THESIS(Jin Hwan Oh).pdf

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Suspended biomass within the interstitial void spaces was considered to be a significant
factor in substrate removal. On the other hand, excessive biomass growth results in a decrease in
the available area for the organic matter to diffuse into the granules, and therefore, potentially
decreases the removal efficiency. Wastewater containing high levels of suspended solids may
cause a gradual accumulation of slow and non-biodegradable solids within the void spaces
between the granules. The slow hydrolysis of entrapped solids at low temperatures also results in
solids accumulation. Consequently, as the pores become occupied by entrapped solids and
biomass, a decrease in the effective porosity will lead to a rapid buildup of head loss, channeling,
and short-circuiting of flow through the reactor. Previous studies have reported that the rate of
head loss buildup increased with the increase in organic loading (Park et al., 2012; Roth and
Ellis, 2004). Park et al. (2012) reported that the increase in the head loss occurred due to a
clogged underdrain system caused by the solids accumulation in the reactor. Therefore, periodic
backwashing is required to minimize problems associated with headloss buildup and clogging of
the underdrain system. Additionally, the potential mixing effect created by the backwashing
process can enhance the contact between the wastewater and the biomass. Although there have
been several reports on backwasing method in operation of the SGBR, no information exist on
backwashing parameters. In this study, optimum backwash flow rate and bed expansion were
determined for proper backwashing and to prevent wash out of sludge granules from the SGBR.
Materials and methods
Backwashing of the SGBR treating dairy processing wastewater in Tulare, CA
For the backwash process, the treated effluent from the storage tank (305 gallons) was