Treatment of Furfural Waste Water

The waste water of all furfural plants contains some carboxylic acids, with acetic acid being the principal load, ranging from 1 to 5 percent by weight, as well as some furfural, in concentrations up to 600 ppm. The furfural concentration depends on the quality of the first distillation column, with good columns going down to 50 ppm. 

Application of this process to furfural waste water was studied in detail by Wirtz and Dague [44]. Contrary to widespread erroneous belief, these authors established beyond any doubt that at the concentrations occurring in furfural waste water, the toxicity of furfural for some microorganisms does not apply to methane bacteria. They not only thrive on acetic acid but eat up furfural as well. For the low concentrations of acetic acid in furfural waste water, these bacteria, known to decompose acetic acid to methane and carbon dioxide according to the reaction 

2 - Fully packed reactor 3 - Separation tank 4 - Bubble flask 5 - Scrubber 6 - Sampling port 7 - Gasometer 

The furfural waste water (from a QUAKER OATS plant in Cedar Rapids, Iowa) had a load in the order of 13 000 mg COD/liter, an acetic acid content of 1.2 % by weight, a pH of approximately 2.6, and a furfural content of 600 mg/liter. 

The digestion was carried out at 35 C to obtain a reasonable reaction rate. The formation of new microorganisms ( biomass ) was extremely small, amounting to less than 0.05 grams per gram of COD removed. 

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Figure 48. Industrial Anaerobic Treatment of Furfural Waste Water.

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