Bio-hydrogen Production From S-te Pretreated Sludge By Anaerobic Fermentation

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.The characteristics of waste activated sludge(WAS) pretreated by physical,chemic or biologic method 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. Compared with other sludge solubilization technology such as ozone oxidation, chlorine oxidation, thermal hydrolysis, acid, alkali, mechanical, ultrasonic and enzymatic directly pretreatment, solubilization by thermophilic enzyme (S-TE) based on microbial cryptic growth is more cost-effective and safer as well as lower energy cost and easier operation.In order to separate and identify the thermophilic bacteria applicating to sludge dissolved in garden soil, the general method of dilution spread was used. A new species of high efficient was selected and morphological observation and physiology-biochemistry tests have been conducted. It was showed that the strain was Gram-possitive, small rod-shaped,sporulation and aerobic or facaltative aerobic bacterium. Its optimum temperature for growth was 65℃, optimum pH for growth was between 6.8 and 7.5. Sequence analysis of this type of clones showed that it was not reported yet in other paper at present and labelled as Bacillus thermophilic bacteria AT07-1(registration number: FJ231108).12 strains of H2-producing bacteria were isolated and purified from anaerobic sludge, aerobicsludge and river bottom sludge by Hungate method. A new species of high efficient hydrogen productionbacterium Enterococcus sp. LG1 (registration number: EU258743 ) was studied deeply. It was showed that the Enterococcus sp. LG1 was an anaerobic and Gram-negative bacterium and could make bio-hydrogen production efficiently.In this research, S-TE was used to pretreat WAS under various inoculated volumes of thermophilic bacterium and differet oxygenous conditon. The effct of inoculated volumes, oxygenous condition and the pretreated time for fellowing process of anaerobic fermentative hydrogen production were examined and the optimal condition were gained. The results showed that the addtion of 5%(v/v) thermophilic bacteria culture to the WAS produced the most hydrogen. Under microaeration the S-TE were more propitious to promote the release of nutrients in waste sludge than under agitation, but the sludge pretreated by S-TE under agitation produced more hydrogen than sludge pretreated under microaeration. The optimum pretreated time for optimum hydrogen production was 24 hours , and the longer pretreated time was , the less hydrogen ullage would be.Batch tests were carried out to analyze the effects of anaerobic fermentative hydrogen production using excess sludge pretreated by S-TE (solubilization by thermophilic enzyme) with and without inoculation of hydrogen-producing bacteria, Enterococcus sp.LG1. The performance of biohydrogen production of the S-TE pretreated sludge and the 65℃thermally pretreated sludge was also compared in batch fermentation tests. The changes of sludge substrates and pH value during the fermentation process were also monitored and discussed. The results showed that sludge pretreated by S-TE without inoculation could make good bio-hydrogen production. The maximal hydrogen yield (H2/VS) was 16.3ml H2/g, 26.4% higher than sludge pretreated by 65℃heat without inoculation and 15.6% than 65℃heat with inoculation. Hydrogen and carbon dioxide were only produced and methane was not observed during the process. The lay time for hydrogen production was only 3~4 hours ,and after reaching its maximun, the bio-hydrogen was able to maintain stable for above 10 hours with little consuming. The bio-hydrogen yield of the S-TE pretreated sludge inoculated Enterococcus sp.LG1 was very low, only 10.7 ml/g. The soluble protein and carbohydrate during the fermentation process first increased to their maximal concentration and then decreased, while SCOD concentration was fluctuant throughout the process. The time soluble protein and carbohydrate sharply decreased was the time biohydrogen sharply increased .The results clearly showed that soluble protein and carbohydrate were the main substrates for bio-hydrogen fermentation from S-TE pretreated sludge.