Palm Oil Mill Effluent (POME) Treatment — PAC and PAM Optimization for Southeast Asian Mills

Introduction

Palm Oil Mill Effluent (POME) is one of the most challenging industrial wastewaters in Southeast Asia. A typical 60-ton FFB/hour palm oil mill generates 350-500 m3 of POME daily, with COD levels of 40,000-80,000 mg/L — 100-200 times higher than typical municipal sewage. PAC and PAM play a critical role in primary treatment, reducing suspended solids and organic load before the anaerobic-aerobic pond system. This guide covers POME characteristics, treatment chemistry, and dosing optimization for mills in Indonesia, Malaysia, and Thailand.

POME Characteristics

Parameter	Raw POME (Typical)	After PAC + PAM*	Discharge Limit (Malaysia EQA 1974)
pH	4.0-5.0 (acidic)	5.5-6.5	5.0-9.0
COD	40,000-80,000 mg/L	20,000-40,000 mg/L (40-50% reduction)	— (pond system dependent)
BOD	20,000-35,000 mg/L	12,000-20,000 mg/L	100 mg/L (final discharge)
TSS	15,000-40,000 mg/L	2,000-5,000 mg/L (85-95% reduction)	400 mg/L
Oil & Grease	4,000-10,000 mg/L	500-1,500 mg/L (80-90% reduction)	50 mg/L (final)
Temperature	80-90°C	35-45°C (after cooling)	<45°C
Total Nitrogen	500-800 mg/L	300-500 mg/L	—

*PAC at 300-800 mg/L + anionic PAM at 3-8 mg/L, after cooling to <50°C

Why POME Treatment Is Challenging

1. Extremely high organic load: COD of 50,000 mg/L means 1 m3 of POME has the organic load of ~100 m3 of municipal sewage.
2. High temperature: Fresh POME is 80-90°C from the sterilization and pressing process. Must be cooled before biological treatment (<40°C) and chemical treatment (<50°C).
3. Acidic pH: Natural pH of 4-5 due to organic acids. Requires pH adjustment or use of acid-tolerant treatment chemicals.
4. High oil content: Residual palm oil (4,000-10,000 mg/L) interferes with coagulation and forms floating scum. Oil recovery is the critical first step.
5. Colloidal stability: Natural emulsifiers in palm oil stabilize the suspension. High PAC doses or specialized coagulants needed to break the emulsion.

Standard POME Treatment Flow

Step 1: Oil Recovery (Essential Pre-treatment)

Before any chemical treatment, recover free oil through:

• API or corrugated plate interceptor (CPI): Gravity separation, 1-2 hour retention. Recovers 60-80% of free oil for resale as sludge oil.
• Decanter/3-phase centrifuge: More efficient (80-90% oil recovery), produces separate oil, water, and solids streams. Higher capital cost but pays back through oil sales.

Never skip this step. Recovered palm sludge oil sells for $200-400/ton. Skipping oil recovery wastes revenue AND overloads downstream treatment.

Step 2: Cooling

Cool POME from 80-90°C to <50°C (for chemical treatment) then <40°C (for biological treatment). Options:

• Cooling pond: Simple, low cost, 1-2 day retention. Land-intensive.
• Cooling tower: More efficient, compact. Higher capital and maintenance.
• Heat exchanger (plate or shell-and-tube): Recovers heat for boiler feed water pre-heating or sterilization process. Best ROI despite higher capital.

Step 3: Primary Coagulation-Flocculation with PAC + PAM

• PAC dosage: 300-800 mg/L (jar test on cooled, de-oiled POME sample)
• PAC type: Medium to high basicity (50-75%), spray dried preferred for rapid dissolution
• PAM dosage: 3-8 mg/L, anionic, high MW (15-20 million)
• pH adjustment: POME pH 4-5 is below PAC’s optimal range. Add NaOH or lime to raise pH to 5.5-6.5 before PAC dosing. For mills wanting to minimize chemical use, some suppliers offer acid-tolerant PAC formulations.
• Clarifier/DAF: After flocculation, solids separation via primary clarifier or Dissolved Air Flotation (DAF). DAF is more common for POME due to the oily nature of the sludge — floating sludge is easier to remove by flotation than settling.

Step 4: Anaerobic Pond System

• Primary anaerobic pond: 20-40 days HRT, removes 80-95% of remaining BOD
• Secondary anaerobic/facultative pond: 10-20 days HRT
• Capture biogas (60-65% methane) from covered anaerobic ponds for boiler fuel or power generation — CDM (Clean Development Mechanism) carbon credits may apply

Step 5: Aerobic Polishing

• Aerobic pond or activated sludge: 5-10 days HRT, final BOD reduction to <100 mg/L
• Final settling pond before discharge to watercourse or land application

PAC + PAM Dosing Optimization for POME

Key Considerations

1. Jar test on cooled, de-oiled sample: Hot POME will degrade PAC polymers. Raw POME with 1% oil will give misleading jar test results — the oil masks coagulation behavior.
2. Test wide PAC dose range: 200, 400, 600, 800, 1000 mg/L. POME’s very high TSS means the dose-response curve may not plateau until high doses. Find the knee of the curve — where incremental PAC gives diminishing TSS/COD removal.
3. Balance PAC vs PAM: Higher PAM (5-8 mg/L) can reduce PAC requirement, but PAM costs $2-4/kg vs PAC at $0.25-0.35/kg. Optimize for total chemical cost per m3, not individual dose rates.
4. Consider lime as coagulant aid: Adding 500-1000 mg/L Ca(OH)2 with PAC improves oil removal and provides alkalinity. Lime + PAC often outperforms PAC alone for POME, but produces more sludge.

Expected Performance (Well-Operated Plant)

Parameter	Raw POME	After PAC+PAM+DAF	Removal %
TSS	30,000 mg/L	<3,000 mg/L	>90%
Oil & Grease	6,000 mg/L	<600 mg/L	>90%
COD	60,000 mg/L	30,000-36,000 mg/L	40-50%
BOD	28,000 mg/L	18,000-22,000 mg/L	20-35%

Primary treatment removes suspended and colloidal organics; the remaining dissolved BOD/COD is handled by the pond system.

Methane Capture and Sustainability

POME anaerobic ponds are one of the largest agricultural sources of methane (CH4), a greenhouse gas 25x more potent than CO2. Installing covered lagoon digesters with biogas capture achieves:

• 28-35 m3 biogas per m3 POME (at 60-65% CH4)
• Energy value: ~18-22 MJ/m3 POME — can replace 30-50% of mill’s diesel/NG consumption
• Carbon credit revenue: $3-8/ton CO2e under voluntary carbon markets or CDM
• PAC + PAM primary treatment improves biogas yield by removing inert solids from the anaerobic feed, increasing the biodegradable fraction

HydroChemix supplies PAC and PAM to palm oil mills across Indonesia, Malaysia, and Thailand. Contact jingshuicc@gmail.com for a POME treatment chemical recommendation, including jar test protocol and cost-per-ton-FFB analysis for your mill.