| The successful application of anaerobic technology, which can economize and generate energy and accords with the principles of sustainable development in approach of wastewater treatment, to the treatment of industrial wastewaters is critically dependent on the development, and use, of high rate anaerobic bioreactors. Periodic anaerobic baffled reactor (PABR), which is a novel reactor based on anaerobic baffled reactor (ABR) design concept, is required to investigate for operating manner optimization, hydrodynamic characteristics and microorganism characteristics in actual industrial wastewater treatment. Therefore, a four-compartment PABR was used to treat actual Chinese traditional medicine wastewater run in various switching manners and frequencies continuously at stable hydraulic residence time (HRT) of 2d, using a feed with average organic loading rates (OLRs) at about 1, 2, 4 and 6 kgCOD/(m3·d) for 12, 24, 24 and 6 d respectively.Operating results showed that methane percentage of biogas and pH and alkalinity increased while volatile fatty acids (VFA) concentrations decreased along the reactor at stable state whichever switching manner the PABR run in. A raised OLR lifted the chemical oxygen demand (COD) concentration and VFA concentrations in effluent. The PABR operated in an'clockwise sequential'switching manner, of which COD removal rate was 86.36﹪at OLR =4.38kgCOD/(m3·d), soured fast after average OLR at about 6kgCOD/(m3·d). Movement and losing of solids caused by great gas production led to the compartment with both maximum gas production and maximum COD removal rate moved along the PABR run in a T=∞switching manner, of which COD removal rate was 92.51﹪at OLR=6.45kgCOD/(m3·d), leaving the two front compartments soured with cumulative VFA. The PABR operated in an'every second'switching manner, of which COD removal rate was 92.51﹪at OLR=6.37kgCOD/(m3·d), had better adaptability and stability treating Chinese traditional medicine wastewater in the long run. The variation trend of qualitative analysis on molecular weight distribution (MWD) chromatogram of influent and of bulk liquid from each compartment was consistent with the alteration trend of COD concentration, COD removal rate, gas production and methane production in each compartment of PABR no matter what the switching manner, and the compartment sequence and the OLR were.Results from hydrodynamic characteristics research showed that the fraction of dead space in PABR was similar to that in ABR, which was low in comparison with other reactor designs. Dead space may be divided into two categories, hydraulic and biological. In RTD studies without biomass the hydraulic dead space in the PABR run in an'every second'switching manner was the lowest while that in the PABR run in a T=∞switching manner was the highest. The same trend was obtained with the total dead space in RTD studies with biomass no matter what the OLR was. Biological dead space was the major contributor to dead space but affected decreasingly at higher OLR whichever switching manner the PABR run in. The flow patterns within the PABRs were intermediate between plug-flow and perfectly mixed under all the conditions tested.Results from denaturing gradient gel electrophoresis (DGGE) analysis of dynamic changes in microbial communities in PABR showed that microbial diversity and community structure were different between the compartments no matter which switching manner the PABR run in. Microbial community structure and dominant community amount in stable state at different OLR were temporally dynamic in one compartment. The trend of dynamic changes in microbial communities in each compartment accorded with the trend of alteration in performance of PABR. Under the same lifting of OLR, the difference in dynamic changes in microbial communities in each compartment depended on the difference in switching manner and frequency.
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