| China is one of the major countries where oranges are producted in the world,thus large amount of wastewater would be produced in the production processes, andthe water is very difficult to treat because there are high concentrations of small pulp,suspended fiber, pectin that is difficult for degradation. According to analysis of theorange can wastewater properties from the producing processes, the pectin wassuggested to be one of the main factors which caused the wastewater to be very hardto treat. Currently, coagulation-biological method is the most widely used fortreatment the organic wastewater containing pectin treatment at home and abroad.Coagulation process can remove most of the pulp and citrus sacs, a part of suspendedsolid such as pectin and so on. As a result, the load of biological treatment also can bereduced. Biological treatment as the follow-up treatment of coagulation stage, canfurther degrade of the pectin and other organic contaminations in the wastewater, andCOD also can be removed. However, pectin can reduce the effect of coagulation to acertain extent because it is very easy to adhere on the surface of coagulant, and wrapthe coagulant. In addition, the part of pectin and pulp would adhere on the activatedsludge in the biological treatment units. Therefore, biological treatment is noteffective, and the wastewater can not meet the discharge standards.In the process of canned citrus production, pectin mainly comes from thepickling wastewater and alkaline washing wastewater, and it’s concentration is about3000mg L-1in the wastewater. Pectin is a kind of pollutant which is very difficult toremove in the wastewater. However, the final pectin product is an essential rawmaterial in the pharmaceutical industry and the cosmetics industry, and there is a highdemand for pectin production in our country. Large amount of pectin imported fromabroad is still need. Therefore, pectin extraction from the pickling wastewater andalkaline washing wastewater was studied in this paper.The effects of pectin extraction from wastewater were investigated underdifferent conditions including salt category, pH, amount of salt, salting outtemperature, and salting out time. The result showed that aluminum sulfate was thebest salting-out agent, and the optimum amount of aluminum sulfate was60g·L-1.Wastewater pH influenced pectin extraction rate from the wastewater, and the optimal pH for that was5as a result showed the extraction rate overpassed50%under thatcondition. In addition, the temperature of wastewater and the salting out time hadhave a significant impact on the rate of recovery of pectin from the wastewater,suitable temperature and salting out time could effectively improve the recovery rateof pectin. When the temperature of the wastewater was60℃and salt out for60min,higher pectin recovery rate could be obtained and the pectin products was much better.Using citrus cans production wastewater for pectin recycling possessed could bringcertain economic efficiency. This study could provide reference for the design ofrecycling pectin from pectin production wastewater in practice.However, when using canned citrus production wastewater recycling pectin, itwas not considered how to dispose the wastewater after the recycling, whichcontained high level of aluminum ions, and it might encounter some other problems inthe treating process. Because Phanerochaete chrysosporium fungus has a non-specificdegradation enzyme system, can degrade many organic substrates with a broadspectrum, can degrade lignin, sugar and polycyclic aromatic hydrocarbons, such aspolymers, dyes, etc. toxic substances, and can absorb the degradation of specificheavy metal ions. Phanerochaete chrysosporium is widely used in papermakingwastewater, biological pulping and bleaching of pulp and other biological wastewatertreatment projects. Therefore, Phanerochaete chrysosporium was directly used fortreatment of the wastewater from orange can production processing in this study.The effects of Phanerochaete chrysosporium on biodegradation of pectin andCOD from pectin wastewater were investigated in a bioreactor under differentconditions of inoculation size, nitrogen source, nitrogen concentration, temperature,and pH. The results showed that the best removal rate of pectin and COD was96%and83%, respectively, when the inoculum concentration was10g·L-1. Ammoniumtartrate was determined as the best nitrogen source, and when its concentration was0.8g·L-1, the highest removal rate of pectin and COD reached96%and84%. It’s alsoobserved that the removal rate of pectin and COD could overpass95%and80%respectively under the optimum water temperature range of25-35℃and pH range of4-5. This study could provide reference for the design of pectin wastewatertreatment process in practice. |
PDF Full Text Request