Application of Water-soluble Chitosan in Treatment of Aquacultural Wastewater

• Main Authors: Chen, Yi-Jye, 陳怡傑
• Other Authors: Chin-Fung Li
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/96179715064555075751

碩士 === 國立臺灣大學 === 食品科技研究所 === 86 === Abstract Maillard reaction was used for preparation of water-soluble chitosan. Their physico-chemical properties, such as yield, solubility, degree of deacetylation, degree of Maillard reaction, stability of solution, and particle size distribution, were measured. Both the water-soluble and acid- soluble chitosans prepared were used as coagulants in the treatment of aquacultural wastewater to compare the effects on turbidity, suspended solid, chemical oxygen demand, and aquacultural pathogen of wastewater. Dosage, range of most suitable dosage, effect of solvent pH and wastewater pH of both chitosans were also determined. On the basic properties of water-soluble chitosan, yield of water-soluble chitosan made from α-chitosan was about 15%, while it was 28%-33% when made fromβ-chitosan. However, the highest solubility of α-water-soluble chitosan among different reaction times was 0.79g/dL(3-days reaction), then that of β-water-soluble chitosan was only 0.4g/dL in water. For this reason, all experiments in this study were all performed withα-water-soluble chitosan.The absorbence at 420nm in 1% water-soluble chitosan was 0.6 after 2-days reaction, and was not raised later. It was seemed Maillard reaction was finished in two days. Water-soluble chitosans was clear and transparent in the solution among pH3 to 12. Two or three peaks appeared in the chart of particle size distribution. It means that modification, polymerization and chain-breakage might happen to chitosans after Maillard reaction. On the effects of different chitosans on treating aquacultural waste water, with dosage of 3ppm, water-soluble chitosans reacted for 1, 3, and 5 days and β-chitosan(DE84%) made turbidity, suspended solid, and COD of wastewater decreased from 15.2NTU, 122ppm, and 81.5ppm to about 3NTU, 25ppm and 20ppm respectively. But addition of 3ppm α-acid-soluble chitosan lowered the turbidity, suspended solid, and COD of the same wastewater to 7NTU, 56ppm, and 41ppm respectively. The reason could be that 3ppm was not in the range of most suitable dosage of α-acid-soluble chitosan. About effects on aquacultural pathogen, addition of α-acid-soluble chitosan and water- soluble chitosan solved in 0.2M acetic acid made Aeromonas & Pseudomonas too few to be counted by plate count when dosage was more than 300ppm, but it seemed part of antimicrobial effect was came from acetic acid. If water- soluble chitosan were solved in pure water, the more the dosage was, the larger the number of Aeromonas & Pseudomonas were. The range of most suitable dosage of water-soluble chitosan was wider, but the dosage needed was more than those of acid-soluble chitosan. When solved in acetic acid solution of pH3, 4, 5, and 6, the lower the pH of solvent of water-soluble chitosan was, the less the dosage was needed. The reason was that the ratio of ionized isolated amino group to non-ionized isolated one is less at higher pH. The results also showed that water-soluble chitosan would work normally, while acid-soluble chitosan would not.