I. Characteristics of Dairy Wastewater
Main pollutants in dairy wastewater include: milk protein, emulsified fat, and lactose; colloidal particles are generally negatively charged, resulting in high COD/BOD, easy putrefaction, and difficulty in separating emulsified oil; Possible water treatment process: equalization tank → oil separator/flotation → biological treatment → secondary sedimentation → sludge dewatering.
II. PAM Selection Recommendations for Different Process Sections
1) Pretreatment: Air Flotation DAF / Coagulation Sedimentation Tank (Removal of Protein, Floating Oil, SS)
Process: First add PAC / Polyferric Sulfate (inorganic coagulant) → Rapidly stir to break emulsions and destabilize colloids → Then add PAM as a coagulant aid
- Normal operating conditions (neutral pH 6.5～8.0): Anionic PAM (APAM) is preferred. Parameter reference: Molecular weight 15 million～20 million, degree of hydrolysis 20%～30% Function: Inorganic flocs are bridged and aggregated through long molecular chains, resulting in large flocs and rapid settling/floating.
- Extreme cases (large amounts of yogurt, whey wastewater, low pH, high colloid content): In some field trials, low-ionic-strength cationic PAM (CPAM) showed better results.
Small-scale beaker tests are necessary for confirmation; do not directly copy other companies’ experiences.
2) Back-end: Dewatering of residual biological sludge (screw press, belt filter press, centrifuge) fixed scheme
Dairy product biological sludge is organic biological sludge, containing a large number of negatively charged microbial cells. Cationic PAM (CPAM) is uniformly selected. Recommended parameters: Ionization degree 30%～50%; Molecular weight 8 million～12 million
- Screw press: Commonly used 30～40 ionization degree
- Belt filter press: 40～50 ionization degree
- Centrifugal dewatering: Medium to high molecular weight, medium ionization degree
Dosage reference: Solution concentration 0.1%; Dosage 3～6kg dry powder / ton of dry sludge Performance standard: Sludge clumps, clear effluent, filter cloth does not stick to sludge, sludge cake moisture content can be controlled to around 80%.
III. Standard Operating Procedures
- Dissolution Specifications: Dissolve in clean water; do not add dry powder directly. Stir at low speed for 40-60 minutes. Prepare the solution immediately and use it within 24 hours. In summer, when wastewater has high organic matter content, it is recommended to prepare and use it on the same day to prevent degradation and inactivation.
- Dosage Order Must Not Be Reversed: Add inorganic PAC first → react for 1-3 minutes → then add PAM. Adding PAM first is basically ineffective.
- pH Control: Cationic PAM is suitable for pH 5-9; anionic PAM is suitable for pH 7-10. In dairy processing workshops where acid and alkali cleaning is frequent, the pH in the equalization tank should be kept as stable as possible; large fluctuations will significantly reduce the flocculation effect.
- Sharing Pipelines for Cationic and Anionic PAM is Strictly Prohibited: Mixing and contacting will directly produce white flocculent precipitate, rendering the agent completely ineffective.
- Hazards of Overdosing: Water becomes viscous, produces excessive foam, clogs filter cloth, causes COD rebound in effluent, and increases operating costs.
IV. Common On-site Problems and Countermeasures
- Small, fragmented, and difficult-to-scrape scum from air flotation → Prioritize increasing the PAC dosage, or replace with a higher molecular weight anionic PAM; check the stirring intensity, avoid high-speed breaking of flocs.
- Flocs in sludge dewatering are easily broken, effluent is turbid, and sludge leaks → Replace with a cationic PAM gradient with a higher/lower ion concentration for small-scale testing; reduce the moisture content of the influent sludge.
- Agent dissolution and clumping → Slowly inject dry powder along the tank wall into the influent, do not pour it all at once; add a dispersed dosing device.
- Decline in effectiveness after a period of treatment → Degradation of the solution due to prolonged storage; drastic fluctuations in the concentration of the influent to the equalization tank; oxidation and destruction of PAM by residual disinfectant in the wastewater.
V. HangRui PAM Beaker Experiment
Experimental Data: Add 5ml of each 5% concentration PAC
Selected Models:
1‰ concentration HRFLOC C8038: Add 1.3ml PAM to 30ml of wastewater
1‰ concentration HRFLOC C8058: Add 1.3ml PAM to 30ml of wastewater
1‰ concentration HRFLOC C8070: Add 1.3ml PAM to 30ml of wastewater .
1‰ concentration HRFLOC C8088: Add 1.3ml PAM to 30ml of wastewater.
1‰ concentration HRFLOC C8038v: Add 1.3ml PAM to 30ml of wastewater.
1‰ concentration HRFLOC C8058v: Add 1.3ml PAM to 30ml of wastewater.
1‰ concentration HRFLOC C8070v: Add 1.3ml PAM to 30ml of wastewater.
1‰ concentration HRFLOC C8088v: Add 1.3ml PAM to 30ml of wastewater.
Experimental Results: HRFLOC C8070v showed the best effect, followed by HRFLOC C8058.
From left to right: HRFLOC C8038, HRFLOC C8058, HRFLOC C8070, HRFLOC C8088, HRFLOC C8038v, HRFLOC C8058v.HRFLOC C8070v.HRFLOC C8088v
Experimental Results Images
Experimental Results Videos
Henan Hangrui Environmental Protection Technology Co.,Ltd. is a polyacrylamide manufacturer with 20 years of experience. We can provide free samples of various ionic strengths for testing. We can also test wastewater samples free of charge. Please contact us if needed.
