Theory, framework, and methodology for physical lifespan prediction of hazardous waste landfills.

Landfill is a predominant method for hazardous waste disposal in both developed and emerging economies due to simple disposal technology and wide applicability. The prediction of landfill lifespan during the design stage provides support for environmental management of hazardous waste landfill (HWL) and technical support for the implementation of national standards. It also provides guidance for necessary responses after the lifespan expires. At present, research on the degradation of main components or materials of HWLs has been paid much attention, however, how to predict the lifespan of HWLs is a big issue for researchers. In this study, the HWL was selected as research subject, and literature research, theoretical analysis, and model calculation, were used to establish a HWL lifespan prediction framework for the first time. Firstly, the HWL life was defined based on the functional characteristics; secondly, according to comprehensively analyzing the functional requirements, system composition, and structural characteristics of HWLs, the indicators of life termination and the thresholds were confirmed. Then, according to Failure Mode, Mechanism, and Effect Analysis (FMMEA), the failure modes of the core components affecting the lifespan of the HWLs were identified. Finally, a process simulation method (Hydrologic Evaluation of Landfill Performance, HELP) was proposed to simulate the performance degradation of the HWL, combined with the core performance parameters variation caused by the deterioration of the main functional unit. The life prediction framework was developed to increase the prediction accuracy of the performance degradation of HWLs and to provide a methodology for further research on HWL life prediction.

Long-term degradation characteristics of cyanide in closed monofills and its effects on the environment and human health: Evidence from nine landfill sites in northen China.

Cyanide residues weighing many millions of tons are disposed of in cyanide residue monofills (CRMs) worldwide. The degradation characteristics of cyanide in the anoxic environments of closed landfills may have been overestimated, leading to an underestimation of the long-term risk of cyanide residue landfills. To study the effect, a total of 387 cyanide residue samples were collected for analysis from nine closed CRMs in northen China that have been closed for more than 10 years. The study shows that the probability of achieving the target cyanide concentration (5 mg/L) in the nine sites was only 2.9%. And there is no significant reduction in the overall concentrations compared to the pre-closure period. The effectiveness of the CRM containment barrier needs to be maintained for at least 220 years to allow cyanide concentrations to degrade to harmless levels. Nine CRMs sites, except for CRMs A and B, had a low short-term risk, but in the long term exposure concentrations can exceed the groundwater Class III water quality limit by a factor of 1.64-30, posing a risk of groundwater contamination. This study reveals the risk of cyanide residue degradation in CRMs and its long-term evolution, providing theoretical support for site management and risk control.