Jianjun Hu

Sludge treatment: Current research trends

Sludge is produced during wastewater treatment as a residue containing most insoluble and adsorbed soluble impurities in wastewaters. This paper summarized the currently available review papers on sludge treatments and proposed the research trends based on the points raised therein. On partition aspect, sludge production rate and the reduction of production rate and the fate and transformation of involved emergent contaminants including endocrine disrupting chemicals and pharmaceuticals and personal care products are widely studied. On release aspect, development of thermal processes on sludge with migration and transformation of heavy metals in sludge during treatment is a research focus. The use of detailed fluid and biological reaction models and advanced instrumentation and control systems is studied to optimize treatment performances. On recovery part, co-digestion of sludge with co-substrates at mesophilic and hyperthermophilic conditions and the recovery of phosphorus at low costs are research highlights.

Kraft lignin biorefinery: A perspective

Lignin is a huge energy and carbon reserve but owing to its highly biologically recalcitrant nature it is commonly regarded as a waste in lignocellulosic biomass biorefinery. To realize the lignin biorefinery, it is proposed to use Kraft lignin, isolated from black liquor from Kraft pulping mills, as starting material to be fragmented by fast pyrolysis or selective catalysis to aromatic sub-units and to be post-refining with additional cleavage reaction and separation/purification as commodity aromatics pool in chemical industries. This Note calls for research efforts on detailed investigation of the feasibility of this proposed scenario.

Photo-fermentative hydrogen production in a 4 m3 baffled reactor: Effects of hydraulic retention time

A 4m3 pilot-scale baffled continuous-flow photoreactor with four sequential chambers (#1-#4) was established and tested to evaluate its photo-fermentative hydrogen production from wastewater that contains (10g/L glucose using a functional consortium at 30°C, under light with an intensity of 3000±200lux with a hydraulic retention time (HRT) of 24-72h. The hydrogen production rate and the broth characteristics varied significantly in the flow direction. The hydrogen production rate was highest in chamber #1, and lower in chambers #2-#4 at an HRT of 72h, while the peak production rate shifted to the latter chambers as the HRT was shortened. The overall H2 production rate increased as HRT decreased, but was not consistent with the predictions that were based on the complete-mixing assumption.

Effect of substrate concentration on hydrogen production by photo-fermentation in the pilot-scale baffled bioreactor.

Effect of substrate concentration on photo-fermentative hydrogen production was studied with a self-designed 4m3 pilot-scale baffled photo-fermentative hydrogen production reactor (BPHR). The relationships between parameters, such as hydrogen production rate (HPR, mol H2/m3/d), hydrogen concentration, pH value, oxidation-reduction potential, biomass concentration (volatile suspended solids, VSS) and reducing sugar concentration, during the photo-fermentative hydrogen production process were investigated. The highest HPR of 202.64±8.83mol/m3/d was achieved in chamber #3 at a substrate concentration of 20g/L. Hydrogen contents were in the range of 42.19±0.94%-49.71±0.27%. HPR increased when organic loading rate was increased from 3.3 to 20g/L/d, then decreased when organic loading rate was further increased to 25g/L/d. A maximum HPR of 148.65±4.19mol/m3/d was obtained when organic loading rate was maintained at 20g/L/d during continuous bio-hydrogen production.

Enzyme hydrolysis kinetics of micro-grinded maize straws

This study applied micro-grinding to disintegrate the maize straws and then use the micro-grinded straws of particle sizes particle size 53-61, 80-96 or 150-180μm, for subsequent enzyme hydrolysis tests. The reducing sugar productivity was increased with reducing particle size. A kinetic model considering product inhibition was developed as follows t=aln[S]0[S]0-[P]+b[P], where S, P and t are the substrate, enzyme and hydrolysis time, respectively, and a and b are fitting parameters. The initial substrate concentration is proportional to the total exposed surface area. Additionally, the mechanical grinding can increase the biomass affinity for enzyme attack, suggesting the enhanced local action of shearing on the fiber matrix surfaces. The enhanced hydrolysis efficiency of the micro-grinded straws is welcomed by the subsequent refinery steps.

Syngas production by chemical-looping gasification of wheat straw with Fe-based oxygen carrier

The iron-based oxygen carriers (OCs), Fe2O3/support (Al2O3, TiO2, SiO2 and ZrO2), for chemical looping gasification of wheat straw were prepared using impregnation method. The surface morphology, crystal structure, carbon deposition potential, lattice oxygen activity and selectivity of the yielded OCs were examined. The Fe2O3/Al2O3 OCs at 60% loading has the highest H2 yield, H2/CO ratio, gas yield, and carbon conversion amongst the tested OCs. Parametric studies revealed that an optimal loading Fe2O3 of 60%, steam-to-biomass ratio of 0.8 and oxygen carrier-to-biomass ratio of 1.0 led to the maximum H2/CO ratio, gas yield, H2u202f+u202fCO ratio, and carbon conversion from the gasified wheat straw. High temperature, up to 950u202f°C, enhanced the gasification performance. A kinetic network interpreted the noted experimental results. The lattice oxygen provided by the prepared Fe2O3/Al2O3 oxygen carriers promotes chemical looping gasification efficiencies from wheat straw.