Lignocellulosic Wastewater Treatment – COD Reduction and Colour Removal

  • Miss Sinduja Sritharan, The University of Sydney, Australia
  • Miss Maryanne Riad, The University of Sydney, Australia
  • Dr John Kavanagh, The University of Sydney, Australia
  • Mr Arthur Kollaras, Microbiogen, Australia
  • Mr Raja Mahanama, The University of Sydney, Australia

Colour and recalcitrant COD removal is a well known problem for ethanol distilleries which use molasses as a feedstock. The US corn ethanol industry generally avoids its waste water problem via evaporation to produce DDGS, which are a valuable animal feed and typically make up 25% of a plants income.

Wastewater treatment is a little researched aspect of the production of ethanol from lignocellulosic feedstocks. This is likely due to the small scale of many of the pilot processes and the use of the US corn ethanol process as a model. Evaporation of such waste streams will be expensive due to the low concentrations of ethanol, and the resulting by product is unlikely to result in similar income to DDGS. To date the published research has concentrated on COD removal but surprisingly has not mentioned colour.

In this work we tested anaerobic and aerobic digestion, followed by chemical dosing for COD and colour removal. Anaerobic digestion was more effective than aerobic digestion, removing 55% vs 33%of the COD and 29 vs 17% of the colour. Colour removal of 50% could be achieved with both 20mM Aluminium sulphate and 40mM ferric chloride.