| Construction and demolition (C&D) waste has been investigated in few studies about its potential leachate contaminants. Hydrogen sulfide has also been recognized as a problematic gas emitted from landfills. Sulfate reducing bacteria has been identified for hydrogen sulfide production from sulfate leaching from gypsum drywall in C&D waste. In order to determine the true nature of the degradation of C&D waste in landfill condition and then provide more data for managing C&D waste, the objectives of this research consisted of examining the potential contaminants from the C&D leachate and evaluating hydrogen sulfide generation from C&D waste in a simulated scenario with a favorable temperature for microorganisms and a high rainfall simulation. Leachate and gas samples were collected from the laboratory column. A number of analysis was performed: pH, conductivity, oxidation and reduction potential, dissolved oxygen, chemical oxygen demand, total organic carbon, chloride, alkalinity, sulfate, sulfide, metals, total solids and total dissolved solids; for gas samples, gas flow rate and hydrogen sulfide concentration. The leachate results were compared with those from other studies conducted under room temperatures and were also evaluated by drinking water standards. It is concluded that iron, manganese, sulfate and total dissolved solids were the most likely contaminants from C&D waste. Among those contaminants, iron, manganese, and total dissolved solids exceeded the secondary drinking water standards while sulfate exceeded the standard limit in the first 400 days of the total experimental duration of 1,000 days. In this study, sulfate reducing bacteria showed strong activities resulting in elevated sulfide in the leachate and hydrogen sulfide gas emission. Sulfide level in the leachate went up to 400 mg/L and hydrogen sulfide gas concentration reached up to 80,000ppmv. This high concentration of hydrogen sulfide gas may pose severe problems to the environment and neighborhood near C&D landfills. Furthermore, about 32% of sulfate in drywall was converted by sulfate reducing bacteria to sulfides: 11% as hydrogen sulfide gas and 19% present in the solid phase as mostly metal sulfides. Compared with municipal solid waste landfill leachate, the leachate from construction and demolition landfill was less problematic. The main reason was that C&D waste contains less of easily biodegradable materials. However, the results from this study demonstrated that in the area with high temperature and humidity, hydrogen sulfide problems will be of a great concern. This laboratory experiment provided valuable data on C&D leachate quality and hydrogen sulfide generation from C&D waste. The results could contribute to developing treatment strategies for C&D landfills leachate and gases as well as helping landfill operators and regulatory agencies to better manage C&D waste at landfills. |
