Palm | Kelapa Sawit

Aerobic treatment of palm oil mill effluent





K. Vijayaraghavan, a, , Desa Ahmada and Mohd Ezani Bin Abdul Aziza


aDepartment of Biological %26amp; Agricultural Engineering, Faculty of Engineering, University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia


Received 7 February 2005; revised 28 November 2005; accepted 29 November 2005. Available online 3 April 2006.











Abstract


In this study treatment of palm oil mill effluent (POME) was investigated using aerobic oxidation based on an activated sludge process. The effects of sludge volume index, scum index and mixed liquor suspended solids during the acclimatizing phase and biomass build-up phase were investigated in order to ascertain the reactor stability. The efficiency of the activated sludge process was evaluated by treating anaerobically digested and diluted raw POME obtained from Golden Hope Plantations, Malaysia. The treatment of POME was carried out at a fixed biomass concentration of 3900卤200 mg/L, whereas the corresponding sludge volume index was found to be around 105卤5 mL/g. The initial studies on the efficiency of the activated sludge reactor were carried out using diluted raw POME for varying the hydraulic retention time, viz: 18, 24, 30 and 36 h and influent COD concentration, viz: 1000, 2000, 3000, 4000 and 5000 mg/L, respectively. The results showed that at the end of 36 h of hydraulic retention time for the above said influent COD, the COD removal efficiencies were found to be 83%, 72%, 64%, 54% and 42% whereas at 24 h hydraulic retention time they were 57%, 45%, 38%, 30% and 27%, respectively. The effectiveness of aerobic oxidation was also compared between anaerobically digested and diluted raw POME having corresponding CODs of 3908 and 3925 mg/L, for varying hydraulic retention time, viz: 18, 24, 30, 36, 42, 48, 54 and 60 h. The dissolved oxygen concentration and pH in the activated sludge reactor were found to be 1.8鈥?.2 mg/L and 7鈥?.5, respectively. The scum index was found to rise from 0.5% to 1.9% during the acclimatizing phase and biomass build-up phase.





2.POME treatment technology


During the processing of fresh fruit bunches (FFB), water is the most needed resource. To process one tonne of FFB, typically 1.5 m3 of water is used (Industrial Processes and The Environment Handbook No.3, 1999). Out of this


amount, 50% will be released as POME and the rest of the water is lost as steam and boiler blow down, wash waters and leakage.Based on the statistical value of total crude


palm oil production in May 2001, the production of 985,063 tonnes of crude palm oil means a total of 1,477,595 m3 of water was used, and 738,797 m3 was released as POME, in that month alone. Without proper treatment, this wastewater


will pollute watercourses receiving it. The current treatment technology of POME typically consists of biological aerobic and anaerobic digestion. Biologically treated effluent is


disposed of via land application system, thus providing essential nutrients for growing plants.This method may be a good choice for disposal of treated effluent. However, considering the rate of daily wastewater production, for example,approximately 26 m3 per day for an average palm


oil mill with an operating capacity of 35 tonnes FFB per day, it is doubtful that the surrounding plantations receiving it could efficiently absorb all the treated effluent.Another new technology under research is the zero waste evaporation technology. By evaporating the POME, water can be recovered while the residual solid content can be utilized as fertilizer.Although this method reclaims about 80% of water from POME, a major drawback is the high energy requirement (Ma, 1996).Since the ultimate goal of wastewater management is towards zero discharge, the best wastewater treatment scheme is inevitably a treatment


that allows 100% reuse and recycling of wastewater.If one considers the volume of water needed by the crude palm oil milling industry, the practice of releasing treated wastewater without further reuse in-house is a wasteful exercise.


Another alternative to minimize fresh water and energy consumption is to reuse wastewater directly from the final treatment pond. This could be as feed water for boiler or hydro cyclone. However,if this is the solution, a higher quality of treated water is required especially when it is to be used


as boiler feed water. The current treatment system of anaerobic followed by aerobic degradation is not capable of producing such high quality treated effluent.


duce higher quality effluent is through the use of membrane technology at the tertiary treatment stage. Membrane treatment is capable of providing a highly efficient treatment, requires minimal energy, and does not introduce any additives to the waste stream.There are many membrane process applications on water and wastewater treatment that has proven to be efficient. Membrane technology covers a large spectrum of separation techniques,ranging from reverse osmosis to microfiltration.Among the various membrane processing technologies,ultrafiltration offers an attractive option for wastewater treatment. It is a low pressure-driven membrane process retaining most effectively


macromolecules sized within 0.001 鈥?0.02 飩祄.


Although the biologically treated POME is already low in biodegradable organic contents, it still possesses significant amount of persistent cellulosic materials and oily residues that usually occur in the form of macromolecules.With membrane ultrafiltration, these molecules could be separated from the waste stream thus producing a higher quality effluent. In this research project, a study has been carried out to examine the feasibility of using membrane ultrafiltration for the final treatment of POME extracted


from the aerobic treatment pond. The general objectives are to


(i) Evaluate the effectiveness of membrane


ultrafiltration of treated POME and


(ii) Investigate the possibilities of water reuse and water recycling of the membrane-filtered treated POME.


Methodology


The experimental part of this study followed the sequence as shown below:


Sample collection


An adequate quantity of sample was collected from a palm oil mill. A portion of the raw sample was preserved and the characteristics of the raw sample were analysed.


(i) Pre-treatment of samples Three types of pre-treatment were applied separately to compare the effectiveness of


each treatment. These treatments were:


A) Filtration


B) Centrifugation


C) Coagulation


(ii) Stirred-cell ultrafiltration


After pre-treatment, samples were ultrafiltered using a bench-scale stirred cell ultrafiltration unit (Spectrum Molecular/Por Stirred Cell-Model No.20062). The membrane material used


was 76-mm Spectrum Cellulose Ester Disc with


MWCO of 5000. A few aspects were studied.


The following parameters were investigated:


a) Pure water flux


Pure water flux characteristics for the membrane was obtained by filtering deionised water at an increment of every 1 bar of transmembrane pressure (from 1 bar to 7 bar).


b) Sample Flux


Flux for each pre-treated sample was obtained for comparison purpose. The flux was observed in the range of 1 bar to 7 bar of transmembrane pressure.


c) Variation of pH value of sample In order to investigate the effect of pH value on rejection characteristics (COD, total solids,suspended solids, ammoniacal nitrogen, total


nitrogen and colour), ultrafiltration of filtered and


centrifuged samples were conducted at two different


pH values at transmembrane pressures of 4.5 bar and 7.0 bar. The two pH values were pH 8 (original value of effluent) and pH 2.2 (pH at iso-electric point of cellulose membrane)(Bowen and Clark, 1984).


Ultrafiltration of the sample that was pretreated with coagulation technique was lastly carried out at the pH value that gave better rejection characteristics on the filtered and coagulated samples.


d) Variation of transmembrane pressure To study the effect of pressure on rejection characteristics, samples pre-treated using filPalm oil mill effluent (POME) filtration and centrifugation methods were ultrafiltered at 2 different values of TMP. Duplicate runs for each sample at TMP of 4.5 bar and 7.0 bar were undertaken. The TMP that gave the


better rejection characteristics was then applied for


ultrafiltration of the sample that was pre-treated using the coagulation technique.


(iii) Characteristic analysis of samples In order to evaluate the efficiency of membrane ultrafiltration, selected parameters were chosen to characterize the various samples


(raw, pre-treated and permeate). These parameters


are of great importance for effluent characterization


and the values need to meet the level of statutory discharge limits in the Environmental Quality Act (Prevailing Effluent Discharge Standards for Crude Palm Oil Mills, 1984) before being released into watercourses. The parameters are


Chemical Oxygen Demand (COD), Ammoniacal


Nitrogen (AN), Total Kjeldahl Nitrogen (TKN),


suspended solids (SS), turbidity and colour.


Results and Discussion


To study the overall treatment efficiency of pre-treatment followed by ultrafiltration, a comparison between untreated and treated sample is necessary.


a) Filtration 鈥?ultrafiltration pretreatment From Figure 1, it is clear that the filtration-ultrafiltration system was able to bring down parameter measurements extensively. Suspended


solids, turbidity and colour content were the best.


treated parameters, with percentage removal reaching 99.2%, 7.9% and 98.2% respectively.COD level was reduced to less than 200 mg/L from the original 1336 mg/L. Total nitrogen concentration was 25.4 mg/L after treatment, showing a 78.8% reduction. Ammoniacal nitrogen only


recorded a 5.8 mg/L improvement, equivalent to 21.3% percentage reduction.


b) Centrifugation 鈥?ultrafiltration pretreatment


For centrifugation-ultrafiltration system,as shown in Figure 2, the final quality of the treated sample was not as remarWhat is the best effective method to treat water effluents in palm oil industry?
Turning palm oil waste into drinking water








NIBONG TEBAL: While Singapore has NEWater, which is waste water that has been purified, Malaysia may soon have drinking water from palm oil waste.





Universiti Sains Malaysia (USM) has scored another first by inventing a system which can turn palm oil waste into drinking water.








USM School of Chemical Engineering鈥檚 dean Professor Abdul Latif Ahmad鈥檚 invention is called the ';novel membrane-based treatment system'; which turns palm oil mill effluents (POME) into crystal clear drinking water.








The environment-friendly technology is set to reduce water pollution as it will help ensure zero discharge of palm oil waste into rivers.








';This invention is an innovative and cost-effective way of preventing sludge from making its way into the rivers and polluting them,'; Abdul Latif said.








At the School of Chemical Engineering in the USM Engineering campus here yesterday, Abdul Latif said he had been working on the project for the past 10 years with a RM500,000 grant provided by Yayasan Felda.








He said the system would help in ensuring a sustainable development of the palm oil industry as it emphasises zero discharge. He said most palm oil mills used the conventional method of treating palm oil waste with the biological treatment system.








';This system uses bacteria to eat and digest the dirty substances in the palm oil waste, which is not really effective as the waste is still murky when released into the river.';








He said his invention only required four steps to treat the waste before it became clean enough to drink.








He said his team of researchers managed to design and set up a membrane pilot plant locally at a cost of RM150,000.








';It is not only cost effective but also uses Malaysian technology,'; he said, adding that a similar pilot plant designed and fabricated overseas costs more than RM500,000