Development of formation mitigation of palm oil mill effluent (POME) crystals

Abstract

Scaling problems in palm oil mill effluent (POME) treatment facility, has a long history of causing adverse impact on the efficiency of the POME treatment process. The accumulation of scaling in POME treatment pipelines has led to consequential impacts of reduced pipe diameter thus affecting the effective flow rate, leading to clogging of pipes as well as reduction in the treatment plant hydraulic retention time (HRT). Its occurrence has become more frequent in recent years with the increase of tank usage in the treatment process of POME. This study was formulated with the objective to determine the physicochemical characteristics of the crystal found in the POME treatment facilities, examine the influence of pH and temperature on the solubility of the crystal grown in POME treatment system and explore reactive crystallization method in growing crystal from POME under a controlled manner and predicting its growth location using computational fluid dynamics (CFD). Scale deposit samples were collected from two palm oil mills in Selangor and Johor in which both were from different stage of POME treatment. The characterization of the crystal found magnesium, phosphorous and oxygen as the major elements in the sample with 21.33, 24.85 and 46.22 wt%, respectively. The scale deposit was found to be a struvite mineral constituted more than 90% of the sample. The POME crystal was found to be soluble in strong acid and alkaline condition. Maximum solubility was recorded at pH of 3 and temperature of 40 oC yielding averaged maximum solubility of 275.6 mg L-1 while averaged minimum solubility of 123.6 mg L-1 was recorded at pH 7 and temperature of 25 oC. 67% of phosphate was removed from POME after being subjected to reactive crystallization. This study concludes that POME crystal has the potential to be regarded as a future value-added product from palm oil milling sector of the oil palm industry. Further research needs to be done to explore the feasible and economical way of producing POME crystal in which with its success, natural grow of POME crystal in POME treatment facility can simultaneously be mitigated.