title: Bulking sludge for PHA production: energy saving and comparative storage capacity with well-settled sludge.
abstract: Two acetate-fed sequencing batch reactors (SBR) were operated under an aerobic dynamic feeding (ADF) model (SBR#2) and with anaerobic phase before aerobic phase (SBR#1) to select mixed cultures with a high polyhydroxyalkanoates (PHA) storage response. Although kinetic selection based on storage response should bring about a predominance of floc-formers, a bulking sludge with storage response comparable to well-settled sludge was steadily established. An anaerobic phase was introduced before the aerobic phase in the ADF model to improve the sludge settleability (SBR #1), however, due to the consequent increased feast/famine ratio, the performance of SBR #1, in terms of both the maximum PHB (polyhydroxybutyrate) cell content and deltaPHB, was lower than that of SBR #2. SBR #2 gradually reached a steady state while SBR #1 failed suddenly after 50 days of operation. The maximum specific substrate uptake rate and storage rate for the selected bulking sludge were 0.4 Cmol Ac/(Cmol X x hr) and 0.18 Cmol Ac/(Cmol PHB x hr), respectively, resulting a yield of 0.45 Cmol PHB/(Cmol Ac) in SBR #2 in the culture enrichment phase. A maximum PHB content of 53% of total suspended solids and PHB storage rate of 1.36 Cmol Ac/(Cmol PHB x hr) was achieved at 10.2 hr in batch accumulation tests under nitrogen starvation. The results indicated that it was feasible to utilize filamentous bacteria to accumulate PHA with a rate comparable to well-settled sludge. Furthermore, the lower dissolved oxygen demand of filamentous bacteria would save energy required for aeration in the culture enrichment stage.
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China. wqxshelly@263.net
authors.forename: Qinxue
authors.initials: Q
authors.lastname: Wen
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Chen
authors.forename: Changyong
authors.initials: C
authors.lastname: Wang
authors.forename: Nanqi
authors.initials: N
authors.lastname: Ren
mesh_terms: D003246:Conservation of Energy Resources / Q000379:methods*; D009584:Nitrogen; D054813:Polyhydroxyalkanoates / Q000138:chemical synthesis*; D012722:Sewage / Q000032:analysis*; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D054813:Polyhydroxyalkanoates; D012722:Sewage; D009584:Nitrogen