Study On Antioxidant Stress Responses Of Earthworms In Vermifilter

Earthworms are the animal species with the hugest biomass interrestrial ecosystems and with many important ecological functions.Theycan cooperate microorganisms to degrade organics, to maintain soilstructure, and to improve soil aeration, drainage and moisture holdingcapacity. Vermifiltration（VF）is developed based on these functions ofearthworms. It is a new ecological sewage treatment technology with lotsof advantages such as few sludge, high efficiency, simple operations andlow cost. VF could bring significant environmental values to China,because its economy is rapidly developing, while there are the lackage ofwater resources and serious water pollution.At present, former studies about VF mainly focused on sewagetreatment efficacy. The earthworms, after being put into VF, may occurstress responses to adapt this environment. However, this point has beenrarely reported so far. In this thesis, Three VFs with different filtermaterials were designed for the treatment of artificial living sewage. Theantioxidant responses in earthworm body, the treatment efficacy of VFand their relevance were investigated.It was found that, the average value of protein contents of all threeVFs are22%higher than those of control groups, presenting a generaltrend of increase since the running of VF. The Super OxygenDehydrogenises（SOD）and Catalase（CAT）activities presented similargeneral trends. During the1stto5thday, activities of these two antioxidantenzymes were significantly higher than those of control groups. After5thday, they declined to control levels. The SOD and CAT activities of VF2became stable and presented a general trend of increase-decrease, whilethe values of VF1and VF3appeared a second increase during the9^thto12^thday, and formed a trend of increase-decrease-increase. As the VFs operation time going, the Glutathione（GSH）contents, Total AntioxidantCapaicity（T-AOC）and Methane Dicarboxylic Aldehyde（MDA）contentsof the three VFs had the same tendency increase-decrease. On the1stday of VFs running, these three items of earthworms became significantlyhigher than those of the control. While after5days, they declined andwere steady at normal level.Through detection of the Chemical Oxygen Demand（COD） andAmmonia Nitrogen（NH₄⁺-N）values of inlet and outlet water, we foundthat COD removal rates also presented a general trend ofincrease-decrease. After2-7days of VFs running, the COD removalrate intended to be stable. But NH₄⁺-N removal rate of three VFs aredifferent. VF1, VF2, VF3presented linear, decrease,increase-decrease tendency respectively.Different filter materials have significant different effects on theantioxidant responses and wastewater treatment efficacy. VF1filled withmixed materials of sawdust, moss-peat-soil and zeolite was the mostsuitable living environment for earthworms, based on the lowest SODactivity and MDA content value. However, pollutant removal rate of VF3was low. The VF3filled with mixed materials of sawdust, moss-peat-soiland lava, is the most suitable filter materials based on the best pollutantremoval performance.VF environment might exert an stress to the earthworms in it, whichwas not so severe but enough to arouse oxidative stress responses.Through correlation analysis between physiological stress indexes ofearthworms and pollutant removal rate of VFs, it was found that CODremoval rate had significantly positive correlation with all thephysiological indexes. It was concluded that to some extent, the moreseverely oxidative stess responses the earthworms had, the betterpollutant removal efficacy the VF performed. Stress responses onmolecular and individual behavior levels and all around pollutant removalability of VF should be investigated in future, in order tocomprehensively reflect the relations between earthworms stressresponses and pollutant ability of VF.