Microbial Community Structure Andecological Network Of Anaerobic Biosystems

The treatment and resource recovery from the pollutants are hot topics in the field of environmental engineering and they belong to the category of sustainable processes. Anaerobic ammonium oxidation(anammox) and anaerobic digestion(AD) are two important and typical biological processes. Both are considered to be promising technologies to treat ammonia-rich wastewater and organic wastes. A bottleneck of anammox technology is the slow startup. An even longer startup of more than one year may happen when there lacks of mature anammox inocula. For AD technology, although some traditional reactor types(i.e. anaerobic digester) have simple configuration, they can only perform well under low organic loading rates(OLRs)(<5kg-COD/(m3?d)) due to the limit by the weak sludge retaining capability. In recent years, there are increasing attention to the wastewater sieving, which is regarded to be able to replace the primary clarifier and alleviate the subsequent processes such as MBR. However, there are very few repo rts about recovering biogas from the fine sieved fraction(FSF) of the wastewater.This thesis targets to solve the problems of slow startup of anammox and the incapability of digestion under high OLRs by traditional anaerobic digesters. Different types of bioreactors were operated and some molecular biological tools were applied to investigate the strategies of anammox startup and the efficiencies of digesting FSF under high OLRs. Microbial ecological networks were also built in order to have a better view of the AD microbial communities.The results showed that both the reactor types and the inocula played important roles to the startup of anammox. By comparing the startup efficiency of two reactor types, i.e. sequencing batch reactor(SBR) and anaerobic membrane bioreactor(An MBR), it is found that MBR performed better than SBR on anammox startup. The total nitrogen loading rate(TNLR) of the SBR increased from 0.03 kg-N/(m3?d)to 0.4 kg-N/(m3?d) within 147 days, but further increased to 0.8 kg-N/(m3?d) with low nitrogen removal efficiency(70%-80%) within six months by adding a membrane module, becoming a An MBR. For another An MBR that was inoculated with activated sludge, the TNLR increased to 0.7 kg-N/(m3?d) but with low nitrogen removal efficiency(30%-40%). In addition, a pre-inoculation process was applied to obtain the inoculating sludge with different ecological properties. The results showed that the more even and the higher concentration of anammox cells(>106 gene copies/m L) contributed to a fast startup of anammox. Anammox species Kuenenia stuttgartiensiswas proven to be dominant, whose amount increased by three orders of magnitude within six month(>109 gene copies/mL).Fine sieved fractions(FSF) of domestic wastewater were collected for biogas production using AD. The FSF consisted of large amount of cellulose. Two anaerobic batch digesters were operated under thermophilic( 55oC) or mesophilic(35oC) conditions for a long period(656 days). The mesophilic digester performed in high efficiency under the OLRs <14 kg-COD/(m3?d) with methane yield about 150 Nm L/g COD but failed if went further. The thermophilic digester had high efficiency even under OLR ~22kg-COD/(m3?d) with methane yield about 120 Nm L/g COD. The 454-pyrosequencing results based on 16 S r DNA genes showed that Caldatribacterium saccharofermentans and Methanothermobacter were pre-dominant bacterial and archaeal genera under the thermophilic condition, respectively. For the mesophilic condition, Bacteroides and Methanosaeta were most dominant. The β-diversity results indicated that the thermophilic community was more sensitive to the increasing OLRs than the the mesophilic one.In order to have a more direct and comprehensive insights into the microbial communities of anaerobic systems, the microbial ecological networks(MENs) of anammox and AD reactors were constructed based on topological principles and methods. The results showed that Kuenenia stuttgartiensis played a leading role in the anammox MEN. For AD systems, thermophilic MEN had higher genetic stability than the mesophilic one, which indicated that the thermophilic community could synchronally evolve and thus performed continuously in response to the i ncreasing OLRs. In order to learn the dynamics of the MENs on the spacial dimension, a dynamic membrane bioreactor(An DMBR) and an upflow anaerobic sludge bed(UASB) were operated, sharing the same inocula and operational temperature(35oC). The MENs were affected by the size of the space and the larger size of the MEN, the more heterogeneity to it. A MEN is affected more by the space than by the time.