1 Production of polyhydroxybutyrate by activated sludge performing enhanced

Recovery of biodegradable plastics from activated sludge is a promising sustainable technology. In this study, polyhydroxybutyrate (PHB) – a biodegradable plastics material- was produced by activated sludge performing enhanced biological phosphorus removal (EBPR) in batch experiments under anaerobic, aerobic and anaerobic/aerobic conditions. Under anaerobic conditions, the PHB content of 28.8% of dry biomass weight was obtained, while under aerobic or anaerobic/aerobic conditions, the maximum PHB content of 49-50 % was achieved. The PHB production rate with respect to the volatile suspended solids (VSS) was 70 mg/g VSS·h under aerobic conditions, and this increased to 156 mg/g VSS·h under anaerobic condition and to 200 mg/g VSS·h under aerobic conditions with energy also supplied from polyphosphate. A side stream, with initially anaerobic conditions for PHB accumulation and phosphorus release, and then aerobic conditions for PHB accumulation, was proposed. In this side stream, biomass with a high PHB content and a high PHB production rate could be both achieved