Organic Wastes Recyclingand Anaerobic Digestion Model Research

The recycling of organic wastes to form bioenergy (biohydrogen or methane) is of great significance academically. This paper combined the Research of Anaerobic Digestion Model and Automatic Control System-the sub-programs of the Eleventh Five-Year Plan on national technology. The study took Chlorella sp. and dairy manure as the objects and made studies about the batch-mode experiment of the anaerobic co-digestion producing hydrogen with Chlorella sp. and anaerobic digestion sludge (ADS) and the experiment about biogas fermentation of dairy manure. Later on, a research was conducted about the Anaerobic Digestion Model 1 (ADM1), and tried to find the restriction factors and adjusted parameters to fit experimental measurements. The aim of the paper is to optimize the anaerobic digestion model based on the two different organic wastes and fermentation type, thus providing basic data for parameter correction and verification of the mathematic model.This study evaluated the influences of inoculum-substrate ratio (ISR), volatile fatty acids (VFAs) and nicotinamide adenine dinucleotide, the reduced form (NADH) on hydrogen production during the anaerobic fermentation of Chlorella sp. in batch tests at 35°C. The results indicated that the hydrogen concentration increased when ISR decreased, and the maximum hydrogen production and hydrogen content, 7.13mL/gVS and 45.3% respectively, were obtained when ISR was equal to 0.3. On the other hand, VFAs concentrations increased with the increase of hydrogen. The NADH increased while the daily output of hydrogen decreased as the fermentation carried on. The results suggested that ISR, VFAs, and NADH were important parameters for effective anaerobic hydrogen production using Chlorella sp. as substrate.During the experiment of anaerobic methane fermentation using dairy manure as substrate using continuous stirred-tank reactor (CSTR), and the total solid (TS) and hydraulic retention time (HRT) were 12% and 20day, respectively. Various anaerobic fermentation indicator monitored during the fermentation process such as gas production,pH,soluble chemical oxygen demand (SCOD),ammonia nitrogen,volatile fatty acid (VFA),methane productivity and so on. Moreover, the stability of the fermentation system was studied as well. The result showed that the fermentation process was not restrained by ammonia nitrogen; meanwhile, the average methane productivity and the average methane concentration were 117.8mL/gVS and 59.3%, respectively.The research of ADM1 model was also conducted by using one group of experimental data. The model was implemented through AQUASIM software by simulation, sensitivity analysis, parameter estimation and so on. Another group of experimental data was used to verify the model. During the modeling of Chlorella sp. anaerobic hydrogen production experiment, found that the influence the productivity of lipid to long-chain fatty acid (LCFA), the absorption rate of sugar and amino acid and saturation rate of sugar and amino acid were the restriction factors of the Chlorella sp. anaerobic hydrogen production. The model could be used to predict the process of Chlorella sp. anaerobic hydrogen production after adjusting the parameters. Based on the understanding of anaeoribic hydrogen production modeling process, some effort was also made to research the modeling method of methane production by dairy manure using CSTR process.