Research On Piggery Wastewater Treatment And Hydrogen Generation By Metal-air Battery-MEC Coupling System

As a kind of high organic wastewater, piggery water has “three highs”, high concentration of pollutants, high ammonia nitrogen and high suspende solids, also with many germs. Direct emissions or falls below the emissions will cause serious effection on the ecological environment and human beings. At present in our country, the piggery wastewater treatment technology has low efficiency and higher cost. For this kind of high concentration wastewater, we need to find a economic and effective method.Microbial electrolysis cell(MEC) is a new kind of technology, can not only be used in various of environmental waste, but also in high concentration wastewater, degrading organic pollutants and generating hydrogen gas at the same time, even with some other valuable productions, such as methane, acetic acid, ethanol and etc. And as a kind of promising power energy, metal air batteries is a new type of fuel cell, with high specific energy, long service life and ect. If aluminum or iron is used as the battery anode, it can produce high power and flocculant, with the process of cell reaction flocculant, for the pretreatment of wastewater.The experiment is based on the Cubic reactor, first we consititued the Al/Fe-metal air battery and optimize the different conditions through the battery discharge performance. The result shows that the battery works best when NaCl electrolyte concentration is 35 g/L, solution pH is around 7, with a small resistance connected in the circuit. And the Fe-air battery can obtain higher potential, while the Al-air battery has a faster reaction.Second we optimize the conditions of flocculant production from metal air batteries, using the flocculant to do the pretreatment of piggery wastewater. The effluent removal rate of COD, NH3-N, SS and turbidity can reach to 61%, 41%, 52% and 55%.Choose the optimal metal air batteries, providing different MEC startup mode with voltage, to deal with the piggery wastewater. Detect the effluent COD as well as the gas composition, combining with high throughput sequencing technology, to study different microbial flora and mechanism of MEC. Results show that the double Fe air battery-MEC get the best efficiency: diluted wastewater COD decreased to 300 mg/L, not diluted water COD finally dropped to 360 mg/L, while the hydrogen recovery rate was 36.14% and 18.46%, the energy efficiency was 94% and 80%. More electric bacterial colonies and similar structure are found in the directly started MEC and the double battery-MECs, like the similar reactor performance. So that the reactors running efficiency has a close relationship with the biological community structure.