Alternative utilization of excess water in Cuban sugar mills

Abstract: The sugar cane industry is one of the most water demanding industries in the world. In spite of the fact that the sugar cane itself contains enough water to supply the entire sugar manufacturing process, supplementary water from other sources is added. As a result, the sugar cane industry consumes and generates water in excess. The generated wastewater contains high amounts of organic compounds, which would cause pollution if it were directly discharged into nature. The sugar mill Carlos Baliño is located in rural Cuba and is the only sugar mill in Cuba to produce organic sugar. Carlos Baliño often experiences stops in production as a result from lack of cane supply. The wastewater management system at this particular mill is out of work and not suitable for the generated excess water. The aim of the study presented in this report is to determine the quality and quantity of the excess water from Carlos Baliño and the possibility of reusing the excess water in the sugar manufacturing process as imbibition water and for irrigation. In order to use this excess water for irrigation, a wastewater management system have been suggested and an economic evaluation have been made. Three models have been constructed in order to find the mass flow of excess water, optimize the water used for imbibition and for irrigation by purification in a wastewater management system. Results showed that the optimum mass flow of imbibition water was 2.7 times the fiber amount and the mass flow of excess water, after adjusting the mass flow of imbibition water to its optimum, was 4 kg/s. It was concluded that a wastewater management system of a total area of 4 792 m2 and a retention time of 27 days would reduce the BOD5 concentration with 99%, which is sufficient for the given mass flow and the quality of the excess water. The increased irrigation requires investment in new equipment. The conclusion of the financial evaluation of the increased irrigation is that the investment is not economically profitable, since the new equipment is too expensive due to the economic situation in Cuba. For the implementation of the wastewater management system to be possible, some factors have to be further investigated. The proposal for future work therefore includes possible water storage for the purified water, further investigations of the financial aspects of the implementation and also the technical and financial aspects of leaching and equipment for decreasing the salinity in the excess water.