Takahiro Kuba | PubMed Health

PubMed2006

Effect of particulate biodegradable COD in a post-denitrification enhanced biological phosphorus removal system.

This research studied the effects of the particulate biodegradable fraction (X(S)) of chemical oxygen demand (COD) in a post-denitrification configuration. Denitrifying polyphosphate-accumulating organisms (DN-PAOs) and nitrifiers were completely separated in a system also known as Dephanox. It was composed by an anaerobic-anoxic (A(2)) process coupled with a parallel Nitrification biofilm tank. The results of a long-term operation of the Dephanox continuous-flow lab-scale system as well as results of sludge characterization assays showed that raw wastewater feeding promoted complete phosphorus (P) removal by double via (i) providing complementary volatile fatty acids (VFAs) for a complete P removal by prefermentation of the X(S) fraction of COD under a long anaerobic SRT, and (ii) assisting the metabolic accumulation and selection of DN-PAOs. Complete P removal was accomplished only when the system was fed with raw wastewater (high XS concentration). When primary effluent was used as influent, lack of VFAs in the anaerobic stage led to an incomplete and instable P removal, suggesting that the use of primary treatment is not only unnecessary but detrimental for simultaneous nutrient removal in a post-denitrification configuration.

Aerobiosis↗

PubMed2004

Promoting nitrification by using functional gel as immobilizing medium under different temperature stimulation patterns.

Nitrification with nitrifiers immobilized by temperature stimuli-responsive N-isopropylacrylamide-Chlorophyll (NIPA-CH) gel was investigated under several patterns of temperature stimulation, compared with that at constant temperature. The results show that in response to a cyclic temperature stimulus of 32-36 degrees C or 32-34 degrees C with a period of 4 or 2 h, respectively, the gel swelled and shrank reversibly and promoted biological nitrification. But in the case of a cyclic temperature change of 32-36 degrees C with a stimulation cycle of 2 h, nitrite oxidization declined. The results suggested that adequate stimulus facilitated substrate transfer into gels that promoted nitrification in the reactor, but quite frequent swelling and shrinking of the gel squeezed nitrifier out of the gel resulting in washing nitrifier out and declining nitrification. When gels that undergone cyclic temperature stimuli began to swell at 32 degrees C, oxygen consumption of nitrifiers in the gels was more than that of nitrifiers in the gels at constant temperature of 32 degrees C all the time, but when gels of two reactors shrank at 36 degrees C, their oxygen consumption reduced and there was almost no difference between them regardless of their undergone temperature stimuli once or not. Practical application of nitrifier immobilized by NIPA-CH gel in wastewater treatment was also discussed.

Acrylamides↗