Bismuth Tungstate Photocatalysis for Marine Oil Sewage
With the development of shipping industry, marine and river water pollution caused by ships is becoming more and more serious. Some researchers have proposed a scheme of photocatalytic treatment of ship oil sewage by pre separation + fine filtration + deep oxidation.
(1) The oil sewage from the upper part of the tank is pumped into the direction of the upper entrance of the pool in tangential direction, forming a rotating flow, which is divided into a cylindrical type. Under the action of the centrifugal force of water, the oil particles with relatively small relative density converge to the central part of the pool and float up, so that the coarse oil particles are separated out in advance.
(2) Through the pre separated oily sewage into the fine filter, the fine filter is in turn from top to bottom, including overflow trough, filter material partition board, biomass filter layer, filter material bearing layer, filter material separator with pore size less than biomass filter material, filter material bearing layer is made up of gravel layer, so that raw material filter material is fixed on filter material separator and filter. Between the bearing layer, the pre separated oily sewage is brought to the overflow slot, and then the filter material is removed, the biomass filter layer and the filter material bearing layer are passed in order to realize the filtration and removal of the fine oil particles.
(3) The oily sewage is filtered into the deep oxidation unit and the deep oxidation unit is coated with bismuth tungstate photocatalyst. When the ozone is attached to small oil particles and emulsified oil particles with micro bubbles, the air flotation oxidation pool is entered with the flow of water. The floating of oil particles is realized through the buoyancy effect of ozone bubbles, and the oil particles are initially oxidized and degraded at the same time. The light ceramsite with the visible light catalyst of bismuth tungstate floating on the surface of the water, and the light source is irradiated. The energy transition produces a strong oxidizing free radical in the water, and further catalyzes the oxidation degradation of the floating oil particles. The flotation, ozone oxidation and photocatalytic oxidation are carried out in the flotation cell to achieve the separation and degradation of the remaining small oil particles and emulsified oil particles and sewage.
The three stage treatment process of "pre separation + fine filtration + deep oxidation" of marine oil sewage can simultaneously complete the separation and deep degradation of oil in oily sewage. It has the advantages of good separation effect, high purification efficiency, low labor cost and convenient operation.
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