| Oil palm (elaeis guineensis) is one of the most versatile crops in the tropical region, notably in Malaysia and Indonesia. The extraction of palm oil from the fruit of elaeis guineensis involves a number of processing procedures: sterilization,stripping,digestion,pressing,classification,purification and vacuum drying. In the extraction process, large quantities of water are required. It is estimated that about 1.5 m3 of water are needed to process one ton of fresh fruit bunch (FFB), half of this amount ends up as palm oil mill effluent (POME). The raw POME is a thick brown liquid and characterized by low pH,high biological and chemical oxygen demand,high salt and suspended solids. As a result, the discharge of palm oil mill effluent has the potential to severely pollute the receiving waterways.Besides immediate utilization such as crop irrigation and using as animal fodder, many methods have been developed to control POME pollution, including decanting and drying,evaporation,coagulation,flotation,ultrafiltration and various aerobic and anaerobic biodegradation technologies. Today about 85% of POME treatment is based on anaerobic/facultative/aerobic pond system by Malaysian palm oil mills, which is characterized by long hydraulic retention time (HRT), often in an excess of 20 days, necessitating large areas of land or digesters. To shorten the treatment time, lessen the land required, besides physico-chemical methods such as decanting and drying, evaporation, coagulation, high rate reactors such as anaerobic filter, anaerobic fluidized bed reactor, anaerobic baffled reactor, UASB and other hybrid reactors are put forward and evaluated in treating POME. In the paper, palm oil mill effluent (POME) from Sungal Burung palm oil mill in Malaysia was treated by a technical flow combined by AnaEG+BioAX+UF+RO, after the foundation research on each step in the system, the performance of the overall sequential system was evaluated. The paper can be divided into four parts:⑴startup and operation of AnaEG reactor;⑵startup and operation of aerobic inner-circulation biofilm reactor——BioAX;⑶decoloring treatment of discharge from aerobic reactor, including coagulation and adsorption decoloring;⑷combination operation of the overall treating system. The main results are listed below:During the 150 days'start-up duration, influent COD of AnaEG was increased stepwise from 5000 to 35000 mg/L, pH in reactor was stable which was in the range of 6.98-7.53, VFA accumulation was not happened, effluent COD was less than 2500 mg/L all the while, the average COD removal efficiency was as high as 92.5%, indicating that AnaEG was in good condition in digesting and transforming the organic compound in POME; the activity of anaerobic granular sludge was good, and the average methane producing activity was 0.488 gCOD/(gVSS·d); methane content in biogas produced was 70% (n/n), acetic acid was the main VFA in effluent from AnaEG, about 2/3 of the total VFA.When aerobic biofilm reactor——BioAX was in steady-state during operation stage, influent COD concentration was 6000 mg/L, pH in reactor was 8.4-8.8, salts concentration was 6000-8000 mg/L, the average removal efficiency of COD and SS was 19.07%, respectively, no NH3-N was detected in the aerobic effluent.Decolorizing experimental results of aerobic effluent by coagulation and adsorption: (1) flocculant FeCl3: the optimum dosage was 500 mg/L, pH had no influence on color removal, and the optimal color removal rate was 40%; (2) flocculant PAC: the optimum dosage and pH were 700 mg/L and 5.0, respectively, and the optimal color removal rate was 90%; (3) flocculant FeSO4: the optimum dosage and pH were 800 mg/L and 10.0, respectively, and the optimal color removal efficiency was 91%; (4) Results got from adsorption using powdered activated carbon indicated that the optimum dosage,adsorption time and pH were 20 mg/L,30 min and 6.0, respectively, and the optimal color removal rate was 91%.Experimental results of combination operation of the overall treating system---AnaEG+BioAX+UF+RO: UF membrane was very efficient in removing turbidity and color from aerobic effluent, the removal efficiency were 96.4% and 68.8%, respectively, but it exhibited inefficient in removing COD,TOC,BOD and electrical conductivity, they were mainly got rid of by RO membrane, and the removal rate were 97.1%,99.3%,90.6% and 93.4%, respectively; After filtrated by UF and RO membrane, all organic compound and most of the salts were removed from aerobic effluent, and RO permeate was colorless and transparent. Further comparison of the characteristics of RO permeate with the boiler feed water standard indicated that the RO permeate should be softened before it was to be used as the boiler feed water.Membrane cleaning: the membrane were first circulated with clean water to flush out POME remaining in membranes, and then circulated with chemical solution mixed by 1% (w/w) NaOH and 0.6% (w/w) NaClO for 25 min, finally, the membrane rinsed again with clean water until a neutral pH was achieved. The flux after cleaning was 95.3% and 91.7% of the initial flux value for the UF and RO, respectively.
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