ACIDOGENIC MICROBIAL SPECIES-DIVERSITY IN ANAEROBIC DIGESTERS TREATING DIFFERENT SUBSTRATES

Microbial species diversity was determined for the acidogenic populati ons of four different digesters treating landfill leachate, a petroche mical effluent and sewage. The digesters were a downflow fixed-bed, co nventional, cold conventional and an upflow hybrid design. The 288 str ains isolated from the digesters were characterized using API test sys tems and identifications confirmed using current taxonomic methods. Th e taxonomic diversity was determined using the Shannon (H') and equita bility (J') indices. The species from the four digesters were very sim ilar with the exception of those from the digester treating the landfi ll leachate. The higher diversity in the latter was probably due to th e diverse composition of the leachate, suggesting that members of this population were more generalists, as opposed to the more narrowly con strained members in the other three digesters. The data indicated that in a digester environment dominated by a more specific carbon contain ing effluent, like a petrochemical effluent, the population becomes st enotolerant and is characterized by a lower species diversity. Such a population would not be able to cope as well with environmental fluctu ations. With a more diverse substrate like the landfill leachate, gene ralists, having a wider range for environmental variables, would domin ate. This is important in terms of anaerobic digester process efficien cy and stability.