|dc.description.abstract||There is potential for the anaerobic baffled reactor (ABR) to be implemented on-site for pre-treatment of
coloured wastewaters. The implementation of waste minimisation and cleaner production strategies in
industry will result in the production of smaller volumes of concentrated wastewaters. With
implementation of the ABR, the concentrated waste stream could be pre-treated, with an acclimated
biomass, which should facilitate sufficient degradation such that the effluent could be discharged to sewer
for further treatment.
The ABR is a high-rate compartmentalised anaerobic bioreactor, the design of which promotes the spatial
separation of microorganisms. The use of molecular teclmiques to characterise the microbial populations
and the dynamics of these populations with time and/or changing operating conditions will add to the
current understanding of the process, which is based on the biochemical pathways and chemical analyses.
This knowledge will allow for optimisation of the design of the ABR.
The hypothesis of the horizontal separation of acidogenesis and methanogenesis through the ABR was
proven. Changes in the HRT affected the operation of the reactor, however, recovery from these upsets
was almost immediate and operation of the reactor was stable.
Two synthetic dye waste streams, one food dye (tartrazine) and one textile dye (Cl Reactive Red 141),
and a real industrial dye wastewater, were treated in separate laboratory-scale ABRs. These investigations
showed that successful treatment of a highly coloured wastewater is possible in the ABR. The design of
the ABR facilitates efficient treatment of concentrated dye wastewaters by protecting the sensitive
methanogens from the inhibitory dye molecules and promoting efficient colour and COD reduction.
The molecular-based method, fluorescent in situ hybridisation, allowed the direct identification and
enumeration of microbial populations active in the ABR. In all of the reported investigations, there was a
definite shift in the microbial populations through the ABR, with a predominance of eubacteria in the first
compartments (acidogenesis) and archaea (methanogenesis) in the later compartments. The number of
compartments involved in each depended on the strength of the substrate (organic loading rate - OLR). A
combination of FISH probing, and the analysis of 98 archaeal l6S rDNA clone inserts provided useful
descriptions of the methanogens actively involved within each compartment. These showed a
predominance of the Methanosaeta spp., particularly in the last compartments of the reactor.
Methanogens present in the first four compartments consisted of species of Methanobacterium and
Methanospirillum, a relatively unstudied methanogen Methanomethylovorans hollandica, and an
unidentified short filamentous species.||en