SUCCESSFUL WATER REUSE - THE FIRST STEP TOWARD ZLD

摘要

After years of record-breaking droughts many aquifers around the World are drying up. Climate change is making it increasingly difficult to support the World's growing population. If water means life then water scarcity represents a significant challenge to growth for industry. A Canadian-based food processor is rising to the challenge of water scarcity at one of its production facilities in Gujarat, India. Until 2013 the facility was able to draw all the water it needed from a well. However, droughts have reduced groundwater resources and the demand for the facility's products has grown. The food processor approached Amec Foster Wheeler to help them with a major expansion. Since additional withdrawals from the aquifer were not permitted, a new Water Reclamation Plant was needed. Water reuse at a food processing facility is rare; however, it has been done before. In this case, the bigger challenge was to satisfy the facility's expanded requirements for process water with limited groundwater resources. Water recovery rates needed to be as high as possible: higher than what had ever been achieved before. As well, production would depend on the new Wastewater Reclamation Plant so the equipment had to be very reliable. Industrial Wastewater Treatment Plants are often difficult to operate and control. Food processing wastewater is typically concentrated and flows are variable. Strong cleaners and swings in pH often lead to biological treatment upset conditions causing extreme foaming, sludge bulking, or conditions toxic for microbiology. However, treatment upsets could not impact the quality or quantity of process water available for production in the future. To achieve these goals the facility's water balance was redesigned around a new high recovery water reuse system with a focus on reliability. The system was based on Ultrafiltration membranes (UF), Granulated Activated Carbon (GAC) and Reverse Osmosis membranes (RO). Since start-up in early 2013 the new Water Reclamation Plant has met all of production's requirements. Water quality has been excellent and performance has been reliable. However, in 2014 the facility's production targets grew again requiring more even process water. As well, the facility requested a permanent, sustainable solution for brine disposal. A Scavenger Reverse Osmosis system was designed to boost water recovery rates and minimize brine disposal requirements. A Multiple Effect Evaporator/ Crystallizer system was then designed to treat the remaining concentrated brine solution and meet the site's needs for Zero Liquid Discharge. The Scavenger RO concentrated the Primary RO Reject to the limits of salt saturation and minimized the amount of waste brine that needed to be evaporated. This reduced the size and cost of the evaporators. As well, by evaporating the RO Reject to a vapour, the facility could recover the condensate for reuse and maximize water recovery rates. The new Scavenger RO and ZLD systems will be commissioned in May of 2016. Once operational they will give the Food Processor complete control of the water balance ensuring the facility's future sustainability in a region of water scarcity.