POME (Palm Oil Mill Effluent)

One of the by-products of the palm oil milling process is POME (palm oil mill effluent). Raw POME is a high strength waste water with BOD more than 25,000 mg/L. Guess what is the BOD of the sewage? It is 100 times less than that of POME which is less than 500 mg/L. How to reduce the BOD down to 100 mg/L or less to meet the discharge limit set by the Department of Environment (DOE)? In Sarawak, DOE has set a more stringent discharge limit which is 50 mg/L or lower. 

BOD (biochemical oxygen demand) is the amount of oxygen needed for the microorganisms to break down the organic matters in the waste water at certain temperature over a specific time period. What we normally see is BOD at 20 degree celcius over 5 days (a worldwide practice). However, for POME, DOE practices BOD at 30 degree celsius over 3 days. The reasons are 30 degree celsius is closer to the temperature of the treated POME and 3 days give a faster results for monitoring purpose.

Usually you will see a thick scum on top of the anaerobic ponds. What are they? They are mainly oily matters and light components in the POME. What you need to do is to break the scum by spraying water or waste water so that the scum can be digested faster by the bacteria. You are encouraged to spray the waste water from the subsequent pond. It contains bacteria. Another benefit is to lengthen the retention time of the waste water as it is recycled back to the previous pond. For the anaerobic ponds to stay in good condition, use one or two mixers to mix the waste water and bacteria evenly. Do not mix the ponds too vigorously as it can introduce some oxygen into the ponds. Oxygen shall not present in the anaerobic ponds. The anaerobes are not going to live happily with the presence of oxygen. I will continue on the waste water treatment process in the next post.