Study On Water Blackening And Smell By Double-drive Dynamic Membrane Pressure Method

Currently, water blackening and smell is one of important subjects about water environmental research and monitoring. So far, related research reports about water blackening and smell mostly focus on the causes, mechanism, judgement indexes, and judgement satandards and on judging some actual water blackening and smelly degree by some judgement methods and so on. In the existent methods, it is mostly by determining some traditional indexes like COD_Cr, DO, BOD₅, NH₃ - N and TP by traditional monitoring methods fistly, then combined with a certain blackening and smelly critical index method or discriminant equation and standards to determine whether some water samples have became black and smelly. However, there are many defects on the traditional monitoring methods such as the high cost, big workload and causing secondary pollution.Study on the index of water blackening and smell is important on judging degree of water blackenging and smell and scientific management of water. Organic pollutants in water are one of the primary factors causing water blackening and smelly. The urban life and industrial sewages are a complicated natural system, which are composed of a great deal of surface-active substances and surfactants. These surafce-active substances have hydrophilic groups and hydrophobic groups, and easily form a layer of film on water surface. To some extent, the organic film covering water surface will affect gas-liquid exchange speed between water and atmosphere, and cause water blackening and smelly. Dynamic membrane pressure method is a method based on the theory of interfacial chemistry, because of the characteristic that organic molecules tend to be enriched in the water surface films and have surface excess. Membrane pressure and hysteresis loop aera are measured by double-drive dynamic membrane pressure method to appraise the organic content in water in this article, and the relationship between water blackening, smell and the organic conntent is explored. The method of dynamic membrane pressure used in this article has the typical advantages like simple and fast, no secondary pollution. The following sollutions are chosen in my research topic: The solution â‘  is the compound of simple carbohydrates and simple acids; The solution â‘¡ is the compound of peptone, beef extract and some inorganic salts; The solution â‘¢ is the water sample in Meichuang zone of Taopu river; The solution â‘£ is the water sample in the overlapping between Taopu river and Qiu river; The solution ⑤ is the raw sewage water sample in Caoyang sewage disposal factory; The solution â‘¥ is the raw sewage water sample in Taopu sewage disposal factory; The solution ⑦ is the two water samples matched by running water and polluted bottom mud from Caoyang sewage disposal factory. The solution â‘  and â‘¡ of which belong to simulated water matched according to references.With different water bodies turning into blackenging and smelly, The membrane pressure and hysteresis loop aera are measured by double-drive dynamic membrane pressure method in the article.at the same time, CH (chroma), COD_Cr, DO, NH₃ - N as auxiliary data are determined and the chang of smell is distinguished by sense of smell. By experimental data, the relations are explored between the membrane pressures, hysteresis loop aera and above auxiliary data and water blackening, smell. It is discussed that whether surface membrane pressure or hysteresis loop aera can be used to describe blackening and smelly water body. From experiments we concluted:I The difference of illumination and evading the light has more effect on water blackening and smell of the solution â‘¡ than the solution â‘ ; With the solution â‘  translating from neither black nor smelly condition into black and smelly condition, the membrane pressure increase gradually, the solution â‘¡ is on the contrary, the critical membrane pressure index that whether simulated water bodies are balck and smelly body or not in the solution â‘ , â‘¡ approximately is 10mN/m.II With the solution â‘¢, â‘£ translating from the black and smelly condition into the condition of neither black nor smelly, the membrane pressure all reduce gradually. With the biodegradation of organic pollutant in water, the decrease of organic pollutant content in water surface film helps the exchange speed between water and atmosphere, then water blackening and smell disappear. The critical indexes that the solution â‘¢ blackening and smell disappear are: CH=21.0, л= 10.13 mN/m, I=4.62, COD_Cr=29.7 mg/L, Area=7.39; The critical indexes that the solution â‘£ blackening and smell disappear are: CH=23.2, л= 15.14 mN/m, I=8.34, COD_Cr=55.4 mg/L, Area=67.7.III With the solution ⑤ translating from the black and smelly condition into the condition of neither black nor smelly, the membrane pressure reduce gradually.The critical indexes that the solution ⑤ blackening and smell disappear are: CH=21.0, л= 6.13 mN/m, I=22.0, COD_Cr=40.1 mg/L, Area=2.83. However, the solution â‘¥ have bad relation between water blackening , smell and the change of membrane pressure, maybe caused by containing purple pigment in water.IV With the solution ⑦ translating from neither black nor smelly condition into black and smelly condition, the membrane pressure, CH, COD_Cr increase gradually, which shows the organic pollutants adsorbed in the particle of bottom mud are released into water gradually and will cause secondary pollution; when the solution ⑦ became black and smelly, COD_Cr>40 mg/L, CH>21.5, I>5, л> 10 mN/m.Considering all experimental analysis and the security of preventing water body blackening and smelly, the control level of membrane pressure index is: л≤10 mN/m for actual water body and л≤6.13 mN/m for seriously polluting urban sewage. Up to now, there are few research reports about water blackenging and smell by using the instrument of double-drive dynamic membrane pressure at home and abroad. This article initially studied on the water quality index for preventing water blackenging and smell by dynamic membrane pressure method , which will build good foundation for the further research and have good application prospect.