operation of the plant with the objective of characterization and evaluation of the efficiency of the system in full scale operation. A mass balance was used to estimate the amount of generated sludge. The results of treatment of WWSC showed that the coagulant floculan was presented the best efficiency in removing turbidity and total suspended solids with 99% and 97% respectively. The suppression of the flocculation step did not change in removal efficiency of turbidity and suspended solids. Not using flocculation resulted in increased turbidity values. The economic study for different alternatives of treatment application showed the application feasibility of coagulant intermittently. Considering the system in full scale operation, it could be predicted a reduction in costs with the use of coagulant and sludge production rates due to the effect of the gradual increase in the quality of the WWSC.

Key Words: primary sedimentation; recycle; sugar cane; water washing of cane.