Chemical wastewater treatment
Source：Jiangsu Envset Time:29 June 2021
Chemical waste water refers to the waste water produced in the production process of chemical plants, such as oily waste water from the production of ethylene, polyethylene, rubber, polyester, methanol, ethylene glycol, oil tank farms, air separation and air compressor stations, etc. After the biochemical treatment, it can generally meet the national secondary discharge standard. Due to the shortage of water resources, the water that meets the discharge standard needs to be further processed after further advanced treatment to meet the requirements of industrial water replenishment. Main pollution factors: PH, SS, TP. Discharge will cause the water body to become acidic and the water body will be affected by eutrophication.
The toxic substances in wastewater from different chemical industries are different, and there are sometimes more than one toxic substances in one kind of wastewater, most of which are substances that cannot be degraded naturally, such as polycyclic aromatic hydrocarbons, organic substances, and heavy metal compounds; the salt content in the wastewater is generally greater than 1%, can inhibit the degradation of organic substances by aquatic organisms; the amount of wastewater discharged and the amount of toxic substances in the wastewater often change. In order to remove these toxic substances, the following treatment technologies are often used in wastewater treatment:
1. Physical method: filtration method, precipitation method, air flotation method and adsorption method are commonly used physical treatment methods, mainly through physical means to achieve solid-liquid separation, thereby removing particulate matter in wastewater, the operation is relatively simple, but This method cannot remove the soluble pollutants in the wastewater, so it is mostly used in pretreatment and deep treatment.
2. Chemical method: chemical oxidation method, coagulation precipitation method, micro-electrolysis technology, etc. are commonly used chemical treatment methods, which are through various chemical reactions to achieve the purpose of removing various impurities in wastewater and removing or reducing the toxicity of wastewater.
The chemical oxidation method uses oxidation reactions, such as the use of oxidants to oxidize the pollutants in the wastewater, so that the pollutants in the wastewater can be easily degraded, and the toxicity of the pollutants can be removed or reduced. This method is suitable for pollutants. For the treatment of wastewater with strong reducibility. The oxidizing power of the oxidant has a relatively large impact on the effect of wastewater treatment. The commonly used better oxidants are ozone and chlorine, which have a strong ability to treat wastewater pollutants, but the cost is high.
The coagulation sedimentation method uses chemical substances that have a coagulation effect to remove the fine particles and colloids in the wastewater. At the same time, it removes the color, microorganisms and larger molecular organics of the wastewater. However, this method affects the pH value of the wastewater. , Temperature, water volume and other requirements are high, mostly used for pretreatment and deep treatment.
The micro-electrolysis technology uses the principle of the primary battery to electrochemically effect the pollutants in the wastewater to change the nature of the pollutants. During the electrolysis process, disinfectant OH and activity rate are produced at the same time, which can further remove bacteria in the wastewater. Micro-electrolysis technology is mostly used for biologically difficult-to-degrade wastewater, and it uses solid waste in industrial production to realize waste utilization. However, the research of micro-electrolysis technology is still slightly insufficient, and only special types of industrial wastewater can be treated. A complete set of technology and theory has not yet been formed.