Navigating the mist surrounding water usage in sugar factories

Most water entering a sugar factory in the Mackay district is present in sugarcane, with raw water supply contributing about 20% of the total. Consequently, changes in CCS levels and in crush rates have a major impact on both raw water consumption and effluent production rates. High rates of raw water consumption invariably lead to increased wastewater flows to the effluent treatment plant and to increased treated effluent flows to the environment. The water usage during factory stoppages and the measures required to reduce raw water usage are discussed. These measures are affected by the specific factory design including the ability to recover and re-use water, tank holding capacities and operator knowledge regarding the nature of the stoppage and steps to be undertaken. Knowledge of factory layouts of how water is distributed and recovered as well as compliance with operational procedures are key to reducing water usage in sugar factories. Site-specific training of production personnel is essential to improve factory performance regarding water management. The annual consumption of raw water in a sugar factory and the quality and quantity of treated effluent are subject to strict government licence conditions. Consequently, to be compliant, the daily raw water consumption volume, the flow rate of wastewater to the effluent treatment plant and the flow rates of effluent discharge to the environment are key performance indicators (KPIs). This paper reviews discussions from a workshop on water management undertaken by the Mackay Institute of Sugar Technologists (MIST) for the Mackay district mills.