| The sediment contains a large number of N,P elements and refractory heavy metals and organics.These harmful substances will migrate with the change of water environment,which affects the quality of the upper water.Aerobic composting technology provides an effective way for the utilization of sediment.However,the traditional technology has some disadvantages,such as high moisture and rich content of nutrients in sediment.This study is to select the optimal parameters for the sludge composting,and to explore the application of compost sediment to the landscaping soil.The composting process taken the sediment as the raw material,selected the stalk,dregs,bran and so on as the conditioner,and added the EM bacterium agent as the reference.Orthogonal composting experiments were done under moderate,high carbon/nitrogen ratio（C/N）and aeration volume.The physical and chemical properties,nutrient transformation and heavy metal transformation were mainly detected during the composting process.The sediment compost product is mixed with peat soil and perlite in 6 different proportions by detecting the nutrient content in the matrix and the changes of plant morphology during the planting of Bermuda grass and Impatiens to determine the optimal matrix formulation.The main results are as follows:（1）The treatment of 8 groups with different C/N ratios,aeration volumes and conditioners had undergone four processes,such as heating stage,high temperature,cooling stage and maturity period,At the same time,the treatment of 30%EM bacteria（in total material quality）was added to the sediment composting material to enter the cooling period in high temperature.The composting material is decomposed more quickly.With the treatment of straw,dregs and bran as raw material,the addition of EM bacteria could extend several days of high temperature period,and the germination rates are higher.（2）With the treatment of straw,dregs and bran as auxiliary materials in moderate C/N condition,the nutrient content of compost was richer than that of garden waste,mushroom residue and bran as amended material,The content of organic matter,NO3-</sup>N,NH4+-N and total phosphorus were 1.31 times times,9.51times times,0.72 times times and 1.27 times times respectively.The treatment of straw,dregs and bran in the process of sludge composting has good ability of nitrogen conservation and phosphorus retention.In the process of sludge composting,the content of Zn was the largest and many forms coexist,with the composting,the content and distribution ratio of each form were not changed.Cu and Cd mainly in exchangeable fraction.The exchangeable Cu treated with garden waste,mushroom residue and bran was increased by 17.91%and 28.53%respectively,Cu has a small increase in its content at different fractionations.The exchangeable Cu treated with straw,dregs and bran were reduced by 69.54%and 64.35%respectively,and the content of Cu is declining.The straw and the dregs are more favorable for the degradation of organic carbon and the formation of humic acid,So that the heavy metals have better complexation adsorption capacity.At the same time,the addition of EM bacteria also affected the bioactivity and heavy metal passivation ability.（3）Under the condition of high C/N ratio,the treatment of straw,dregs and bran as auxiliary materials,The nutrient contents of the compost were,Organic matter77.85%,NO3-</sup>N 336.05g/kg,NH4+-N 9.99 g/kg,total phosphorus 457.35 mg/kg;The treatment of garden waste,mushroom residue and bran as auxiliary materials,The nutrient content of compost was 50.11%,NO3-</sup>N 237.32g/kg,NH4+-N 157.04 g/kg,total phosphorus 576.79 mg/kg.There were obvious differences in treatment between the two groups,the organic matter content of straw,dregs and bran in the process of sludge composting was high,and the treatment of garden waste,mushroom residue and bran as auxiliary material had better ability of nitrogen conservation and phosphorus retention.The variation of Zn,Cu and Cd in the composting process is similar to that of moderate C/N ratio.The content of Zn is highest.At the end of composting to straw,Zn in sediment composting with dregs and branis 221.97 mg/kg.The composting process with garden waste,mushroom residue,and bran contained lowest Zn,which is 101.30 mg/kg.Cu and Cd are mainly in exchangeable fraction.In the four groups,the contents of exchangeable Cu treated with straw,dregs and bran were reduced by 63.77%,and the content of added bacteria was increased by 43.88%.The exchangeable Cu in the treated materials of garden waste,mushroom residue and bran was reduced by 26.89%and 47.12%respectively;The exchangeable Cd in the treatment of straw,dregs and bran was reduced by 93.24%and 71.67%,respectively.The exchangeable Cd in the treatment of garden waste,mushroom residue and bran were reduced by 78.38%and 75.76%respectively.The conversion of heavy metals in four groups was reduced,and the addition of EM agent had heavy metal passivation effect when the sludge was composting with garden waste,mushroom residue and bran as amended material.（4）The experiment of Bermuda grass cultivation showed that the germination rate of Bermuda grass was 89.12%,and the plant fresh weight,plant height and leaf area were the best in accordance with the proportion of"70%sludge compost+10%peat+20%perlite".The experiment of balsam cultivation shows that when the sludge compost,peat soil and perlite are mixed according to the ratio of volume to 7:1:2,it is beneficial to increase the porosity of the matrix aeration and the oxygen supply to the root of the Balsam,and provide the nutrients for the growth of the seedlings,and ensure the good growth substrates of the Bermuda.Fresh weight and plant height increased obviously,and the fresh weight of plant increased from 2.08g to6.32g,2.86g to 8.27g,and plant height increased from 8.83cm to 17.00cm,8.00cm to18.50cm respectively. |
