Study On Land Use Technology Of Stacked Sludge

The research object of this paper is the stockpiled sludge of a sewage treatment plant in suzhou city,The basic physical and chemical properties of sludge were analyzed,In view of the high moisture content,fluidity,long-term release of unpleasant smell of sludge,and will also wash with the rain pollution nearby water sources and other characteristics.Three groups of curing passivating agents including lime,lime + fly ash and lime + gypsum were added to the sludge,The leaching amount,pH value,organic matter,total nitrogen,total phosphorus and water content of five common heavy metals in sludge were observed and screened.The selected passivated sludge is mixed with soil in different proportions,The effects of different proportions of passivated sludge mixed with soil on the growth of ryegrass and tall fescue were observed.Main research contents and results are as follows:(1)Judging from the dewatering performance of sludge,the dewatering effect of lime on sludge is better than that of fly ash and gypsum.When lime is mixed with fly ash or gypsum respectively,the dewatering effect is better than that of sludge with only lime.The addition of alkaline materials will increase the pH value of sludge.Lime has the greatest influence on the pH value of sludge,followed by fly ash and building gypsum.During the experiment,The content of organic matter in sludge will be consumed with the increase of time,and the higher the alkalinity,the faster the consumption rate,the greater the consumption,Therefore,in order to prevent high pH of sludge,the amount of lime should not exceed 5% and the amount of fly ash should not exceed 15%.(2)Sludge is alkaline after adding curing passivating material,under alkaline environment,the content of TP in all experimental sludge was basically unchanged.However,the TN content in the sludge will be consumed along with a series of complex reactions in the sludge,until the change of TN becomes flat on the 21 st day of the experiment.The maximum loss rate of TN in the experimental sludge was as high as 44.14%,but the content of TN in most of the sludge was still between 12 to 14g/kg and that of TP was between 6 to 9g/kg.(3)Through passivation experiment,the leaching amount of five common heavy metals Cu,Zn,Ni,Cd and Pb in sludge was studied.It was found that the leaching amount of heavy metal ions in sludge with solidified passivation material was reduced to some extent compared with the control group.among them,lime + gypsum sludge had the least amount of heavy metal ions leaching,followed by lime + fly ash sludge,lime sludge had the most amount of heavy metal ions leaching.The leaching amount of heavy metal ions in the sludge will also decrease with the increase of curing time.On the 28 th day of the experiment,the leaching amount of heavy metal ions from most of the experimental sludge was less than the surface water environmental quality standard III water standard and the farmLand irrigation water quality standard.Finally,5% lime,15% fly ash(A1B2),5% lime and 15% gypsum(A1C2)were screened out.(4)Through the pot experiment of two groups of sludge A1B2 and A1C2,it can be concluded that:When the sludge application rate of the two groups was low,the germination and growth of the two herbaceous plants were promoted.With the increase of the amount of sludge,the inhibition effect on the two herbs was obvious.From the growth of two herbs,the amount of sludge used in the two groups should not exceed5%.