Ethanol Science

Wastewater Discharge

In order to reduce organic compounds in wastewater streams from ethanol plants, some technology providers have incorporated the use of anaerobic digesters. Wastewater streams are directed to an anaerobic (without oxygen) reactor that degrades the organic compounds. This process produces methane gas which can be used as an alternative energy source for the boiler or dryer.

This process allows full recycling of the process water, greatly reducing the amount of wastewater discharged. Plants now only discharge non-contact cooling water and water from the makeup water softener or reverse osmosis system. The balance of the water loss in the plant is through cooling tower evaporation and the water in the distillers grains.

Several major advantages come with this technology. First, anaerobic digester systems remove 85 to 95% of the organic compounds. The removal of these compounds improves yeast performance in the fermenter. Another advantage is that new plants can eliminate the traditional waste treatment process, which can often save $500,000 to $1,000,000 in capital equipment costs.

Finally, with processes adopting "zero process water discharge" operations, the need to connect to local wastewater treatment services is often not required, thus allowing for plants to be built in more rural locations nearer to the sources of raw materials.

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