Application Study Of Bio-zeolite Filter On Micro-polluted Source Water Quality Treatment

At present, the shortage and the pollution of water resource in our country is more and more serious, and the range of contaminated water source is increasingly enlarged. As a result, the water plants in our country have to take more contaminated raw water for the domestic drinking water or other purposes. However, the traditional water purification technique can not eliminate such contamination in the raw water as organic substance, ammonia nitrogen. Therefore, the purification technique for the contaminated raw water has been an important and urgent research subject.With the introduction of zeolite as the filling material for filter, this research subject takes a medium-test, studying its effect on eliminating ammonia nitrogen, organic substance . The paper first analyzes the technique start-up process in the condition of natural membrance, and then studies the contaminant-elimination effect of the biologic zeolite under the different work conditions. At last, the paper derives a nitration speed constant, from the test data, which would give instructions on the design of the zeolite biofilter programme.The test shows that: when the temperature is above 20℃, the relative stable and high ammonia nitrogen eliminate rate taken as a parameter indicating whether the biomembrance is successful, the time of the natural biomembrance is about 18 days, and the technique starts up quickly. At that time, the surface of the zeolite is full with plentiful nitrobacteria, and nitrosobacteria, which can help zeolite eliminate the ammonia nitrogen in the water. The medium test through the whole year shows that: When the water temperature is above 18℃, and the length of water stay is controlled within 17 min, the elimination effect of the zeolite filter is quite good . When the average density of ammonia nitrogen in the inlet water is 3.2mg/L, the elimination rate for ammonia nitrogen is around 70%. While the water temperature is about 9.5℃, and the length of water stay is controlled within 25 min, the elimination effect of the zeolite filter is around26.7%. In that case, the increase of the length of the water stay can enhance the elimination effect. As there is less soluble biodegradable organic substance in the raw water, the average elimination rate for the CODmu of this biologic zeolite filter is relatively low, about 21.8%. The water temperature influences on the nitration effect greatly, but on the CODmd elimination slightly. Due to the special air-dissolving method adopted in this technique, the mass transfer efficiency of the dissolvent oxygen in the filter chamber is high. When the volume rate of the air and water is 0.5, the above density of dissolvent oxygen in the outlet water can reach 5.1mg/L. In this condition, DO would not be a limit on nitration. Despite of the different work condition, there is no great change in the turbidity and chromaticity of the inlet or outlet water. Meanwhile, the filter can eliminate some Fe and Mn in the raw water. The upward flow adopted in the technique can decrease the deposition of the zeolite filling material and the filter bottom, which results in the long backwash period. Working with a low temperature, and high loading of ammonia nitrogen, the equipment for the medium-test would accumulate the nitrite. This technique can eliminate the algae to a certain extent, and the elimination effect in summer is better than the effect in winter. The mensuration of microorganism indicates that: the nitric acid bacteria in the biological system are more than the nitrous acid bacteria. With the temperature falls, the microorganism in winter would be decreased a little. If this equipment is turned off for 4 days in winter, it may need 8 days to reach the elimination effect, while turned off for 35 days, a month is needed.The medium-test arrives at a conclusion: it is feasible in the technique, adopting the biologic zeolite as the filling material for the filter, to eliminate the contaminants such as ammonia nitrogen, NO2-N, CODmii, turbidity, chromaticity, Fe, Mn and so on. Compared with the ordinary biofilter, this home-made zeolite biofilter is provided with higher air-dissolving efficiency, longer recoil period, stronger resistance for impaction of ammonia nitrogen, simple structure, and easy operation. This technique has a good future for application.