Research And Analysis On Land Use Of Thermally Hydrolyzed Digested Sludge

Since the implementation of the two three-year pollution control action plans in Beijing in 2013,the construction of sewage treatment facilities has achieved leapfrog development,and the sewage treatment capacity has been significantly improved,but the problem of sludge treatment and disposal has become increasingly prominent,and the way of sludge land use is not Smooth restriction of resource development.In this paper,the quality of the finished products produced by the four sludge thermal hydrolysis pretreatment anaerobic digestion centers was monitored and analyzed by monitoring and analyzing the sludge quality of the four reclaimed water plants operating in the central city of Beijing The main physical and chemical indicators,nutritional indicators,heavy metal indicators and toxic organic pollutant indicators characteristics and suitability.Carry out monitoring and analysis of sludge woodland tracking experiments and radish,forsythia,and rose plot planting experiments to study the impact of finished sludge products on soil and plants,and provide a theoretical basis for the better utilization of sludge resource products for land use Technical support.Research on monitoring of sludge from sewage treatment plants and thermal hydrolysis pretreatment of anaerobic digestion sludge products showed that:pH value,heavy metal content,roundworm egg detection value,total cyanide,PCB and volatile phenol content in line with current sludge Land use standard limit requirements,monitoring and measurement of heavy metal mercury is close to the standard limit,the total number of bacteria,mineral oil is exceeded.The sewage plant sludge and thermal hydrolysis anaerobic digestion products are rich in total nutrients and organic matter.Due to the high water content,they need to be further dried and dehydrated before agricultural and forest use.The monitoring studies of the typical projects in the built sites show that the heavy metal content in the surface soil of the built projects before and after the application of s ludge did not increase significantly.The heavy metal content in the 20-40 cm soil showed a decreasing trend,and only the heavy metal mercury content in the 40-60 cm soil increased.The comprehensive index of heavy metal pollution is lower than the safety limit of 0.7,indicating that the soil(20~40cm,40~60cm)of the constructed project has not been polluted by heavy metals.Experimental study on thermal hydrolysis pretreatment of anaerobic digestion sludge production planting plots shows that the application of sludge finished products has a certain improvement effect on the surface soil of planting plots.With the increase of the application rate,the content of heavy metal lead in the surface soil(0-20cm)of the radish planting community has been greater than that of the control group,and the content of heavy metal cadmium and boron in the surface soil(0-20cm)of the forsythia planting community has increased.The comprehensive index of heavy metal pollution in the soil showed a significant increase trend.The surface soil(0~20cm)and rose and forsythia planting community(0~80cm)in the radish planting community have heavy metal contents far below the standard limits for agricultural soil pollution risk control,and the comprehensive indexes of heavy metal pollution are below the safety limit of 0.7,Indicating no pollution to the soil of the planting community.The yield of water radish was significantly correlated with the application rate.The application rate was 5kg/m~2.The yield of water radish was the largest.The high growth of rose and the application rate were significantly positively correlated.The increase in length and weight is related to the application rate.When the application rate is 5 kg/m~2,the biomass of Forsythia suspensa increases the most.With the increase of the application rate,the content of heavy metals mercury,arsenic and zinc in radishes showed an increasing trend,indicating that compared with other heavy metals,radishes have a stronger ability to absorb heavy metals mercury,arsenic and zinc.The heavy metal lead and mercury content in water radish has exceeded the food standard limit,indicating that it is not suitable for planting with thermal hydrolysis digestion sludge,which will cause heavy metal pollution;the heavy metal content of rose has decreased to varying degrees,combined with the increase of rose branch length and ground diameter The decrease in growth and the weight of the branches indicate that the growth of the rose is inhibited,which affects the adsorption of heavy metals in the soil.The contents of heavy metals lead,mercury,copper,nickel,and boron in the forsythia have different degrees of increasing trend.The increase in weight indicates that Forsythia has a certain adsorption effect on so il heavy metals.