The Electrical Properties And Changes On The Substrates Of Microbial Fuel Cells Using Excess Sludge As Fuel

With the popularization and capacity increase of wastewater treatment facilities, higher stern standards of effluent discharge and development of wastewater tertiary treatment, it will produce large amounts of surplus sludge. Costs for traditional treatment and disposal of excess sludge are quite expensive. However, excess sludge is a kind of available resources, which contains abundant organic matter, researches on sludge minimization and resource utilization becomes a new international tendency. The characteristics of waste activated sludge (WAS) were changed through physical, chemical or biological pretreatments. Combined with the follow-up process, sludge can achieve the purpose of recycling. In addition, the pretreated sludge products bio-hydrogen by anerobic fermentation way is a kind of the following process. This method reaction conditions moderation, the fermentation production--H2is high-energy value and no pollution fuel.At present, compared with other sludge hydrolysis technology, such as physical, chemical and biological treatment, People attach importance to bio-technology based on advantages of the low energy consumption, pollution and cost, even more safe. Hydrolysis by additional enzyme can not only cut down digesting time, improve sludge digestibility, and reduce disposal costs, but also can be easily controlled, and its products are harmless to environment. In this investigation, two kinds enzyme containing alpha amylase and neutral protease was added to pretreat excess sludge. In order to obtain the optimal dosing quantity, protease and α-amylase were added with the dosage of enzyme (0,30,60,120,180mg enzyme/gTS) and the hydrolysis time (4,8,12h) respectively, the ratio of SCOD/TCOD was used as a basis. We discuss the changes of soluble protein and carbohydrate, which reflect the effect of sludge disintegration under different hydrolysis time to obtain the optimal time. Comparison was also made to determine bio-hydrogen production with α-amylase pretreated sludge and protease pretreated sludge in batch fermentation tests. The results indicated that hydrolysis completed within4h under anaerobic digestion, and the optimal dosage of enzyme is60mg enzyme/g TS. After four hours hydrolysis with α-amylase addition, SCOD/TCOD rose from6.36%(raw sludge) to23.47%and the concentration of soluble protein and carbohydrate achieved8.65and51.65times of raw sludge. Pretreating with protease, SCOD/TCOD rose from6.36%(raw sludge) to19.51% and the concentration of soluble protein and carbohydrate achieved7.48and14.1times of raw sludge. Hydrogen yield of the former is1.56times of the latter.Experiments were carried in batch model to characterize anaerobic fermentative hydrogen production using excess sludge pretreated by a-amylase with and without inoculation of hydrogen-producing bacteria, Enterococcus sp.LG1. Comparison was also made to determine bio-hydrogen production with a-amylase pretreated sludge and the60℃thermally pretreated sludge in batch fermentation tests. It was showed that the process pretreated by a-amylase and with Enterococcus sp.LG1inoculation could get a maximal hydrogen yield (H2/VS)13.92ml H2·g-1, which was1.875times of sludge pretreated by α-amylase without inoculation,2.834times of sludge pretreated by60℃heat with inoculation and3.085times of60℃heat without inoculation. During the process, the average utilization coefficient of soluble carbohydrate reached to62.87%, which proved that soluble carbohydrate was the dominant substrate for bio-hydrogen fermentation.