Temperature monitoring during a water-injection test using a vertical well in a newly filled MSW layer of a landfill.

High temperature may adversely affect municipal solid waste (MSW) biodegradation and lead to an increase in the deformation of high-density polyethylene (HDPE) pipes used for the collection of leachate and landfill gas in landfills. The test in this study was to change the waste temperature around the vertical injection well by water injection using a vertical well. The test was conducted intermittently with two different flowrates in a newly filled MSW layer of a landfill. The temperature, gas pressure and leachate level in the test area were simultaneously monitored during this study. The results showed that the waste temperature around the vertical injection well was effectively changed by water injection, which did not result in a significant rise in the leachate level. During water injection, the waste temperature influence distance in the horizontal direction increased with depth from the leachate level to the bottom of the injection well. The bottom temperature of the injection well decreased to near the water-injection temperature. The range of influence of the waste temperature caused by intermittent water injections slightly increased in this test. After water injection was stopped, the waste temperature near the vertical injection well increased quickly initially, and then the increments became more gradual with time. When the leachate level recovered stably, there was still a temperature gradient around the injection well within the range of influence. The temperature and gas pressure in the waste above the leachate level and far away from the injection well were slightly influenced by water injection.