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Industrial Wastewater Treatment System ETP Effluent Process Technologies

The pollution caused by industrial wastewater mainly includes: organic aerobic material pollution, chemical toxicant pollution, inorganic solid suspended matter pollution, heavy metal pollution, acid pollution, alkali pollution, plant nutrient pollution, thermal pollution, pathogen pollution, etc. Many pollutants have color, odor or foam, so industrial wastewater often presents an aversive appearance, resulting in large areas of water pollution, directly threatening people's life and health, so it is particularly important to control industrial wastewater.

A characteristic of industrial wastewater is that the water quality and quantity vary greatly depending on the production process and mode of production. Such as electricity, mining and other sectors of the wastewater mainly contains inorganic pollutants, and paper and food and other industrial sectors of the wastewater, organic matter content is very high, BOD5(five-day biochemical oxygen demand) often more than 2000 mg/L, some up to 30000 mg/L. Even in the same production process, the water quality in the production process will change greatly, such as oxygen top blowing converter steelmaking, different smelting stages of the same furnace steel, the pH value of wastewater can be between 4 ~ 13, suspended matter can be between 250 ~ 25000 mg/L.

Another characteristic of industrial wastewater is: in addition to indirect cooling water, it contains a variety of materials related to raw materials, and the existence form in wastewater is often different, such as fluorine in glass industry wastewater and electroplating wastewater is generally hydrogen fluoride (HF) or fluoride ion (F-) form, and in phosphate fertilizer plant wastewater is in the form of silicon tetrafluoride (SiF4); Nickel can be in ionic or complex state in wastewater. These characteristics increase the difficulty of wastewater purification.

The amount of industrial wastewater depends on the use of water. Metallurgy, paper making, petrochemical, electric power and other industries use large water, the amount of waste water is also large, such as some steel mills smelting 1 ton of steel waste water 200 ~ 250 tons. However, the actual amount of wastewater discharged from each factory is also related to the recycling rate of water.

    Industrial wastewater refers to the wastewater, sewage and waste liquid generated in the process of industrial production, which contains industrial production materials, intermediate products and products lost with water, as well as pollutants generated in the production process. With the rapid development of industry, the types and quantities of wastewater are increasing rapidly, and the pollution of water bodies is becoming more and more extensive and serious, threatening human health and safety. For the protection of the environment, the treatment of industrial wastewater is more important than the treatment of municipal sewage.

    industrial wastewater (industrial wastewater) includes production wastewater, production sewage and cooling water, refers to the wastewater and waste liquid generated in the industrial production process, which contains industrial production materials, intermediate products, by-products and pollutants generated in the production process lost with water. There are many kinds of industrial wastewater with complex composition. For example, electrolytic salt industrial wastewater contains mercury, heavy metal smelting industrial wastewater contains lead, cadmium and other metals, electroplating industry wastewater contains cyanide and chromium and other heavy metals, petroleum refining industry wastewater contains phenol, pesticide manufacturing industry wastewater contains various pesticides and so on. Because industrial wastewater often contains a variety of toxic substances, environmental pollution is very harmful to human health, so it is necessary to develop comprehensive utilization, turn harm into benefit, and according to the composition and concentration of pollutants in wastewater, take corresponding purification measures for disposal, before discharge.11yr8

    Classification of waste water

    There are usually three methods for wastewater classification:

    The first is classified according to the chemical properties of the main pollutants contained in industrial wastewater. Inorganic wastewater is the main containing inorganic pollutants, and organic wastewater is the main containing organic pollutants. For example, electroplating wastewater and mineral processing wastewater are inorganic wastewater; Waste water from food or petroleum processing is organic waste water.

    The second is classified according to the products and processing objects of industrial enterprises, such as metallurgical waste water, papermaking waste water, coking gas waste water, metal pickling waste water, chemical fertilizer waste water, textile printing and dyeing waste water, dye waste water, tanning waste water, pesticide waste water, power station waste water, etc.

    The third is classified according to the main components of the pollutants contained in the wastewater, such as acidic wastewater, alkaline wastewater, cyanogen wastewater, chromium wastewater, cadmium wastewater, mercury wastewater, phenol wastewater, aldehyde wastewater, oil wastewater, sulfur wastewater, organic phosphorus wastewater and radioactive wastewater.

    The first two classifications do not refer to the main components of the pollutants contained in the wastewater and do not indicate the harmfulness of the wastewater. The third classification method clearly points out the composition of the main pollutants in wastewater, which can indicate the harm of wastewater.

    In addition, from the difficulty of wastewater treatment and the harm of wastewater, the main pollutants in wastewater are summarized into three categories: the first category is waste heat, mainly from cooling water, cooling water can be reused; The second category is conventional pollutants, that is, substances without obvious toxicity and easily biodegradable, including biodegradable organic matter, compounds that can be used as bionutrients, and suspended solids, etc. The third category is toxic pollutants, that is, substances containing toxicity and not easy to biodegrade, including heavy metals, toxic compounds and organic compounds that are not easy to biodegrade.

    In fact, one industry can discharge several wastewater of different nature, and one wastewater will have different pollutants and different pollution effects. Dye factories, for example, discharge both acidic and alkaline wastewater. Textile printing and dyeing wastewater, due to the different fabrics and dyes, the pollutants and pollution effects will be very different. Even the wastewater from a single production plant may contain several pollutants at the same time. For example, distillation, cracking, coking, laminating and other devices of the refinery tower oil vapor condensation water, containing phenol, oil, sulfide. In different industrial enterprises, although the products, raw materials and processing processes are completely different, they may also discharge wastewater of similar nature. Such as oil refineries, chemical plants and coking gas plants, may have oil, phenol wastewater discharge.


    Waste water hazards

    1. Industrial wastewater directly flows into channels, rivers and lakes to pollute surface water. If the toxicity is relatively high, it will lead to the death or even extinction of aquatic plants and animals.

    2. Industrial wastewater may also penetrate into groundwater and pollute groundwater, thus polluting crops.

    3. If the surrounding residents use polluted surface water or groundwater as domestic water, it will endanger their health and death in serious cases.

    4, industrial wastewater infiltration into the soil, causing soil pollution. Affects the growth of microorganisms in plants and soil.

    5, some industrial wastewater also has a bad smell, pollution of the air.

    6. Toxic and harmful substances in industrial wastewater will remain in the body through the feeding and absorption of plants, and then reach the human body through the food chain, causing harm to the human body.

    The damage of industrial wastewater to the environment is considerable, and the "Minamata Incident" and "Toyama Incident" in the "eight major public hazard incidents" in the 20th century are caused by industrial wastewater pollution.

    Principle of treatment

    The effective treatment of industrial wastewater should follow the following principles:

    (1) The most fundamental thing is to reform the production process and eliminate the generation of toxic and harmful wastewater in the production process as much as possible. Replace toxic materials or products with non-toxic materials or products.

    (2) In the production process of toxic raw materials and toxic intermediate products and products, reasonable technological processes and equipment shall be adopted, and strict operation and supervision shall be implemented to eliminate leakage and minimize loss.

    (3) Wastewater containing highly toxic substances, such as some heavy metals, radioactive substances, high concentration of phenol, cyanide and other wastewater should be separated from other wastewater, so as to facilitate the treatment and recovery of useful substances.

    (4) Some wastewater with large flow and light pollution, such as cooling wastewater, should not be discharged into the sewer, so as not to increase the load of urban sewage and sewage treatment plants. Such waste water should be recycled after proper treatment in the plant.

    (5) Organic wastewater with composition and properties similar to municipal sewage, such as papermaking wastewater, sugar production wastewater and food processing wastewater, can be discharged into the municipal sewage system. Large sewage treatment plants should be built, including biological oxidation ponds, sewage tanks, land treatment systems and other simple and feasible treatment facilities built according to local conditions. Compared with small sewage treatment plants, large sewage treatment plants can not only significantly reduce the capital construction and operation costs, but also easy to maintain good operating conditions and treatment effects due to the stability of water quantity and water quality.

    (6) Some toxic wastewater that can be biodegradable, such as wastewater containing phenol and cyanide, can be discharged into the urban sewer according to the allowable discharge standard after treatment in the plant, and further biooxidative degradation treatment by the sewage treatment plant.

    (7) Wastewater containing toxic pollutants that are difficult to biodegrade should not be discharged into urban sewers and transported to sewage treatment plants, but should be treated separately.

    The development trend of industrial wastewater treatment is to recycle wastewater and pollutants as useful resources or implement closed circulation.

    Method of treatment

    The main methods for the treatment of high concentration refractory organic wastewater include chemical oxidation, extraction, adsorption, incineration, catalytic oxidation, biochemical method, etc. Biochemical method has mature process, simple equipment, large treatment capacity, low operating cost, and is also the most widely used method in wastewater treatment.

    In wastewater treatment projects, traditional biochemical processes, such as A/O method, A2/O method or improved processes, are mostly used. Activated sludge process in wastewater biochemical process is the most commonly used organic wastewater biological treatment method. Activated sludge is the most efficient artificial biological treatment method with large specific surface area, high activity and good mass transfer.
    Industrial wastewater treatment method:

    1. Ozone oxide:

    Ozone has purification and disinfection effects due to its strong oxidation capacity, so this technology is widely used in the treatment of xanthate wastewater. Ozone oxidation is an effective method to remove xanthate from aqueous solution.

    2. Adsorption method:

    Adsorption is a water treatment method that uses adsorbents to separate pollutants from water. Adsorption method is widely used because of rich raw material resources and high cost performance. Common adsorbents are activated carbon, zeolite, cinder and so on.


    3. Catalytic oxidation method:

    Catalytic oxidation technology is a method that uses catalysts to speed up the chemical reaction between pollutants and oxidants in wastewater and remove pollutants in water. Catalytic oxidation method includes: photocatalytic oxidation method, electrocatalytic oxidation method. This method has a wide range of applications and remarkable results. It is an advanced oxidation technology and has excellent effect on the treatment of difficult organic industrial wastewater.

    4. Coagulation and precipitation method:

    Coagulation precipitation method is a common method of deep purification treatment of sewage by using coagulant. It is necessary to add coagulant and coagulant aid to water to destabilize the colloidal substances that are difficult to precipitate and polymerize with each other, so as to settle and remove. Commonly used coagulants are iron salt, ferrous salt, aluminum salt and polymer.

    5. Biological method:

    Biological method generally adds microorganisms to xanthate wastewater, artificially controls the nutritional conditions suitable for its production, and uses the principle of degradation and metabolism of organic matter to treat xanthate wastewater. The technical advantages of biological method are excellent treatment effect, no or small secondary pollution and low cost.

    6. Microelectrolysis method:

    Micro-electrolysis method is to use the micro-battery system formed by the potential difference in space to achieve the purpose of electrolytic purification. This method is especially suitable for the treatment of organic wastewater that is difficult to degrade. It has the characteristics of high efficiency, wide range of action, high COD removal rate and improved wastewater biochemistry.

    The purpose of wastewater treatment is to separate the pollutants in wastewater in some way, or decompose them into harmless and stable substances, so that the sewage can be purified. Generally to prevent the infection of poisons and germs; To meet the requirements of different uses, avoid visible objects with different smells and unpleasant sensations.
    Wastewater treatment is quite complex, and the choice of treatment method must be considered according to the water quality and quantity of wastewater, the receiving water body discharged or the use of water. At the same time, it is necessary to consider the treatment and utilization of sludge and residue generated in the process of wastewater treatment and the possible secondary pollution, as well as the recycling and utilization of flocculant.

    The choice of wastewater treatment method depends on the nature, composition, state and water quality requirements of pollutants in wastewater. General wastewater treatment methods can be roughly divided into physical method, chemical method and biological method.

    Physical method: the use of physical action to treat, separate and recover pollutants in wastewater. For example, the suspended particles with relative density greater than 1 in water are removed by precipitation method and recovered at the same time; Flotation (or air flotation) can remove emulsion oil droplets or suspended solids with relative density close to 1; Filtration method can remove suspended particles in water; Evaporation method is used to concentrate non-volatile soluble substances in wastewater.

    Chemical methods: the recovery of soluble wastes or colloidal substances by chemical reactions or physicochemical actions. For example, neutralization methods are used to neutralize acidic or alkaline wastewater; The extraction method uses the "distribution" of soluble waste in two phases with different solubility to recover phenols, heavy metals, etc. REDOX method is used to remove reducing or oxidizing pollutants in wastewater and kill pathogenic bacteria in natural water bodies.
    Biological method: using the biochemical action of microorganisms to treat organic matter in wastewater. For example, biological filtration and activated sludge are used to treat domestic sewage or organic production wastewater to purify organic matter by converting and degrading it into inorganic salts.
    The above methods have their own scope of adaptation, must learn from each other, complement each other, it is often difficult to use a method can achieve good governance effect. What kind of method is used to treat a kind of wastewater, first of all, according to the water quality and quantity of wastewater, water discharge requirements for water, the economic value of waste recovery, the characteristics of treatment methods, etc., and then through investigation and research, scientific experiments, and in accordance with the indicators of wastewater discharge, regional situation and technical feasibility and determined.

    Prevention and control measures

    Strengthen the management of industrial pollution sources to implement various environmental management systems, strengthen the environmental management of industrial enterprises, pay attention to pollution control of large and medium-sized enterprises, and strengthen the environmental management of small and medium-sized enterprises. We will continue to implement the declaration and registration system, the charging system and the permit system for the discharge of pollutants by enterprises, strengthen the monitoring of pollution sources, standardize sewage outlets, regularly monitor the operation of industrial wastewater treatment facilities, and eliminate outdated production capacity, processes and equipment. New projects will be strictly managed and approved in accordance with the requirements for total pollutant discharge control.
    Improve the sewage charge system and promote the operation of industrial wastewater treatment facilities Make appropriate adjustments to the sewage charge system, re-determine the sewage charge principle, charging method and its management and use principles, establish a new sewage charge mechanism, so that the sewage charge system is conducive to the operation of industrial wastewater treatment facilities by enterprises.

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    Technical measures for prevention and control of industrial waste water pollution

    1. Product improvement: adjust product structure and optimize product formula composition;

    2. Waste generation source control: energy, raw materials and production process optimization, process equipment transformation and innovation

    3. Comprehensive utilization of waste: recycling and reuse;

    4. Improve production management: post responsibility system, staff training system, assessment system), terminal processing (processing degree determination -- processing technology and process optimization -- standard scheduling

    Industrial wastewater recycling

    Industrial wastewater treatment and reuse is one of the important ways to save water, which can involve cooling, ash removal, circulating water, heat and other systems. The cooling water system is mainly used in circulation, step by step and cascade according to the different water quality requirements of the system. The thermal system is mainly used for steam recovery and utilization. The drainage of other systems is mainly used for hydraulic ash and slag removal after treatment, and the miscellaneous water for production and living is further treated as water replying for the cooling system.

    Most enterprises have sewage treatment plants, but only the production wastewater and domestic sewage treatment standards after direct discharge, only a few enterprises can do wastewater treatment and reuse, but the recycling rate is not high, resulting in a serious waste of water resources. Therefore, the sewage and wastewater treatment of industrial enterprises can be reused, especially for the production process, which has great potential to be tapped.

    In the production and operation of enterprises, according to the different requirements of water quality in each process, the series use of water can be realized to the maximum extent, so that each process gets what it needs, and the cascade use of water can be achieved, so as to reduce the water withdrawal and minimize the discharge of sewage; Different water treatment methods can also be taken according to the different properties of sewage and wastewater, which can be used in different production steps, so as to reduce the amount of fresh water taken and reduce the discharge of sewage.

    The water saving potential of wastewater treatment and reuse is great. Transportation equipment manufacturing industry, can be oily waste water, electrophoresis waste water, cutting fluid waste water and cleaning liquid waste water treatment, recycling for greening, living miscellaneous and production. In the process of organic production in the petrochemical industry, the steam condensate can be recycled and used as the water supplement of the circulation system. The well water used for production is recycled and used as water replenishment in the circulation system; Also can increase the reuse water depth processing device, the treated water as the circulation system water; Some coolers and special parts require process water cooling, but reuse water can also be considered. Textile printing and dyeing industry is an industrial industry with large water consumption. The wastewater discharged by different production processes in the production process can be treated and then reused in this process, or all the wastewater can be centrally treated and reused in whole or in part. The beer industry can install condensate recovery device, effectively reduce the boiler water; The bottle washing water of the canning workshop can be recycled for alkali Ⅰ, alkali Ⅱ water of the bottle washing machine, water of the sterilization machine, equipment and plant sanitation, etc. Production water is treated and precipitated, pumped to each water point by pressure, can be used for boiler stone dust removal and desulfurization, slag, toilet flushing, greening and bad field flushing, car washing, construction site water, etc. The wheat leaching wastewater can be treated and reused for boiler dust removal and desulfurization.