Sensing transmitter devices protected from liquid ingress when completely immersed in a leachate for measuring leachate level and converting it to a 4-20mA current output signal to send to other instrumentation on a landfill site used to bury waste material.
Due to the decomposition of buried waste material over time, a landfill site presents a potential hazard to the environment unless precautions are taken to contain pollutants and prevent contamination.
A wide range of harmful liquids are released from waste material as part of the decomposition process, which then mix with rainwater which percolates through the waste. The resulting liquid poses a major contamination risk to the surrounding environment.
This polluted water, which is called Leachate, has to be contained within the confines of the landfill site, otherwise it could reach the water table and contaminate water supplies. To prevent leachate escaping a landfill, a membrane lining is buried in the landfill site during construction to create a tank to contain the leachate.
Various measurement devices are installed around the landfill site to monitor the leachate and provide feedback to control systems which ensure the integrity of containment.
A submersible device can be installed in leachate without causing any damage as long as the installation instructions are adhered to, and the specified depth and time duration limits for submersion are not exceeded.
Assembled devices are vulnerable to leachate ingress, which can enter the device through seals and joints or permeate through components that incorporate thin membranes or porous materials.
To achieve a long lasting submersible construction, the device is constructed from materials which will not easily corrode when exposed to leachate. Corrosion may cause the material to fail and allow leachate to enter the device, or interfere with the seal joining the corroded material to another component.
The seals used to join device components together are pressure leak tight, resilient to the expected temperature variations and resist corrosion from the surrounding leachate.
All components and seals are designed to withstand the pressure expected at the maximum required leachate depth, and this may involve a series of seals and backfilling with a potting compound or other fill material to improve longevity and reliability at greater depths.
A leachate level transmitter is an instrument for measuring the height of leachate in a landfill site and converting it to a 4 to 20 milliamp current loop output, which is sent to other instrumentation to display, monitor, log or control the leachate level.
The level transmitter is lowered into a tank, borehole or collection pit and immersed in the leachate. Typically a pressure transmitter is used which will measure the pressure generated by gravity acting on the surrounding leachate.