The coagulation method includes two processes of coagulation and flocculation. The treatment object is mainly small suspended solids and colloidal impurities in water, and has the advantages of convenient operation, high efficiency and low investment. Coagulant is the key to ensure the coagulation effect, mainly divided into special coagulant, organic polymer coagulant and microbial coagulant. At present, microbial coagulant has not been applied in a large area. The use of organic polymer coagulant will increase the chemical oxygen demand (COD) of the effluent, and the price is relatively expensive. The inorganic coagulant is widely used in the advanced treatment of wastewater. The composite coagulant has begun to be valued because it combines the advantages of a single coagulant and overcomes the shortcomings of a single coagulant.
The coagulation method is mature and simple to operate, but the coagulation method alone cannot often meet the discharge or reuse requirements. In the application, the coagulation method is generally combined with other advanced treatment technologies, such as Fen-ton oxidation, electrochemical methods, adsorption methods, membrane separation methods and the like.
The principle of the adsorption method is to use the large specific surface area of the adsorbent and the developed microporous structure to enrich the pollutants in the wastewater, thereby purifying the wastewater. Commonly used adsorbents are activated carbon, fly ash, diatomaceous earth, bentonite and the like. The adsorption method can effectively remove organic pollutants and inorganic substances in wastewater, including some toxic heavy metals. At present, the research on adsorption method mainly focuses on the following aspects: 1 Research and development of new adsorbents. For example, solid waste such as slag, lignin, and gasifier ash is modified by a certain method and used as an adsorbent for wastewater treatment. 2 modification of the adsorbent. For example, the surface of the activated carbon on the surface of the activated carbon and the surface-loaded ions or compounds are modified by surface oxidation, surface reduction, load atom and compound methods, acid-base methods, etc., thereby improving the adsorption performance of the adsorbent. 3 Optimization of adsorption process conditions. For example, the dosage of the adsorbent, the adsorption time, the adsorption temperature, and the like are optimized. 4 combination of adsorption process and other processes. Such as ozone + activated carbon technology. Coagulation and sedimentation + activated carbon technology, activated carbon + membrane method, and coupling of adsorption and biotechnology.
The adsorption method has problems such as difficulty in regeneration of the adsorbent and easy secondary pollution, and further exploration is needed in the method of regenerating the adsorbent and improving the adsorption performance after the regeneration of the adsorbent.