Type 0092...

Type 0092 is one of the most difficult filamentous microorganisms to identify. According to the manuals, the filaments of Type 0092 are rather thin (less than 1 micro - m in diameter) and relatively short with a length of up to 60 micro - m. The filaments can be found mostly within the flocs but they are not easy to observe in native samples. The reaction to the Gram stain is negative and to the Neisser stain positive. The reaction to the Neisser stain, when the entire trichomes are stained (diffused staining, no positive granules), helps to visualize the filaments. Sometimes filamentous microorganisms corresponding to the description of Type 0092 can be found in activated sludges, but they are much longer. Thus, a question arises as to whether the trichomes of Type 0092 may reach a greater length than is given in the manuals.

Although Type 0092 occurs quite frequently, the literature on its physiology, kinetic and metabolic properties is scarce. Because it occurs so frequently in nutrient removal activated sludge systems, Type 0092 is suspected to be able to denitrify and to utilize organic substrates under anoxic and / or anaerobic conditions.

Two researchers measured some kinetic parameters of Type 0092 isolated from activated sludge. In batch growth studies under rather high concentrations of substrate (the range of COD was 300 - 1,000 mg / L) based on tryptone and yeast extract, they found the maximum growth rate of Type 0092 mu_max = 7.9 1 / day. This value is quite high, higher than for Sphaerotilus natans and other filamentous microorganisms. In addition, the growth rate of Type 0092 is expected to be lower than that of filaments from conventional activated sludge system, just because it is found mostly in nutrient removal sludge systems with long retention times of biomass, which supports the slow growers.

An indirect proof that Type 0092 could be a slow - growing filamentous microorganism can be obtained from the experiments of some researchers with the VIP process. The VIP process is a US modification of the UCT (University of Cape Town) process developed from the BARDENPHO process in South Africa. The UCT process was developed to protect the anaerobic zone against nitrate in return activated sludge. Like other South African activated sludge systems the UCT process is also low - loaded, i.e., with high biomass retention times. On the other hand, the US modification - called the VIP process - can be characterized as a highly loaded system with a typical biomass retention time of about 5 days. The process flowsheet of the VIP process is schematically shown in figure given below.

"Definition Sketch for Operational Modes"...

Two researchers describe a bulking period after the start - up of this highly loaded system with Type 0092 as the dominant filamentous microorganism. Type 0092 was presumably introduced with the seed sludge but was gradually eliminated from the system because of the high - rate operational mode.