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Screening of Composite Flocculants for Food Wastewater Treatment


Food wastewater contains abundant nutrition substances causing high biological load on the environment. Inorganic and organic synthetic high-polymer flocculants have been most commonly used because of their flocculating efficiency and low cost. Natural organic flocculants possess a certain synthetic advantage. To investigate the optimal flocculant for food wastewater treatment, effects of five organic and chemical flocculants, being Chitosan (CTS), Polyaluminum sulfate (PAS), Polyaluminium chloride (PAC), Polyaluminum ferric silicate (PSAF), Polyacrylamide (PAM) and their pair composite flocculants by stirring have been studied. Under the condition of 300 rpm for 30 min by magnetic stirring apparatus, the optimal dosages of PSAF, CTS, PAC, PAM and PAS were 3.30, 2.19, 5.69, 6.56, and 3.30%, respectively. Therefore, effect of CTS was optimal because of its 87.24% maximal absorbance reduction. CTS demonstrates biodegradability and antibacterial activity, and the hydrophilicity introduced by the addition of polar groups is able to develop secondary interactions (–OH and –NH2 groups involved in H bonds with other polymers), which results in its excellent flocculant property. The optimal proportions of two components in composite flocculant A (CTS-PSAF), B (PAC-PAM), C (P SAF-PAC), D (PAS-PAM), E (CTS-PAS), F (CTS-PAM) were respectively determined as 0.53, 0.87, 0.46, 0.40, 1.33, and 1.67. Correspondingly, the optimal stirring speeds of every composite flocculant were 20, 20, 125, 125, 160, and 20 rpm. Thus, composite flocculant A was optimal due to 42.89% maximal CODCr removal efficiency and 51.54% maximal BOD5 removal efficiency (CODCr—chemical oxygen demand determined by potassium dichromate method). The results have presented that CTS and its pair flocculants CTS-PSAF are effective for food wastewater treatment, indicating that CTS-based flocculants exhibit effective pollution removal ability with wide applications.

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This work was supported by Guangzhou Municipal Science and Technology Bureau livelihood project (201903010084), Guangdong Education Department project (2021ZDZX4045), Science and Technology Planning Project of Guangdong Province, China (2021B1212040008).

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Correspondence to Chunming Wang.

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Chunming Wang, Huang, Z., Lee, X. et al. Screening of Composite Flocculants for Food Wastewater Treatment. J. Water Chem. Technol. 44, 88–95 (2022).

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  • food wastewater
  • composite flocculants
  • chitosan
  • CTS-based flocculant
  • optimal effect