Wastewater treatment has become an urgent and pressing issue in environmental protection. During the wastewater treatment process, flocculants play a significant role in effectively purifying the effluent. However, numerous flocculants are available for wastewater treatment, including
polyaluminium chloride, ferric sulphate polymer, polyacrylamide, and other products. How then should we select the appropriate flocculant for wastewater treatment?
When choosing a flocculant for wastewater treatment, it is essential to select a suitable flocculant based on the state of the sludge. For sludge with a relatively high organic content, cationic polyacrylamide is the most effective flocculant. Cationic flocculants are particularly effective when organic content is high. For sludge predominantly composed of inorganic matter, anionic polyacrylamide may be considered. The differing properties of sludge can directly impact treatment efficacy, potentially leading to difficulties in dewatering suspended solids and residual sludge. Generally, sludge that is harder to dewater requires a higher dosage of flocculant. Similarly, finer sludge particles can increase flocculant consumption. A high inorganic content and alkalinity within the sludge also necessitate increased flocculant dosage. Furthermore, the sludge's solids content influences the required flocculant quantity. Specifically, higher solids content demands greater flocculant application.
The pH of the sludge also influences flocculant dosage. pH essentially represents the form of hydrolysed products; the same flocculant may exhibit varying treatment efficacy across sludges with different pH levels. For instance, aluminium salts are significantly affected by sludge pH during their hydrolysis reaction. High-iron salts exhibit relatively minor pH sensitivity. Conversely, ferrous salts demonstrate higher solubility within sludge pH ranges of 8-10. Consequently, when selecting inorganic salt flocculants, the specific pH of the sludge must be considered. Should pH deviate significantly from the optimal flocculation range, flocculant replacement becomes necessary.
Finally, the concentration of the flocculant is crucial. Flocculant concentration not only impacts treatment outcomes but also influences dosage requirements and sludge dewatering yield. Generally, for organic polymeric flocculants, lower preparation concentrations necessitate reduced application rates, yielding superior results. However, both excessively concentrated and excessively diluted flocculants can compromise treatment efficacy, a point requiring particular attention.
