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Biofiltration, activated sludge diffusion, biotrickling filtration, chemical scrubbing, activated carbon adsorption, regenerative incineration, and a hybrid technology (biotrickling filtration coupled with carbon adsorption) are comparatively evaluated in terms of environmental performance, process economics, and social impact by using the IChemE Sustainability Metrics in the context of odor treatment from wastewater treatment plants (WWTP). This comparative analysis showed that physical/chemical technologies presented higher environmental impacts than their biological counterparts in terms of energy, material and reagents consumption, and hazardous-waste production. Among biological techniques, the main impact was caused by the high water consumption to maintain biological activity (although the use of secondary effluent water can reduce both this environmental impact and operating costs), biofiltration additionally exhibiting high land and material requirements. From a process economics viewpoint, technologies with the highest investments presented the lowest operating costs (biofiltration and biotrickling filtration), which suggested that the Net Present Value should be used as selection criterion. In addition, a significant effect of the economy of scale on the investment costs and odorant concentration on operating cost was observed. The social benefits derived from odor abatement were linked to nuisance reductions in the nearby population and improvements in occupational health within the WWTP, with the hybrid technology exhibiting the highest benefits. On the basis of their low environmental impact, high deodorization performance, and low Net Present Value, biotrickling filtration and AS diffusion emerged as the most promising technologies for odor treatment in WWTP.

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The potential of biogas (with and without H 2 S) and volatile fatty acids (VFAs) to support microbial growth and accumulation of polyhydroxyalkanoates (PHAs) in type II methanotrophs was evaluated batchwise under aerobic conditions. Methylocystis hirsuta was able to grow on artificial biogas (70 % CH 4 , 29.5 % CO 2 , 0.5 % H 2 S) and accumulate PHA up to 45 ± 1 % (wt %) under N-limited conditions. The presence of CO 2 and H 2 S did not significantly influence the growth and PHA synthesis in M. hirsuta compared to control tests provided with pure CH 4 at similar concentrations. Likewise, *Revised Manuscript (clean for typesetting) Click here to view linked References the addition of VFAs to the cultivation broth at initial concentrations of 100-200 mg L-1 did not hamper the growth of this strain on artificial biogas. Indeed, the addition of 10 % extra carbon in the form of individual VFAs resulted in an increase in the maximum PHA yield and final PHA content up to 0.45-0.63 gPHA gSubstrate-1 and 48-54 % (wt %), respectively, at the expense of a higher energy demand. Valeric acid supplementation supported the highest 3-hydroxyvalerate content (13.5 %) within the biocomposite. In this context, this study demonstrated for the first time that 3hydroxyvalerate synthesis by M. hirsuta did not depend on CH 4 assimilation.