Sewage Treatment Plants and Septic Tanks to suit every Sewage and Septic Tank application and budget, great or small. The Crystal Sewage Treatment Plant range includes industry renowned 'Green' FilterPod sewage treatment plant which requires no electricity for the process.If you have enough land and easy draining soil, then a Septic Tank may be all you need. Crystal Tanks can advise you on the best way to treat your sewage. Crystal Tanks has been a recognized name in the sewage treatment industry for nearly 20 years and all our units conform with current UK regulations.