1. Introduction
In China, 82% people drink shallow wells and rivers, of which 75% are seriously polluted by bacteria, and the drinking water population polluted by organic matter is about 654.38+0.6 billion. For a long time, people have always thought that tap water is safe and hygienic. However, tap water is no longer sanitary because of water pollution. According to a survey, there are as many as 222/kloc-0 chemical pollutants in tap water all over the world, some of which are confirmed as carcinogens or cancer promoters. Judging from the drinking standard of tap water, China is still at a low level. At present, tap water can only be simply processed into drinking water through precipitation, filtration and chlorination. Chlorination of tap water can effectively kill bacteria and produce more halogenated hydrocarbon compounds. The content of these chlorine-containing organic compounds has doubled, which is the largest source of various gastrointestinal cancers in human beings. At present, the composition of urban pollution is very complicated. In addition to heavy metals, polluted water also contains many harmful residues, such as pesticides, fertilizers and detergents. Even if the tap water is boiled, the residue on it will not be driven away. However, the concentration of harmful substances in boiling water increases, which reduces the dissolved oxygen content beneficial to human health and increases carcinogens such as nitrite and chloroform. Therefore, the safety factor of drinking boiled water is not high. According to the latest data, only 23% of the residents in major cities in China have reached the hygienic standard, and the qualified rate of drinking water in small towns and rural areas is even lower. The urgent task of water pollution prevention and control is to ensure that drinking water is qualified. Therefore, water pollution monitoring should be strengthened and water supply source protection areas should be established. The mother river Yellow River was cut off for the first time in 1972, and it was cut off for 226 days in 1997, and nearly 700 kilometers of riverbed dried up. There are 300 tributaries in Haihe River, none of which is dry and none of which is smelly. Groundwater in North China is seriously over-exploited, forming the largest groundwater funnel area in the world, covering an area of more than 70,000 square kilometers. The ground sinks and the sea invades. Among the 668 cities in China, more than 400 cities are short of water, and 100 cities are seriously short of water. Since the end of11990s, the rate of land desertification has increased to more than 3,400 square kilometers per year.
What is even more frightening is that the total water resources in China are still declining. The total amount of 1997 was 2,785.5 billion cubic meters, which decreased to 24 13 billion cubic meters in 2004. Since 1950s, more than 20 rivers in the upper reaches of the Yangtze River have shrunk by 37. 1% on average. WWF published a report on March 19, and listed the Yangtze River, the third longest river in the world, as one of the 10 major rivers facing drying up in the world. Water pollution affects industrial production, increases equipment corrosion, affects product quality, and even makes production impossible. Water pollution affects people's lives, destroys ecology, directly harms people's health and causes great damage. At present, people have realized that we can't develop the economy by destroying the ecological environment, which is too costly. China put forward the strategy of sustainable development of social economy and protection of people's health, and adopted a series of powerful measures to control water pollution.
There are three methods for water pollution treatment: physical method, chemical method and biodegradation method.
Physical method: the choice of wastewater treatment method depends on the nature, composition and state of pollutants in wastewater and the requirements for water quality. General wastewater treatment methods can be roughly divided into three categories: physical method, chemical method and biological method.
Treatment, separation and recovery of pollutants in wastewater by physical action. For example, the suspended particles with relative density greater than 1 in water are removed by precipitation method, and these particles are recovered at the same time; Flotation (or air flotation) can remove emulsified oil droplets or suspended solids with relative density close to 1; Suspended particles in water can be removed by filtration; Evaporation is used to concentrate insoluble soluble substances in wastewater [2].
Chemical method: recovery of soluble waste or colloidal substances through chemical reaction or physical and chemical action, such as neutralization of acidic or alkaline wastewater; The extraction method uses soluble wastes with different solubility in two phases. Issue? , recycling phenols, heavy metals, etc. ; Redox method is used to remove reducing or oxidizing pollutants in wastewater and kill pathogenic bacteria in natural water [2].
Biological method: organic matter in sewage is treated by biochemical action of microorganisms. For example, biological filtration and activated sludge process are used to treat domestic sewage or organic production sewage, so that organic matter can be transformed and degraded into inorganic salts and purified [2].
For a long time, activated sludge process has been used in sewage treatment, which is also the most widely used biological treatment process in the world. It has the advantages of large treatment capacity and good effluent quality.
2. Project name, professional level, students and instructors.
Effect of trivalent aluminum chloride on degradation performance of activated sludge
Professional level: first-class applied chemical technology
Member:?
Instructor:?
3. Theme content
① Cultivation of activated sludge
Laboratory activated sludge culture is an intermittent culture method. The activated sludge is aerated by an aeration device, that is, the activated sludge is suffocated, only oxygen is introduced, and it is allowed to stand for one hour every once in a while, then water is changed, and appropriate nutrients are added for culture, and so on, so as to maintain the concentration of activated sludge required by the experiment.
(2) Research methods of degradation of activated sludge by trivalent aluminum chloride.
The judgment of water quality mainly depends on some indicators, including DO, COD, BOD and so on. Where is the cod? Chemical oxygen demand? The abbreviation of ""is an index reflecting reducing pollutants (including organic and inorganic reducing substances) in water. Here it is represented by COD index. There are many methods to determine chemical oxygen demand. Referring to a large number of documents, a determination method is summarized, that is, adding a known amount of potassium dichromate solution to the sample, in a strong acid medium, using silver sulfate as a catalyst, and then determining the COD value by spectrophotometry after high temperature digestion. When the COD value in the sample is from 1000mg/L to1000 mg/L, it is at 600? The absorbance of trivalent chromium ions produced by potassium dichromate reduction was measured at the wavelength of 20 nm. The COD value in the sample is directly proportional to the added value of the absorbance of trivalent chromium ions, and the absorbance of trivalent chromium ions is converted into COD value. When the COD value in the sample is from 65438 0.5 mg/L to 250mg/L, it is at 440? The total absorbance of hexavalent chromium ions and trivalent chromium ions produced by potassium dichromate reduction was measured at the wavelength of 20 nm. The COD value in the sample is directly proportional to the decrease of the absorbance of hexavalent chromium ion and the increase of the absorbance of trivalent chromium ion, and the total absorbance is converted into COD value [3-8].
Prepare trivalent aluminum chloride water samples with different concentrations, heat them in a reflux device, boil them for 1 hour, then put them in a conical flask for cooling, then add the prepared standard solution of ammonium ferrous sulfate with known concentration as an indicator for titration, and record the data. Repeat the above operations to study the effect of trivalent aluminum chloride on the degradation performance of activated sludge.
③ verification
According to the experimental data, the variation curve of COD value of water samples with different aluminum chloride concentrations with time is made, so as to analyze whether trivalent aluminum chloride has an effect on the degradation performance of activated sludge.
4. The purpose and significance of this topic.
With the development of society, the paper and chemical industries discharge a lot of industrial wastewater. Wastewater containing heavy metals pollutes the environment, destroys the ecological balance, affects the growth of animals and plants, and seriously harms human health. Therefore, scholars at home and abroad are actively exploring and studying the methods of efficiently degrading activated sludge.
This paper mainly studies the influence of different concentrations of aluminum chloride in wastewater on the degradation performance of activated sludge. By measuring the COD value of industrial wastewater before and after sludge treatment, the growth of activated sludge and its degradation of organic matter under different concentrations were studied, which provided strong data support for further promoting the application of activated sludge in industry [9].
5. Main reagents and instruments used
① Reagent:
Aluminum trichloride (analytical purity), ammonium ferrous sulfate hexahydrate (analytical purity), potassium dichromate (excellent purity), concentrated sulfuric acid (analytical purity), mercury sulfate (analytical purity), silver sulfate (analytical purity), glucose (excellent purity) (50g/L), 1,10.
② Instrument:
Intelligent constant temperature electric heating sleeve, bubbler, tray balance, electronic balance, round bottom flask (250mL), air condenser tube, small beaker (50mL), measuring cylinder (100mL), measuring cylinder (10mL), measuring cylinder (5mL) and conical bottle (250mL).
6. Expected objectives
There are many factors that affect the activity of activated sludge, but this experiment only studies whether different concentrations of aluminum chloride affect the degradation ability of activated sludge. Therefore, we choose aluminum chloride as the research object, measure the COD value of sewage before and after sludge treatment, and study the growth of activated sludge domesticated with different concentrations of aluminum chloride and its degradation of organic matter, which can provide objective data support for the research on the degradation ability of activated sludge. In addition, the influence of chloride ion should be eliminated as much as possible in the subject experiment to achieve objective and accurate measurement results.
7. Staged work
Literature review of 4 ~ 5 weeks.
In the sixth week, the opening report and literature review were completed, and the experimental scheme was made.
In the seventh week, prepare the laboratory, collect instruments and medicines, and prepare the required reagents.
From the eighth week to 14 week, the experiment was completed according to the experimental plan, and the shortcomings, phenomena and conclusions in the experimental process were summarized, and the data were recorded and processed.
15 to 16 weeks, organize materials, make tables, draw pictures, and write graduation thesis.
Week 17 thesis defense
refer to
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Sun Huixiu. Drainage works. Fourth edition. Beijing: China Building Industry Press,1999:105-107.
Sue. Study on the correlation between CODcr and BOD5 [J]. Heilongjiang Environmental Bulletin, 20 10/0,34 (2): 75-78.
[5] Gu. Li xiuxia Analysis of influencing factors on determination of COD by potassium dichromate method [J]. Small nitrogenous fertilizer, 2009,37 (3):18-20.
Li Guogang, Wang Delong. Summary of BOD determination methods [J]. China Environmental Monitoring, 2004,20 (2): 54-57.
, Chen,. Analysis of influencing factors of BOD5 determination [J]. Chemical Engineering and Equipment, 2009,9:176-177.
Wang Ruigang. Kinetics of phosphorus removal by activated sludge [D]. School of Environmental Monitoring, China University of Mining and Technology, 2009:9- 1 1.
Xu Hang. Discussion on the analysis of chemical oxygen demand potassium dichromate [J]. Chemical Engineering and Equipment, 20 10/0,6:171-kloc-0/72.
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