Study On The Treatment Of Source Separated Swine Wastewater By Chlorella Bio-cathode Microbial Fuel Cell System In Continuous Operation

Under the background of continuous scale and standardization of our country's live pig industry,large-scale and intensive pig farms discharge a large amount of swine wastewater every day,about 20-25 m³ everyday per thousand heads of soaking process,which are rich in high concentration pollutants of COD?5000-30000 mg/L?,TN?800-6000 mg/L?and TP?100-1400 mg/L?,etc.Compared with the traditional swine wastewater treatment process,in the microbial fuel cell?MFC?process,high concentration organic matter contained in wastewater can be used as its ideal reaction substrate and can additionally recover electrical energy.Therefore,the microbial fuel cell?MFC?process is a recycled and utilized wastewater treatment technology with great development potential.In this paper,a continuous flow Chlorella bio-cathode MFC was constructed,and was used to treat the source separated swine wastewater?COD concentration of 1200¹800 mg/L,TN concentration of 280⁴20 mg/L,TP concentration of 18²8 mg/L?.The efficiency of MFC synchronous wastewater treatment and electric energy recovery,as well as the feasibility of indoor energy Chlorella culture in cathode were explored.The characteristics of electricity generation during the long-term operation of the device,as well as the regeneration and reuse of polluted proton membrane were studied.?1?Start a pre-experimental study.By intermittently starting the MFC device under the condition of stirring the anode,it was found that the MFC started faster under the stirring state,the starting time was 25.13%faster than no stirring,and the removal efficiency of COD,ammonia nitrogen and total phosphorus were increased4.16%,11.23%and 16.07%respectively.Compared with the anaerobic blank device,the removal efficiency of COD,ammonia nitrogen and total phosphorus in MFC devices were 90.58%,73.60%and 58.41%,which increased by 22.44%,48.67%and 13.42%,respectively.After 1 year of using,the pre-experimental output voltage of the reactor after the proton membrane regeneration was107.02±8.15 mV,which was 22.78%of the electricity production performance of the pre-regeneration MFC unit.And the removal efficiency of COD,ammonia nitrogen and total phosphorus were 66.82%and 51.15%and 39.20%,respectively.On the 20th day after the start,the MFC device formed a flocculent and well-grown Chlorella biofilm on the cathode electrode under the condition of anode agitation.?2?The startup was completed.Under the three equivalent starting conditions,the average output voltage of the anode stirring MFC device was 438.18±29.26 mV,and the average removal rates of COD,ammonia nitrogen and total phosphorus were 89.57±1.81%,71.02±2.29%,19.23±7.92%,respectively,indicating that the starting was completed.The start-up time of this experiment was 25 d.At this time,the maximum power density of MFC was 138.4.47 mW/m³,and the OCV was 549.35 mV.At the same time,the internal resistance was 288.10?,and the system coulombic efficiency was 7.13±0.96%.?3?The effect of the anolyte flow rate on the MFC unit.When the influent flow rates were 1ml/2.5min,1ml/3.0min,1ml/5.0min,1ml/6.5min,1ml/10min,the OCV obtained by MFC were 329.57 mV,384.44 mV,622.68 mV,and 697.81 mV,and 535.42 mV,respectively.At a flow rate of 1 ml/3.0 min,the internal resistance of the battery reached a maximum of437.14?.After further adjusting the anolyte flow rate to 1ml/5.0min,the MFC obtained the minimum internal resistance value,only 195.73?.At 1 ml/6.5 min anolyte flow rate,the system exhibited the best electrical performance and the growth performance of the Chlorella.When the influent flow rate was 1mL/10min,the COD removal efficiency in the wastewater reached the maximum,which was 77.58±0.48%that was increased by 17.99%compared with the influent flow rate of 1ml/6.5min.?4?The effect of cathode aeration on the MFC unit.The stable output voltages obtained by MFC were 525.37±21.88 mV,554.98±9.20 mV,591.28±10.26 mV,and 568.96±11.75 mV when the cathode was not aerated,the cathode was subjected to air and CO₂ aeration,and the anode exhaust was introduced into the cathode chamber respectively.Under the condition of CO₂ aeration of the cathode,the growth of the Chlorella was the fastest in the reactor,and the cell density of the suspension of Chlorella was 15.09×10⁶ cell/mL in the 7th day.When the air and CO₂ aeration of the reactor cathode were carried out and the anode exhaust gas was introduced into the cathode chamber,the internal resistance of the system was not much different,which was 190.91?,195.65?and 199.56?,respectively.When CO₂ aeration was applied to the cathode,MFC had the best removal effect on COD,and the removal efficiency was 66.56±1.29%.?5?Polluted proton membrane was recycled and reused in MFC.After 7 months of using,the internal resistance of the MFC device increased to 972.13?,and the stable output voltage dropped to 114.51±14.94 mV.After the proton membrane was regenerated by H₂O₂ and dilute sulfuric acid treatment,the internal resistance of the MFC device was reduced to 298.73?,which was close to the initial starting MFC internal resistance,and the stable output voltage was increased to 240.85±11.15 mV,which was 54.97%of the initial starting output voltage.At the same time,after regeneration,the removal efficiency of COD in wastewater reached60.78±3.59%,and the coulombic efficiency of the system was 4.73±0.88%,which was67.10%and 66.34%of the initial start-up,respectively.