Study On The Measurement Of Moisture And Harmful Elements In Landfill Waste Based On PGNAA Technique

Bioreactor landfill technology becomes an attractive topic for research in the field of municipal solid waste landfill, which promotes enhanced microbiological activity to decompose and stabilize the organic fraction of the municipal solid waste. Maintaining of optimum moisture content is considered as an essential part of this technology. Online measurements of moisture content and concentrations of environmentally harmful elements play an important role in successful and safe operation of bioreactor landfills. In this paper, measuring moisture content and harmful elements concentrations based on prompt gamma-ray neutron activation analysis technology was investigated. The main works are as follows:(1) According to the landfill environment, a measurement model was established by using MCNP simulation software, where the compounds of polyethylene balls, glass balls and deionized water were selected as the alternatives of MSW. The hydrogen peak counts under different geometry conditions were recorded. Furthermore, the available detection range of model was determined. A PGNAA setup with a 300 m Ci Am-Be neutron source and a 4 inches×4 inches(diameter × height) BGO detector was developed according to the above model.(2) The samples with different moisture contents from 40% to 70% were prepared by changing the quantities of polyethylene balls and glass balls. The results obtained by MCNP simulation and experiments show that a rising trend of hydrogen peak count can be observed when moisture content increases, and a good linearity can also be figured out between the hydrogen peak count and moisture content. The k0 method was used to determine the moisture content by analyzing the results from MCNP simulation. The results show that the mean absolute error is 1.84%, which indicate that the method can provide an available way for online measurement of moisture content in landfill waste.(3) Simulative and experimental methods have been used to determine the concentrations of environmentally harmful elements. The results show that the characteristic peak counts of the chlorine, manganese, nickel and chromium increase with the increase of the element concentration. Also, the good linear relations between them can be observed. Minimum detectable concentration of chlorine is about 114.1 mg/L which is relatively low due to its greater absorption cross section. Finally, the effect on determination of moisture content caused by the presence of chlorine was determined.