Specialist Group on ANAEROBIC DIGESTION Newsletter - IWA

Development of High-Rate Anaerobic Granular Sludge Bed Process for Low
Strength Wastewater Treatment at Low Temperature
by Wilasinee Yoochatchaval (wilasinee.y@nies.go.jp)
New PhD Contact:
Post doctoral researcher, Water and Soil Environment division,
National Institute for Environmental Studies, 16-2 Onogawa,
Tsukuba, Ibaraki, Japan 305-8506
Email: wilasinee.y@nies.go.jp, wilasinee_y@hotmail.com
Supervisors:
Dr. Kazuaki Syutsubo, Senior Researcher of National Institute for Environmental
Studies, Japan
Dr. Takashi Yamaguchi, Associate Professor of Nagaoka University of Technology,
Japan
Dr. Hideki Harada, Professor of Tohoku University, Japan
Abstract:
In this study, the anaerobic granular sludge process and its operation mode were established for efficienttreatment
of the low strength wastewater at low temperature. First of all, the feasibility of an expanded granular
sludge bed (EGSB) reactor for low strength wastewater with 0.6-0.8 g COD/L was tested at 20°C. In this
process, methanogenic granular sludge was used as seed and recirculation of effluent was made to fluidize the
sludge bed. As a result, sludge retention in this process was very well (over 40 days). Consequently, this process
was possible to achieve high rate treatment of low strength wastewater at hydraulic retention time of 1.5 h with
COD loading rate of 12.8 kg COD/m 3 /day.
The influence of decreasing in the temperature and the organic concentration of the wastewater was
evaluated in lab-scale EGSB reactor. The reactor exhibited sufficient COD removal efficiency until 10°C
operation due to the good-microbial adaptation of granular sludge at low temperature. The significant increase
of hydrogen-fed methanogenic activity between test temperatures of 15°C and 20°C was observed. At this time,
proliferation of psychrotolerant methanogen (hydrogen utilizing Methanospirillum spp.) in the retained sludge
was confirmed. On the other hand, decrease of organic concentration of wastewater (from 0.8 to 0.4 gCOD/L)
has caused the deterioration of organic removal efficiency and physical property of retained sludge due to the
inactivation of anaerobic bacteria. To solve this problem, new operational technology was proposed. Control of
ORP of influent and intermittent the effluent recirculation are possible to active the microbial activity of
methanogens in the retained sludge.
To clarify the effect of sucrose content of fed-wastewater on the physico-microbial characteristics of
granular sludge, we operated two reactors at 20°C by sucrose based wastewater (sucrose, 90% of COD) and
volatile fatty acid based wastewater (sucrose, 0% of COD). Sucrose founded much negatives effects on the
granular sludge physical properties and microbial properties (bulking and wash out of retained sludge due to the
overgrowth of acidogens) at low temperature condition.
IWA <strong>Specialist</strong> <strong>Group</strong> on Anaerobic Digestion
28 June 2009 Newsletter