Process conditions affect properties and outcomes of polyhydroxyalkanoate accumulation in municipal activated sludge

[Display omitted] •Pulse feeding favored PHA production compared to excess substrate supply.•An acclimation step combined with pulse feeding resulted in higher PHA contents.•PHA molecular weights in the order of 1500 kDa were obtained.•Extractable PHA was influenced by its molecular weight and melt properties.•A standard protocol for PHA accumulation tests with activated sludge was developed. The developments of mixed culture polyhydroxyalkanoate production has been directed to maximize the biomass PHA content with limited attention to polymer quality. Direct comparison of PHA accumulation literature is challenging, and even regularly contradicting in reported results, due to underlying differences that are not well expressed. A study was undertaken to systematically compare the commonly reported process conditions for PHA accumulation by full-scale municipal activated sludge. A biomass acclimation step combined with a pulse-wise feeding strategy resulted in maximum average PHA contents and product yields. pH control and active nitrification did not result in observable effects on the PHA productivity. Under these conditions a high molecular weight polymer (1536 ± 221 kDa) can be produced. Polymer extraction recoveries were influenced by the PHA molecular weight. A standard protocol for an activated sludge PHA accumulation test including downstream processing and standardized extraction has been developed and is available as supplementary material.