Functions of Polyacrylamide in Granite and Marble Processing Wastewater
Functions of Polyacrylamide in Granite and Marble Processing Wastewater
Polyacrylamide (PAM) serves as a high-efficiency flocculant in the wastewater treatment of granite and marble processing. Its core function is to achieve rapid solid-liquid separation through efficient flocculation, significantly improving wastewater treatment efficiency, and helping enterprises realize clean water recycling and meet environmental protection discharge standards.
The wastewater from stone processing is dominated by inorganic stone powder suspended solids. Anionic polyacrylamide is the preferred choice, with a recommended molecular weight range of 12 million to 18 million, which is suitable for flocculation and sedimentation of wastewater from most cutting and grinding processes.
Ø Core Action Mechanisms
a) Charge Neutralization: The suspended stone powder particles in granite and marble processing wastewater usually carry positive charges. The active groups on the PAM molecular chain can neutralize the surface charges of the particles, eliminate the electrostatic repulsion between particles, and make tiny particles approach and aggregate with each other;
b) Adsorption Bridging: As a linear polymer compound, its long molecular chain can adsorb multiple dispersed stone powder particles at the same time, connecting small particles like a bridge, and quickly form large, structurally dense flocs with a size of several millimeters.
Ø Specific Functions for the Two Types of Processing Wastewater
a) Enhance Flocculation Sedimentation and Improve Treatment Efficiency
The fine abrasive debris and stone powder particles generated during granite and marble processing originally settle extremely slowly under natural conditions. After adding PAM, the sedimentation speed can be increased by 10-15 times, greatly shortening the sedimentation time and significantly improving the sewage treatment capacity.
b) Facilitate Clean Water Recycling and Reduce Production Costs
The suspended solid content in the upper clear water after treatment can be reduced to below 10ppm, which can be directly reused for cooling and flushing processes such as cutting and grinding. This can save enterprises 30%-50% of water resource consumption and reduce the cost of purchasing fresh water.
c) Optimize Sludge Dewatering and Achieve Solid Waste Reduction
PAM also acts as a filter aid, which can greatly improve the filtration and dewatering efficiency of the precipitated sludge, making the filter cake easier to peel off, reducing the operation difficulty of the subsequent filter press process, and minimizing the final sludge disposal volume.
d) Reduce the Footprint of Treatment Facilities and Cut Management Costs
Compared with the traditional multi-tank alternating process that relies on natural gravity sedimentation, the use of PAM eliminates the need for a large number of sedimentation tanks, greatly reducing the floor area of the sewage treatment system and the daily operation and maintenance management costs.
e) Assist in Scale Inhibition and Corrosion Inhibition to Protect Production Equipment
The carboxylic acid groups in its molecular structure can form soluble complexes with calcium and magnesium ions in the wastewater, inhibiting scaling on the inner walls of pipelines and circulating water equipment, extending the service life of the equipment and reducing the frequency of equipment backwashing.
Ø Practical Selection and Dosing Scheme of PAM
a) Anionic PAM (for sedimentation): Prepare a concentration of 0.1%-0.15%, that is, add 1-1.5kg of dry powder to 1 ton of clean water, stir and dissolve for 60 minutes until it is completely transparent without particles;
b) Cationic PAM (for sludge dewatering): Prepare a concentration of 0.1%-0.3%, that is, add 2-3kg of dry powder to 1 ton of clean water, stir and dissolve for 90 minutes.
Operation tips: Turn on the stirring first and then slowly sprinkle the dry powder to avoid pouring the material all at once to cause agglomeration; dissolve with normal temperature clean water, the water temperature should not exceed 60℃, the solution should be prepared and used immediately, and the storage time should not exceed 24 hours.
Ø On-site Dosing Operation Specifications
Adopt the combined process of "PAC first, then PAM" for the best synergistic effect:
1) First add polyaluminum chloride (PAC) to the wastewater to quickly condense the fine stone powder into small alum flocs;
2) Then add the diluted anionic PAM solution, and use the adsorption bridging effect to gather the small alum flocs into millimeter-level large flocs, which can increase the sedimentation speed by 10-15 times;
3) Reference for conventional dosing amount: Add 0.5-2g of PAM dry powder per ton of stone processing wastewater, and the dosage can be increased to 2-3g/ton of water for high-turbidity concentrated water. Excessive dosage will cause the water body to become sticky and the flocs to re-disperse;
4) It is preferred to use a metering pump for dosing to accurately control the dosage. The dosing point is set at the front end of the reaction tank to ensure full mixing and reaction between the chemical and the wastewater.
Ø Key Pitfall Avoidance Points
It is forbidden to use metal dissolution tanks. Corrosion-resistant plastic containers are preferred to avoid metal ions destroying the chemical activity.
Operators need to wear acid and alkali resistant gloves and goggles to avoid powder inhalation that irritates the respiratory tract.
Different ionic types of PAM are strictly prohibited from being stored and mixed together, to prevent charge neutralization and failure.
