Abstract
There is a growing interest to immobilize desired bacteria using inexpensive materials in order to improve the wastewater treatment process. Three different types of carriers namely natural zeolite, magnesium-exchanged natural zeolite and quartz sand of different particle size were used to immobilize the phosphate-accumulating bacteria Acinetobacter calcoaceticus and to determine which one was the most effective. Bacteria were cultured for 24 h in various reactors containing different particle sizes of each of the carriers. The majority of the cultured bacterial population was immobilised onto the different carriers by means of adsorptive growth while a minority of free cells was observed in the supernatant. The number of immobilised viable cells (CFU) depended on the type of carrier and the particle size. The highest loading rate of immobilised cells (68.61±1.11 x 108 CFU/g) was observed with the smallest particle size (<0.125 mm) of magnesium-exchanged natural zeolite.
Highlights
Enhanced biological phosphorus removal (EBPR) from wastewater, a biological alternative to chemical phosphate (P) precipitation, is based on the activity of P-accumulating bacteria
At a lower initial P concentration more than 30% P was adsorbed by NZMg and natural zeolite (NZ) while only 9% P was absorbed by Quartz sand (QS)
It is shown that naturally occurring materials such as NZ and QS and adsorptive growth can be successfully used for the immobilisation of P-accumulating bacteria
Summary
Enhanced biological phosphorus removal (EBPR) from wastewater, a biological alternative to chemical phosphate (P) precipitation, is based on the activity of P-accumulating bacteria. Bacteria from the genus Acinetobacter have been reported to be the most efficient P-accumulating species (Muyima and Cloete, 1995; Sidat et al, 1999; Hrenović et al, 2003a; Hrenović et al, 2003b). Attention is being drawn to the immobilisation of bacteria in order to achieve a higher cell density in bioreactors; based on this, smaller reactors, shorter residence/retention time or higher flow rates can be employed. Immobilisation of Acinetobacter spp. has been investigated using alginate (Muyima and Cloete, 1995) or ceramic (Kariminiaae-Hamedaani et al, 2003) carriers. The extent of bacterial colonization depends on the chemical properties and particle size of NZ
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