The Organics Separation And Ammonia And Phosphorus Recovery Of Alkaline Fermentation Sludge

Much attention has been paid in recent years to using sludge own carbonsproduced in sewage sludge alkaline fermentation as carbon source of nitrogen andphosphorus removal of municipal wastewater treatment plants.But the sludgedewaterability after fermentation will be deteriorated and it is difficult to separate theorganics from the alkaline fermentation sludge.In addition, the alkaline fermentationliquid contains high concentration ammonia and orthophosphate，which could influencethe nitrogen and phosphorus removal efficiency in fellow-up system.This thesis focusedon the carbon source separation and nitrogen and phosphorus removal in alkalinefermentation liquid—a key step to applying the alkaline fermentation liquid to removethe nitrogen and phosphorus of sewage.First of all,The variations of the sludge dewaterability during alkalinefermentation was investigated by controlling the temperature at25℃and35℃and usingCa（OH）₂and NaOH to adjust the pH and the factors influencing the dewaterability ofthe alkaline fermentation sludge was analyzed.It was showed that the dewaterability ofthe sludge fermented at35℃was worse than the sludge fermented at25℃using thesame alkaline regent, the dewaterability of the sludge pH adjusted by Ca（OH）₂wasbetter than those pH adjusted by NaOH at same temperature. The analysis combiningZeta potential, particle size with soluble carbohydrates and proteins indicated that thetemperature and the concentration of Ca²⁺may be root cause for the dewaterability ofthe alkaline fermentation sludge.The CST （Capillary Suction Time）correlated with thesoluble proteins concentration in alkaline fermentation sludge within a certain range,thecorrelation equation were y=1.0873x+766.8041and y=0.4473x+228.4308respectively.FT-IR further proved that Ca²⁺could interact with the function groups ofsludge surface.Secondly,It studied the variations of dewaterability and organics in chemical andfreezing-thawing conditioning process of the alkaline fermentation sludge.The resultsshowed that chemical conditioning could improve the dewaterability of two kinds ofsludge.But the sludge pH adjusted by Ca（OH）₂gained a higher organics recovery（90%above） efficiency than sludge pH adjusted by NaOH（65%below）.Proteins and carbohydrates were the main loss ingredient during chemical conditioning.Incontrast,the shorty fatty acids had little loss.On the other hand,freezing-thawingconditioning has enhanced the dewaterability of sludge pH adjusted by Ca（OH）₂,theCST decreased to21.4s under-19^-13℃6h and18.5s under-8℃24h from71.5s. Forthe sludge pH adjusted by NaOH the CST decreased from1058.6s to33.9s at the end offreezing-thawing conditioning,which means a better dewaterability. Furthermore,freezing-thawing conditioning obtained a higher organics recovery efficiency thanchemical conditioning for two kinds of sludge.Finally,it researched the simultaneous recovery of NH4–N and SOP from thealkaline fermentation sludge sludge pH adjusted by NaOH by truvite precipitation anddemonstrated the optimal conditions recovering NH4–N and SOP wasMg:P:N=1.8:1.2:1at pH=10,88.85%，92.08%recovery effciency respectively inrepeating experiment.The truvite precipitation process enabled to improvedewaterability of sludge pH adjusted by NaOH with the CST falling to230.7s from1010.8s.The CST reached the organics reached25.7s finally by CPAM：TSS=0.6:100conditioning with87.86%organics recovery effciency and relatively constant SCFAsconcentration.