Simultaneous COD Removal and PHA Production in an Activated Sludge System under Different Temperatures

The purpose of this study was to investigate PHA production by activated sludge biomass under different temperatures. The two-step approach, i.e. utilizing a growth phase followed by a nutrient(s) limitation phase, was applied to stimulate PHA accumulation. Each of three intended temperatures, 10oC, 20oC and 30oC, was investigated with combined N&P limitation. Four liter (L) fully aerobic SBRs were used for all experiments, and operated with a 6 h cycle time, a 10 h HRT and a 10 day SRT. The maximum PHA cellular contents and total concentrations achieved during the N&P limitation periods in the 10 and 20oC systems were very similar, i.e. 45 and 43% of the TSS and 2133 and 2239 mg/l, respectively, whereas the 30oC results were lower at 33% of TSS and 1476 mg/l. The biomass temperature clearly had a strong inverse effect upon PHA productivity. It decreased from 427 and 204 to 148 mg/l-day as reactor temperature increased from 10 to 20 and 30oC, respectively. As well, the PHA yields decreased from 0.38 to 0.16 and 0.11 mg PHA/mg CODu, respectively. The results strongly indicate that activated sludge PHA accumulation stimulated by combined N and P limitation is inversely correlated with temperature

Performance Improvement of a Sequencing Batch Reactor for Treating Tannery Wastewaters

[EN] Tannery wastewater has a high environmental impact due to its low biodegradability. Sequencing batch reactors (SBRs) are an established method for treating highly polluted wastewater. To minimize the hydraulic retention time (HRT) of the SBRs, various HRT values were tested and the best value was chosen according to the removal efficiency of the soluble chemical oxygen demand (COD). A series of experiments was then carried out with two cationic polyelectrolytes added to the system in two different modes to improve the effluent quality. Both modes were evaluated in terms of the soluble COD, suspended solid concentration, and turbidity of the final effluent. The results showed that reducing the HRT to two days did not diminish the COD removal efficiencies.This work was supported by the Universitat Politecnica de Valencia (Project Ref.: PAID-06-10-2269).Balaguer-Arnandis, E.; Cuartas Uribe, BE.; Bes-Piá, M.; Mendoza Roca, JA.; Galiana Aleixandre, MV. (2017). Performance Improvement of a Sequencing Batch Reactor for Treating Tannery Wastewaters. Chemical Engineering & Technology. 40(9):1666-1673. https://doi.org/10.1002/ceat.201600410S1666167340