The effectiveness of chitosan, a biopolymer derived from crustacean, was evaluated in reducing the turbidity of drinking water through flocculation. In this study, Chitosan with molecular weight ranges in 50 – 1000 kDa effectively reduced turbidity by 90-99% in water containing bentonite and kaolinite clay. Optimal results are achieved at low dosages (1-3 mg/L) making chitosan a potential eco-friendly alternative to traditional metal-based coagulants. With its cost efficiency and reduced sludge toxicity, chitosan not only provides effective water treatment but also offers significant environmental and economic benefits, promoting more sustainable water treatment practices.
Managing turbidity is essential for water treatment, particularly in large-scale plants and community systems. Effective turbidity control boosts treatment efficiency and safeguards public health by facilitating the removal of contaminants. It is the critical first step to ensuring the success of subsequent processes like filtration and disinfection, ultimately providing safe, clean water to millions.
Traditional coagulants are still widely used in the treatment of drinking water due to their high efficiency and ability to handle large volumes. However, their use often results in sludge containing heavy metals and other pollutants, which requires complex and costly treatment before safe disposal to prevent environmental contamination. Additionally, these chemicals can leave metal residues in treated drinking water, raising concerns about potential health risks for human consumption. Therefore, chitosan, a natural biopolymer, is considered as an alternative for effectively reducing turbidity at low doses. It holds the potential to partially or fully replace traditional metal-based or synthetic coagulants, providing a safer, environmentally friendly, and non-toxic solution for drinking water treatment.
The use of non-toxic materials in water treatment such as Chitosan could reduce costs associated with the disposal of hazardous sludge by making it safer and easier to handle compared to traditional chemicals. Moreover, recovered sludge from nutrient-rich streams can even be utilized as animal feed ingredient or organic fertilizer. While this approach addresses many current challenges, it sets a promising foundation for cleaner, more sustainable water treatment solution in the future.
GENERAL INFORMATION:
- Location: University of North Carolina, USA.
- Duration: 2019
- Chitosan types: 11 types of acid-soluble Chitosan and 6 types of water-soluble Chitosan with different specifications.
- Chitosan specifications:
+ Molecular Weight (MW): 5 – 1,000 kDa
+ Deacetylation (DD): 70 – 95%
+ Viscosity: 5 – 12,500 mPa·s
+ Derivatives: Carboxymethyl (CMC), Lactate, Acetate, Hydrochloride (HCl)
+ Sources: Commercial chitosan product supplied by Heppe Medical Chitosan (Germany), Acros Organics (USA) and HaloSource (USA)
- Subject: Artificial surface water – As guided by UEPA (1989) and NSF International (2008)
+ Method: Kaolinite and bentonite are used to create turbidity in the test water.
+ Artificial surface water characteristic parameters:
EXPERIMENTAL DESIGN:
- Prepare chitosan solutions with different MW and DD, then apply to turbidity-controlled artificial surface water with kaolinite and bentonite.
- The flocculation test was performed using the Jar Test method, with different chitosan doses (1, 3, 10, 30 mg/L).
RESULTS
- Processing efficiency of different molecular weights: Chitosan has a higher molecular weight (50 kDa -1,000 kDa) for the best turbidity reduction results, especially at doses of 1 and 3 mg/L, achieving turbidity reductions of up to 99% for bentonite and 90% for kaolinite. The lowest molecular weight (5 kDa) gives the worst efficiency, reducing turbidity by only about 46%.
- Treatment efficacy of deacetyl varies: Chitosans with deacetyl content of 70% to 95% all achieve good turbidity reduction at a dose of 3 mg/L, with a reduction of 99% for bentonite and about 90% for kaolinite. However, at higher doses (10-30 mg/L), the treatment efficacy decreases for Kaolinite water
- Efficacy of different chitosan derivatives: Chitosan derivatives such as HCl, Acetate, and Lactate have the same turbidity reduction effect on bentonite water as unmodified chitosan, reaching 98-99% reduction. For kaolinite water, HCl and lactate derivatives show an 88-91% reduction in kaolinite turbidity at a dose of 3 mg/L. Carboxymethyl Chitosan has the worst effect, It only reduces bentonite turbidity by about 60% and is ineffective with kaolinite at all doses.
Chitosan is an effective flocculant in reducing the turbidity in drinking water treatment, with optimal efficacy achieved at doses of 3 mg/L. Chitosan has a high MW (from 50 kDa to 1,000 kDa) showing superior ability to reduce turbidity, especially for bentonite due to its large surface area and high cation exchange capacity enable it to react more efficiently with chitosan. In contrast, kaolinite, with its distinct structure and chemical properties, is less efficient in treatment with chitosan.
Besides, chitosan derivatives, such as HCl, acetate, and lactate, have all shown similar efficacy in reducing turbidity of bentonite water, while carboxymethyl derivatives are less effective. When Carboxymethyl Chitosan is in solution form, the carboxymethyl group (COO–) attenuates the interaction between the amino group (NH3+) and the clay particles, resulting in lower flocculant efficiency compared to other derivatives. From these findings, chitosan emerges as a promising alternative to traditional flocculants, is not only effective in reducing turbidity, but also safer for the environment, which play an important role in more sustainable and economical water treatment solutions in the future.
Vietnam Food Joint Stock Company (VNF) is able to provide a diverse portfolio of Chitosan by utilizing advanced biotechnology, for the ability to customize specifications of viscosity, deacetylation, solubility and other derivatives (HCl, Lactate, Acetate), to meet diverse needs in water treatment. VNF has conducted many successful tests in surface water treatment and turbidity reduction, with the company’s chitosan products showing outstanding effectiveness in removing suspended organics, metals, improving water transparency, and ensuring environmental safety. These tests prove that VNF’s chitosan is suitable for large-scale applications, providing a sustainable and economical solution for water treatment.
Source: Ampai Soros (2019) Turbidity reduction in drinking water by coagulation-flocculation with chitosan polymers LINK