Study On Waste Activated Sludge Pretreatment And Biohydrogen Fermention Production From The Pretreated Sludge

With the increase of amount of municipal wastewater and sewer-laid rates and expansion of active sludge (AS) system, it brings about large amount of sludge and generates a new international tendency of sludge minimization and resource utilization. We used the different methods including water bath heating, ultrasound and microwave to pretreat the waste activated sludge (WAS). The characteristics of WAS were changed. Combined with the following process realize high effective wastewater biodegradation or enhancement of biogas production. And the pretreated sludge products bio-hydrogen by anerobic fermentation way is also a kind of the fellowing process. This method reaction conditions moderation, the fermentation production-- H2 is high–energy value and no pollution fuel.We used the different methods including water bath heating, ultrasound and microwave to pretreat the waste activated sludge (WAS). And the parameters (pH value, soluble protein, carbohydrate and SCOD) were carried out to investigation the effect of sludge disintegration. The experimental results showed that pretreatment methods have small effect on pH value but have great impact on other sludge parameters such as soluble protein, carbohydrate and SCOD. In general, sludge disintegration increased with the treatment intensity and the consumption of energy. The optimum disintegration effect came into being only when ED (energy density) equals to 2w/l and time is 10min. Under the situation, the concentration of soluble protein, carbohydrate and SCOD were 1013.6 mg/L, 512.6 mg/L and 4184 mg/L, and the ratio SCOD/TCOD enhanced 41.73% compared to the raw sludge. However , considering the practical application and economic factors, low-intensity and long time treatment also could reach good disintegration effect, so called the thermal pretreatment (t=75min,t=45℃), ultrasonic pretreatment(t=10min,ED=0.5w/L),microwave pretreatment (t=300s , p=70w). In addition, under the same energy consumption, ultrasonic pretreatment was the best, and thermal pretreatment was the weakest.Batch tests of anaerobic fermentative hydrogen production by Pseudomonas sp. GL1 were investigated by using sterilization, microwave and ultrasonication pretreated sludge as substrate. The profiles of soluble COD,protein,carbohydrate and pH value during the fermentation process were monitored. The results showed that only hydrogen and carbon dioxide were produced and methane was not observed during the process. A maximal hydrogen yield (30.07mLH₂. g-1VS) and bio-hydrogen content (81.45%) were obtained from the sterilization pretreated sludge run. The shortest lag time for hydrogen production was in ultrasonication pretreated sludge run (3 hours), while the longest one was in sterilization pretreated sludge run (15 hours), and the medial one was in microwave pretreated sludge run (12 hours). It was found that the changes of sludge substrates (soluble COD,protein,carbohydrate and pH value)were various with different pretreated sludge during the fermentation process, especially in the sterilization sludge run, which implied that the pretreatment method could affect substrate utilization by Pseudomonas sp. GL1.