Effects Of Earthworms On The Change Of Microfauna Community In Municipal Sludge

Vermicomposting is expected to provide a new outlet for current sludge treatment because it is environmentally friendly,safe and sustainable.There are a large number of protozoa and micro-probiotics in the activated sludge.After entering the dewatered sludge,they form a sludge peat food net together with the microorganisms and the exogenous inoculated cockroaches.The existing research mainly focuses on the microbes and earthworm of the food web.Little research on micro-animals,the role of micro-animals in food web and the nature of sludge is important for composting.Two groups of experiments were set up:1)The earthworm group and the control group were set at 15 and 20 C,respectively.2)The earthworm sludge mass ratio was 1:10 and 1:5,and the control group was selected.The changes of earthworm biomass,micro-animals community structure and physical and chemical indexes of organic matter?OM?,conductivity?EC?,pH,NO₃^--N,NH₄⁺-N,TN and SWC in sludge were investigated.The main conclusions were as follows:?1?The degradation of organic matter content in the sludge was accelerated.The higher the temperature,the lower the OM content at the end of the experiment,and the experimental group was lower than the control group.The change trend of NH₄⁺-N content was similar at different temperatures.The NO₃^--N content increased at 20°C after 45 days.The TN and pH at 20°C in the early and late stages of the experiment were all lower than 15°C,and the temperature effect was not obvious in the middle of the experiment.The higher the temperature,the higher the EC and the experimental group was higher than the control group.Correlation analysis showed that OM was significantly positively correlated with the number of worms and rotifers?r>0.75,p<0.01?,indicating that the worms and rotifers may be the main contributors to urban sludge OM.?2?During the composting process,the ambient temperature had no effect on the number and proportion of difflugia.The higher the temperature,the smaller the number of arcella but the greater the proportion in the community.The number of branchlets and rotifers at 15°C was greater than 20°C,but the proportion of branchlets at 15°C was less than 20°C;the proportion of rotifers at 15°C was stable at 20°C,ranging from 3%to 5%.The number of nematodes showed a trend of increasing first and then decreasing.The higher the temperature,the smaller the number of nematodes.The proportion of nematodes at 15°C increased with time,while the proportion of nematodes at 20°C increased first and then decreased.?3?The change of density was not significant for the accelerated degradation of sludge organic matter,and sludge stabilization was achieved almost simultaneously at both densities.Due to the hypoxia in the H group,the strontium biomass of the H group was not much different from that of the L group.The OM change trend of the two treatments was similar,and the L group was slightly higher than the L group.?4?The change of density had no effect on the number of arcella and difflugia.The proportion of low-density arcella was higher than that of high-density groups,and the frequency of difflugia was discontinuous,which was relatively small;Density does not change the number and proportion of branchlets and rotifers;The effect of density on the number of nematodes was reflected in the late stage of the experiment.The number of nematodes in the 30⁶0d period was H>W>L.The higher the density,the larger the number of nematodes,the larger the proportion,and gradually became the dominant species.The effect of density on the number of nematodes was reflected in the late stage of the experiment.The number of nematodes in the 30⁶0d period was H>W>L.The higher the density,the larger the number of nematodes,the larger the proportion,and gradually became the dominant species.The cause of this phenomenon may be attributed to the lack of oxygen inside the sludge of Groups H and W,while the anaerobic environment was suitable for the large-scale reproduction of nematodes.