Influence of temperature on mixed microbial culture polyhydroxyalkanoate production while treating a starch industry wastewater

The influence of temperature on the production of enrichment biomass and polyhydroxyalkanoates by activated sludge was evaluated within a practical case study. Two laboratory-scale sequencing batch reactors (SBRs) were operated in parallel over 131 days to treat a wastewater from a potato-starch modification facility, and produce surplus activated sludge biomass with PHA accumulation potential. The SBRs were operated similarly but at different temperatures (15 and 25 °C). Temperature did not influence wastewater treatment performance (average 97% COD removal). Replicate PHA accumulation experiments were conducted on the SBR surplus biomass at 15, 20, 25 and 30 °C. Surplus biomass accumulated PHA with acetic acid to between 60 and 65%, gPHA/gVSS for all temperatures tested and with estimated Arrhenius temperature coefficients (θ) of 1.048 for the PHA production, and 1.062 for the COD consumption specific rates. The MMC PHA production process was adaptable within a common range anticipated for seasonal fluctuation of temperature for the influent wastewater and PHA production feedstocks without loss of performance. This outcome suggests a broad range in the practical feasibility and reliability with MMC method and process implementations. PHA production was predicted to be more efficient at lower temperatures. Strategies can be engineered in the bioprocess design and operations to accommodate for temperature shifts in practical applications of PHA production as a route to resource recovery from organic waste management services.