Preparation Of Composite Filter Materials And Performance On Treating Domestic Sewage

The article mainly includes three parts: charactistic of natural zeolite, the preparation of composite clinoptilolite filter materials and the performance of BAFs filled with the composite clinoptilolite filter materials, ceramsite and granular clinoptiloite to treat domestic sewage.To determine the species of the two kinds of zeolite, chemical analysis and XRD phase analysis were done on them. The clinoptilolite which was heated at a certain temperature has better ability to absorb ammonia nitrogen in water. Activated experiments were tested to find out the best temperature to activate zeolite. The adsorption isotherms of ammonia nitrogen on the two kinds of zeolite were drawn to determine which kind of zeolite is more suitable as the main component of the composite clinoptilolite filter materials.Spheroidal composite filter materials were prepared with activated clinoptilolite powder as the main component. The optimized composition of the filter materials determined by orthogonal test wasωclinoptilolite:ωbond:ωadditive=55%: 35%: 10% with activation temperature at 150℃for 3h. The piled density, cylinder pressure and apparent porosity of the composite filter materials are 674Kg/m~3, 4.32MPa and 59.02%. Compared with ceramsite, the composite filer materials have larger specific surface area, higher porosity. From the adsorption isotherms of ammonia nitrogen on the composite clinoptilolite filter materials and ceramsite, we can find out that the ceramsite does not have the ability to removal ammonia nitrogen by adsorption, while the adsorption isotherms of ammonia nitrogen on composite filter material could be well described by the Langmuir formula.Three BAF reactors filled with the composite clinoptilolite filter materials, ceramsite and granular clinoptilolite operated for a period to test the performance of treating domestic sewage. In the early days of start-up, these three kinds of filter material didn't have biofilm, removing ammonia nitrogen only by the adsorption and ion-exchange ability, so the composite clinoptilolite filter materials reactors had higher ammonia nitrogen removal rate while the removal rate of ceramsite reactor was nearly zero. As the operating time increasing, the rate of ammonia nitrogen removal by three reactors increased too. The granular clinoptilolite reactor had a high removal rate on CODcr of which nearly reached 50% in start up. The shape of granular clinoptilolite is irregular, the granular clinoptilolite filled in reactor is very compactive, which endowed the granular clinoptilolite reactor had a better filter ability, so it had a higher CODcr removal rate than the other reactors in start up.In steady condition, the composite clinoptilolite filter materials reactor also had well ability on removing CODcr, ammonia nitrogen, turbidity, colurity at the influent of h=0.6m/h, h=0.8m/h and h=1.0m/h. Because of the property of the BAF, the removal rate of total phosphorus is not as well as the other pollutants, but with the help of chemical method, the total phosphorus in domestic sewage also can be well removed.With the analysis of the composite clinoptilolite filter materials on its treatment ability and economic benefits, using composite clinoptilolite filter materials as BAF's filter media is available.