The results obtained in the present study have demonstrated that it is possible to recover up to 23 lipase units per gram of lyophilised solid from activated sludge, in a process that comprises extraction using ultrasonication (without detergent) followed by dialysis and lyophilisation. The extracted enzymes could be used, without any further treatment, to improve the sludge degradation, thus improving the amount of biogas produced after anaerobic digestion. However, to obtain lipase suitable for other industrial applications (like as additive for detergents or biocatalyst in esterification reactions) requiring a higher degree of purity and a high specific enzymatic activity, a further purification and concentration procedure should be stated. The establishment of a protocol to purify and concentrate all the enzymatic fractions present in the activated sludge is still a challenge due to the own variations in the activated sludge (daily, seasonal, etc.) and its low enzyme concentration.