Poster Presentation 2-27

 

Hydrogen production from Molasses by anaerobic Activated sludge in pilot-Scale Bioreactor

 

 

N.Q. ren1, J.Z. Li1, S.N. Sin1*, H. Chua2 and P.H.F. Yu3

 

 

1School of municipal and environmental Engineering

Harbin institute of technology

202 haihe road

Harbin 150090, China

Phone:  +00852-98089228

E-mail:  ceshsin@polyu.edu.hk

 

2Joint Research Centre for Water and Wastewater Treatment Technology

Hong Kong Polytechnic University

Hong Kong, China

 

3Department of Applied Biology and Chemical Technology

The Hong Kong Polytechnic University

Hung Hom, Hong Kong, PRC

 

 

 

Anaerobic hydrogen-fermenting bacteria produces hydrogen from organic wastewater and other biomass without the need for photo-energy.  However, available literature is limited to bench-scale and pure-culture studies. In this paper, hydrogen production from sugar mill wastewater by anaerobic activated sludge in a pilot-scale bioreactor (HBPR) was investigated for 200 days.  Biogas production was substantial two weeks after the BHPR was started up at an organic loading rate (OLR) of 6.32 kgCOD/m3·d and the anaerobic activated sludge was acclimated 40 days start up.  Biomass concentration in the reactor increased from 5.74 to 7.45 gMLVSS/l (mixed liquor volatile suspended solids) and the biogas yield reached 0.2 m3/d.  Maximum hydrogen-production rate of 5.57 m3/m3·d was achieved.  The BHPR system operated steadily, maintaining a COD removal rate above 20% even when the OLR was progressively changed from 3.11 to 85.57 kgCOD/m3·d.  Typical ethanol-type fermentation took place, generating a CO2 - H2 biogas with 40-50 % H2.  With CO2 absorber and the water separator, the purity of hydrogen evolved reached over 99%.  The hydrogen-production rate increased rapidly with increasing OLR, and reached a relative steady level with OLRs between 12.7 and 49.64 kgCOD/m3·d.  Maximum hydrogen production of 26.13 molH2/kgCOD was observed.  With further increase of OLR beyond 49.64 kgCOD/m3·d, the hydrogen-production rate began to decrease.  The hydrogen-production rate appeared to be influenced by the ethanol-acetate ratio and the maximum of 26.13 molH2/kgCOD(removed) was obtained when the ratio was around one. Good settleability of the anaerobic activated sludge increased the density of biomass in the BHPR.  The mixed liquor volatile suspended solids were over 7 g/l even when the hydraulic retention time was as short as 4.11 hours.  In general, the optimal OLR for the BHPR ranged from 35 to 55 kgCOD/m3·d, giving a highest hydrogen production of 0.75 m3/kgMLVSS·d.