The high concentration organic wastewater is one of the main pollution sources for Chinese water environment. The fermentation, food, chemical and medicine filed produced lots of this kind of wastewater. The anaerobic and aerobic treatment for the wastewater is the main solution for high concentration organic wastewater pollution. And we have optimized the design of large-scale UASB reactor, mastered the method of anaerobic active sludge culturing, and we have developed CAAS reactor, combined the UASB and CAAS, so that form UASB-CAAS system for high concentration organic wastewater treatment.
Now this process is already applied in high-concentration organic wastewater treatment projects in Huaihe River, Taihu River and Yangtze River, and the treated wastewater should reach the discharge requirements. This technology can remove the pollutants in the water, make the water outlet reach the state discharge standard, also can turn more than 90% of the organic into marsh gas for power generation or substitute for fuel, so that make the whole treatment project become the energy production system. So, this technology can be applied high concentration wastewater treatment for all fields, it has important social profit, environmental profit and certain economic profit.
A. EYBC reactor working principal
The EYBC reactor is the actual application of solid fluidization technology in organic wastewater treatment. The solid fluidization technology improves the touch of the solid particles and liquid, make them appear in fluidization status, and it is widely used in petroleum, chemical, metallurgy and environment protection etc.
According to carrier fluidization theory, the EYBC reactor should be equipped with certain particle sludge carriers, when the organic waste water and produced marsh gas flow from top to bottom through the particle sludge bed, the actions between the carriers and the fluid will be different, so that the sludge bed will appear different working conditions. When the waster water surface in low ascending speed, the particle sludge in the reactor will keep quite, and the waste water will go through the particle distances, and the sludge bed keep a stable void age, but the pressure difference will increase according to the liquid surface ascending speed increase. When the ascending speed reaches certain ＆#118alue, the pressure difference will be equal to the carrier weight, and if continue to increase the ascending speed, the bed void age will increase also, so the sludge particles will appear the status of suspending, and the particle bed is fluidized, at that time if still continue to increase the ascending speed, the bed void age is increased also, but the bed pressure difference will almost keep stable; then if increase the ascending speed to the maximum speed, will result in big loss of the carrier particles.
And the working condition of carrier fluidization showed that, EYBC reactor is in the preliminary fluidization period, e.g. expansion stage (volume expansion ratio about 10-30%), and in this area the inlet water in a low speed, so can ensure complete touching and mixing of inlet water basic media and sludge particles, fasten the biochemical reaction speed, on the other hand can reduce the phenomena of overload in the bottom which is easy found in static bed, and increase the bearing ability to organic load especially the toxic material.
2. EYBC reactor characteristics
The EYBC reactor is one improved UASB reactor, and very similar in structure and sludge appearance, but its operation model is obvious different with the UASB reactor, as EYBCnormally take the ascending speed for 2.5-6m/h (max. for 10m/h), and the liquid surface high ascending speed make the particle sludge bed in expansion, not only make the inlet water touch the particle sludge completely, improve the transfer efficiency, but also benefit to the diffusion and transfer of the basic media and metabolite in the particle sludge, ensure the reactor in normal operation in high volumetric load. The EYBC reactor characteristics see Table 1.
3. EYBC reactor structure
a. Inlet water distribution system
The inlet water distribution system mainly distributes the wastewater to the whole reactor evenly, and should have the function of hydraulic mixing. It is one of the key parts for high efficiency running of the reactor.
b. Reaction area
Including sludge bed area and sludge suspending area, and the organics will be decomposed by anaerobic bacterial; it is the key part of the reactor.
c. Three-phase separator
Composed by precipitation area, backflow seam and air seal, its function is to separate the marsh gas, sludge and liquid. The sludge will precipitate in the precipitation area, then backflow from the backflow seam to the reaction area, and the marsh gas will enter the gas chamber. The separation effect of the three-phase separator will influence the treatment effect of the reactor directly. The ascending speed in EYBC reactor is quite big, so should give special change to the three-phase separator. And the change can be in following methods: 1. Increase one rotational blade, and the three-phase separator bottom will produce one downward stream, which is good for sludge backflow. 2. Equip with screen-drum or thin griller, remove the small-size particle sludge 3. Equip the mixer in the reactor, separate the air bubble and particle sludge; 4.Equip the retainer on outlet weir to remove particle sludge.
d. Outlet water cycling system and discharge system
EGSB reactor is different with UASB reactor in outlet cycling part, its main function is to improve the ascending speed in the reactor, make the particle sludge bed in complete expansion, make the waste water and microbial touch completely, improve the transfer effect, and avoid the dead corner and short current happen in the reactor. The function of the discharge system is to collect the treated water in the precipitation area and discharge out of the reactor.
e. Air chamber
Also called air collection cover, its function is to collect the marsh gas.
f. Dross removing system
Its function is to remove the dross in precipitation area and air chamber surface. Ignore this process if less dross.
g. Sludge discharging system
Its function is to remove the remained sludge in reaction area evenly.
Normally the EYBC reactor no needs heat can make use of the wastewater temperature. If need heating to fasten the reaction speed, should heat in the same method for digestion tank. But normally the reactor need insulation, and the method same as for digestion tank. The reactor should be anti-corrosive treated.
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