Printing and dyeing wastewater refers to wastewater containing organic and inorganic substances such as dyes, auxiliaries, pH, suspended matter, etc. generated during the printing and dyeing process. Because it contains a large amount of harmful substances, if it is not properly treated, it will cause serious pollution to water bodies and soil if it is directly discharged into the environment, endangering human health and the ecological environment. Therefore, the treatment of printing and dyeing wastewater is very necessary.
The treatment process of printing and dyeing wastewater is mainly divided into three types: physical, chemical and biological treatment. Among them, physical treatment includes precipitation, filtration, adsorption and other methods; chemical treatment includes neutralization, oxidation-reduction, precipitation and other methods; biological treatment uses microorganisms to degrade organic matter. Different processes can be selected according to the nature of the wastewater.
1. Physical treatment
Physical treatment mainly removes suspended matter and solid impurities such as pigments in wastewater by physical methods, including precipitation, filtration and adsorption.
Sedimentation method refers to separating suspended matter in wastewater by gravity sedimentation. Commonly used precipitants include iron salts, aluminum salts, calcium salts, etc. These precipitants can react with suspended matter in wastewater to form precipitates, thereby achieving the purpose of purifying water quality.
Filtration refers to removing suspended matter from wastewater by passing it through filter media. Commonly used filter media include quartz sand, activated carbon, ceramic membranes, etc. These filter media can effectively remove pigments and suspended matter from wastewater.
Adsorption refers to the use of adsorption materials to adsorb harmful substances in wastewater onto the surface, thereby achieving the purpose of purifying water quality. Commonly used adsorption materials include activated carbon, nanomaterials, etc.
2. Chemical treatment
Chemical treatment mainly changes the pH or redox properties of wastewater by adding chemical agents, so that harmful substances undergo chemical reactions and precipitate or become soluble substances, thereby achieving the purpose of purifying water quality.
Neutralization refers to neutralizing the acid or alkali in acidic or alkaline wastewater into neutral wastewater by adding an appropriate amount of neutralizer. Commonly used neutralizers include sodium hydroxide, calcium hydroxide, etc.
Redox method refers to changing the redox properties of harmful substances in wastewater by adding oxidants or reductants, so that they undergo redox reactions and precipitate or become soluble substances. Commonly used oxidants include potassium permanganate, hydrogen peroxide, etc., and commonly used reducing agents include sodium sulfite, ferrous sulfate, etc.
The precipitation method refers to the process of adding an appropriate amount of precipitant to make harmful substances in wastewater react with the precipitant and form a precipitate, thereby achieving the purpose of purifying water quality.
3. Biological treatment
Biological treatment mainly uses microorganisms to degrade organic matter and convert organic matter into inorganic matter through microbial metabolism, thereby achieving the purpose of purifying water quality. Biological treatment processes include aerobic biological treatment and anaerobic biological treatment.
Aerobic biological treatment refers to the use of aerobic microorganisms to convert organic matter in wastewater into harmless substances such as carbon dioxide and water under sufficient oxygen supply conditions. Aerobic biological treatment processes include aeration tanks, activated sludge methods, etc.
Anaerobic biological treatment refers to the use of anaerobic microorganisms to convert organic matter in wastewater into harmless substances such as methane and carbon dioxide under anoxic or anaerobic conditions. Anaerobic biological treatment processes include anaerobic tanks, anaerobic filters, etc.
Chemicals play an important role in the treatment of printing and dyeing wastewater. Commonly used agents include precipitants, defoamers, dispersants, etc. Precipitants can precipitate solid impurities such as suspended matter and pigments in wastewater; defoamers can eliminate foam generated by stirring in wastewater; dispersants can evenly disperse pigments in wastewater for subsequent treatment.
In summary, the treatment of printing and dyeing wastewater is a very necessary task. Choosing appropriate treatment processes and agents can effectively purify printing and dyeing wastewater and protect the environment and human health.
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