Study On Ammonium Removal Of Low Ammonium Concentration Wastewater By Bio-plastic Foam And Ceramic Reactor

Nowadays, the events of environmental pollution which have made great harm to the human kind and the aquatic are frequently arising. Moreover, the water eutrophication of many lakes and reservoirs which are caused by emission of nitrogen and phosphorus, is threatening the human's life, production and the ecological balance. Ammonia is one of the most important factors. In order to meet the public's continuously improving demands on the environmental quality. Researching and developing an economic and efficient wastewater treatment of ammonia pollution control technology has become the focus of research in this field of topics.Physical and chemical methods can only remove some particular form of nitrogen, having a lot of drawbacks, such as the correspondingly complicated process, high cost, secondary pollution on the environment, incomplete regeneration method, only being suitable for small and medium-sized water supply quality, difficult to generalize. However, biological nitrogen removal methods have the widest scope of application, the minimum investment and operating costs, simple operation, no secondary pollution, and reliable wastewater standards of discharge. It therefore becomes the best approach. Usually, nitrogen compounds in the wastewater under the effect of microorganisms, will removed by amination reaction, nitrification and denitrification. Since the 1980s, China has started nitrogen and phosphorus removal research works about sewage, and some progress has been made, as the biological nitrogen removal technology has made a comparatively rapid development, putting forward a series of denitrification process, and some new concepts during the denitrification theoretical research. Nitration not only can be completed by some autotrophic bacteria, but also by some heterotrophic bacteria; and denitrification can happen not only in the anaerobic conditions, but also under aerobic conditions to some bacteria. Meanwhile many aerobic denitrifying bacteria can also become heterotrophic nitrification bacteria. They can oxidate NH4+ to NO2-, then denitrificating directly. Biological denitrification is available through the process of NH4 +→NO2-→N2, and so on. According to the reaction mechanism developed on the basis of biological denitrification technology which was developed by these new theoretical concepts, can be generally divided into several aspects, such as simultaneous nitrification and denitrification biological denitrification, anaerobic ammonia oxidation, shortcut nitrification and denitrification and so on.Biological aerated Filter is a biological membrane process: microorganisms attaching to the surface of carrier filter, the sewage flowing through the filter surface in the process, accomplishing the adsorption of organic nutrients and oxygen by diffusing from the liquid to the internal part of biofilm ,the biological oxidation happening in the biofilm, and so on .Through these processes mentioned above, the oxidation of pollution substances, and purification of sewage can be obtained.Test result showed:1. Under the same influent condition, to the comparison test between the ceramic fillers reactor and the ceramic and plastic foam fillers reactor, the plastic foam and ceramic reactor used less 12days to finish the biofilm attach to the fillers. After several day stable operations, the average removal rate of ammonia and CODcr in the bio-ceramic and plastic foam reactor is 11% and 17% higher than in the bio-ceramic reactor. The comparison of the different layers of fillers(4cm and 8cm)shows the removal rate of ammonia and CODcr in the 4cm filter is 3~8% and 10% higher than in the 8cm filter. It also demonstrated the layers are more frequent, the removal rate is higher.2. Bio-ceramic plastic foam reactor can obtain good treatment effect on the removal of ammonia, which can basically be stable at around 85 percent, while in the higher load influent ammonia, the removal rate can still reach to about 89 %; it shows that the bio-foam ceramic reactor has a strong impact resistance to the high ammonia load. At the same time, the experiment also confirms the changes of free ammonia in the low ammonia wastewater do not affect the removal of ammonia.3. Low organic loading is beneficial to obtain the high ammonia removal efficiency. Increasing organic loading, the heterotrophic bacteria increase the intake of ammonia, because the biological anabolism results in the decrease of substrate which can be utilized by denitrifying bacteria; with the increasing of heterotrophic bacteria activity, the ammonia and nitrite bacteria affinity decreases. When heterotrophic bacteria are rapidly proliferating ,heterotrophic bacteria are"packed"by a large number of nitrifying bacteria, making the transfer resistance increase between the ammonia and nitrite bacteria which result in the reduce of ammonia removal rate.4. Along the flow way, the number of heterotrophic bacteria gradually decreases. During this experiment, the removal rate of CODcr and ammonia mainly occurs in the 0 ~ 0.3 m. According to the figure, the heterotrophic bacteria dominant in the 0 ~ 0.2 m, and the denitrifying bacteria during 0.2 to 0.3 m, the number of heterotrophic bacteria reduce, but still exist. Because nutriment and dissolved oxygen diffusion is limited, this part of biofilm has clear stratification,and there are a small number of heterotrophic bacteria on the surface of biofilm. Since the columnⅡis kept in anaerobic environment, the activity of heterotrophic microbe is inhibited.5. The aeration of low ammonia wastewater takes little impact on the removal of ammonia. Obviously, the removal of ammonia was mainly due to biological denitrification and transforming into the own material of the microbe. 6. Dissolve oxygen is an important factor affecting the nitrite conversion. During the test, when the DO concentration is kept between 1 to 2 mg / L by controlling gas- water ratio between (2 to 3): 1 with intermittent aeration, the system can maintain higher nitrite conversion rate. If we decrease the value of DO, the concentration of ammonia in the effluent will increase, and nitrite conversion will diminish or disappear. If the value of DO increases, the steady nitrite conversion rate disappears, turning into nitrate-nitrification.7. The plastic foam and ceramic filler is a new style of combined packing which can be utilized in treating the low ammonium concentration. Low CODcr loading contribute to the high ammonium removal. According to the experiment,the best C/N ratio is 3:1 with the ammonium removal rate being about 92%.