Enhanced anaerobic treatment of synthetic protein-rich wastewater promoted by organic xerogels

Abstract

BACKGROUND: Carbon-based materials have been shown to enhance anaerobic digestion (AD) processes by promoting direct interspecies electron transfer in methanogenic consortia. However, little is known on their effects during the treatment of complex substrates, such as those derived from proteinrich wastewaters. Here, organic xerogels (OX) are tested, for the first time, as accelerators of the methanogenic activity of an anaerobic consortium treating a synthetic protein-rich wastewater.RESULTS: Three OX with distinct pore size distribution (10 and 1000 nm for OX-10 and OX-1000, respectively) and structural conformation (graphene oxide (GO) incorporation for OX-10-GO) were synthesized. OX-1000 promoted the highest methane production rate (5.21 mL/g*h, 13.5% increase with respect to the control incubated without OX) among the synthesized OX. Additionally, batch bioreactors amended with OX achieved higher chemical oxygen demand (COD) removal (up to 88%) as compared to the control, which only showed 50% of COD removal. Interestingly, amendment of bioreactors with OX also triggered the production of medium-chain fatty acids, including caprylate and caproate. Moreover, OX decreased the accumulation of ammonium, derived from proteins hydrolysis, probably due to their adsorption capacities. CONLUSIONS: For the first time, OX were successfully applied as methanogenic accelerators for the anaerobic treatment of synthetic protein-rich wastewater. Addition of OX increased the methane production rate and COD removal as well as triggering the production of medium chain fatty acids and attenuating the accumulation of ammonium. Therefore, OX are proposed as suitable materials to boost the efficiency of anaerobic systems to treat complex industrial wastewaters.

Immobilized Nanomaterials for Environmental Applications

“…More recently, GO was immobilized in organic xerogels, which were applied for the treatment of protein-rich wastewater. The addition of this composite promoted higher methane production and the superior removal of organic matter and ammonium, as well as the production of medium chain fatty acids [ 14 ].…”

“…While biogenic methane, produced from waste treatment, is considered a renewable energy source [ 14 ], there are important discharges of this gas during the exploitation of fossil energies. Additionally, methane is also released from wastewater-treatment plants and landfills.…”