Polyurethane adhesive, also known as urethane adhesive, is an adhesive containing carbamate group (-NHCOO-) or isocyanate group (-NCO) in its molecular chain. It is mainly divided into two categories: polyisocyanate and polyurethane. It has high activity and polarity and can form excellent chemical adhesion with porous materials such as foam, plastic, wood, leather, fabric, paper, ceramics and other materials with smooth surfaces such as metal, glass and rubber. Polyurethane adhesive has been widely used in various structural adhesive fields because of its excellent shear strength, impact resistance, flexibility and rubber properties, and is one of the eight important synthetic adhesives.
Second, sources and characteristics of polyurethane adhesive wastewater.
A certain amount of wastewater will be produced during the production and use of polyurethane adhesive, which mainly comes from equipment cleaning water, cooling water, workshop cleaning water and backwashing water. Polyurethane adhesive wastewater has the following characteristics:
1. High-concentration pollutants: The wastewater mainly contains pollutants such as COD (chemical oxygen demand), BOD (biological oxygen demand) and SS (suspended substance), with high concentrations, such as COD up to 4000mg/L, BOD up to 1000mg/L and SS up to 500mg/L.
2. The water quality and quantity fluctuate greatly: due to the uncertainty in the production process, the water quality and quantity of wastewater often fluctuate greatly.
3. Poor biodegradability: Most organic substances in wastewater are long-chain polymer compounds, which are difficult to be directly degraded by microorganisms.
Third, polyurethane adhesive wastewater treatment process.
According to the characteristics of polyurethane adhesive wastewater, the following technological processes are usually adopted for treatment:
1. Regulating tank: first, introduce the wastewater into the regulating tank to balance the water quality and quantity, to provide stable water inlet conditions for subsequent treatment.
2. Coagulation and sedimentation: coagulants such as PAC (Polyaluminum Chloride) and PAM (Polyacrylamide) are added into the coagulation tank, and pollutants are aggregated into larger particles or flocs by stirring and then sent to the sedimentation tank for sedimentation and separation.
3. Hydrolytic acidification: the pretreated wastewater is sent to a hydrolytic acidification tank, and macromolecular organic matter is degraded into micromolecule organic matter through the action of hydrolytic acid-producing bacteria, thus improving the biodegradability of wastewater.
4. Biological contact oxidation: the wastewater enters the biological contact oxidation tank, and the organic matter is further degraded through aeration and oxygenation of activated sludge and the metabolism of microorganisms.
5. Sedimentation separation: after biological treatment, the wastewater enters the sedimentation tank for mud-water separation, so as to ensure that the effluent reaches the standard and is discharged.
6. Advanced treatment: according to the effluent requirements, advanced treatment technologies such as ozone oxidation and activated carbon adsorption can be further adopted to improve effluent quality.
In the past, many companies used the traditional sewage treatment method, that is, the production wastewater was treated by reverse osmosis and then entered the domestic sewage treatment station for treatment, and finally discharged into the sewage treatment plant in the high-tech zone. However, this method has caused excessive waste of water resources. In response to the call for environmental protection, more and more companies choose to build new and better sewage treatment systems. It not only effectively reduces the consumption of water resources, but also contributes to the construction of the future.
To sum up, the treatment of polyurethane adhesive wastewater is a complex and important work. Through scientific and reasonable treatment technology and technical means, not only the wastewater can be discharged up to the standard, but also the water resources can be recycled, making positive contributions to the sustainable development of enterprises and environmental protection.
