What is a stench?

Odor refers to all the gas substances that stimulate the olfactory organs and cause people to be unhappy and damage the living environment. Odor concentration is a comprehensive characterization factor of air quality, and its value is a comprehensive reflection of mixed air quality. The source of odor is diverse, the composition of odor is more complex, so it is necessary to use a comprehensive index to limit it, China's method of limiting odor is based on the country.Emission Standard for Odor Pollutants (GB 14554-93)Among them, the limit value for the odor concentration of the factory boundary environment is 20OU.

The Necessity of Establishing Online Monitoring System for Odor

With the development of the city and the requirements of energy conservation and emission reduction, all localities have accelerated the construction of sewage treatment plants and related facilities. However, in the process of sewage treatment, odor will be generated in the aeration tank, sedimentation tank, anaerobic tank and sludge treatment area, which will affect the quality of life and health of citizens. In order to prevent the odor gas from polluting the environment and disturbing the people in all aspects of sewage treatment, it is necessary to realize daily environmental monitoring and take effective and reasonable measures to control the impact of odor gas on the surrounding environment.

The sewage treatment plant itself is a benign environmental protection project, which will have a great effect on improving the local environment and water quality after completion. However, the operation of sewage treatment facilities will also have a certain impact on the surrounding environment. In order to prevent the odor gas from polluting the environment and disturbing the people in all aspects of sewage treatment, in order to implement the daily environmental monitoring plan, effective and reasonable measures should be taken to control the influence of odor gas on the surrounding environment. Of course, before taking measures, it is necessary to conduct in-depth monitoring and analysis of the odor gas situation in the sewage treatment plant.

China's "GB14554-93 Odor Pollutants Comprehensive Emission Standards" lists the following eight kinds of gases with relatively low odor thresholds: ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, methyl sulfide, dimethyl disulfide, carbon disulfide, and styrene. These eight kinds of gases have organic matter and inorganic matter. As long as they are sulfides, they account for five of them. They often smell odors and odors in life.

The odor composition of the sewage treatment plant is complex and changeable, which can be roughly divided into 5 categories:

(1) Sulfur-containing compounds, such as hydrogen sulfide, thiols, and thioethers;

(2) chlorine-containing compounds, such as amines, amides, indolins;

(3) hydrocarbons, such as alkanes, alkenes, alkynes, aromatic hydrocarbons;

(4) Halogens and derivatives, such as chlorine, halogenated hydrocarbons;

(5) oxygen-containing organic compounds, such as alcohols, phenols, aldehydes, ketones, organic acids, etc.

2, the main source of odor gas

(1) The distribution of malodorous substances carried by incoming water. Whether it is industrial wastewater or domestic wastewater, it contains a large amount of organic matter. In the process of being sent to the sewage plant, complex biochemical reactions will occur, which will make the incoming water have a foul smell, and the organic volatile gas itself has a peculiar smell. The concentration of these malodorous gases changes with temperature. The higher the temperature, the faster the evaporation of water and harmful gases, and the higher the concentration of malodorous gases. This is the reason why the concentration of malodorous gases is lower in winter and higher in summer.

(2) the biochemical stage of sewage treatment produces malodorous gases. During the operation of the sewage treatment plant, in order to remove organic matter, biochemical treatment will be adopted, and incomplete biochemical reaction will produce a large number of malodorous gases. NH3 mainly comes from the degradation of organic matter, and H2S is mainly produced by incomplete biochemical anaerobic reaction.

(3) The generation and emission of odor in the sludge treatment and disposal process of sewage treatment plant. Sludge is easy to produce local anaerobic substances, which will produce a large number of hydrogen sulfide, hydrogen sulfide volatilization and air contact diffusion, malodorous gas.

(4) Malodor emission caused by improper disposal of grid slag and grit chamber slag;

(5) Aeration of wastewater treatment process containing more volatile organic compounds. Insufficient aeration, uneven distribution of violent gas head, insufficient supply of biochemical oxygen demand, resulting in local anaerobic, resulting in malodorous gas.

There are many sulfur-containing and malodorous gas generation points in the municipal sewage treatment plant, which are scattered, but mainly concentrated in the intake water area such as the intake pump, aerated grit chamber, and grid of the sewage treatment plant, as well as the sludge treatment area such as the sludge dewatering room and the sludge thickening tank. Moreover, the contents of hydrogen sulfide, methyl mercaptan, ethyl mercaptan, sulfur dioxide, carbon dioxide, dimethyl sulfiamidine, diethyl sulfide and methyl butyl ethosulfate showed a gradual decay trend as they were farther away from the pollution source. Among them, the concentration zui of carbon disulfide in the source of sulfur-containing waste gas from sewage treatment plant is high, 11.16mg/m3, followed by diethyl sulfide, sulfur dioxide and dimethyl sulfide. The concentration zui of carbon disulfide at 50m is high, 12.05mg/m3, which is higher than that at the source.

The data collected from the monitoring in the following figure shows that the overall trend of sulfur-containing and odorous gases in urban sewage treatment plants shows that the concentration of sulfur-containing and odorous gases gradually decreases with the increase of sampling distance. The diffusion attenuation of sulfur-containing malodorous gases includes two forms of physical and chemical attenuation. The former is gradually diluted by diffusion due to the influence of three-dimensional space, while the latter is mainly affected by factors such as ultraviolet rays and sunshine around the urban sewage treatment plant.

Improperly handled odor pollution will not only pollute the atmospheric environment, but also have a serious impact on the lives of residents living near the industrial park. Because the rate of residents' complaints caused by odor is increasing year by year, the odor pollution A series of problems have also attracted the attention of relevant departments, then according to the different nature of targeted deodorization treatment.

So the current sewage treatment plant odor gas monitoring and governance should be how to carry out?

Monitoring malodorous gases can no longer rely on traditional artificial smell and identification. What we are doing now is to quantify the detection of malodorous gases and transform sensory things into a number that can be judged. In view of the different ways and sources of odor generation, the online odor monitoring system (also known as odor electronic nose) can be used for internal self-control of enterprises or departments such as chemical plant monitoring, sewage treatment, landfill, petroleum refining, cement and fertilizer, etc., to carry out rapid and effective monitoring and information early warning of odor gas leakage caused by other emergencies. Provide data-assisted support for enforcement of various environmental odor pollution, monitor daily business operations and emissions, and record sudden odor sources.

By deploying high precision in the plantOdor gas acquisition sensorIn an air environment:Ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, methyl sulfide, dimethyl disulfide, carbon disulfide, styrene, malodor OU valueThe 24-hour online monitoring of multiple odor indicators has the characteristics of fast response, high measurement accuracy and good stability. It has a wide and mature application.

Odor gas monitoring sensor solution:

In view of the odor pollution of the sewage treatment plant, the monitoring work in the early stage should be done first, and the corresponding deodorization treatment should be adopted in the later stage according to the different properties of the odor gas. Through the integrated process of monitoring and treatment, the odor gas can be controlled from the source to ensure the smooth operation of the sewage treatment work. If you want to know more about the relevant sensor products for odor monitoring and treatment, please contact.