Screen And Fermentation Trials Of Anaerobes Acclimatized To Cassava Alcohol Wastewater

Cassava alcohol wastewater contained plenty of organic contaminants, and the concentration of its COD and suspended solids were very high. The anaerobes which was used to the cassava alcohol wastewater treatment were successfully screened from cow manure, and the effects of substrate concentration, strains dosage and some other factors on the COD degradation and methane yield in the anaerobic fermentation were also studied. At the same time, two-phase anaerobic fermentation were adopted in the cassava alcohol wastewater treatment, and its results were also compared with single-phase anaerobic fermentation in order to supply useful data to industry applications.In the experiment, at mesothermal temperature and no extra influential ions as premise, the optimal results happened at the conditions that substrate concentration was10times dilution, strains dosage was16.5g/L and COD:N was100:2.5, which achieved85.2%of the accumulated COD removal rate and223.4ml/gCODremoved of methane yield in15days.Both the addition of extra influential ions and the use of high temperature influenced the anaerobic fermentation:at the optimal condition above, addition of trace elements can make the accumulated COD removal rate arrive at92.3%and the methane yield arrive at236.9ml/gCODremoved; when the alkali metals combined with alkaline-earth metals were added, there were no significant difference of accumulated COD removal rate and methane yield between the two experiments, but the fermentation time of the experiment with additive can be obviously reduced; In another two experiments of different designs, the addition of ferrous ion brought about some inhibitions in the COD degradation, but the methane yield increased42.9%; In the experiment of high temperature, the COD degradation could reach91%, and methane yield could arrived at289.1ml/gCODremoved, which had obvious advantages when compared with the control group.The separation of the two phases was not successful when the acid phase was inoculated with anaerobes, and after the acidic fermentation came to an end, the COD value of VFAs account for11%～14%of the total COD; But when the acid phase was inoculated with aerobes, the ratio can reach47.9%. At the same time, the conclusion below were also discovered:the result of acidic fermentation in high temperature was better than the one in mesothermal temperature; in the process of acidic fermentation, the degradation rate of carbohydrates was faster than the degradation rate of proteins; in the acidic fermentation, alkalinity tended to decrease as the accumulation of VFAs, and in the methanogenic phase, alkalinity would increase slightly as the release of ammonia which was produced in the degradation of organics containing nitrogen.Moreover, the operation of methanogenic phase would suffer a failure due to the low alkalinity even the pH was adjusted before the residues of the acidic phase came into the methanogenic phase.When compared with single-phase anaerobic fermentation, the two-phase anaerobic fermentation could reduce the fermentation time and increase the methane yield on the premise of the similar effects in COD degradation. Moreover, the following results were also discovered:the specific anerobes production of two-phase anaerobic fermentation was lower than the single-phase anaerobic fermentation, and there were also difference exsiting between the two treatments in the COD character of the bacteria.