As a highly effective water treatment chemical,
polyacrylamide is an organically derived polymeric flocculant developed at an early stage. It exhibits excellent flocculation properties and provides effective coagulation assistance. Consequently, it finds extensive application in both potable water treatment and wastewater processing. However, due to the presence of trace toxic acrylamide monomers within the amide structure, stringent regulations govern its use. The permissible concentration must not exceed 0.01 mg/L, limiting its application methods in potable water treatment. Nevertheless, it finds extensive use in industrial water treatment, papermaking, metallurgy, and other sectors.
To achieve optimal performance during operation, particular attention must be paid to handling and dissolution procedures. For solid products, dissolution requires pre-mixing with lukewarm water (≤60°C) in the dissolution vessel to prevent fish-eye formation from incomplete dissolution. Gradually add the product while stirring continuously, then top up with water until complete dissolution is achieved. Alternatively, specialised equipment may be employed for preparation. The prepared solution typically has a concentration of 0.1%–0.05%, or may be formulated as a 0.1%–0.2% solution for subsequent dilution during use. However, once dissolved, polyacrylamide products have a limited storage life not exceeding five days. Prolonged storage may cause degradation, adversely affecting final performance.
Dosage varies according to water quality and application. For flocculation, the standard dosage ranges from 0.1 to 3 mg/kg. When used as a filtration aid, the dosage is typically 0.03 to 0.3 mg/kg. Dosage requirements differ across applications. It is advisable to conduct preliminary trials to determine the optimal dosage prior to use. Both excessive and insufficient dosages compromise efficacy. Overdosing not only fails to enhance performance but also increases product consumption in wastewater treatment. Excessive application may diminish treatment effectiveness while elevating COD levels in effluent, potentially leading to exceedances of pollutant limits during discharge. Concurrently, it may cause sludge flotation and excessive colouration. Increasing dosage may also impair the flocculant's solubility, diminishing flocculation efficiency. Therefore, when employing polyacrylamide products, it is essential to determine an optimal dosage. The most suitable dosage ensures effective treatment while minimising costs.
