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Investigation of struvite crystals formed in palm oil mill effluent anaerobic digester

Ngatiman, Muzzammil and Jami, Mohammed Saedi and Abu Bakar, Mohd Rushdi and Subramaniam, Vijaya and Loh, Soh Kheang (2021) Investigation of struvite crystals formed in palm oil mill effluent anaerobic digester. Heliyon, 7 (1). pp. 1-8. E-ISSN 2405-8440

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The formation of struvite crystals or magnesium ammonium phosphate (MgNH4PO4) in palm oil mill effluent (POME) occurs as early as in the secondary stage of POME treatment system. Its growth continues in the subsequent tertiary treatment which reduces piping diameter, thus affecting POME treatment efficiency. Hypothesis. The beneficial use of the crystal is the motivation. This occurrence is rarely reported in scientific articles despite being a common problem faced by palm oil millers. The aim of this study is to characterize struvite crystals found in an anaerobic digester of a POME treatment facility in terms of their physical and chemical aspects. The compositions, morphology and properties of these crystals were determined via energy dispersive spectroscopy (EDS), elemental analysis, scanning electron microscopy (SEM) and x-ray diffraction (XRD). Solubility tests were carried out to establish solubility curve for struvite from POME. Finally, crystal growth experiment was done applying reaction crystallization method to demonstrate struvite precipitation from POME. Results showed that high phosphorous (P) (24.85 wt%) and magnesium (Mg) (21.33 wt%) content was found in the struvite sample. Elemental analysis detected carbon (C), hydrogen (H), nitrogen (N) and sulfur (S) below 4 wt%. The crystals analysed by XRD in this study were confirmed as struvite with 94.8% struvite mineral detected from its total volume. Having an orthorhombic crystal system, struvite crystals from POME recorded an average density of 1.701 g cm�3. Solubility curve of struvite from POME was established with maximum solubility of 275.6 mg L�1 at pH 3 and temperature 40 �C. Minimum solubility of 123.6 mg L�1 was recorded at pH 7 and temperature 25 �C. Crystal growth experiment utilizing POME as the source medium managed to achieve 67% reduction in phosphorous content. This study concluded that there is a potential of harnessing valuable nutrients from POME in the form of struvite. Struvite precipitation technology can be adapted in the management of POME in order to achieve maximum utilization of the nutrients that are still abundant in POME. At the same time maximization of nutrient extractions from POME will also reduce pollutants loading in the final discharge.

Item Type: Article (Journal)
Additional Information: 5545/87868
Uncontrolled Keywords: Crystal Industrial wastewater Nutrient recovery Palm oil mill Struvite precipitation
Subjects: T Technology > TP Chemical technology > TP155 Chemical engineering
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button): Kulliyyah of Engineering > Department of Biotechnology Engineering
Kulliyyah of Engineering
Depositing User: Prof. Ir. Dr. Mohammed Saedi Jami, PhD CEng MIChemE
Date Deposited: 18 Jan 2021 10:18
Last Modified: 25 May 2021 16:07
URI: http://irep.iium.edu.my/id/eprint/87868

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