The biopharmaceutical industry is a major source of pollution. The wastewater it discharges not only has high concentrations of organic pollutants but also contains various factors that inhibit microbial growth. By employing conventional wastewater treatment technologies, excellent treatment results can be achieved. The biopharmaceutical industry uses grains as raw materials to ferment and cultivate specific medicinal microorganisms; after pressing and filtering the fermentation broth, the filtrate can be further extracted using chemical methods. During the pharmaceutical production process, there are two main types of wastewater: fermentation wastewater and extraction wastewater. Fermentation wastewater contains fermentation residues and microbial cells, with a high suspended solids content and strong inhibitory effects on certain microorganisms. Adding coagulants can cause these suspended solids to settle out, significantly reducing the inhibitory effect of the clear liquid on microorganisms. Extraction wastewater is the effluent generated after the filtrate has been processed chemically to extract the active pharmaceutical ingredients.

In the process of treating pharmaceutical wastewater, polyacrylamide flocculants are commonly used. For biochemical sludge treatment, it is generally advisable to choose cationic polyacrylamide products with a higher ionic degree. When the organic concentration is particularly high, it may even be best to opt for cationic polyacrylamide with an ionic degree of 60 or higher. In cases involving electrochemical treatment or preliminary air flotation treatment, the selection of cationic polyacrylamide flocculant should be based on the water quality of the wastewater, with the most critical technical indicator being the pH value. As a general rule, when the pH is below 7, non-ionic polyacrylamide is often preferred as a coagulant aid or for sludge thickening and settling.

If the pH is above 7, anionic polyacrylamide is the most commonly used.

As far as I know, polyacrylamide (PAM) is a water-soluble polymer that is insoluble in most organic solvents. It exhibits excellent flocculation properties and can reduce the frictional resistance between liquids.

PAM in water treatment primarily operates in two aspects:

1. In coagulation and sedimentation, act as a coagulant aid.

Second, in sludge dewatering, the sludge is aggregated into clumps, making it easier to dewater.

Common processes for PAM in wastewater treatment: pre-treatment followed by coagulation and subsequent treatment. Pre-treatment processes typically include adsorption and filtration. Subsequent treatment processes, depending on the characteristics of the wastewater, may involve oxidation, biological treatment, air flotation, and other methods.

The pH value has a significant impact on the flocculation effect in wastewater treatment.

1) It can alter the electrical properties of solid surfaces and the thickness of the electrical double layer, thereby influencing the adsorption of solid particles by PAM.

2) It can alter the conformation of the flocculant molecule chains. Generally, NPAM is effective at a pH range of 1 to 6, APAM at a pH range of 6 to 10, and CPAM at a pH range of 1 to 10.

The suspended solids content in wastewater directly affects the dosage of flocculants and the efficiency of flocculation. If the concentration is too high, it will hinder the free settling of flocs; if it’s too low, the frequency of particle collisions will decrease, thereby impairing floc formation. For wastewater with extremely low suspended solids content, consider recirculating sludge from the bottom of the sedimentation tank or adding readily settleable solid particles externally to increase the solid-liquid ratio.

The effect of temperature on wastewater flocculation is relatively complex. As temperature rises, the viscosity and density of the liquid decrease, which favors the settling of flocs. However, excessively high temperatures can impair the adsorption of PAM onto particle surfaces.

PAM serves as a coagulant aid and is typically used in combination with a flocculant (main coagulant), PAC.

The function of the PAC is to induce sludge flocculation, forming granular suspended solids through the mesh-like entrapment of flocs.

After PAC, PAM is used to cause granular suspended solids to form large flocs, which aggregate into larger floccules and settle in zones, thereby achieving a better SS removal effect.