Preparation Of Chitosan Flocculant By Microwave And Application To Treatment Of Wastewater With Highly Concentrated Protein

In general, food-processing wastewater contains abundant proteins and fat. It can, if drained directly before treatment, pollute seriously the accepted water body. This would not only increase the burden of wastewater treatment facilities, but also result in the waste of resources.Chitosan, deacetylated product of chitin, is a kind of natural , non-toxic organic polymer. It is a cationic polymeric flocculant, which has good adsorption properties and biodegradation. The most advantage of chitosan flocculant is to treat food-processing wastewater and can adsorb proteins with negative charge from wastewater efficiently. The chitosan-sludge can be used as an additive for pig food without further separation.Many in-depth and comprehensive studies on preparation of chitosan have been conducted , but most of those studies are concerned on original technology, which has high production cost and long reaction time. Compared with original technology, studies on preparation of chitosan under microwave with changeless power have been reported, but there are hardly research works on preparation of chitosan under microwave with change power in the world at present. On the other hand, studies on application of chitosan to wastewater focus on limited fields such as decolor, removal of metal ions, and so on, most of which were carried out in the 1980s and 1990s. Study reports on application of chitosan to food-processing wastewater have seldom been seen.In the paper, the preparation conditions of chitosan under microwave with change power are studied firstly. By controlling temperature , the combinations ofmicrowave power are optimized. Based on the analysis of degree of deacetylation, viscosity and reaction time, the optimal combination of microwave power are detected. The chitosan flocculant which satisfies with wastewater treatment is preparated on the condition of the optimal combination of microwave power. It, compared with one producted under changeless power wicrowave, has slightly lower degree of deacetylation, but its viscosity goes up 12.9%, relative molecular mass increases 8.3% and energy consumption is reduced by 40%.Second, the flocculating process and conditions in highly concentrated protein wastewater treatment are studied. By researching the effect of wastewater pH, chitosan dosage, temperature and hydraulic condition on flocculating process, the most desirable flocculating condition and the optimum woking area for 55-65% COD removal are found out. Compared with carboxy methyl cellulose (CMC) , chitosan is able to give stable and good treatment efficiency over broad pH range, and the consumption of pH-adjusting acid is fewer,decreasing wastewater treatment cost. In addition, studies on the effect of chitosan on (?) and protein recovery are also carried out. The results indicate wastewater pH has great impact on protein recovery and when pH=4.5, chitosan dosage 15mg/L, the protein recovery rate reaches maximal 81.54%.