Variation of oxygen concentration in pig-manure composting piles under different aeration flowrates
不同通风量下猪粪好氧堆肥中氧气浓度的变化

Aerated static composting is one of the best choices for treating animal waste.Oxygen is an important factor influencing the composting process.The growth of aerobic microorganism,the composting duration and the quality of final product depend largely on the oxygen concentration in the pile and the oxygen suppling process.Aeration is necessary for aerobic composting.Different strengths of aeration have different effects on composting process.In order to estimate the optimal aeration flowrate and control the oxygen concentration in the composting process,It is necessary to examine the actual variation of oxygen concentration and oxygen consumption rate in the composting process.Forced aeration static barrel was used in this experiment.The barrel contained pig manure and bulking agent.The equipment used to measure the oxygen concentration was portable and numerical.The oxygen concentrations were measured at 0,5,10,15 and 20 minutes after cessation of ventilation.And the variation of oxygen concentration during the first 5 min interval after stopping ventilation was used as a measure of oxygen consumption.In order to study the oxygen dynamics,the oxygen concentration was monitored at the same time every several days,and the measured data were used to analyze the oxygen variation during the composting process.Initially,the oxygen consumption rate during the composting process decreased,which was influenced by moisture,then increased and finally decreased slowly again.In the whole composting process,the oxygen concentration showed a tendency of increase,which was especially faster in middle-process and late phase of the process.The rate of oxygen decrease in the pile was fast during the first 5 minutes and then slowed down.The four piles showed different characteristics under different levels of aeration.It was concluded that the optimal flow rate of aeration is 0.35 m~3/min.