Activation of Methanogens by Trace Metal Elements

For the treatment of whey-treated wastewater, when Fe, Co, Ni and yeast extracts were added, the COD removal rate increased from 6 kg/(m3.d) to 40 kg/(m3.d), and the increase in COD removal rate was mainly analyzed. Because of the addition of Fe, Co, Ni and yeast extracts, the bioconcentration in the reactor increases.

Domestic sewage: Owens starts the domestic wastewater anaerobic reaction system under low load, and the effluent VFA gradually increases from about 400mg/L to the outlet water VFA concentration drops to 400mg/L. Stop the addition of Fe, Co, Ni salt mixture, VFA concentration again The concentration of effluent VFA dropped to 400 mg/L after 10 additions to the mixture of Fe, Co, and Ni salts. Henry and Collanan1 reported that when the system is started or the load is changed, trace element deficiency is most likely to occur and trace element energy is added. Increasing the stability of the system and the impact energy of the impact of nine elements to a large extent affect the operation of the anaerobic reaction system. When the anaerobic system of whey processing wastewater only processes N, P, the effluent VFA is still high, but at the same time Fe is added. In the case of Co, Ni, or a combination thereof, the effluent VFA rapidly decreases. For example, when the trace element is not added at 30°C, the effluent VFA is 3 300 g/L, but the effluent VFA after the addition of the above trace elements is rapidly reduced to 700 mg/L. Anaerobic fluidized bed system fund project: Natural Science Foundation of Shanxi Province (971021) Anaerobic wastewater treatment system will slowly appear nutrient deficiency, but adding a small amount of Co can make the system run well with 1.2 methanogens Need for Ni It is generally believed that Ni is not essential for the growth of methanogens, but studies have shown in recent years that Ni is an essential trace metal element for A. aeruginosa. It was found that Ni is an essential component of F43. Fe, Co, and Mo are not included; Whitman and Wolfe also found that F430 is the first low molecular weight biological material that contains Ni. Diekert et al. also reported that Ni is also present in certain proteins. DoddemaP reports that the hydrogenase of methane bacteria may be a protein containing Ni. Considering that F430 is widely found in methanogens and F43 is similar to hemoglobin, its central metal ion is not Fe but Ni. Therefore, F430 has a large demand for Ni. Began to pay attention to the Ni nutrition source of methane bacteria, because the nutrient solution that used to cultivate methanogens did not contain Ni nutrition. For example, Balch et al. performed the methanogenic bacteria study. The medium used contained 0.2% yeast extract and 0.2% trypsin, but Do not add Ni salt. Diekert et al. think that this is also the reason people have neglected the need for the nutrition of Ni element for methanogens for a long time. In addition to the need for Ni, other trace elements such as Fe, Co, Mo, Se, and W are required for the growth of methanogens, but for the methanogen F430 In other words, other trace metal elements cannot replace Ni for speece reports. In anaerobic biofilters, 10 nmol Ni and 50 nmol Co are added, and the rate of conversion of acetic acid to methane is increased. For the treatment of wastewater from food industry, the production of methane was increased by 42% due to the supplementation of these trace metals, shortening the report by HRT Speece et al. that supplementation with Fe, Co, and Ni helps maintain a higher VSS concentration when only yeast extracts are added. , dss=1. 0g/L; When supplementing Ni and yeast extracts at the same time, dss=7. 1.4 Addition of trace elements and change of predominant species of methanogens Takashima and Speece report, Trace metals Fe, Co. Ni The chloride is mixed with other substances in the inorganic nutrient solution. When the bioretention time SRT is 20d, only a very low acetic acid utilization rate of 4-8 kg/(m3.d) can be achieved; but if the chloride of Fe, Co, and Ni is When directly added to the reactor, the acetic acid utilization can be as high as 30kg/(m3.d) when the bioresidence time SRT is 5d. Such high acetic acid utilization is due to the fact that Fe2, Ni2 and CoCl2 are directly added to the reactor. The predominant species of methanogens have changed, predominating from the genus Mathanosata (Methanothx) to Methanosarcina (mostly M. maxei), both methanogens are able to Using acetic acid, but both Rate is very different filamentous fungus is lower than the activity of the methane, so it has a low acetic acid concentration prevailing in the system, and in case a high concentration of acetic acid, and the required micronutrients sufficiently, it is Methanosarcina dominant. And the latter is 3 to 5 times more active than the former.

The addition of micronutrients is very important. Speece reported that if trace metal salts are not added directly to the reactor, even at particularly high concentrations of acetic acid, M. sulphur is dominant, and when Fe, Co, and Ni salts are directly added to the reactor, Methaneococcus predominates. It is characterized by high utilization of acetic acid and short generation time, and it is reported that if the nutrients are sufficient and properly controlled, the dominant bacteria will change about 2 to 3 weeks.

2 Antagonism of trace metal elements to toxic substances Methane bacteria in anaerobic treatment tend to be more sensitive to toxic substances than broth, and acetate bacteria are more susceptible to toxic substances than methane bacteria using H2/CO2. The presence and concentration of methionine are important factors affecting anaerobic treatment. The response of methanogens to toxic substances is affected by nutritional conditions. Adequate nutrition will reduce or enhance the impact of toxic substances on methanogens. According to Li and Speece, the addition of trace metals Fe, Co, and Ni can speed up the tame rate of methanogens to high-sodium ion environments. 9. Tigers (LWdk is the same process with yeast extracts and Ms can be high sodium. Inhibition of Ion to Trichophyton Inhibition The Daoming and Forstei'K ions are inhibitory substances that are present in coffee wastewater. Ca+ can effectively antagonize it. Li Yaxin and Dong Chunjuan etc. performed anaerobic digestion to supplement N,P. The cost of 8 kinds of inorganic nutrients such as S, Ca, Mg, Fe, Ni, Co and other methanogens for every 1,000 kg of acetic acid converted requires inorganic nutrient cost 3.08. Among them, N, P is 2.29 and S is 0.29. If it is assumed that each conversion 1000kg of acetic acid produces 368m3 of methane. Its value is 50, and the cost of supplementing 8 kinds of inorganic nutrients only accounts for 6% of the value of methane, but the cost of adding 6 kinds of inorganic elements other than N and P only accounts for 1.5% of the value of methane production. It can be seen that the cost of supplementing inorganic nutrients other than N and P is far less than the economic benefits brought about by increasing methane production. 4 Conclusion Although N, P are the main nutrient elements in the anaerobic digestion process, some other inorganic nutrients, Fe, Co, Ni, Mo, Se, etc. are also required The addition of trace metal elements, especially Fe, Co, and Ni, makes it possible to change the predominant species of methane bacteria in the reactor, from the predominance of M. sakazakii to that of M. multocida, thus making The utilization rate of acetic acid is increased by several times but Fe, Co, Ni and other nutrients need to be directly added to the reactor, so as to ensure that the sufficient contribution of the methanogen to the trace metal nutrients can strongly antagonize the toxic substances and replenish the methane in the anaerobic digestion process. The necessary inorganic nutrients for bacteria, especially the addition of trace metal elements, are important ways to improve the efficiency and stability of anaerobic digestion process.