| In recent years, as a result of continuous development of industry and rapid growth ofpopulation, water pollution and eutrophication, which is increasingly serious, has become thekey factor to the advancement of society and sustainable development of economy in ourcountry. Therefore, researching and developing a economic and efficient, as well as stable andhigh capacity for shock load, municipal wastewater treatment has growingly become a hotissue in the field of sewage treatment.In allusion to contradiction existing in the conventional denitrification and phosphorusremoval system, Prof. Bo Zhang firstly proposed reversed A~2/O process. Because of thepre-anoxic, carbon source for nitrogen removal was satisfied preferentially, while the adverseeffects toward anaerobic environment induced by the nitrate in the returning sludge had beenavoided. As a result, many inherent contradictions in biological denitrification andphosphorus removal have been solved. Consequently, based on result of previous research andpractical experience, this issue is designed to contrastively study the performance of nitrogenand phosphorus removal and influencing mechanism between reversed and conventional A~2/Oprocess by changing C/N/P ratio. This test explore the efficient reaction mechanism ofreversed A~2/O process in oerder to provide theoretical guidance and practical basis forachieving its optimal control and raising efficiency and saving energy, at the same time, revealthe deep reason of high efficiency and energy saving of reversed A~2/O process by themicroscopic indexes reflecting microbial metabolism activity, which has a important guidingsignificance to further optimizing the reversed A~2/O process.The results show that:1)The results of comparative study on performance of nitrogen and phosphorus removalbetween the two systems shows: C/N/P ratio has effects on ability of organics, nitrogen andphosphorus removal of the two systems, and the microbial adaptable ability to different C/N/Pratio of different processes differs. Because of reversed A~2/O system is prior to meet thedemand of carbon source of denitrification, while phosphorus absorption power ofconventional A~2/O system is wasted inefficiently in anaerobic zone, ability of denitrification and phosphorus removal in reversed A~2/O process is superior to the conventional. Comparedwith conventional A~2/O process, denitrification ability under high, medium and low C/N/Pratio in reversed A~2/O process is increased by1.69%,1.77%and1.77%, correspondingly,ability of phosphorus removal is respectively increased by0.43%,0.88%and0.88%. It shows,compared with conventional A~2/O process, the scantier carbon source in wasterwater is, thebetter ability of denitrification and phosphorus removal in reversed A~2/O process would bewhen the carbon source is deficient to the demand of microbial nitrogen and phosphorusremoval, and it shows that the ability of nitrogen and phosphorus removal in reversed A~2/Oprocess is more resilient to the water quality. It will enhance the ability and stability ofnitrogen and phosphorus removal when sludge load reduce, and compared with theconventional, the higher sludge load is, the better ability of nitrogen and phosphorus removalin reversed A~2/O process would be.2)The results of comparative study on mechanism of microbial biochemistry betweenthe two systems shows: compared with conventional A~2/O process, utilization efficiency ofPHAs under high, medium and low C/N/P ratio in reversed A~2/O process is increased by1.00%,5.79%and5.79%, correspondingly, ability of intracellular phosphorus metabolismunder medium and low C/N/P ratio in reversed A~2/O process is respectively increased by13.36%and17.77%, while utilization efficiency of intracellular glycogen is increased by21.62%and32.54%. It can be seen that metabolism activity and utilization efficiency ofintracellular substance in reversed A~2/O process is significantly higher than those of theconventional and the ability to adapt to changing water quality is also stronger. In additiongly,the lower C/N/P ratio is, the more obvious advantage in reversed A~2/O process would be.Compared with conventional A~2/O process, intracellular ATP under high, medium and lowC/N/P ratio in reversed A~2/O process is increased by4.84%,7.55%and7.55%,correspondingly, intracellular NAD+/NADH is respectively increased by4.84%,7.55%and7.55%. It can be seen that efficiency of substrate degradation and activity of electron transportsystem in reversed A~2/O process are higher than the conventional, so is the ability resisting tothe change of carbon source. This result tells the reason why metabolism activity and utilization efficiency of intracellular substance in reversed A~2/O process is significantly higherthan those of the conventional from angle of efficiency of substrate degradation and activityof electron transport system. It will enhance the improving percentage of efficiency ofsubstrate degradation and activity of electron transport system reversed A~2/O process is biggerwhen sludge load reduce, so are the metabolism activity and utilization efficiency ofintracellular substance. In additiongly, this test tells the reason why the improving percentageof efficiency of substrate degradation and activity of electron transport system reversed A~2/Oprocess is bigger when sludge load reduce from angle of microbial metabolism. |
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