Palm oil mill effluent (POME) treatment plants cater all raw effluent produced. Approximately 0.65 tonnes of raw POME is produced for every ton of fresh fruit bunches (FFB) processed. In 2003, a total of 2,106,956 tonnes of FFB were processed, resulting in 1,369,521 tonnes of POME being produced.

Generally, palm oil mill effluent treatment plants (ETPs) are operated on two–phase anaerobic digestion process followed by extended aeration process. This two-phase anaerobic process gives excellent pollutant destruction efficiency of above 95% while extended aeration ensures that the final pollutant levels in the effluent are within the stipulated limits set by the Department of Environment (DOE).

In the anaerobic digestion process, the raw POME is first converted into volatile fatty acids by acid forming bacteria. The volatile acids are then converted into methane and carbon dioxide.

The advantages of anaerobic digestion system are:

1. The two phase system allows greater control of digester environmental conditions.
2. Long solid retention times allow better biodegradation efficiencies.
3. Additional settling of liquor ensures minimum loading to the aerobic process.
4. There is capability to cope with full effluent load, regardless of fluctuation

Extended Aerobic Process

In the extended aerobic system, the anaerobic liquor is aerated to further reduce the BOD content. In addition to providing oxygen, the floating aerators also ensure complete mixing is achieved and the pod contents are always in suspension. In this process, levels of beneficial micro-organisms are increased which in turn hasten the conversion of pollutants into carbon dioxide, water and energy. The aerobic suspension is allowed to settle in a settling tank to ensure production of a fairly clean supernatant.

The main advantages of extended aerobics systems are its high BOD removal efficiency and low solid yield.

The raw effluent is treated using a ponding system comprising of three phases, i.e. anaerobic, facultative, and algae processes. Although the system takes a longer retention time of 90 days, it is less sensitive to environment changes, stable, efficient and could guarantee excellent pollutant biodegradation efficiency of above 95%.

The composting system offers an effective solution to the oil palm industry’s perennial problem of waste disposal. The composting system utilizes 100% POME and EFB and uses a technically advanced method to convert these waste matters into compost. EFB are firstly shredded using a high speed hammer mill and then stacked into windrows of 1.5 meter high by 45 meter length in an open field. POME with BOD levels less than 10,000 ppm is then pumped from the pond and sprayed onto these windrows at a specified rate at 3 days intervals. The windrows are turned regularly using a windrow-turner for better mixing and aeration. Composting accelerants are sprayed once at the start of the process to accelerate the composting process. Throughout the composting process, the windrows are covered by an air-permeable covering to avoid drenching by heavy rain and to prevent leaching of nutrients. The covering is crucial for the control of temperature and moisture content, two key factors that affect the speed of composting and quality if the end product. The compost is mature after 70 days and is ready for use. The compost, when used in sufficient quantity, is capable of replacing 66% of chemical fertilizes.