| Centralized urban wastewater sanitation systems play a dominant role in terms of improving water environmental quality. However, the fact that can not be avoided is that investment and operation cost of centralized urban wastewater sanitation systems are very high. In recent years, although large-scale centralized urban wastewater sanitation systems were built and operated, the water environment in China has not been improved, and many water environmental problems emerged one after another. The water environmental problems have been can not be completely solved only by depending on centralized urban wastewater sanitation systems.At the same time, decentralized domestic sewage treatment technologies and small-scale domestic sewage treatment plants (SDSTP) gradually attract people's attention in today's China. More high efficient and lower cost technologies to treat the domestic sewage need to be developed. Based on this background, MSBFR (Multi-stage Biofilm Filtration Reactor) process, which mainly based on"Reverse Grain bio-filtration"theory and application of light suspended media, was developed. Meanwhile, the concept and technical route of"Pre-oxygen biological coarse filtration"were put forward. A successful high efficient and low cost multi-stage biofilm domestic sewage treatment process with independent intellectual property right was developed. What's more, systematical experiment (capacity Q=515L/h) to treat domestic sewage by continuous flow process was carried out. The research including hydrodynamic behavior of MSBFR, operation stability to treat domestic sewage, treatment efficiency and effect factors, process operation style and the effect of process adjustment on enhancing the treatment efficiency were carried out as well. Moreover, PCR-DGGE and FISH technologies were used to analyze microbial population structure of multi-stage biofilm process from the level of molecule biology. Then the relationship characteristics between MSBFR operation efficiency and microbial structure changes were systematically discussed.The research for the hydrodynamic behavior in MSBFR showed that the reactor's hydrodynamic behavior of every stage of the sub-reactors was plug flow style. The Pre-oxygen biological coarse filtration based on"Reverse Grain bio-filtration"theory could efficiently remove SS and COD. MSBFR system had high and stable removal efficiency of COD, NH4+-N and SS.The effect on the removal efficiency of COD, NH4+-N and SS of some factors, such as water temperature, hydraulic load, influent water concentration, volumetric load and the gas-water ratio, were researched. The results showed that the water temperature, hydraulic load, influent water NH4+-N concentration and its volumetric load and COD volumetric load had a noticeable effect on the nitrification of the MSBFR. When the filtration rate was lower than 1.0m/h, the effluent NH4+-N was near entire nitrification. When the load of influent water was lower than 0.85kg NH4+-N/ (m3·d), the effluent NH4+-N would be stably lower than 2mg/L. When COD load was less than 3.0 kgCOD/ (m3·d), NH4+-N removal efficiency could maintain above 95%. Furthermore, gas-water ratio is also a key factor of nitrification.The effects of DO, C/N ratio on simultaneous nitrification and denitrification (SND) were also researched respectively. The results showed that DO had great effect on SND. The highest SND performance point happened when DO=1.5mg/L. The TN removal efficiency could reach 67.5% and C/N ratio was also a key factor in influencing SND. When C/N ratio reached 4, the highest TN removal efficiency through SND was achieved. The effects of DO and FA (free ammonia) to shortcut nitrification-denitrification of MABSFR system were also researched respectively. The results showed that DO was a key factor of shortcut nitrification-denitrification. When DO maintained 1.5±0.3mg/L, Nitrous Acid Nitrogen accumulation rate could reach around 90%. FA had great effect on shortcut nitrification-denitrification of MABSFER system. But the control of shortcut nitrification-denitrification through FA was not very stable comparing with DO.MSBFR with pre-denitrification operation mode could improve the operation performance. When the return sludge rate was100%300%, high COD removal was achieved by MSBFR. The Effluent COD could maintain lower than 50mg/L. Reflux ratio had a relatively high effect on TN removal efficiency. When reflux ratio was 200%, the TN removal efficiency reached the highest level, and the effluent TN could stably maintain lower than 15mg/. COD/TN ratio had great effect on denitrification performance of pre-denitrification performance. The system TN removal efficiency maintained in high level when COD/TN ratio was between 4.07.0. The results also showed that DO had certain effect on TN removal efficiency.The system odor control improved greatly when the humus earth reactor was grafted into the system to cultivate earth microorganism. The results of FISH analysis demonstrated that the microbial community structure of sludge changed after grafted the humus earth. The amount ofβ-Proteobacteria was apparently higher than the control system, accounting for 44% of DAPI-stained bacteria. The results of PCR-DGGE analysis also showed that the introduction of humus earth induced the directional succession of the microbial community structure.Using the PCR-DGGE and FISH technologies, the associating characteristics between MSBR treatment efficiency and bacteria structural succession were also mainly researched. The analysis of PCR-DGGE of the aerobic reactors'biofilm in various stages showed the rich varieties of the microbial community in the stable operation periods. FISH analysis showed that, on different levels of the aerobic reactor along the flow direction, the average ratio between EUB338 and DAPI-stained bacteria decreased gradually from average 58.4% to 31.5%. The quantity of AOB,NOB increased quickly with the decrease of influent organic concentration along the process flow. At the peak point, AOB reached around 7.9% of DAPI-stained bacteria, and NOB reached around 4.5% of the total bacteria. In addition, the research also covered the effect of the influent water quality on the bacterial community structure of the biofilm. FISH tests showed the evident effect of influent water COD/NH4+-N on bacterial community structure.
|
PDF Full Text Request