| Activated sludge biological treatment process has been widely used, which is still facing the problem that primary nutrient removal efficiency of the corresponding lower energy consumption is too high, and the impact the system load is less stable. Floc structure is one of the most important basic parameters in the flocculation process,which affect the adsorption and the mass transfer of organic substrate in the microorganism biochemical reaction, and also determines the compression, settlement and stability of sludge on the macroscopic. It has an important impact on treatment efficiency.based on floc structure, this paper is studing at a new performance and mechanism of modified A2/O process, and the influencing rule of impacted different floc structures, which provide a new idea to improve the sewage treatment efficiency and system stability. The contents and results of the study include:1、Through adjusting the modified bio-reactor technology A2/O selector, and monitoring changes occur within 40 days of the parameters and found:(1) Increasing the flow rate of biological processes in modified A2/O selector can achieve dense floc enrichment. The peak of aerobic tank floc particle size increased from 280μm to 410μm in 40 days of increased flow rate, which increased by 46%, SV5,SV30 and SVI and the other settling parameters decreased by 44%, 48% and 78%, The microbial floc size has a corresponding increase,either.(2) As biological selector selects attachment filtering,which makes autotrophic bacteria grow easier. In that way, dense floc enrichment of denitrifying bacteria can be achieved, thereby increasing the efficiency of nitrogen on dense floc. At the beginning of process of dense floc enrichment within 40 days, the total nitrogen removalefficiency increased from 42 % to 62 %.(3) In the course of this experiment on achieving dense floc enrichment in biological selector, there is no notable change rule in phosphorus removal. Removal basically fluctuated between 40% to 50 %. Phosphorus removal can not be determined dense and loose floc which was better, may be affected by factors such as temperature and sludge age, which still needs further study.2、To further study and analysis the environmental sensitivity of dense floc which seleced by modified A2/O selector. continue to design a short-term impact experiment of sludge which representatives different floc structure to investigation, the results showed that:(1)After short-term impact occured, loose sludge floc density decreased, settlement became worse; while dense floc density became larger continuously, settlement changed for the better. Through the choice of substrate can change the density and performance of floc settling in the short term. After consolidating floc sludge, the degree of compaction and subsidence had been impacted but turned better. It impacted less on the subsequent settlement and dewatering, sludge less prone to swelling.(2)Heterotrophic activity the proportion of total respiration of loose floc both continuously declining, and heterotrophic activity of dense floc had a rapid rise recovery after a transient suppression, the proportion of total respiration even was higher than Initial. Heterotrophic bacteria played a key role during the impact on the activity in floc structure, and dense floc when subjected to short-term impact of the total respiration rate faster recovery, which heterotrophic bacteria dominated the respiration rate recovery.(3) According to the fluorescence intensity, the Peak B of humic substances changes after substrate changed impact, the peak was decreasing even disappeared, so the peak B was related to the original water components; there is little change in A tryptophan peak area during the impact, but there is no certain rules,because of a lack of reasonable explanation. Overall,fluorescence peaks of EPS had little associate with variations of floc structure. |
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