The Experimental Study On Applying Tea Extract To Deodorization In Sewage Treatment Plant

Recently, the number of population has increased sharply and the urban scale has broadened, which leads to the fact that the urban sewage treatment plant has become closer to the residential blocks. As a result, the stench released by the sewage treatment plant has become the main source of the urban stench, which mainly contains NH₃ and H₂S. Focusing on tea extract—tea-polyphenlos (TP), NH₃ and H₂S as the main study subject, this thesis mainly investigates the feasibility to apply tea extract to sewage treatment. Also, this thesis explores the principle of deodorization, which provides a theory basis and is very valuable for the further study and industrialization.The main implements in the experiment are devices for gas-producing, bottles for chemical reaction, and bottles for exhaust-absorbing. The two kinds of bottles are both 500ml-volume gas-gathering bottles. Ways to be used for gas-producing depend on different gas to be produced. For example, when producing NH₃, we use a way to heat and decompose NH₄HCO₃. When producing H₂S, we use a simple Kipp's Generator. Driven by airflow from the micro airblower, through the glass pipes and aeration head, stench produced in gas-producing bottle then enters the reaction bottles. After a complete reaction, the surplus exhaust is absorbed by water in the exhaust-absorbing bottle, and the rest gas overflows through the pipe. By examining the amount of NH₃ and S in the bottles, we can work out the deodorization rate of the tea extract solution.The following conclusions are achieved through analysis:1. Applying tea extract to sewage treatment is experimentally feasible.2. There are four factors affecting the result to apply tea extract to the deodorization of NH₃ and H₂S: the mass of tea extract; the time length for deodorization; the density of stench, and the temperature for deodorization. With a 0.09g mass of tea extract, 30min long for deodorization, a 1000mg/m³ density of stench and a higher temperature about 50℃, there will be a best result for deodorization.3. Illustrated in the experiment, the result to deodorize NH₃ is better than to deodorize H₂S, no matter what density of stench it is. It has little effect on deodorization when the value of PH is about 5.5 to 6.0, and the temperature is about 20 to 50℃. When the time is limited to about 20 minutes, it can reach a best result of deodorization.4. TP plays a crucial role in the process when tea extract interacts with NH₃. The coactions of an element "-OH" in TP and a single pair of electron in N produce ammonium, which can lead to the deodorization of NH₃. The ammonium produced is unstable, and it can be decomposed into N and an unknown matter.5. TP also plays an important role in the process when tea extract interacts with H₂S. The particular structure of TP makes its element have a strong polarity and easy to be broken, which makes it can combine with other molecule and produce new matters. As a result, H₂S can be deodorized.6. In general, the great merit of this method is that the process of deodorization is harmless, which will not produce other pollution. What is most different in this method is that, in the process to deodorize H₂S, it produces little H₂SO4 and has little effect on water quality. This is a great progress in S deodorization.7. Compared with others, this method has some advantages on technological and economic aspects. This system greatly reduces the consumption of energies, saves the land, and it is very easy to operate and maintain. Meanwhile, because of the open design, the method avoids the anaerobic process produced by the process to seal for gathering gas, which can decrease the pipes laid. Therefore, it is very significant and valuable for theory study and practical application to apply tea extract to sewage treatment.