| In this study,sludge samples were selected from three sewage treatment plants????and??in Handan,the concentration and the different fractions of heavy metals?Cu?Zn?Pb?Cr?Cd?Ni?were analyzed after atmospheric pressure digestion.Then,evaluated the pollution degree,potential ecological risk and agricultural potential of sludge.Choose one of the the sludge in sewage treatment plant as the compost matrix according to certain proportion mixed with wheat straw,corn straw,mushroom residue,sawdust to proceed aerobic composting in order to studied the impact of different conditioner on composting effect and composting quality.The results show that:?1?The average content of organic matter in Handan municipal sludge was higher than the average of Chinese urban sludge,and the content of TN,TP and TK varied from 3.9%to 4.5%,1.75%to 2.18%,and 1.35%to 1.72%,respectively.The average contents of Cu,Zn,Pb,Cr,Ni and Cd in the sludge of the three sewage treatment plants were 93.09 mg·kg-1,887.01 mg·kg-1,70.29 mg·kg-1,124.23 mg·kg-11 and 34.09 mg·kg-1?Cd was not detected?,all of which were lower than the national standard limit and had good agricultural potential.Where,Cu and Ni mainly exist in residual fraction and oxidizable fraction,Zn mainly exists in exchangeable acid soluble fraction and reducible fraction,and Pb and Cr mainly exist in residual fraction.In addition to Zn,the stable state of other heavy metals accounts for a higher proportion and lower bioavailability.?2?The results of geo-accumulation index method showed that Zn belong to the heavy pollution,Cu belong to the moderately-moderate pollution,Pb,Cr and Ni belong to light pollution.The Nemerow integrated pollution index was 6.65,8.12 and 5.19,indicating that heavy metal pollution was relatively serious in the three sewage treatment plants.The potential ecological risk index of the three sewage treatment plants were 67.86,75.43 and 66.61,and all indices reached slight ecological risk level.?3?Composting process were successfully with different conditioner into sludge,and the heating rate is mushroom residue>corn stalk>wheat stalk>sawdust,and the high temperature lasts for days meeting the composting health requirements.At the end of composting,the moisture content dropped to about 40%,the pH value remained at about 7,and the EC value was all less than 4.3ms/cm,which was within the range of safe crop growth.At the end of composting,the GI values of the four piles were 108.0%,105.8%,110.2%and 102.6%,respectively,which had no toxic effect on plants.?4?The organic matter content of the four reactors showed a trend of gradual decline,and the organic matter content of reactor C had the highest degradation rate.The change trend of total nitrogen content in the four reactors was similar.Compared with before composting,the total nitrogen content of reactor C increased by 8.7%,while that of heap A,B and D decreased by 6.9%,6.5%and 2.8%respectively.The content of total phosphorus and total potassium in the four reactors increased gradually.?6?At the end of composting,the metal content of the body weight of the four piles decreased to different degrees,and the final result was lower than the"agricultural sludge pollutant control standard"?GB/T4284-2018?. |
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