Polyacrylamide (PAM), as an efficient flocculant, has significant application value in the treatment of stone cutting wastewater.
The following analysis is conducted from aspects such as technology selection, mechanism of action, and process optimization:
I. Selection and Mechanism of Action of Flocculants
The applicability of anionic PAM
Suspended particles (such as grinding swarf and stone powder) in stone cutting wastewater usually carry a positive charge. Anionic PAM promotes flocculation through electro-neutralization and the adsorption bridging effect of high-molecular chains. Studies show that anionic PAM has a high molecular weight (over 8 million), good extensibility, and its turbidity removal rate can reach 98%-99.3%. For instance, in the treatment of stone wastewater in Zhuzhou, anionic PAM combined with inorganic flocculants (such as PAC) can rapidly form large flocs, increasing the sedimentation rate by 10 to 15 times.
Special application scenarios of cationic PAM
Some stone wastewater contains organic pollutants or complex components. Cationic PAM (such as a molecular weight of 8 million and an ion degree of 20%-30%) can enhance the flocculation effect through charge neutralization. A certain case in Suzhou shows that cationic PAM has a remarkable effect on the treatment of suspended solids and also has an auxiliary effect on the rotational speed of cutting machines and the reuse of wastewater.
The advantages of compounding technology
The combined use of modified starch and PAM (such as the combination of modified starch and polyacrylamide in Webpage 1) can significantly reduce turbidity. For instance, in wastewater with a turbidity of 5000 NTU, the removal rate of the compound dosage (2 mL of modified starch +0.2 g of PAM) reached 99.3%. Similarly, the combined use of PAC and PAM can enhance flocculation efficiency and reduce treatment costs by 8%.
Ii. Key Process Parameters and Operational Points
Dosage and ratio optimization
Anionic PAM: The recommended concentration is 0.2%-0.3%. When dissolving, stir at a uniform speed (100-300 rpm) and control the water temperature below 60℃.
Compound system: Inorganic flocculants (such as PAC) are added first, followed by PAM to form a synergistic effect of “adsorption first, then bridging” 28.
The specific dosage needs to be determined through beaker experiments. Excessive dosage will lead to the re-dispersion of flocs.
Adaptive adjustment of water quality
The pH value of the wastewater needs to be adjusted to an appropriate range (usually neutral to weakly alkaline) to enhance the charge activity of PAM.
For high-turbidity wastewater (such as 16,000 NTU), the dosage of PAM should be increased (such as 7 mL of modified starch +0.7 g of PAM). 1.
Treatment effect and economy
After treatment, the content of suspended solids can be reduced to less than 10 ppm, and the water quality is close to the standard of clear water, meeting the requirements for recycling.
Although the initial investment in the compounding system is relatively high, its operating cost is low (saving 30%-50% of water consumption) 28.
Iii. Technical Advantages and Challenges
Advantage
High efficiency: The sedimentation velocity reaches 100-150 mm/min, with a large processing capacity and a small footprint.
Environmental friendliness: It realizes the recycling of wastewater, reduces water resource consumption, and sludge can be treated harmlessly after pressure filtration. 26
Adaptability: By adjusting the type of PAM and the compounding plan, it can deal with different water qualities (such as marble and granite wastewater) 45.
Challenges and improvement directions
Organic pollution: If the wastewater contains organic matter, oxidation or biological treatment processes should be combined 35.
Complexity of chemical agent selection: It is necessary to determine the optimal flocculant in combination with water quality experiments (such as Zeta potential analysis) to avoid blind addition. 46
Operation specification: PAM must be strictly dissolved to avoid caking or degradation failure. 36.
Iv. Application Cases and Promotion Prospects
Typical case
Henan Secco Environmental Protection Technology: It uses 8 million molecular weight cationic PAM to treat stone wastewater, with a suspended solids removal rate of over 95% and a 40% increase in reuse rate.
Henan Senoway: In the application of the anionic PAM and PAC compound system in Zhuzhou Stone Factory, the sludge dewatering efficiency has increased by 30%
Promotion potential
With the tightening of environmental protection policies, the demand for wastewater treatment in the stone industry is increasing. PAM technology, due to its high efficiency and economy, will become the mainstream choice. In the future, the treatment effect can be further optimized by developing new modified PAM (such as amphoteric ionic type) 18.
Summary
Polyacrylamide shows significant technical advantages in the treatment of stone cutting wastewater, but it is necessary to optimize the selection and process parameters through experiments in combination with the specific water quality. The application of compounding technology and intelligent control (such as online monitoring of pH and turbidity) are the key directions for future development.
