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High‐Rate Treatment of Terephthalate in Anaerobic Hybrid Reactors
Author(s) -
Kleerebezem Robbert,
Ivalo Maarit,
Pol Look W. Hulshoff,
Lettinga Gatze
Publication year - 1999
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp9900561
Subject(s) - hydraulic retention time , hybrid reactor , bioreactor , terephthalic acid , biomass (ecology) , anaerobic exercise , pulp and paper industry , chemical oxygen demand , chemistry , mesophile , wastewater , nuclear chemistry , materials science , chemical engineering , chromatography , waste management , organic chemistry , polyester , biology , composite material , physiology , agronomy , genetics , blanket , bacteria , engineering
The anaerobic degradation of terephthalate as sole substrate was studied in three anaerobic upflow reactors. Initially, the reactors were operated as upflow anaerobic sludge bed (UASB) reactors and seeded with suspended methanogenic biomass obtained from a full‐scale down‐flow fixed film reactor, treating wastewater generated during production of purified terephthalic acid. The reactors were operated at 30, 37, and 55 °C. The terephthalate removal capacities remained low in all three reactors (<4 mmol·L −1 ·day −1 , or 1 g of chemical oxygen demand (COD) ·L −1 ·day −1 ) due to limitations in biomass retention. Batch experiments with biomass from the UASB reactors revealed that, within the mesophilic temperature range, optimal terephthalate degradation is obtained at 37 °C. No thermophilic terephthalate‐degrading culture could be obtained in either continuous or batch cultures. To enhance biomass retention, the reactors were modified to anaerobic hybrid reactors by introduction of two types of reticulated polyurethane (PUR) foam particles. The hybrid reactors were operated at 37 °C and seeded with a mixture of biomass from the UASB reactors operated at 30 and 37 °C. After a lag period of approximately 80 days, the terephthalate conversion capacity of the hybrid reactors increased exponentially at a specific rate of approximately 0.06 day −1 , and high removal rates were obtained (40–70 mmol·L −1 ·day −1 , or 10–17 g of COD·L −1 ·day −1 ) at hydraulic retention times between 5 and 8 h. These high removal capacities could be attributed to enhanced biomass retention by the development of biofilms on the PUR carrier material as well as the formation of granular biomass. Biomass balances over the hybrid reactors suggested that either bacterial decay or selective wash‐out of the terephthalate fermenting biomass played an important role in the capacity limitations of the systems. The presented results suggest that terephthalate can be degraded at high volumetric rates if sufficiently long sludge ages can be maintained, and the reactor pH and temperature are close to their optima.