Identification and Assessment of Pollutional Aspects in Vegetable Oil Manufacturing in Sudan 1 By Tagelsir Mustafa Abdelsalam 2, Abdel Aziz Abdel Mageed Abdel Aziz 3 and Isam Mohammed Abdel-Magid 4 Abstract Vegetable oil manufacturing is an old and widespread industry in Sudan. The sources of pollution in oil manufacturing are partly attributed to the intrinsic properties of oil seeds and partly to techniques of processing. This study is an attempt to identify the sources of pollution in oil processing and assess the significance of their impact in environmental pollution. A statistical procedure based on Randomized Blocks and Factorial models of experimental design was adopted. The percent loss in processing, which goes into wastewater or disposed with refuse in the ground, was used as a measure to qualify the effect of the process on pollution. The study has established a model for assessment of effects on environmental pollution. However, the numerical results and the obtained quantification of pollution require further confirmation through more elaborate and proper selection of samples using random techniques. Introduction The economy of Sudan is mainly dependent upon agriculture and agro-industries. Vegetable oil manufacturing is one of the first agro-industries established in Sudan. The manufacturing of vegetable oils and allied processes are industrial activities that have fairly gone Up-to-date development in Sudan. It started in the middle of the 19 th century by the camel driven presses, then developed into the mechanical screw presses and recently applied modern techniques of solvent extraction. Also, the processes of oil refining and soap making have been greatly improved during the last two decades. Vegetable oil production and soap making are industrial processes which may compound pollution of the environment {9}. Due to this fact, intensive studies on pollutional characteristics potential in oilseeds and on waste resulting from the vegetable oil processing are of great importance. In Sudan this area is still virgin and needs more work to investigate the pollution qualitatively and quantitatively. Moreover, other studies are required to minimize the loss of resources resulting from the wastes in oil processing and soap making operations and hence improve the efficiency of production. 1 Published in The Sudan Engineering Society Journal, Issue No. 30, June 1988, pp 30-36 2 Lecturer, Chemical Eng. Dept. Faculty of Engineering, University of Khartoum 3 Private Engineer, Khartoum North, Sudan 4 Lecturer, Civil Eng. Dept. Faculty of Engineering, University of Khartoum 1
One of the objectives of this work is to identify the types, sources and content of pollution caused by the vegetable oil industry as practiced in Sudan, then assess their significance on the pollution of the environment. Hence, the study is an attempt to develop a model for identification, quantification and assessment of pollutional aspects of vegetable oil industry in Sudan. Vegetable Oils in Sudan Generally, many oilseeds are used for production of edible oil, and the most widely used is soyabean. In Sudan, the main oilseeds which are used to produce edible oils are cotton seeds, groundnuts and sesame. All of these seeds have intrinsic pollutional constituents which introduce some limitations on the use of their products in food making {4}. Typical examples are the secretion of toxic polyphenol gossypol and some pigembryo cells in cotton seeds. Also if aspirglius flavus infect groundnuts, highly toxic Alfatoxins will be initiated. Some of these pollutants are partially removed by processing, e.g. gossypol can be reduced by cooking. Hence, food products like edible oil and cakes have been made from these seeds. On the other hand, storage aspects may subject the oil seeds to some attacks and/ or bacteria, fungi and spoilage organisms {4}. These attacks are dependent upon physical and chemical properties of the media such as nutrients, moisture content, relative humidity, ph and temperature. The control of seed deterioration may be governed by controlling the concentration of dissolved oxygen. Vegetable Oils Processing Before starting processing, the oilseeds must undergo some preparations {14}. The seeds are cleaned to remove foreign matter, then dehulled or decorticated to improve the yield, as the case may be. Prior to extraction, by mechanical expression or solvent extraction, the seeds undergo size reduction so as to facilitate the extraction process. In the case of mechanical expression, cooking by heat treatment is believed to improve the yield via coagulating or destroying of proteinous matter, unraveling of natural structure and breakage of some cross linking bonds, decreasing the oil affinity for solid surface attachment, giving the seeds proper plasticity, detoxicating gossypol, increasing fluidity of the oil, destructing bacteria and spoilage organisms {14}. The solvent extraction achieves high yield with less heat treatment. However, the relatively mild heat processing may result in products containing toxic matters which are not removed or inactivated and thus require further treatment to minimize the toxicity. The oil refining process may include neutralization, bleaching, deodorization and hydrogenation {1}. These processes involve the reaction of oil with chemical materials like caustic soda and bleaching agents which contain halogenated compounds. Some of these chemicals remain in wastewater and when discharged with water, they act as source of pollution in form of B.O.D., suspended solids, oils and grease and impurities {11}. These contribute to deoxygenation, toxic pollutants and alkalinity or acidity build-up. Typical characteristics of waste water from oil processing are shown in table 1, {5}. 2
For comparison between wastewater characteristics and the composition of industrial effluents, tolerable limits of these industrial effluents in Khartoum North are shown in table 2, {8}. There are considerable amounts of solid waste from spent bleaching materials, spent catalysts, seed residues, sludge from settling basins, off-quality raw materials and waste from packing materials {13}. In the case of solvent extraction, air may be polluted by vapor of hexane and odourferroussubstances, but these are found to be insignificant. Table 1 Industrial process Volume, liter per 1000 kg raw oil BOD, kg per 1000 kg raw oil SS matter, kg per 1000 kg raw oil CIL, kg per 1000 kg raw oil Solvent extraction & 148 0.06 0.04 - degumming, Nuetralization, 1084 4.67 1.69 1.62 bleaching & deodorization Nuetralization, 1542 9.36 3.35 2.82 bleaching, deodorization& dehydrogenation Tank, car cleaning 225 0.49 0.19 0.2 Margrine from refined oil 1501 1.93 1.34 2.96 For comparison between the above characteristics and the composition of industrial effluents, the tolerable limits of these industrial effluents in Khartoum North are shown in table 2. Table 2 Tolerable Limits of Industrial Effluents Discharge into Public Sewers Parameter Limits PH 5.5 10.0 Temperature 60 C Grease and Oils 15 mg /litre Suspended solids &BOD 800 mg /litre Petroleum products Flas point 85 C Sulphates & sulphides 10mg /litre Iron &magnesium 5.0 mg /litre Chromium 1.0 mg /litre Calcium 0.2 mg /litre Copper o.1 mg /litre Zinc o.3 mg /litre Nickel 2.0 mg /litre 3
Investigation Procedure To carry out this study, existing factories of vegetable oil are classified according to the technological processes, operation and techniques of pollutional control applied in these factories. The criteria of technical practice have revealed different levels of processing technology i.e the operations of oil extraction from seeds varies from early camel-driven method to the most advanced solvent extraction. Also different levels of refinery processes are identified in different oil mills while some factories do not practice any refining operations. The main processing criteria adopted for the classification of factories are the following: a. Full refining processes: neutralization, bleaching and deoderization b. Semi-refinery process i.e. neutralization only c. No refining at all. From the view- point of pollution control, the following criteria were considered: 1. In-site or off-site pretreatment of waste materials 2. Recycling, recovery and reuse of suitable materials 3. No pretreatment and direct discharge of waste into the available disposal facilities. According to the above classifications, five categories of the factories have been designated as shown in table 3. Table 3 Categories of Oil Factories Refining Category Extraction by screw pressing Batch neutralization Continuous neutralization Bleach& Deodorization Pollution control I * NA * * * II * NA * * NA III * * NA * NA IV * * Na Na Na V * NA NA NA NA * : Designates that the process is applied in the category. NA: Designates that the process is not applied in the category. Analysis and Discussions For proper investigation, random selection of a sample of factories is necessary. In this study, the sample selection was governed by practical considerations. The main restrictions are availability of technical information, ease of accessibility to information if available and cooperation of the factory management to release the information. Due to lack of proper randomization, the data used in this work was just enough for the purpose of identification and qualification of pollution as well as the assessment of the process effect on the environment. In fact, the data obtained for this study is fairly useful for establishing a model for assessment of pollution which can be used with any reliable data to quantify more accurately, the pollutional aspects in oil industry. The investigation techniques adopted in this work are based on the design of experiments for study of variation between the categories of factories as well as variation within the same factory at different conditions. The Randomized Block Model was used to test the significance of variation, 4
in terms of percent waste, between the categories of factories (treatments) during one year over two-months intervals considered as (blocks) as shown in table 4, {7}. Table 4 Randomized Blocks Table Treatments Blocks Mean II III IV V 1 7.8 8.8 10.1 7.5 8.6 2 8.3 9.5 10.0 6.8 8.7 3 7.9 9.3 11.0 6.7 8.7 4 8.6 8.9 11.1 6.9 8.9 5 8.8 9.1 10.5 7.1 8.9 6 9.4 8.7 9.7 7.3 8.8 Mean 8.5 9.1 10.4 7.1 8.8 For the investigation of each category of factories, the Factorial Design model was adopted. The factors were considered as the following ones: a. Pretreatment of wastewater to recover fatty acids. b. Bleaching and deodorization processes Batch or continuous neutralization. c. Batch or continuous neutralization. Each of these factors was tested at two levels and a model of 2 {3} was developed as depicted in table 5. Table 5 Two Factorial Design Table Ao A1 Process Mean (Bo) (B1) (Bo) (B1) (Co) 6.0 8.7 5.0 7.9 6.9 (C1) 7.3 10.4 6.4 9.4 8.4 Average 6.7 9.6 5.7 8.7 7.7 Ao : The category uses no pretreatment of wastes A1 : The category makes treatment of wastes Bo : The category uses no bleaching & no deodorization B1 : The category uses bleaching only Co : The category uses continuous neutralization C1 : The category uses batch neutralization Statistical manipulation of the data in table 5 was carried out and the analysis of variance reflected the following findings There is no significant variation between periods of time during the year The pretreatment of wastewater is fairly significant at 95% level of confidence 5
The effects of bleaching and deodorization and that of batch or continuous neutralization are only significant at a level of 99% of confidence. 6. Findings and conclusions The following general findings and conclusions have emerged from the results of this study: a. In the analysis, the measure percent waste designates the percent of pollutants that are lost from the manufacturing processes and entered the wastewaters, evolved in the atmospheric air and dumped in the ground. b. In general terms, the study revealed the fact that the different processes in oil mills have significant effects on the pollution problem in the sub sector of industry. Bleaching, deodorization and neutralization seem to have similar effects. The average percent waste was found as follows: 133 kg/ton crude oil in the case of mechanical pressing with no refining processes. 71 kg/ton crude oil in the case of extraction with neutralization but no bleaching nor deodorization. 33 kg/ton crude oil in the case of extraction with all refining processes. c. Pretreatment of wastewater to recover fatty acids before final disposal has a fairly significant role in minimizing pollution. d. The best combination of processes is the full refining with continuous neutralization and pretreatment of wastewater to recover fatty acids. e. Despite the fact that the results agree with the local norms, they are found unaccepted when compared with international standards. This may be due to the fact that most of the factories discharge their wastewaters in sewers without pretreatment. f. The last mentioned result reflects the need for some preventive measures based on legal grounds so as to control; the disposal of wastewater from oil industries. g. Because all numerical data were obtained from production logbooks of he investigated factories, whose selection was not strictly random, the numerical results may need further confirmation. h. Despite the need for confirmation of the results, the application model of experimental design and statistical procedures for the qualification assessment of pollutional aspects in oil industry is valid and can be used with any reliable data. References 1) Anderson, A. J. C., Refining of oils and fats for edible purposes, 2 nd Revised Edi., Pergamon Press, 1962. 2) Austin, J. E., Agro industrial project analysis, The Johns Hopkins University Press, London, 1981. 3) Cocks, L.V., and Van Rede, C., Laboratory handbook for oil and fat analysis, Academic Press, London and New York, 1966. 4) Duffs, C. M., and Slaughters, J.C., Seeds and their uses, John Wiley and Sons, New York, 1980. 5) El Zein, E. O., Environmental assessment of the industrial wastes, M. Sc. thesis, Inst. Of Environmental Studies, U. of K., 1982. 6) Environmental health act, the Gazette of Republic of the Sudan, 1975. 7) George, E.P., et al, The design and analysis on industrial experiments, 2 nd Edi., Longman Group Ltd., London, 1956. 6
8) Industrial waste local order for the local council of Khartoum North, 1971. 9) Lund, H. F., Industrial pollution control handbook, McGraw Hill Book Co., London, 1971. 10) O Riordan, Timonthy, Tumer and Kerry, Progress in resources management and environmentl planning, Vol. 3, John Wiley and Sons, New York, 1981. 11) Ouano, E. and Lohnni, A. R., Water pollution and control in developing countries, Proceedings of international conference at Bangkok, Thailand, 1978. 12) Pirie, N. W., Food protein sources, International biological program 4, Cambridge University Press, 1975. 13) Royston, and Michael, Pollution prevention, Pays Pergamon Press, London, 1979. 14) World conference on oil seeds and vegetable oil processing technology, The American oil chemists society, Amsterdam, the Netherlands, March, 1-5, 1976. 15) WHO, Compendium of environmental guidelines and standards for industrial discharges, EFP/83.49, WHO, Geneva, 1983. 16) Personal communication with production managers of oil factories in Khartoum. 7