Alkaline extraction of wastewater activated sludge biosolids

Activated sludge produced by wastewater treatment facilities are a sub-utilized by-product whose handling and disposal represent significant costs to these facilities. In this work, we introduced a simple and effective alkaline extraction technique that extracts up to 75% of the sludge’s organic matter into a liquor containing potentially useful organic material (proteins, carbohydrates, etc.). The results suggest that at pH 11 and above, cell lysis occurs, liberating substantial quantities of organic material into the alkaline solution. When compared to a cation exchange resin (CER) extraction developed for analytical purposes, the alkaline extraction recovered 3× more organic material. The alkaline extract was highly surface active, despite containing a relatively small fraction of lipids. At pH 12 and above the lipid fraction was enriched with C15–C16 fatty acid residues, likely associated with cell membrane phospholipids as suggested by nuclear magnetic resonance spectroscopy (31P NMR). Size exclusion chromatography studies show that the extract is enriched with biopolymers or assemblies of molecular weights in the order of tens of thousands of Daltons. Potential uses for the extract are discussed.