Study On The Various Iron Enhanced Methanogenic Process Of Cyanobacterial Biomass

In recent years, the blue algae blooms frequently in Chaohu lake and a lot of bluealgae were salvaged causing a severe environmental pollution. Currently in the world asthe third generation of energy resources the algal biomass is being paid more and moreattention as was the lignocellulosic biomass. Compared to other processes, anaerobicdigestion not only can convert the cyanobacterial biomass into methane, but also doesnot require advanced dewatering or further chemical extraction processes. However, thereported methane yield was much lower than the theoretical value. As one of the microelements for the microbial growth, a suitable dosage of iron has significance for theanaerobe.Results were concluded as follow:1. Influence of different ferric chloride concentration on methane production fromalgae.The effect of different ferric chloride concentration on methane production anddegradation rate of algae were investigated. Results showed that Fe(III) was onefeasible additive for the anaerobic digestion of cynobacterial biomass. Methanegeneration rate and yield were both enhanced. The methane yield reached234mLg-1based on the degraded volatile solid when the dosed FeCl3were0.25g L-1, while themethane yield was only131mLg-1in the control. Decomposition efficiency ofcyanobacterial biomass were promoted in the presence of iron compared to the control.2. Influence of different goethite concentration on methane production from algae.The methane production, VFAs production, decomposition of organic matters andspecies of iron in solid were valued. The results showed that different goethiteconcentration could promote or inhibit methane-generating. Methane generation yieldwas decreased when the dosed goethite was2mmol. The optimum goethite additionwas20mmol, the methane yield reached263mL/g VS and promote the degradationrates of proteins, carbohydrate and VFAs. It is concluded that goethite can alter theforms of Fe. The proportion of residual Fe increased gradually with the elevatedgoethite addition concentration.3. In order to explain these phenomena, PCR-DGGE method was applied to studysamples. Results indicated that goethite effect the microbial community structure tosome extent. In the2mmol goethite dosed reactor, the dominant bacteria wasiron-reducing bacteria, which has been shown to reduce significant quantities ofgoethite. In the20mmol goethite dosed reactor, the dominant bacteria was methanogens. This resulted in that substrate was more abundant and would be beneficialfor the methane-generating.4. Influence of different kinds of Iron oxide on methane production from algae.Results showed that methane generation yield was decreased when the ironconcentration was low.