Recovery of antioxidants from sugarcane molasses distillery wastewater and its effect on biomethanation.
Antioxidants (melanoidins and polyphenols) present in sugarcane molasses distillery wastewater are not readily biodegradable. However, these compounds exhibit potential physiological properties which may be tapped for food, cosmetics and pharmaceutical applications. Recovery of these compounds from distillery wastewater could thus lead to products of commercial interest while improving the conventional biological (anaerobic) treatment step. Three processes viz. ultrafiltration (UF), adsorption-desorption and solvent extraction were investigated for antioxidants recovery from distillery wastewater and selected fractions were subjected to biomethanation (anaerobic digestion). The effect of different adsorbents and solvents as well as operational parameters on antioxidants recovery was studied and the separated fractions were analyzed for melanoidins content, polyphenols content and antioxidant activity. UF through 100 kDa membrane resulted in an antioxidant rich retentate (245 mM TEAC) but the permeability was low. Solvent extraction with methyl ethyl ketone (MEK) led to 113 mM TEAC recovery in organic phase. Adsorption on XAD16 resin followed by desorption with acidified ethanol enabled antioxidants recovery of 192 mM TEAC. Antioxidant removal from the wastewater improves biomethanation. Overall, adsorption on XAD16 resin followed by biomethanation (74% COD reduction and 71% methane in biogas within 25 days) appears to be promising for improving the existing biomethanation facility while recovering antioxidants with potential commercial value. Further analysis of the antioxidants fraction is required to ascertain the content of specific commercially viable polyphenols.