EVALUATION OF 5 BIOCARRIERS AS SUPPORTS FOR IMMOBILIZED BACTERIA - COMPARATIVE PERFORMANCE DURING HIGH CHEMICAL LOADING, ACID SHOCKING, DRYING AND HEAT SHOCKING
Ma. Heitkamp et al., EVALUATION OF 5 BIOCARRIERS AS SUPPORTS FOR IMMOBILIZED BACTERIA - COMPARATIVE PERFORMANCE DURING HIGH CHEMICAL LOADING, ACID SHOCKING, DRYING AND HEAT SHOCKING, Environmental toxicology and chemistry, 12(6), 1993, pp. 1013-1023
Immobilized bacteria technology (IBT) utilizes inert biocarriers to su
pport high concentrations of chemical-degrading bacteria in reactors d
esigned to provide optimal conditions for microbial activity. This stu
dy evaluated IBT performance in packed bed reactors (PBRs) using a por
ous inorganic biocarrier (diatomaceous earth), nonporous biocarriers (
glass beads), and organic biocarriers having carbon adsorption propert
ies (granular activated carbon) with different porosity. Each reactor
was challenged with high chemical loading, acid, dryness, and heat sho
ck conditions. Benchtop PBRs inoculated with a p-nitrophenol- (PNP)- d
egrading Pseudomonas sp. and fed a synthetic waste containing 100 to 1
,300 mg/L of PNP showed removal of PNP from effluents within 24 h of s
tart-up. Chemical loading studies showed maximum PNP removal rates of
6.45 to 7.35 kg/m3/d for bacteria in PBRs containing diatomaceous eart
h beads, glass beads, and activated coconut carbon. A lower PNP remova
l rate of 1.47 kg/m3/d was determined for the activated anthracite car
bon, and this PBR responded more slowly to increases in chemical loadi
ng. The PBR containing bacteria immobilized on activated coconut carbo
n showed exceptional tolerance to acid shocking, drying, and heat shoc
king by maintaining PNP removal rates >85% throughout the entire study
. The other biocarriers showed nearly complete loss of PNP degradation
during the perturbations (except for drying), but all recovered high
rates of PNP degradation (>98% removal) within 48 h after an acid shoc
k at pH 2, within 8 d after an acid shock at pH 1.0, within 24 h after
drying for 72 h, and within 48 h of heat shocking. The resiliency and
high chemical removal efficiency demonstrated by immobilized bacteria
in this study support the concept of using IBT for the biotreatment o
f industrial wastes.