Leachate - Something's Brewing There
Landfill leachate results from permeating surface water and water pressed out during compaction of the waste mass. It can contain harmful substances such as various salts, ammonium and carbon compounds which are flushed out in the process and represent a serious threat to underground and surface water. For that reason, the leachate is gathered via a ground seal into drainage pools and wells and fed to a multistage treatment plant. Level measurement in the well controls a drainage pump and also gives the landfill operator important information on the status of the landfill.
Level Measurement in Wells with the VEGAWELL 72
Well galleries are used to systematically gather leachate. They are made of long steel tubes driven vertically through the cross section of the dump. Water collects at the bottom of the tube and is forwarded to the leachate treatment plant via special submersible pumps. The level in the individual tube is measured with a VEGAWELL 72 suspension pressure transmitter. With its PE coating, it has optimum protection against the corrosive leachate. The output signal controls the frequency converter of the pumps. By means of this measurement, the special pumps are protected from dry running, and the leachate level is prevented from getting too high.
Leachate Treatment
The free oils contained in the leachate are separated by gravity into plastic settling tanks. After further chemical treatment, the leachate arrives at a stripper column. This is a slender, approximately 10 ft (3 m) high reactor into which air is pumped from below and leachate from above. Here, nitrogen compounds are converted and carbon compounds degraded with the help of microorganisms. This pre-treated leachate is finally cleaned and filtered in additional physical stages and then separated as distillate. To ensure the optimal operating conditions inside the stripper column, an accurate level measurement in the bottom area of the column is necessary.
Level Measurement in the Stripper Column with the VEGAPULS 63
To facilitate the reaction, the middle zone of the column is packed with carrier material. Due to the influx of air, the surface of the liquid medium is very agitated. Direct level measurement inside the column is impossible. For this reason, level measurement is carried out in a bypass tube. A VEGAPULS 63 radar sensor is used for this application. Its highly resistant antenna system guarantees a precise and reliable measurement.
