Warning,Migration And Control Of Heavy Metal Pollution By Drilling Cuttings Utilization In Building Materials Of Shale Gas

Shale gas is a clean,new-style energy,and it has become one of the major motivations in the economic development of China.But,their will generate large quantities of drilling cuttings in the exploration and exploitation process.The drilling cuttings occupy a great quantity of land,and it also induces some environmental safety risks.So,based on the physicochemical properties of drilling cuttings,this study has developed a complete set of new technologies of resource utilization of the drilling cuttings as a raw material for preparation of building materials.In addition,we analyze the contaminant of drilling cuttings.And then ascertain the specific pollutants index of recycling products,the heavy metal release and migration characteristic was also studied,revealing the key factor which to optimize the preparation conditions for products.At last,the environmental safety control requirement is initially determined.In addition,the influence of microbial community succession in tested materials at different stages was investigated,combining with the coupling relationship of specific heavy metals and environmental microorganism.Through these tests and analyses,a new representative bacterial strain can be found to early-warning the specific heavy metals,and further ensure the environmental safety.The main results are as follows:?1?The physicochemical property and contaminant of drilling cuttings were analyzed.?1?The drilling cuttings are mainly constitute of siliceous and calcium material,the particle size distribution of them mainly existed in 30?m,so gotten the base of mineral admixtures.In addition,the mortar strength activity index are 58.3%and 66.4%,amorphous phase content are 23%and 32.4%,bound water content are 0.13 and 0.19,respectively.All this shows the drilling cuttings have a certain pozzolanic activity,and the activity index of oil-based drilling cutting pyrolysis residues?ODPR?is higher than water-based drilling cutting?WDC?has.?2?The benzene series of WDC are all non-detected.The specificity?inflammability,reactivity and corrosivity?,acute toxicity and bio-toxicity of ODPR are all can meet the First Grade Standard of GB8978-1996.According to the results of leaching toxicity and toxic substance content,the specific pollutants are Cu,Zn,Cr,Pb,Ni and As.?2?Based on the properties of drilling cuttings,the behaviors of hydration mechanism and hydration kinetic of the composite gel compound system of?drilling cuttings-cement-fly-ash?was studied,to make clear of its physical chemistry essence.The results show that:?1?For non-fired bricks,the following optimal mix proportion is 0.2kg cement,0.05kg fly-ash,0.5⁰.625kg WDC/ODPR,0.625⁰.75kg manufactured sand,amount of water,and the molding pressure is about 10MPa.All the performances of products can basically meet the requirements of Chinese standard GB/T 8239-2014.?2?For concrete,the best water-binder ratio and sand ratio were selected in 0.52 and 41%,respectively.So,the following optimal mix proportion is:for WDC concrete,270kg cement,70kg fly-ash,375kg WDC,1060kg gravel,345kg sand,182kg water and 5kg water reducing agent;for ODPR concrete,240kg cement,30kg fly-ash,275kg ODPR,1060kg gravel,590kg sand,175kg water and 3.9kg water reducing agent.?3?For aerated concrete block,the best water-material ratio,steam curing temperature and time were selected in 0.61,80?and 24hours,respectively.So,the following optimal mix proportion is:25%³0%fly-ash,15%²0%WDC/ODPR,20%³0%cement,15%²0%quicklime and 4%gypsum.?3?This article clears the affected objects of heavy metal leaching under the action of rain washing and deterioration,and clear objectives of environmental protection.As well as,creating evaluate scene,and the heavy metal release and migration characteristic was also studied.At last,revealing the key factor which to optimize the preparation conditions for product.So,the pollution control index and limiting value were finally determined as:Cr⁶⁺?0.1 mg/L,Cu?1.0 mg/L,Zn?1.0 mg/L,Ni?0.1 mg/L,As?0.05 mg/L and Pb?0.1mg/L.?4?The recycling product were soaked using fluid medium,and for further study the effect of product on growth of bacteria and heavy metal warning,which is help to develop a warning bacteria strain of heavy metal migration to further ensure the safety of the environment.The results showed that:?1?According to the growth situation of the bacillus subtilis,which present a promote variation tendency.In addition,the growth situation of the ODPR-concrete,WDC-non-fired bricks and ODPR-aerated block outperforms the other products.?2?According to the growth situation of the escherichia coli,which present a inhibit variation tendency.In addition,the growth situation of the WDC-concrete,ODPR-non-fired bricks and WDC-aerated block outperforms the other products.Furthermore,the concentration of Pb decrease significantly,this illustrates the escherichia coli has better biological accumulation.?3?According to the growth situation of the candida albicans,which present a inhibit variation tendency.In addition,the growth situation of the ODPR-concrete,WDC-non-fired bricks and ODPR-aerated block outperforms the other products.Furthermore,the concentration of Pb and Zn decrease significantly,illustrating the candida albicans has better biological accumulation.