Due to stringent local discharge restrictions, a lack of available wastewater municipalities, and with the nearest discharge stream over 30 miles away, Big River Resource was left with no other option except to build a zero liquid discharge (ZLD) ethanol plant.

Due to stringent local discharge restrictions, a lack of available wastewater municipalities, and with the nearest discharge stream over 30 miles away, Big River Resources, West Burlington, Iowa, was left with no other option except to build a zero liquid discharge (ZLD) ethanol plant.

U.S. Water Services, Plymouth, Minn., served as the lead process design and construction management firm for Big River’s water treatment facility. A four-step process was developed to achieve allow water reuse and minimization inside the plant and to achieve zero liquid discharge. This included dual softening, decarbonation, high efficiency reverse osmosis, and finally evaporation and crystallization. These four applications have never been combined in an ethanol plant prior to the Big River project.

To date, Big River is successfully operating as an efficient “green technology” facility. Much of the water used at the plant is evaporated from the cooling tower. Discharge unable to be evaporated is removed from the plant in the form of salt-cakes, which are nonhazardous and land-fillable. (Recyclable solutions for these salt-cakes currently are being researched.) Big River was the first of its kind but increased government regulation is making ZLD facilities more common.

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