Polyhydroxyalkanoate (PHA) production from sludge and municipal wastewater treatment

Abstract

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with comparable properties to some petroleum-based polyolefins. PHA production can be achieved in open, mixed microbial cultures and thereby coupled to wastewater and solid residual treatment. In this context, waste organic matter is utilised as a carbon source in activated sludge biological treatment for biopolymer synthesis. Within the EU project Routes, the feasibility of PHA production has been evaluated in processes for sludge treatment and volatile fatty acid (VFA) production and municipal wastewater treatment. This PHA production process is being investigated in four units: (i) wastewater treatment with enrichment and production of a functional biomass sustaining PHA storage capacity, (ii) acidogenic fermentation of sludge for VFA production, (iii) PHA accumulation from VFA-rich streams, and (iv) PHA recovery and characterisation. Laboratory- and pilot-scale studies demonstrated the feasibility of municipal wastewater and solid waste treatment alongside production of PHA-rich biomass. The PHA storage capacity of biomass selected under feast-famine with municipal wastewater has been increased up to 34% (g PHA g VSS(-1)) in batch accumulations with acetate during 20 h. VFAs obtained from waste activated sludge fermentation were found to be a suitable feedstock for PHA production.

Unveiling PHA-storing populations using molecular methods

“…Following the outcomes of Coats et al (2007b) and Morgan-Sagastume et al (2014), where the authors showed the feasibility of selecting a biomass with PHA storage capacity under feast-famine with municipal wastewater, efforts were made to integrate wastewater treatment with the PHA production. At lab scale, Valentino et al (2015) conducted a MMC selection stage using a synthetic medium mimicking municipal wastewater similar to an activated sludge process.…”

Survival of the fastest: Selective removal of the side population for enhanced PHA production in a mixed substrate enrichment

“…Nonetheless, when using real wastewater the experimental results indicated that PHA production is primarily associated with the VFA fraction of the wastewater (Coats et al, 2007;Bengtsson et al, 2008;Beccari et al, 2009;Albuquerque et al, 2010;Morgan-Sagastume et al, 2010;Jiang et al, 2012;Tamis et al, 2014a;Morgan-Sagastume et al, 2014, 2015Korkakaki et al, 2016). This correlation is based on the fact that the VFA carbon fraction serves as a PHA precursor and efficiently enriches for a PHA accumulating community.…”

Estimating the Energy Content of Wastewater Using Combustion Calorimetry and Different Drying Processes

“…Further concepts are already discussed for optimizing the energy management of primary wastewater treatment, e.g., using moving bed biofilm reactors or applying full anaerobic treatment of wastewater (McCarty et al, 2011;Jenicek et al, 2012;Ødegaard, 2016). Furthermore, microorganisms converting wastewater in valuable products (e.g., fatty acids and polyhydroxyalkanoates) and microbial electrochemical technologies (METs) constitute examples of further opportunities for wastewater treatment and valorization (Yamasaki et al, 2006;Logan, 2009;Rabaey and Rozendal, 2010;Morgan-Sagastume et al, 2014). Independent from the specific process for exploiting the chemical energy of wastewater, comprehensive information on its energy content is necessary to evaluate the economic viability of such processes.…”