Several common fillers in contact oxidation process
I. Semi-soft filler
The semi-soft filler consists of a single filler, a plastic sleeve and a central rope. All parts are made of low density polyethylene, which has good acid resistance, alkali resistance and aging resistance. After melt injection molding, it is radiated from the central hole to obtain a circular single sheet as a semi-soft filler body. The central rope passes through the central hole of each single sheet in turn, and plastic pipes are nested in series between the single sheets at a fixed distance to form the required length.
Semi-soft packing has special structure and hydraulic performance, large porosity (greater than 96%) and low flow resistance. When water flows through the packing layer, it can produce obvious turbulent flow pattern, which improves the contact efficiency between water and biofilm and increases the ability to remove pollutants. The filler has certain rigidity and flexibility, and has a strong ability to redistribute water and gas. For the large bubble gas supply in blast aeration, it has the function of multi-stage repeated bubble cutting, thus improving the oxygen transfer rate. The specific surface area is large (up to 130m2/m3), which provides sufficient space for the growth of microorganisms. It has the characteristics of high mass transfer efficiency, energy saving, difficult blockage, corrosion resistance and aging resistance.
Second, combined packaging.
Combined packing concentrates on soft and semi-soft structural features. The middle of the packing unit is a small semi-soft packing, and the periphery is connected with softened fiber bundles. Most of these fillers are different in the central ring structure and the number of fiber bundles, mainly in the following aspects. 、
1, combined double-ring packaging
A plastic ring is used as the skeleton, with a relatively small semi-soft filler in the middle, a softened fiber bundle connected to the periphery, and vinylon filaments are tensioned on the plastic ring. In sewage, the tow is evenly dispersed, and it is easy to hang and remove the film, which has good adaptability to the change of sewage concentration.
2. Combined porous ring packing
There are 40 square holes around the plastic ring, and 8 bundles of vinylaldehyde wires are evenly distributed around the square holes, which are radial. The fiber bundle is interlocked with 8 square holes, which is very firm.
Combined packing combines the advantages that soft filler is easy to film and semi-soft filler is not easy to wrap and block, and overcomes the disadvantage that semi-soft filler is not easy to film, so it is widely used in contact oxidation treatment of various wastewater.
Three, elastic solid filler
Elastic three-dimensional filler is made of polymer and additives such as antioxidant, hydrophilic agent, stabilizer and adsorbent through special stretching. There are fine burrs on the surface of the elastic wire to increase the specific surface area. During installation, 600~ 1000 strips are inserted and pressed between two plastic circular plates, so that the strips are spread radially and evenly, and the suspended fillers are strung together according to different plate distances. The filler is made of all-plastic material, which has a longer service life than soft filler. During aeration, each filament vibrates constantly, so the gap between fillers is variable and the biofilm is easy to update. At present, it is widely used in the hydrolysis and acidification section of refractory organic matter treatment to improve the biodegradability of wastewater.
IV. Suspended fillers
The density of suspended filler is close to that of water, and it exists in suspended form in the aeration tank, and its dosage (by volume) is about 20%~70% of the volume of the aeration tank. Suspended fillers widely used in engineering mainly include the following types:
1, polyhedral hollow sphere filler
There is a reinforcing ring in the middle of the ball along the whole circumference, and there are twelve petals above and below the ring. The spherical protrusions are perforated into a mesh or non-mesh, and arranged radially along the central axis.
2. Built-in floating ball filler
The filler consists of a grid spherical shell and a built-in carrier. The shell is made of high molecular polymer by injection molding, and the spherical surface is grid-shaped. The built-in carrier materials are aldehyde vinylon yarn and vinyl flat yarn. The former has a shaft in the shell and two plastic buttons on the shaft. Six bundles of aldehyde vinylon yarns are fixed on each buckle, and the fiber yarns can swing freely with the water flow. The latter is made of polyethylene, which is drawn into thin flat wire and then packaged into a shell in the shape of shavings. The mesh size is moderate, which not only has certain mechanical strength, but also will not be blocked by falling biofilm.