Study On The Waste Degradation Behavior And Stabilization Of Dumping Sites In Northeast China

At present dumping sites takes up a great proportion in waste treatment method proves. There is a large number of life dumping sites in the vast majority of cities around of China. Not only lots of lands were occupied by dumping sites, but also many events such as fire hazard and explosion often occur in dumping sites. Meanwhile, environment was polluted and impacted very seriously by dumping sites.In this paper, Harbin City as an example, we studied on the variation of indexes, such as organic matter, bio-degradable materials(BDM), total sugar, crude fiber, heavy metals and other water quality indicators and landfill leachate(COD, BOD, Bio-degradability and ammonia nitrogen) of solid waste in the life dumping sites of municipal solid waste in northeast regions with the time passing by and studied deeply on the stabilization of the dumping sites through simulation experiments and field sampling and analysis; built dynamic models of landfill leachate and each index of solid components; analyzed and compared key factors influencing on stabilization of waste and accordingly predicted stabilization time of waste and studied on microbial community structure in the dumping sites condition by use of polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE) technique.We collected waste of these four dumping sites in Harbin, and analyzed organic matter, bio-degradable materials, total sugar and crude fiber, as well as indexes of heavy metals, and studied the relation between each indicator and stacking time. The results showed that organic matter in solid waste, BDM, total sugar and crude fiber had reduced by 50.77%, 43.34%, 83.38% and 24.49%, respectively after 10 years waste was dumped. We also analyzed the indexes, such as organic matter, bio-degradable materials and heavy metals in waste piling up in the different depths of these two dumping sites through excavation test in the Dongbu dumping site and the Wanggang dump site, and studied the relation between each index and stack depth. The results showed that the content of the components of solid waste decreased with the increase of stacking time and increased with the increases of stack depth. We studied the influence of environmental temperature on degradation of the waste through simulating test. The time that used for indexes of landfill leachate and solid components achieving maximum value when temperature of simulation experiments was 40℃were shortened by 10 and 10~20 days than those at 19℃, respectively. The results showed that starting time of waste degradation was shortened under higher temperature (in the range of test). In the accelerated simulating test, the degradation rate of organic matter and BDM index in solid waste at 40℃was at 19℃1.41 and 1.22 times, respectively. The results showed that waste was easier to degrade with higher temperature.In this paper, waste degradation of dumping sites in different environmental conditions was studied through simulation dumping sites tests. The results showed that the degradation of landfill leachate and solid components indexes under natural environmental conditions test device were faster than those under artificial precipitation conditions simulation experimental setup. The degradation rate of COD, BOD and conversion rate ammonia nitrogen of leachate under natural environmental conditions test device was 1.39, 1.10 and 1.60 times those under artificial precipitation conditions simulation experimental setup, respectively. The degradation of organic matter and BDM index in solid waste under natural environmental conditions test device was 1.29 and 1.60 times those under artificial precipitation conditions simulation experimental setup, respectively. Though the analysis and comparison, it is founded that the ambient temperature was not the only critical factor to affect the rate of waste degradation. Some factors such as rainfall, nutrient substance, dissolved oxygen; micro-organisms as well as dissipation of released heat in the process of degradation had much important influence on the degradation of landfill leachate, organic matter in solid waste and BDM.We studied the structure of microbial community structure in two different waste layer of artificial precipitation conditions simulation test and natural environmental conditions simulation test by use of PCR-DGGE technology. The results showed that there are rich diversities of microbial communities in these two simulation test devices. The common bacteria existed in four different samples and there were respective comparative advantages bacteria also existed in each sample. It could be seen that diversities of microbial communities of natural environmental conditions simulation test device were better than those of artificial precipitation conditions ones, and the microbial types of the lower layer of trash were more than those of upper's through abundance analysis of DGGE spectrum. It was found that there is great difference between microbial community under natural environmental conditions and that under artificial precipitation conditions because environment for microorganism growth is different through similarity analysis of DGGE spectrum. Similarity of microbial communities in different waste dump increased obviously with stacking depth.Based on biochemical reaction kinetics equation,we carried outmathematical fitting of the changes that landfill leachate and solid comPonents ofall indexes of simulated landfill test and simulated dumP test with time Passing by,and got kinetics fitting equation of each index,and concluded that the required timeof leachate of the dumPing sites in Harbin to achieve stabilization(COD≤100mg/L,BOD≤30mg/L,arnrnonia nitrogen≤15mg/L)was 11 years and the required time ofsolid waste indicators of the dumP in Harbin to achieve stabilization(organicmatter≤7%,BDM≤5%)was 19 years.In sununary,we studied landfill leachate,waste of organic matter,BDM,totalsugar,crude fiber and heavy metals of the dumPing sites in Harbin,and the detailsof thes加cture of microbial PoPulations in every waste layer,and further studiedthe stability Process of the dumPing sites.These results Provided a strongtheoretical basis for reuse of the future dumPing sites.