Effective oil and grease removal POME treatment is an important consideration for palm oil mills seeking to improve wastewater treatment performance. Palm oil mill effluent (POME) contains substantial amounts of organic matter, suspended solids, and residual oil that can complicate downstream treatment if not adequately managed. While biological processes play a central role in POME treatment, the condition of the wastewater entering these processes can influence their overall performance.
Removing recoverable oil and grease before biological treatment can help reduce the pollutant load, improve process stability, and support more efficient wastewater management. The objective is not necessarily to eliminate every oil fraction at the first stage, but to separate what can be recovered and manage the remaining wastewater according to its characteristics and treatment requirements.
Why Residual Oil and Grease Matter in POME
POME is generated during palm oil milling operations, including processes involving sterilization, clarification, and oil extraction. Its characteristics vary depending on the production process, operating conditions, and the effectiveness of oil recovery.
Residual oil and grease may remain in the wastewater as free oil, dispersed droplets, or emulsified oil. These forms behave differently during treatment. Free oil can often be separated by gravity, while smaller droplets and stable emulsions may require additional physical or physicochemical treatment.
A review published in Bioresource Technology in 2022 highlights the importance of pretreatment in managing POME pollutants, including oil and grease, before subsequent treatment stages. The review also discusses the limitations of existing pretreatment approaches and the need to improve treatment efficiency.
When residual oil is carried into downstream treatment, several operational concerns may arise:
- Additional organic loading: Oil and grease contribute to the wastewater’s organic content, which is commonly assessed through chemical oxygen demand (COD) and biochemical oxygen demand (BOD).
- Potential interference with biological processes: High concentrations of oil and grease can affect contact between microorganisms and wastewater constituents. Depending on the oil characteristics and reactor design, accumulated fats and oils may also contribute to fouling or operational disturbances.
- Solids accumulation and maintenance requirements: Oil can combine with suspended solids and other materials, contributing to deposits that require monitoring and removal.
- Variable treatment performance: Changes in the amount and physical form of residual oil can affect the consistency of the wastewater entering downstream treatment units.
These effects depend on the wastewater composition, oil concentration, and treatment configuration. Nevertheless, they demonstrate why oil separation deserves attention during the design and operation of a POME treatment system.
Read Also: What Is POME and Why Does It Need Treatment?
How Oil and Grease Removal Supports Biological Treatment
Biological treatment uses microorganisms to break down biodegradable organic matter in wastewater. Depending on the treatment configuration, POME may undergo anaerobic treatment, aerobic treatment, or a combination of both.
These processes can effectively reduce organic pollutants, but their performance depends on influent characteristics and operating conditions. Excessive or fluctuating oil loads can create additional challenges for the treatment system, making appropriate pretreatment an important consideration.
1. Recover Free Oil Before It Enters the Treatment System
The first step is to identify opportunities to recover oil that remains in the wastewater. Gravity separation and oil separator tanks can help remove free oil when sufficient separation time and suitable operating conditions are provided.
This approach offers two practical benefits: reducing the amount of recoverable oil lost with the wastewater and limiting the oil load carried into subsequent treatment stages.
However, gravity separation has limitations. Fine droplets and emulsified oil may remain in the water, so separator performance should be assessed against actual influent characteristics rather than assumed to remove all oil and grease.
2. Apply Additional Separation When Necessary
Where residual oil remains after primary separation, additional pretreatment may be required. Options can include coagulation-flocculation, dissolved air flotation (DAF), or other suitable separation technologies.
The appropriate method depends on factors such as oil droplet size, emulsion stability, suspended solids, wastewater flow, and the required removal efficiency.
Research published in Desalination and Water Treatment in 2017 evaluated mechanical pretreatment methods for POME before biogas production. The study reported improved oil removal using coalescer filtration and dissolved air flotation, demonstrating the potential value of pretreatment before biological processing.
These findings should be interpreted in the context of the study conditions. Actual performance and operating costs must be established through wastewater characterization and, where appropriate, treatability testing.
3. Protect the Performance of Downstream Biological Units
After oil separation, the remaining wastewater can proceed to biological treatment based on the selected process configuration.
Monitoring the wastewater after pretreatment helps operators determine whether the oil load has been reduced sufficiently and whether additional treatment is needed. Relevant parameters may include oil and grease, COD, BOD, total suspended solids (TSS), pH, and flow rate.
The purpose is to manage the loading conditions entering the biological stage, not simply to achieve the highest possible oil removal percentage in isolation. Pretreatment should support the overall treatment objective while balancing removal performance, chemical consumption, energy use, sludge generation, and maintenance requirements.
Designing an Effective Oil and Grease Removal Strategy for POME
A practical oil and grease removal POME strategy begins with understanding the wastewater rather than selecting equipment based on a single parameter.
The following considerations can help guide the assessment:
- Wastewater characterization. Determine the concentration of oil and grease, COD, BOD, TSS, pH, and flow variations. Identify whether the oil is predominantly free, dispersed, or emulsified.
- Separation requirements. Assess whether gravity separation is sufficient or whether additional treatment is necessary to achieve the desired influent quality for biological processing.
- Integration with existing facilities. Review available space, hydraulic capacity, current treatment performance, and potential modifications to existing equipment.
- Operational monitoring. Establish sampling points before and after pretreatment to evaluate removal efficiency and identify changes in wastewater characteristics.
- Downstream performance. Assess whether the pretreatment stage contributes to more stable biological treatment, manageable operating costs, and consistent final effluent quality.
A 2021 review in Processes discusses the range of biological, physicochemical, membrane, and other treatment technologies used for POME. Its findings reinforce the importance of considering the treatment train as a whole, since individual technologies have different capabilities and limitations.
Read Also: Removal of TSS in Palm Oil Wastewater Treatment: Practical Approaches for Better Effluent Quality
Supporting POME Treatment Through LAI’s Water Treatment Expertise
Every palm oil mill has different wastewater characteristics, operational constraints, and treatment objectives. Selecting an appropriate oil and grease removal approach therefore requires an understanding of both the pretreatment stage and its impact on downstream processes.
Lautan Air Indonesia (LAI) provides water treatment expertise across treatment chemicals, engineering, and operational support. Depending on the wastewater characteristics and project requirements, LAI can support the assessment of treatment needs, the selection of suitable treatment approaches, and the integration of pretreatment with downstream wastewater treatment processes.
For POME applications, this may involve evaluating where oil separation is needed, whether chemical-assisted treatment warrants further investigation, and how operating parameters can be monitored to support consistent performance. The recommended approach should be based on wastewater analysis, process requirements, and the performance objectives of the overall treatment system.
Looking to improve your POME treatment process? Contact Lautan Air Indonesia to discuss your wastewater characteristics and explore suitable approaches to pretreatment and downstream treatment integration.
Reference
- Ratnasari, A., Syafiuddin, A., Boopathy, R., Malik, S., Mehmood, M. A., Amalia, R., Prastyo, D. D., & Zaidi, N. S. (2021). Advances in pretreatment technology for handling the palm oil mill effluent: Challenges and prospects. Bioresource Technology, 344(Pt B), 126239.
- Yaeed, S., Suksaroj, T. T., & Suksaroj, C. (2017). Mechanical pretreatment processes for enhancement of biogas production from palm oil mill effluent (POME). Desalination and Water Treatment, 67, 133–139.
- Mohammad, S., Baidurah, S., Kobayashi, T., Ismail, N., & Leh, C. P. (2021). Palm Oil Mill Effluent Treatment Processes—A Review. Processes, 9(5), 739.
- Manikandan, S. K., Hasnain, M., Zainab, R., Ridouane, F. L., Moalla, A. A., Sheteiwy, M., Abideen, Z., & El-Keblawy, A. (2026). Treating palm oil mill effluent (POME): Opportunities, challenges, and sustainable practices. Environmental Technology & Innovation, 42, 104857.
