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After 6 months of operation a long-term biofilter was stopped for two weeks and then it was started up again for a second experimental period of almost 1.3 years, with high toluene loads and submitted to several physical and chemical treatments in order to remove excess biomass that could affect the reactor’s performance due to clogging, whose main effect is a high pressure drop. Elimination capacity and removal efficiency were determined after each treatment. The methods applied were: filling with water and draining, backwashing, and air sparging. Different flows and temperatures (20, 30, 45 and 60 °C) were applied, either with distilled water or with different chemicals in aqueous solutions. Treatments with chemicals caused a decrease of the biofilter performance, requiring periods of 1 to 2 weeks to recover previous values. The results indicate that air sparging with pure distilled water as well as with solutions of NaOH (0.01% w/v) and NaOCl (0.01% w/v) were the treatments that removed more biomass, working either at 20, 30 or 45 °C and at relatively low flow rates (below 320 L h−1), but with a high biodegradation inhibition after the treatments. Dry biomass (g VS) content was determined at three different heights of the biofilter in order to carry out each experiment under the same conditions. The same amount of dry biomass when applying a treatment was established so it could be considered that the biofilm conditions were identical. Wet biomass was used as a control of the biofilter’s water content during treatments. Several batch assays were performed to support and quantify the observed inhibitory effects of the different chemicals and temperatures applied.

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The extraction of feather keratin biopolymer structures was studied using chicken feathers as a biomass material by the cold acid hydrolysis reaction; the recrystallization stage was performed using microwave or ultrasound irradiation, and conduction heating was used as a reference. The microwave or ultrasound irradiation modified the texture and the morphology of the obtained materials, and they can be controlled depending on the time exposure and the power of the irradiation; this has high relevance in the design of new materials to obtain nanostructures depending on the specific application. It was found that the microwave irradiation promotes the growth of the beta sheet over the alpha helix, and in the case of ultrasound irradiation, the growth is reversed being similar to the conduction heating; the porosity properties remain invariant, modifying the particle sizes depending on the exposure time and power of irradiation. Therefore, the feather keratin biopolymer, when modified by microwaves and ultrasound in the recrystallization stage, is a fibrous protein that has good mechanical, structural, morphological, and thermal properties with potential applications such as development of biocompatible materials with cellular interaction and in catalysis as catalytic and enzymatic support to mention just a few.