aaa alkaline battery.Water treatment process knowledge

　　Water treatment process knowledge

　　Water treatment process knowledge Sewage treatment generally includes the following three-level treatment: Primary treatment uses mechanical treatment, such as grilles, sedimentation or air flotation, to remove stones, sand, fat, grease, etc. contained in sewage. Secondary treatment is biological treatment, in which pollutants in sewage are degraded and converted into sludge under the action of microorganisms. Tertiary treatment is the advanced treatment of wastewater, which includes the removal of nutrients and disinfection of wastewater through chlorination, ultraviolet radiation or ozone technology. Depending on the treatment goals and water quality, some sewage treatment processes do not include all the above processes. Mechanical treatment section

　　The mechanical (primary) treatment section includes structures such as grilles, grit tanks, and primary sedimentation tanks, with the purpose of removing coarse particles and suspended solids. The principle of treatment is to achieve solid-liquid separation through physical methods to separate pollutants from sewage. , which is a commonly used sewage treatment method. Mechanical (primary) treatment is a must for all sewage treatment processes (although sometimes some processes omit the primary sedimentation tank). The typical removal rates of BOD5 and SS in the primary treatment of urban sewage are 25% and 50% respectively. In biological phosphorus and denitrification sewage treatment plants, aeration of grit chambers is generally not recommended to avoid the removal of rapidly degrading organic matter; when the water quality characteristics of raw sewage are not conducive to phosphorus and denitrification, the setting and setting of primary sedimentation The method needs to be carefully analyzed and considered based on the subsequent processes of special water quality injection to ensure and improve the incoming water quality of subsequent processes such as phosphorus removal and denitrification.

　　Wastewater biochemical treatment

　　Biochemical treatment of sewage is a secondary treatment, with the main purpose of removing unsinkable suspended solids and soluble biodegradable organic matter. Its process composition is diverse and can be divided into activated sludge method, AB method, A/O method, and A2/O Method, SBR method, oxidation ditch method, stabilization pond method, land treatment method and other treatment methods. Currently, most urban sewage treatment plants use the activated sludge process. The principle of biological treatment is to complete the decomposition of organic matter and the synthesis of organisms through biological action, especially the action of microorganisms, and convert organic pollutants into harmless gas products (CO2), liquid products (water) and organic matter-rich products. Solid product (microbial community or biological sludge); excess biological sludge is separated from solid and liquid in the sedimentation tank and removed from the purified sewage. In the process of biochemical sewage treatment, factors affecting microbial activity can be divided into two categories: matrix and environmental:

　　1. The matrix category includes nutrients, such as organic compounds based on carbon elements, namely carbon source materials, nitrogen sources, phosphorus sources and other nutrients, as well as trace elements such as iron, zinc, manganese; in addition, it also includes some toxic and harmful chemicals Such as phenols, benzene and other compounds, as well as some heavy metal ions such as copper, cadmium, lead ions, etc.

　　2. Environmental influencing factors mainly include: (1) Temperature. Temperature has a wide range of effects on microorganisms. Although certain types of bacteria are also active in high temperature environments (50°C to 70°C) and low temperature environments (-5 to 0°C), most microorganisms in sewage treatment are the most The suitable temperature range for growth is 20-30℃. Within a suitable temperature range, the physiological activities of microorganisms are strong, and their activity increases with the increase of temperature, and the treatment effect is better. Beyond this range, the activity of microorganisms becomes worse and the biological reaction process will be affected. Generally, the maximum and minimum limits for controlling the reaction process are 35°C and 10°C respectively. (2) pH value. The most suitable pH value range for microorganisms in the activated sludge system is 6.5-8.5. An environment that is too acidic or alkaline is not conducive to the survival and growth of microorganisms. In severe cases, the sludge floc will be destroyed and the bacterial gel will disintegrate. The treatment effect deteriorates sharply. (3) Dissolved oxygen. For aerobic biological reactions, maintaining a certain concentration of dissolved oxygen in the mixture is crucial. When the dissolved oxygen in the environment is higher than 0.3mg/l, both facultative and aerobic bacteria perform aerobic respiration; when the dissolved oxygen is lower than 0.2-0.3mg/l and close to zero, the facultative bacteria switch to anaerobic respiration. Oxygen respiration, most aerobic bacteria basically stop breathing, but some aerobic bacteria (mostly filamentous bacteria) may still grow well, and often lead to sludge expansion after taking advantage of the system. Generally, it is advisable to keep the dissolved oxygen at the outlet of the aeration tank at about 2 mg/l. If it is too high, it will increase energy consumption and be economically uneconomical. Among all influencing factors, matrix factors and pH value determine the quality of the incoming water. The control of these factors mainly relies on daily monitoring and strict implementation of relevant regulations and laws. For general urban sewage, most of these factors will not have much impact, and each parameter can basically be maintained within an appropriate range. Temperature changes are related to climate. For a 10,000-ton urban sewage treatment plant, especially when using the activated sludge process, temperature control is difficult to implement, and it is not very feasible economically or engineeringly. Therefore, the processing requirements of different temperature changes are generally met through appropriate selection of design parameters to achieve the processing goals. Therefore, the main goal of process control falls on the activated sludge itself and the environmental factors that can be changed through control means. The main task of control is to take appropriate measures to overcome the influence of external factors on the activated sludge system so that it can Function continuously and stably. The key to realizing process control of biological reaction systems lies in the selection of control objects or control parameters, which in turn is closely related to the treatment process or treatment objectives. As mentioned before, dissolved oxygen is a very important indicator parameter in the type and process of biological reactions. It can intuitively and relatively quickly reflect the operating status of the entire system. It is easy to operate and manage, and the installation and maintenance of instruments and meters are also relatively simple. This is also the reason why all newly built sewage treatment plants in my country in the past ten years have basically implemented on-site and online monitoring of dissolved oxygen.

　　Tertiary treatment is an in-depth treatment of water. Currently, not many sewage treatment plants in my country are put into practical use. It denitrifies and dephosphorizes the secondary-treated water, removes remaining pollutants in the water using activated carbon adsorption or reverse osmosis, disinfects with ozone or chlorine to kill bacteria and viruses, and then sends the treated water into the central Waterways serve as water sources for flushing toilets, spraying streets, watering green belts, industrial water, fire prevention, etc.

　　It can be seen that the role of the sewage treatment process is only to purify the sewage and enrich the pollutants into the sludge through biodegradation and solid-liquid separation, including the primary sludge generated in the primary treatment section, The remaining activated sludge produced in the secondary treatment section and the chemical sludge produced in the tertiary treatment section. Since this sludge contains a large amount of organic matter and pathogens, and is easily putrefactive and smelly, it can easily cause secondary pollution, and the task of eliminating pollution has not yet been completed. Sludge must be properly disposed of through certain volume reduction, volume reduction and stabilization harmless treatment wells. The success of sludge treatment and disposal has an important impact on the sewage plant and must be taken seriously. If the sludge is not treated, it will have to be discharged with the treated effluent, and the purification effect of the sewage plant will be offset. Therefore, in the actual application process, sludge treatment in the sewage treatment process is also very critical.

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