Pressurized oxygen saturation filters

The added oxygen required for aerobic purification to develop is provided by saturating the raw water in air at the inlet to the filter battery along with  

Given the impact of recycling, BOD5 of 40 to 50 mg l can be satisfied by the O2 input. The BOD5 fraction removed with the SS is low, inasmuch as these colloidal, almost unfilterable SS can escape filtration. As a result, the filtered water can still contain 15 to 30 mg r SS. 

The cost of treatment is governed by the power used for pumping around 8 kWh per kilogram of oxygen transferred. 

Metatlic filters have diameters ranging up to 5 or 6 m and are used in batteries of several parallel units with the following operating conditions  

The added oxygen required for aerobic development is provided by maintaining an air cocurrent jointly with the rising water current through tire filter. The filter is generally open and can be built of concrete on a larger scale than pressurized filters. The facilities must nevertheless be made up of several units because excess velocities when a unit is being washed are even less acceptable than in pressurized facilities. 

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The surface silylated zeolites were prepared by suspending the H-ZSM-5 or FeH-ZSM-5 zeolite in n-hexane into which a calculated amount of tetraethyl orthosilicate was added to obtain addition of 1.5 wt. % of Si in the final product (abbrev. SiH-ZSM-5 or SiFeH-ZSM-5). n-Hexane was evaporated and the zeolites were dried and calcined in an oxygen stream at 770 K for 5 hours. To add some Fe cations to the surface of silylated zeolites, the SiH-ZSM-5 was introduced into a FeCl solution, filtered and dried (abbrev. FeSiH-ZSM-5). The characteristics of the parent and modified zeolites are given in the Table. The alkylation of toluene with ethylene was carried out in a vapour phase continuous flow microreactor at atmospheric pressure. Nitrogen as a carrier gas was saturated with toluene to 18.5 vol. %, the toluene to ethylene molar ratio was 3.8. The reaction products were analyzed by an "on-line" gas chromatograph (Hewlett-Packard 5890) with MS and FID detection. 

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