Study On The Effect Of Adding Matured Sludge On N₂O Production And Related Functionsl Gene Abundance Of MSW

Composting is an effective means of MSW recycling use,but the composting process is often accompanied by a large amount of greenhouse gas N₂O,leading to nitrogen element lossing and fertilizer efficiency reducing.Most of the current research are focused on optimizing composting process parameters to limit the N₂O emission,however,the diversity of composting technology that leading to the simple improvement of process parameters is not a reasonable way of controlling N₂O emission.Therefore,the further study of microbiology mechanism of N₂O emission is of great importance for reducing N₂O emissions.As the product of composting of raw sludge,compositing sludge owns many advantages,such as soft texture,loose structure,and strong adsorption ability,meanwhile when the moisture content change is high,it can still maintain a certain amount of porosity,gas diffusion,and contain a large number of microorganisms.Therefore,using composited sludge to reduce N₂O emissions is not only feasible theoretically and low cost,achieving the goal of the recycling of waste.In order to solve the serious problems of N₂O emissions during aerobic composting process,Three mass ratios of MSW and mature sludge were set as 1: 1,2: 1 and 4: 1,and control was set with only MSW.This research studied the effects of mature sludge on N₂O missions during aerobic composting process and the influence of adding matured sludge on functional genes abundance related to the N₂O emissions using RT-PCR technology,and the microbiological mechanism of N₂O produced was also explored.The results indicated that:1.Compared with separate MSW,The losses of organic nitrogen and TN decreased obviously with the 1: 1 and 4: 1 ratios.The levels of ammonium nitrogen and nitrate nitrogen in the four composting groups were increased in different degrees in the end of composting compared to the early stage of composting,and the highest increase of ammonium nitrogen and nitrate nitrogen were 32.3% and 86.1%respectively in 4:1 group.The content of nitrite in the whole composting process had been falling constantly.The emissions of ammonia and N₂O in the composting process decreased with the increase of mature sludge adding.2.four denitrification of functional genes?narG,nirK,nirS,nos Z?abundance of four groups in the process of composting have almost the same change trend,however,adding different amount of mature sludge has obvious influence on abundance of four denitrification of functional genes.According to correlation analysis,nirS and nirK genes abundance was significantly positively related with the N₂O emissions in the process of compost,and the abundance nos Z gene had the opposite trend..This research showed that microbial denitrification is the main reason of N₂O emissions in composting process.Adding mature sludge increased the number of nitrite reducing bacteria and Nitrous Oxide reducing bacteria during composting process.On the one hand,it reduced nitrite nitrogen accumulation,on the other hand,it promoted the reduction of N₂O into N₂ and thereby reducing N₂O emission during composting process.