Clogging due to Struvite Formation in Horizontal Leachate Recirculation Pipes of Bioreactor Landfills

摘要

A primary operational issue associated with bioreactor landfills is the potential clogging of leachate recirculation pipes due to the formation of deposits. Studies on calcium carbonate formation have been performed in the past. Struvite (MgNH_4PO_4.6H_2O) is another chemical precipitate, reported as a wide problem in the wastewater treatment industry. This study presents results from laboratory experiments conducted to investigate the possibility of Struvite scale formation in leachate recirculation horizontal pipes. Two types of pipes, HDPE (High-Density Polyethylene) and PVC (Polyvinyl Chloride), were tested under three different flow rates using a simulated leachate. Significant concentration reductions of magnesium, total phosphorous, and ammonium-nitrogen were observed when simulated leachate was passed through the test pipes. The crystal structure and composition of the deposits after each experimental run were closely related to Struvite characteristics. The highest scale deposition was observed for the low flow rate, irrespective of the pipe material. HDPE pipe material had less accumulation during high and medium flow rates than the PVC pipe, whereas for the low flow rate the highest accumulation was in the HDPE pipe.