edible oil ghee
TRANSCRIPT
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The Edible Oil & GheeSector
Environmental Report
DRAFT
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Table of Contents
Preface
Executive Summary
1. Introduction
1.1 Environmental Technology Program for Industry (ETPI)1.2 Demonstration Project1.3 Environmental Problems of Edible Oil Industry of Pakistan
2. The Edible Oil Industry2.1 Raw Material2.2 Process Chemicals2.3 Utilities2.4 Process Description
2.4.1Vegetable Ghee2.4.2Cooking Oil2.4.3Acid Oil2.4.4Carbon Oil2.4.5Soap
3. Environmental Stresses and their Quantification3.1 Wastewater
3.1.1 Sources and Disposal3.1.2 Quantification
3.1.3 Characterisation3.1.4 Pollution Load
3.2 Solid Waste3.3 Soil Contamination3.4 Air Emissions3.5 Noise Emissions3.6 Occupational Health and Safety (OH&S)
3.7 Energy Inefficiency
4. Impacts4.1 Impacts Associated with Wastewater4.2 Impacts Associated with Solid Waste4.3 Impacts Associated with Soil Contamination4.4 Impacts Associated with Air Emissions
4.5 Impacts Associated with Noise4.6 Implication Associated with Occupational Health and Safety4.7 Impact Associated with Energy Wastage
5. Recommendations5.1 Wastewater Reduction & Treatment
5.1.1 Size Optimisation of Separation Chambers
5.1.2 Recycling of washing water after neutralisation5.1.3 Replacement of Gravity Settling by Centrifuge after
Neutralisation5.1.4Use of Pressurised Water for Floor Cleaning5.1.5Improvement of Foam and Soap Removal from Fat
Traps5.1.6Reorganisation of Water Systems5.1.7Use of Flow Meters5.1.8Construction of a Wastewater Treatment Plant
5.2 Solid Waste5.2.1 Improvement of Waste Management and Land Filling
5.2.2 Use of Tankers with Internal Coils to Minimise Sludge5.2.3 Increased Recycling of Nickel Catalysts
5.2.4 Recovery of Oil from Spent Earth
5.3 Soil Contamination Prevention5.4 Air Emissions Control
5.4.1 Recovery of FFA at Deodoriser
5.4.2 Recovery of CO2 from Gas Cracking Plant5.4.3 Optimisation of Combustion at Boiler
5.5 Safety and Health (S&H)5.5.1 Exhaust Combustion Gases out of Gas Cracking
Building5.5.2 Improvement of Noise Abatement and Protection
5.5.3 Improvement of Working Conditions at the Tin Shop5.5.4 Use of Material Safety Data Sheets (MSDS) of Raw
Products
5.6 Energy
5.6.1 Recovery of Heat from Cooling Water Used duringHydrogenation
5.6.2 Pre-heating of Incoming Oil with Outgoing Oil atHydrogenation
5.6.3 Pre-heating of Incoming Oil with Outgoing Oil atDeodorization
5.6.4 Improvement of Steam Pipes Insulation
5.6.5 Increasing Temperature during Deodorization5.6.6 Installation of a Cogeneration Plant
5.7 General Recommendations5.7.1 Inert Atmosphere after Deodorization
5.7.2 Covering of Lye Preparation Area5.7.3 Insulation of Chilling Rooms Doors
5.7.4 Environmental Management Systems (EMS)
LIST OF TABLES
Table 2.1: Edible Oil Local Production and Imports (1995)
Table 2.2: Process Chemicals and their UsageTable 2.3: Utilities and their Consumption
Table 3.1: Daily Wastewater DischargeTable 3.2: Wastewater AnalysisTable 3.3: Daily Pollution Load
Table 3.4: Details of Solid WasteTable 3.5: Air Emission from Different Sources
Table 5.1: Design Data of Primary Treatment SystemTable 5.2: Cost Estimates for Primary Treatment SystemTable 5.3: Design Data of Secondary Treatment System
Table 5.4: Cost Estimates for Secondary Treatment System
LIST OF FIGURES
Figure 2.1: Ghee Process Flow SheetFigure 2.2: Cooking Oil Process Flow Sheet
Figure 5.1: Gravity Settling TankFigure 5.2: Chemically Enhanced Dissolved Air FlotationFigure 5.3: Process Flow Diagram of Activated Sludge System
Figure 5.4: Proposed System for Pre-heating of Incoming Oil with
Outgoing Oil at Hydrogenation
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Preface
This report is a part of the ETPI demonstration projectcomponent. The purpose of this report is to address the
environmental problems of edible oil sector.
The report has been prepared on the basis of the findings of
the environmental audits of three edible oil mills whichwere conducted by ETPI in February, 1998. The study wasjointly carried out by two leading firms of the ETPIconsortium i.e. National Environmental Consulting (Pvt.)
Ltd. and Haskoning Royal Dutch Consulting Engineers andArchitects, The Netherlands.
This report is a step towards the dissemination of
information, about the environmental problems of theedible oil and ghee manufacturing facility along with the
possible solutions and investment required to mitigate these
problems and to comply the present and futureenvironmental legislation.
It is envisaged that this effort will help to enable edible oil
mills to initiate efforts to combat the environmental
problems to produce environmentally clean products.
In addition it is hoped this report would also support theefforts of R&D institutions, environmental equipment and
chemical suppliers, and environmental researchers/studentsworking towards the betterment of the environment.
We acknowledge the participation of PVMA and edible oil
mills in the program and for extending their co-operation inall aspects of the study and thank them for their continuous
support and encouragement.
April, 1999
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Acronyms
BOD Biochemical Oxygen Demand
COD Chemical Oxygen DemandCT Cleaner Technologies
dB DecibelE O P END-OF-PIPE
FFA Free Fatty AcidsGCP Ghee Corporations of Pakistan
IHI In-House ImprovementsMP Melting Point
MT Metric TonNCS National Conservation Strategy
NEQS National Environmental Quality StandardsNG Natural Gas
O&G Oil and GreaseO H & S Occupational Health and Safety
PM Particulate Matter PPM Parts per Million
RBD Refined Bleached and Deodorized
TDS Total Dissolved Solids
th Thermies = 1000 caloriesTSS Total Suspended SolidsVOC Volatile Organic Carbon
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Executive Summary
Environmental degradation by the industrial sector is amatter of serious concern in Pakistan. The Federation of
Pakistan Chambers of Commerce and Industry (FPCCI)with the assistance of the Government of the Netherlands
has undertaken the Environmental Technology Program for
Industry (ETPI) to facilitate the industrial sector inimplementing environmental control projects in Pakistan.This occurs by initiating measures to combat pollution,
thereby, enabling the industries to comply with theNational Environmental Quality Standards (NEQS) and the
forthcoming ISO 14000 certification.
ETPI aims at the implementation of demonstration projectsof environmental cleaner technologies. ETPI definesdemonstration project as a project under which thoseenvironmental technologies will be implemented whichoffer both technological solutions for pollution abatementand economic benefits for the industry. At the same time,the solutions should suit the local conditions for successfulimplementation."
ETPI is being implemented in alignment with the NationalConservation Strategy (NCS). It will be implemented in 20industrial sectors in two successive phases. Six priorityindustrial sectors including edible oil and ghee sector areincluded in the first phase.
This study focuses on environmental problems caused byedible oil industries and recommends measures to abatethem.
There are around 160 small and medium sized vegetable oiland ghee plants in Pakistan with a total capacity of overtwo million tons. Most of the mills have integratedfacilities of manufacturing soap as a by-product. The majorraw material used is raw oil extracted from different
botanical species. Pakistan imports 70-80% of the raw oil,
mostly from Malaysia. Water, electricity and natural gasare the major utilities consumed.
The main processes for cooking oil refining include:degumming, neutralisation, bleaching and deodorization.For ghee manufacturing, hydrogenation is also carried outin addition to these processes.
An edible oil industry generates large quantities ofwastewater. On average, for every ton of oil produced, thedischarge of wastewater is about 30 m3. The wastewater ofedible oil mills can be categorised into process wastewaterand non-process wastewater. Process wastewatercontributes to most of the pollution load in the effluent
being drained by the industry; while non-processwastewater constitutes the major portion of totalwastewater quantity. The process effluent is high in BOD,
COD, TSS, TDS, oil, phosphate, sulphate and chloride.Concentration of these pollutants in the process effluent ismuch higher than allowable NEQS limits. These pollutantsneed to be removed from the effluent to prevent the damage
being done to the environment, as well as to avoid payingthe Environmental Improvement Charges (EIC).
Spent fullers earth, spent nickel and filter cloth are themajor solid wastes of oil mills. Spent fullers earth andnickel are sold for down-stream use.
Spillage of oil on uncovered ground around oil storagetanks results in soil contamination, which can further leadto contamination of groundwater.
Major sources of air pollution are boiler and generatorexhausts, and emission from the gas cracking unit. From
these sources, carbon monoxide (CO) is emitted in veryhigh concentration. NOx emission is high in the generator
exhaust. CO and NOx have been suggested by Pakistan
Environmental Protection Agency (PEPA) for self-monitoring and reporting and emissions exceeding NEQSwill be liable for EIC. In some industries gas cracking unit
also emits huge amount of carbon dioxide which is agreenhouse gas.
In general, occupational health and safety (OH&S)situation is very poor in the edible oil mills. Use of any
protective gear by employees is almost non-existent.Inefficient and obsolete processes consume and wastemuch energy as compared to modern technologies.
The recommendations to improve environmentalperformance are categorised as in-house improvements,cleaner technologies, and end-of-pipe treatment. In-houseimprovements and cleaner technologies will not only result
in the improvement of economical and environmentalperformance of the mill, but will also reduce the cost of theend-of-pipe treatment.
Oil losses in the effluent can be reduced either byincreasing the size of the separation chambers beneath the
pre- and post- neutralisation vessels or by replacing gravitysettling by centrifuge separators. This measure will alsoreduce BOD and COD of the effluent. Water consumptionas well as discharge can be reduced significantly byreusing/recycling the cooling water and vacuum water after
proper treatment. End-of-pipe treatment options, whichinclude oil skimmers and biological treatment of the
process wastewater, are the ultimate solution forcompliance with the NEQS. The oil concentration in theeffluent can be reduced either by gravity settling or
chemically enhanced dissolved air floatation. Aeratedlagoons or activated sludge are the recommendedbiological treatment options to remove organic pollutants.
The solid waste management system can be improved bygood working practices. By applying solvent extraction, theoil content in spent earth can be reduced to 5%. Paving thearea near oil storage tanks and collecting spills will reducethe risk of soil contamination.
Air emissions can be reduced by optimising the combustionat boiler and recovering CO2 from the gas cracking plant.Installation of a stack on the gas cracking exhaust, use of
protective gears such as gloves, goggles, ear muffs, etc.,will improve the working conditions in the plants.
The wastage of energy can be minimised by efficiently
performing the processes, such as preheating of incomingoil with outgoing oil at hydrogenation and deodorization.The edible oil industry is an energy intensive industry andthe industrys normal working is effected because of powerfailure. The new concept of producing electric as well asheat energy together at the plant, known as Cogeneration,has been developed recently in developed countries. It is avery efficient and cost-effective way to generate electricityand heat for the industry.
To improve the overall environmental conditions of the
industry Environmental Management System (EMS)should be implemented. This is also a requirement of ISO
14000.
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1. Introduction
This report aims to address the environmental pollutionproblems of the Edible Oil sector. It has been compiled on
the basis of the findings of three environmental audits,conducted in three edible oil mills under the Environmental
Technology Program for Industry (ETPI). The objective of
this report is to assess the nature and extent ofenvironmental problems caused by an edible oil industryand to recommend solutions to mitigate their impacts. Thelimitation of this report is that the information has been
generalised on the basis of the data obtained from threeenvironmental audits for the whole sector. This limitation
has been minimised using substantial national andinternational secondary information available for the edible
oil sector.
1.1 Environmental Technology Program forIndustry (ETPI)
The Environmental Technology Program for Industry
(ETPI) is a joint project of the Federation of PakistanChambers of Commerce & Industry (FPPCI) and the
Government of The Netherlands. The primary objective ofETPI is to promote the use of environmentally safe
technologies for the production of environmental safeproducts by Pakistans manufacturing/industrial sector.
To provide the required technical expertise and support to
industries, a consortium of local and foreign consultingfirms has been hired to execute ETPI. The members of the
consortium are.
National Environmental Consulting (Pvt.). Ltd.(NEC), Pakistan; the lead consultant;
HASKONING, Royal Dutch Consulting, Engineeringand Architects, The Netherlands;
KRACHTWERKTUIGEN (KWT), The Netherlands;
Management for Development Foundation (MDF),The Netherlands; and
Hagler Bailly, Pakistan.
This five year project began in 1996 and works with
Pakistani industries and their associations in identifyingthose pollution prevention and abatement technologies
which are economically most feasible, and in implementingthese solutions. The five components of the program
include the development of a user-friendly database ofrelevant information, institutional networking within and
between key industrial institutions of the country,dissemination and communication to promote cleanerindustrial production, institutional support and training to
create in-house environmental capability within chambersand industrial associations and demonstration projects in 20
selected industrial sectors to demonstrate the economicfeasibility and environmental efficacy of environmental
technologies.
1.2 Demonstration Project
Each component of ETPI has been given specificdefinition, and carries its own objective, scope of work and
methodology. The present study is part of the
demonstration project component. Hence, this report willfocus mainly on this component.
As discussed above, physical interventions in the form of
demonstration projects are an integral part of ETPI, which
is defined as a project under which those environmentaltechnologies will be implemented which qualify both thetechnical and the financial feasibility criteria, and at the
same time are relevant to the local industrialists.
Improvements in processing practices will also be anessential part of the demonstration projects.
Objectives of the demonstration project include:
To establish live examples in the major industrialsectors of Pakistan for the direct dissemination of
environmental technologies in the country.
To prepare a representative database in the shape of anindustry specific Environmental Audit for establishingthe environmental policy implication, financial and
institutional support requirements. To create a more aware and committed constituency of
industrialists for undertaking environmental
investment.
To identify industry sector specific research anddevelopment areas in the discipline of environment
and industry for local and international researchinstitutions.
For the implementation of a demonstration project, a
comprehensive procedure for the selection of industries in
each sector has been developed. According to thisprocedure, three industries are selected for an
environmental audit from each sector. Subsequently one ofthese three is selected for the demonstration project.
1.3 Environmental Problems of Edible Oil Industry of Pakistan
The biggest problem faced by an edible oil industry iswastewater, both quantitatively and qualitatively.
Wastewater generation in an edible oil industry can bedivided into two categories:
Wastewater generated directly from processes e.g.neutralisation washings etc.
Wastewater generated from auxiliary systems e.g.cooling and vacuum systems etc.
Wastewater generated from both these sources variesgreatly in pollution load and concentration. Process
wastewater contains high amounts of BOD, COD, oil &grease, TSS, TDS, and nickel etc. Wastewater generated
from the auxiliary systems is huge in quantity andrelatively higher in temperature. It sometimes contains
traces of VOCs. Boiler condensate recovery system is notefficient in some, and practically non-existent in most.
Apart from liquid waste, solid waste and air emissions are
also generated. Solid waste generation is mainly in the formof spent earth, filter cloth, and spent catalyst. Spent earth
and spent catalyst are in slurry form and are combinedtogether to extract what is known as Carbon Oil before
their final disposal. After carbon oil extraction, the left overslurry is sold to contractors.
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Soil contamination can be seen around oil storage tanks in
oil mills due to spillage on uncovered ground. This alsoposes risk of contaminating the groundwater.
Air emissions are generated mainly from boiler and
generator stacks. Besides, process emissions may also bepresent, comprising of volatile organic substances from
bleaching, deodorization, etc. In some cases, air emissions
have pollutants higher than the limits mentioned in theNational Environmental Quality Standards (NEQS).
Noise and odour levels at many places in every mill arehigh. Temperature of the working areas is generally
acceptable during winter season, but it becomes quite highduring summer. General rating of the lighting andventilation arrangements is on a scale of satisfactory to
poor.
A variety of chemicals are used in edible oil processing.While other chemicals also contribute, use of nickel as
catalyst during the hydrogenation process is the mostimportant concern from an environmental point of view.
Chemicals used pose a twofold problem. Firstly, they comein the wastewater or as waste products of chemical
processes. Secondly, they might come into direct contactwith the persons handling them. Generally, practices for
handling of chemicals in oil mills are poor and need drasticimprovement. Open air storage and transportation, manual
feeding, and dripping of chemicals is common. In most ofthe mills, workers are improperly attired. Use of protective
gears is very rare, and most of the workers work withoutshirts.
Edible oil processing requires quite an intensive use of
energy. It is due to the fact that for different processes andoperations, different temperatures have to be maintained.
The most common modus operandi is to heat up watereither to steam, or to higher temperature, and then to
transfer the energy contained by this water to the material
being processed. Some amount of this energy is consumed
during the processes, while the remaining is lost eitherduring the cooling of the product for the subsequent
process, or in terms of heat contained by the wastewater. Inalmost all cases, an efficient arrangement of heat transfer to
save this energy does not exist.
Though some edible oil mills have acquired ISO 9000
certification and some are passing through theimplementation phase of ISO 9000 standards, others stilllag far behind. A lot more could be achieved from the
occupational health and safety (OH&S) perspective. Themanagement is keen to undertake environmental initiatives
in many cases. Still, the awareness level in workers and linestaff is dismally low, making the implementation of betterin-house management practices difficult. This, however,
does not liberate the management from the responsibilityand the resulting consequences.
Since it is perceived that environmental protection calls to a
large extent for investments with low or nil payback, it isnatural that most of the industries tend to postpone
environmental protection projects for as long as possible.This perception is not true in every situation, and often is a
misperception.
With the promulgation of the Pakistan EnvironmentalProtection Act 1997, the Pakistani edible oil industry will
be required to comply with the regulations forenvironmental protection. The Pakistan Environmental
Councils Environmental Standard Committee hasproposed certain Environmental Improvement Charges to
be imposed on the industries not complying with NEQS. Aformula for calculations of these charges has already been
devised. Therefore, every edible oil mill would have tothoroughly investigate its existing operations with the aim
of identifying opportunities for containing theenvironmental impacts through implementation of
appropriate in-plant measures.
2. The Edible Oil Industry
Pakistani society has traditionally been consuming butterfatDesi Ghee prepared from butter by heating, as a cookingmedium of choice. However, this product has been in shortsupply for a long time due to numerous reasons. Therefore,the past few decades have witnessed an increasingdependence on the vegetable oil, and products derived fromit. Until the mid-seventies, domestic production of edibleoils was sufficient to meet 75% of the domesticrequirements. A high rate of growth in vegetable oilconsumption afterwards due to population growth, increasein per capita income, and decrease in the real price ofvegetable ghee, created a gap between production and
demand. The share of imported oils and fats has thus beenincreasing gradually to fill up this gap.
Presently, the per capita consumption of vegetable oil/gheeis 16-18 kg per annum. The average demand growth is
projected at 4.4% per annum between 1988-2000, and thedomestic production is expected to increase by 7.3% duringthe same period.
Pakistans Edible Oil industry was nationalised in 1972 anda public sector organisation i.e. Ghee Corporation ofPakistan (GCP) was created to run this industry. Since1988, private sector has been allowed to emerge and grow.Most of the units under the control of GCP have been
privatised. At present 94% of the sector is under private
sector control. A total of around 160 small and mediumsized vegetable oil and ghee plants are operational with atotal capacity of over two million tons.
Two institutions in Pakistan represent the edible oilindustry. The Pakistan Vanaspati ManufacturingAssociation (PVMA) is an association of over 100 millswhich import refined crude oil, process and package it, andmarket it. The total installed capacity of these units isaround 1.8 million ton. The All Pakistan Solvent ExtractionAssociation (APSEA) is an association of five mills. Thesemills process oil from raw oil seed through solvent
extraction process. The total installed capacity of theseunits is around 550,000 tons.
2.1 Raw Material
The edible oil industry uses a variety of raw oils such asRBD soft and hard1, palmolein, soybean oil, corn oil,cottonseed oil, rapeseed oil, sunflower oil, and canola oil.The last five raw materials are used occasionally, either dueto the shortage of the soybean supply, or because ofspecific requirement of the product.
1
RBD soft oil is refined, bleached, and deodorized oil withno hydrogenation. RBD hard oil is refined, bleached anddeodorized oil with hydrogenation.
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The local production and imports for 1995 is shown in
Table 2.1. Cottonseed, corn oil, and canola (recently) arepurchased from the local market. The local oil seed
production caters to only 20-30% of the requirement,whereas the rest is imported. Palm oil, which has 80%
share in the imports of oil and fat, is being imported fromMalaysia, while sunflower and soybean are imported from
the Eastern European Block. In fact, by importing over a
million ton of palm oil, Pakistan has become worldslargest importer of palm oil from Malaysia.
Table 2.1: Local Production and Import ofEdible Oil (1995)
Quantity (Ton)S. # Type
Local Imported
1. Cottonseed Oil 374,400 14,000
2. Sunflower Oil 30,000 24,600
3. Rape Seed Oil 66,000 -
4. Butter Fat 379,900 -5. Soybean Oil - 200,000
6. Palm Oil - 1,059,0007. Palm Kernel Oil - 5,800
8. Tallow - 57,000
Total 850,300 1,360,400
Source: PORIM Karachi
Oils mainly consist of triglycerides, however, some
impurities such as gummy matter, pigments, and long chainfree fatty acids (FFA) are also present in them. These
unwanted substances are removed from the oil duringvarious refining processes.
2.2 Process Chemicals
Various chemicals are used at different stages of the
refining process. A list of these chemicals, and their
utilisation is shown in Table 2-2.
Table 2-2 : Process Chemicals and their Usage
Chemicals Usage
Phosphoric acid De-gumming
Caustic soda FFA removal, oil extractionfrom fullers earth and soap
manufacturingFullers earth Pre- and post-bleaching
Nickel sulphate Catalyst in hydrogenationCitric acid Odour Removal
Vitamins ( A, D &E) To improve nutritional value ofoil
Butyric acid & Ethylbutyrate
For flavouring the ghee
Antioxidant BHT For stability of the productSulphuric acid For acid oil production.
Common salt (NaCl) For soapstock graining and forthe regeneration of cation resin
Monoethanolamine(MEA)
To absorb CO2 in thepurification of H2 gas.
Source: ETPI primary & secondary surveys
2.3 Utilities
The consumption of different utilities in oil mills is
presented in Table 2-3.
Table 2.3: Utilities and their Consumption
Utility Quantity Usage
Water
(m3)
12 - 45 Washing of oil, cooling &vacuum systems, steam
production, etc.
Electricity(kwh) 45 130 Process house operations,vacuum pumps, waterpumps, natural gascracking unit, boiler house.
Natural Gas
(Mcf)
3 25 H2 gas manufacturing, soapmanufacturing, boilers, etc.
Steam (tons) 1.4 3.4 Process house, gas crackingunit, heating of oil instorage tanks, decanting.
Source: ETPI surveysNote: The quantities are based on 1 ton of oil or gheeproduced.
2.4 Process Description
The major process being carried out in the oil mills is the
refining of raw vegetable oil to render it edible.Hydrogenation is also carried out for ghee manufacturing.Apart from cooking oil and ghee, soap, acid oil, carbon oil,and bottled carbon dioxide are also produced as by-
products. The unwanted material, removed during the oilrefining process, is utilised either for soap or acid oilmanufacturing.
2.4.1 Vegetable Ghee
Vegetable ghee is produced by blending and processingdifferent raw oils. A detailed process flow sheet is shown inFigure 2.1.
De-GummingThe first step is the removal of gummy matter such as
phospholipids and lipoproteins etc. from raw soybean orcottonseed oil. It is accomplished by exposing the oil towater and adding the phosphoric acid at 50oC. As a result
precipitate of gum is generated which is removed from theoil.
Pre-NeutralisationPre-neutralisation process is done to remove FFA from rawoil. Caustic Soda solution proportionate to FFA is mixedwith oil. This results in the neutralisation of the FFA. Theresulting soapstock is allowed to settle and then drained outfrom the refining kettle. Three hot water washings aregiven to remove residual soap.
Pre-BleachingThe purpose of oil bleaching is to eliminate its colouring
pigments through the adsorption on bleaching earth.Fullers earth is used for bleaching because of its excellentadsorption power.
The bleached oil containing fullers earth is passed througha series of filter presses to remove the spent earth.
HydrogenationHydrogenation process is the hardening of oil to reduce itsun-saturation. At the same time, it improves the stability ofthe product against its oxidation. Chemically, the degree ofun-saturation decreases by passing hydrogen gas throughoil in the presence of nickel catalyst at 150oC.
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-
FILTER PRESS
Spent Ni
POST NEUTRALIZATIONINCLUDING WASHINGS
POST-BLEACHING
POST FILTER PRESSSpent Fullers
Earth
Ni Recycle
VacuumWastewater
Soap Stock Wasteater to Soaps Pits
HARDENING STORAGE
CO2, CO, NOx
Fresh Ni
HARD OIL TANK
RAW OIL MAIN STORAGE
DEGUMMING / PRE-NEUTRALIZER /
WASHING
Soap Stock &Wastewater to Soap Pits
PRE-BLEACHERVacuumWastewater
PRE-FILTER PRESS
NATURAL GASCRACKING UNIT
HYDROGENATION
H2
Spent Fullers
Earth
DEODORIZER
POLISH FILTER
SEAMING MACHINE
Vacuum WasteW ater
CHILLING SECTION
WARE HOUSE /DESPATCH
Phosporic Acid +Lye + Water
Spent earth + Oil +Filter cloth washing
Effluents
Fullers Earth
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Post-NeutralisationPost-Neutralisation is performed in the same way as pre-neutralisation, except that dilute lye is used because hardoil has a low FFA content at this stage.
Post-BleachingPost-bleaching is performed in the same way as pre-
bleaching.
DeodorizationMost of the odorous substances along with FFA, sterols,tocopherols, saturated and unsaturated hydrocarbons and
pesticides are stripped out by injecting dry steam into oil at235 245oC. Citric acid is also added to remove the odour.
After deodorization, the deodorised oil is cooled in the de-cooler to about 85oC. The remaining odorous substancesare removed during the de-cooling under vacuum.
After cooling the hard oil is passed through a final filterpress called Polish Filter, which removes undissolvedcitric acid, remaining particles of the fullers earth or nickelcatalyst, and any other fine impurities. It also reduces theintensity of the final colour of the oil/ghee.
FortificationBefore sending to the filling section, vitamin A+D, andvitamin E are added. Antioxidant BHT is also added forstability and for the taste of the product. Some flavours arealso added like butyric acid and ethyl butyrate, in a ratio of88:12.
The finished product after packaging is stored in a chillingroom at a temperature of 0oC for 8-12 hours. This processconverts the hard oil from the molten state into finegranules and improves its appearance. Afterwards it is sentto the warehouse.
2.4.2 Cooking Oil
Manufacturing of cooking oil is similar to gheemanufacturing except that hardening (hydrogenation) of the
cooking oil is not required. Therefore, hydrogenation, post-neutralisation, post-bleaching, and post-filtration are notperformed.
Generally, pure soybean oil (100%) is used in the cookingoil manufacturing. Cottonseed, canola, sunflower or cornoil are also occasionally used for this purpose. A processflow diagram is shown in Figure 2.2.
2.4.3 Acid Oil
Production of acid oil is mainly concerned with thedisposal and treatment of soapstock. Soapstock is generally
treated with excess alkali to enhance saponification of anyremaining neutral oil present in it. Later, it is boiled for 30-
45 minutes through steam coils fitted inside the vessel.Sulphuric acid is added which reacts with soapstock to
form acidulated soapstock or acid oil.
2.4.4 Carbon Oil
Carbon oil is extracted from the spent fullers earth through
the alkali reaction. Spent catalyst is also mixed with spentearth for carbon oil extraction. The spent earth collected
from both pre-and post-filter presses is sent to the soapsection. Caustic soda is added in it and the slurry is heated
through steam coils fitted inside the vessel.
Water is also added to facilitate the decanting of oil from thespent earth. Continuous stirring enhances the skimming of oil
at the upper surface of the slurry. After stirring, the decanted
oil floating above the surface of the slurry is skimmedmanually and is collected in a large drum. Most of this oil is
used in the preparation of soap. Fullers earth after carbon oilextraction is sold to contractor for final disposal.
2.4.5 Soap
Raw materials used in soap manufacturing are soapstock,
oil/ghee spills, soap foam collected from fat traps/soap-pits,and acid oil or carbon oil.
Caustic soda solution is added to a batch of raw material
and saponified by boiling with live steam. After fatstockhas been saponified, common salt is added to it and boiling
continues. At a certain stage of salt concentration, whensoap becomes insoluble boiling is stopped and the soap is
allowed to settle overnight. It settles to form four layers.
The uppermost layer is foam below this is neat soap, thethird layer is of dirty soap or nigre and at the bottom is
some spent lye.
After settling, foam is pushed aside and neat soap ispumped out and filled in frames for solidification.
3. Environmental Stresses and their Quantification
The edible oil industry is one of the many chemical process
industries, which contribute to environmental pollution. In
the following sections pollution from edible oil industriesthrough various sources have been discussed in detail.
3.1 Wastewater
Generation of large amounts of wastewater is the biggestenvironmental problem faced by the edible oil industries.
Wastewater is generated through various sources, varyinggreatly both in quantity and quality.
3.1.1 Sources and Disposal
The wastewater generation sources from an edible oil millcan be broadly divided into four categories:
Process wastewater
Cooling water
Vacuum water
Boiler and softening plant
Detail of these sources is given in the following section:
Process wastewaterFollowing processes contribute to process wastewater:
Neutralisation
Generation of wastewater from the pre-/post-
neutralization process is periodic. Wastewatercontaining soapstock is transferred into a separationchamber, with generally three compartments. Soapstock,
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Fi ure 2-2: Cookin Oil Process Flow Sheet
DECANTING UNITRAW OIL
MAIN STORAGE TANK
* DEGUMMING
NEUTRALIZATIONINCLUDING WASHING
BLEACHING
FILTER PRESS
DEODORIZER
COOLERS
SEAMING MACHINE
WARE HOUSE /DESPATCH
HOT OIL TANKS
DRYING
Waste Water & SoapStock to Soap Pits
Vacuum (wastewater)
Spent Fuller Earth
(to Soapry & Oil)
* Cotton Seed / Sunflower Oil
POLISH FILTER
Phosphoric Acid
Fullers Earth
Vacuum (Condensate)
Lye + H2O
Effluent
Good Oil
Vitamins + BHT(30 g. + 20 g.)
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oil, and water are separated in the successive
compartments. Wastewater goes to the fat trap after
separation of soap stock and water.
Acid Oil Production
Acid oil production is another source of wastewater.
Wastewater stemming from this source is small in
quantity but qualitatively it is significant.
During this process acidulated soapstock or acid oil
rises upward in the reaction vessel due to its low
density, while the acid water, containing remaining acid,sodium sulphate and water-soluble impurities, settles
down. The acid water is drained out to the fat trap from
where it is discharged into the sewer.
Soap Manufacturi ng
The brine water from the graining process during soap
manufacturing is drained out after settling. This wastewater
goes to the soap pit and after decanting oil and soap, it isdischarged into the sewer.
Fi lter Cloth WashingThe filter cloths, used in the filter press, are washed using
caustic soda, water, steam and detergents. The caustic bath,
which is very small in quantity, is retained and is drained
once every three months. Water bath is drained every
month and detergent washing is intermittent. All the above
three streams go into the final trap and after decanting oil,
wastewater is discharged into the sewer.
Cooling WaterWater is used for equipment/product cooling purposes inhydrogenation, deodorization, gas cracking unit andammonia compressors. The cooling water is recirculated
after dissipating its heat by spraying. The capacity of
spraying system is generally insufficient to dissipate
enough heat quickly, hence most of the water is drainedout.
Vacuum WaterWater is used in the vacuum system to provide vacuum forcertain operations. Vacuum water having relatively high
temperature (average 35oC) is cooled through spraying and
then is re-circulated. As the spraying system does not have
the required efficiency in most cases, a portion of water has
to be discharged to maintain the temperature to the desired
level.
Boiler and Softening PlantThe boiler generates wastewater as blowdown. Somewastewater is also generated during the regeneration of the
softening plant. The pattern of wastewater generation is
periodic, however it is distributed almost evenly over 24
hours.
DisposalEdible oil industries usually dispose off all their effluent
into nearby receiving water bodies, such as canal, river or
sea, without any treatment.
3.1.2 Quantification
The quantification of wastewater was done on the basis ofwater balance, flow monitoring, and water consumption.
Based on the information of audited mills, the typical
ranges of wastewater generation are tabulated in Table 3-1.
Table 3-1: Daily Wastewater Discharge
Source Wastewater Quantity
m3/100ton of oil/ghee
Processes 50 - 80
Auxiliary Systems 1400 - 3600
Total 1450 - 3680
Source: ETPI survey
3.1.3 Characterisation
Wastewater of an edible oil mill can be divided into two
separate classes i.e. process wastewater and non-process
wastewater. The process wastewater was found to be highly
polluted as compared to non-process wastewater. The
characteristics of process wastewater and non-process
wastewater are given in Table 3.2.
Table 3.2: Wastewater Analysis
Parameter
Process
Wastewater
Cooling &
Vacuum
Wastewater
pH 11 12 6 - 8
Temp (oC) 40 50 -
BOD5 450 700 -
COD 1300 2100 -
TSS 2000 16500 -
TDS 3000 20000 350 - 10000
Oil & Grease 100 180 0 - 5
Nickel 2 - 2.5 -
Phosphate 10 20 -
Sulfate 10000 - 15000 -
Chloride 1525 - 5300 -
Conductivity 30 - 1400 -
Total Alkalinity 6000 - 22200 -
Source: ETPI survey, 1998Note: All values are in mg/l, except pH, Temp. (
oC) &
conductivity (ms/cm).
3.1.4 Pollution Load
The pollution load generated daily by edible oil mills is
presented in Table 3-3. This has been calculated by
multiplying quantity of wastewater with the concentration of
each parameter.
Table 3-3: Daily Pollution Load
Pollution Load
Parameters Mill-1 Mill-2 Mill-3
BOD5 60 230 1,600
COD 170 380 3,000TSS 280 130 3,100
TDS 3,750 960 5,400
O&G 15 0.8 15
Ni 0.05 0.5 0.5
PO4--- 4.2 -- --
SO4 200 -- --
Cl- 304 1,530 95,000
Total Alkalinity 1,150 1,000 1,800
Source: ETPI survey
Note: All quantities are in Kg per 100 tons of oil/ghee
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3.2 Solid Waste
Solid waste generated by edible oil mills can be classified in the
following general families:
- General waste
- Tin scrap
- Filter cloth
- Sludge from settling ponds, fat traps and raw oil tanks
- Spent earth
- Spent catalyst
- Spent lubricants
General type of waste produced usually contains pipes, mild
steel (MS) sheets, iron angles, wires, cans, bottles, and waste
paper. Some of this solid waste is sold to a contractor on
monthly basis, while the remaining is disposed off at municipal
garbage dumps.
Tin scrap consists of rejected tin containers, lids and waste from
tin can manufacturing area. Tin waste is temporarily stored
inside the mill and afterwards is sold for recycling. The quantity
of scrap is estimated to be 2-10% of the total tin used.
Filter cloth is used in the filter press. Once the filter cloth is
fixed in a filter press, it could serve for 4-6 batches after which,
the filter press is dismantled and filter cloths are washed. One
piece is used twice or thrice before it is discarded. After
rejection, filter cloths are used for floor cleaning and general
cleaning purpose.
When water ponds are cleaned the sludge is produced. The
quantity is dependent on the quality of water stored. Sludge is
also produced in the fat trap, where the oily wastewater from
pre- and post- neutralisation is stored. This sludge is used for
soap manufacturing. Wastewater from the filter cloth washing,
acid oil production, soapstock tanks and soap manufacturing
goes to another fat trap. The sludge from this trap is also used to
make soap.
Raw oil tanks are emptied twice a year for cleaning purposes.Raw oil storage tank also produces sludge. The sludge that is
settled at the bottom is salted and heated. The upper layer of oil
is skimmed to be used in the process. The rest is sent to the soapsection for soap production.
Fullers earth is used in the pre-and post-bleaching process. Oil
content of spent Fuller's earth after filtration of the oil coming
from bleaching is about 40% by weight. This earth is scraped
from the filter clothes and processed to extract carbon oil.
Afterwards, it is sold to outside vendors. The cleaning is done
manually and needs considerable labour force, as spent earth is
put into used fullers earth bags and taken out of the building by
workers.
Nickel (Ni) is used in hydrogenation process as a catalyst. The
general practice is to recycle some of the used nickel and to add
fresh catalyst for the total required quantity. The ratio of
recycling to fresh varies from mill to mill. After about 5 batches,
the spent Ni is completely replaced by fresh Ni. Spent Ni ismixed with spent earth and treated for carbon oil extraction.
Afterwards it is disposed off, generally with spent earth.
Spent lubricants come from the machinery and equipment
maintenance. These are sold for reuse or for burning in cement
kilns or brick furnaces. The details of solid waste generated by
edible oil mills, with its per annum quantities, are tabulated in
Table 3-4.
Table 3-4: Details of Solid Waste
S. No. Category Type/Source Quantity Fate
1 General Pipes, MS sheets, iron angles,wires, cans, broken glass,
bottles, paper, plastic, etc.
Sold or disposed off
2. Tin Scrap Tin workshop Sold for recycling3. Filter Cloth Filter press 0.1 - 0.2 m Mostly used for cleaning etc.
Finally thrown with garbage
4. Sludge From water pondsFrom small fat trapFrom big fat trap
From raw oil storage tanks
Disposed off at solid waste disposal sitesUsed for soap makingUsed for soap makingUsed for soap making
5. Spent FullersEarth
Pre-bleaching, post-bleaching,
carbon oil making6 - 9 kg Sold after Carbon oil extraction
6. Spent Nickel Hydrogenation 20 - 160 g Mixed with spent fullers earth and carbon oilis extracted from the mixture. Afterwards, thespent mixture is sold to contractors for down
stream uses
7. Spent Lubricants From machinery Sold to contractors for burning in kilns orfurnaces.
Source: ETPI Survey
Note: Quantities of wastes are based on per ton of oil/ghee produced.
3.3 Soil Contamination
Soil contamination in an edible oil industry is due to oil
spillage. Oil spillage on soil can be found, in the following
areas:
Underground furnace oil deposit: Uncovered soil near
underground furnace oil deposit gets highly polluted
with furnace oil spillage.
Raw oil tanks: Uncovered soil near raw oil tanks gets
highly polluted with raw oil spillage.
Carbon oil manufacturing area: Bags containing spentearth are stored on unprotected soil and in the open air.
This means that polluted rainwater and leachates from
this area go into the soil.
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3.4 Air Emissions
In general, vegetable oil refining processes does not have
significant air emissions. In the refining process, materialsare volatilised, but in every case the volatilised material is
condensed either for recovery or to maintain low pressuresin the systems.
Vents from storage tanks of raw oil and products that havea certain vapour pressure can be a source of vapours. This
emission occurs principally on the filling of the tanks.
However, the vapour pressure of vegetable fats and oils issuch that the contribution is not significant.
Air emissions emitted by an edible oil mill come chiefly
from the auxiliary systems, i.e. boiler, gas cracking plant,and power generator etc. Samples from these sources were
analysed. The results of these analyses are presented in
Table 3-5.
Table 3-5: Air Emission from Different Sources
S. No. Emission Boiler Generator Gas Cracking
Plant
NEQS
1. CO, mg / Nm3 40-130 2060 3000 800
2. CO2, VOL % 2 205 0.8 18 -
3. NOx, mg/Nm3 60-125 1300 -- 400
4. SO2, mg/Nm3 -- 110 -- 400
5. Smoke, Ringlemann Scale -- 5 -- 2
6. Particulate Matter, mg/Nm3
-- 275 -- 300Source: ETPI survey
3.5 Noise Emissions
Industrial equipment and machinery create high noise levels
during operation. The main noise sources in edible oilindustry include:
Steam ejectors at the roof of main process building
Tin can manufacturing
Gas cracking plant
Boiler
Hydrogen compressor
Ammonia compressor
The noise levels in the above mentioned areas are quite high,
although they were not measured. The allowable noise levelunder NEQS is 80 dB.
3.6 Occupation Health and Safety (OH&S)
In edible oil mills OH&S hazards are due to the following
reasons:
Improper handling of chemicals.
Poor ventilation
Slippery floors
High noise levels
The use of protective gears in handling of chemicals is non-
existent. Workers were found bare handed working with
chemicals such as caustic soda.
Because of poor ventilation in the process area, fumes
emitted from different processes stay inside for longer time.
Floors get slippery because of oil spills in refining area.
Also industry uses detergent to wash the floor after every
shift, which makes the floor even more slippery.
3.7 Energy Inefficiency
Refining of edible oil includes a number of heating and
cooling operations where the transfer of thermal energy takes
place. This transfer of energy is not efficient in most of theedible oil mills of Pakistan. Wastage of energy is due tofollowing reasons in oil mills:
Cooling of oil after hydrogenation and deodorization.
Improper insulation of steam pipes.
Prolonged deodorization at low temperature.
Steam distributing pipes without proper insulation results indecrease of steam temperature hence more steam is required.
In some industries deodorization of edible oil is carried out
at 190oC for a period of 1.5 hours. However, in theliterature it is reported that the process is carried out at 235-
245oC, which is accomplished only in 25 minutes. The low
temperature deodorization, not only reduces the productionrate, but also increases the oil losses in terms of
polymerisation.
4. Impacts
The major adverse impacts of environmental pollution
caused by the edible oil mills are discussed in this chapter.
These impacts have been described with respect to the local
and global environment, workers health & safety and
deviation from the NEQS.
4.1 Impacts Associated with Wastewater
Pollution of water is the most important environmental impact
of edible oil mills. Impacts of wastewater generated from
edible oil mills are evaluated while keeping in mind the
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final destination of wastewater. Adverse effects of
pollutants on the ecosystem as well as on the surrounding
population are also taken into account. These impacts are
discussed pollutant wise in the following sections.
pH
Most of the processes discharge highly alkaline (pH >10)wastewater but some processes such as acid oil production
discharge highly acidic effluent. Aquatic life is severely
effected by the pH of the water and a larger deviation from
neutral pH could alter the natural biological activities. Also,
acidic or basic wastewater does not facilitate the bio-
degradation of organic pollutants. Wastewater with a high
pH value is also corrosive to the sewer system of the area.
Organic Pollutants
The COD value is the amount of oxygen required todegrade the pollutants present in the wastewater through
chemical degradation. COD indicates the chemically
degradable pollutants. Similarly BOD indicates the
biodegradable organic pollutants. BOD and COD cause the
depletion of dissolved oxygen in the water body.
Deficiency of oxygen in receiving water could causeadverse effects on biological activity in the water
environment. In the worst case this can result in the total
depletion of oxygen in the receiving water, causing an
anaerobic environment. This would be fatal to aerobic life
and would also create odour problems.
High COD/BOD ratio indicates the persistence ofchemicals present in effluent. Persistent chemicals always
pose risk of entering into the food chain.
Phosphates
Phosphorus is an essential nutrient for algae and otherbiological organisms. A high concentration of phosphates,
if discharged into the surface water, can result in the
growth of undesired aquatic life such as algae. This can
lead to the eutrofication of the receiving water body. Inmost of the countries, the phosphate concentration
allowable for discharge in water bodies is less than 1ppm
because of these characteristics.
Presently NEQS do not have any limit for phosphate in
wastewater but it is likely that phosphate limits will be
imposed in near future.
Sulphates
Under anaerobic conditions sulphate is reduced to sulphideand can form hydrogen sulphide. H2S is highly malodorous
gas and toxic at high concentration. Offensive odour can
cause poor appetite for food, impaired respiration, nausea,
vomiting and mental perturbation. Also, H2S can be
oxidised biologically to sulphuric acid which is corrosive todrain pipes.
Chlorides
Chloride concentration in wastewater is not significantlyreduced by conventional wastewater treatment methods,
hence finds its way into the receiving water. High
concentration of chloride in the water may convert the
agricultural land into saline land and unfit for agriculture if
the receiving water is used for irrigation purpose.
Particulate and Sediments
Suspended solids present in process wastewater arepartially organic in nature. Upon settling in the bottom of
the water body, they decompose aerobically as well as
anaerobically, depending on the prevailing condition. In
aerobic decomposition, dissolved oxygen of the water body
is consumed, creating a potential for adverse effects on the
ecological system of the water environment. Anaerobic
decomposition of organic compounds will generate odour.
Suspended solids also reduce the aesthetic value of the
receiving water body.
Total Dissolved Solids (TDS)
Process effluent from the edible oil mills also containslarge quantities of TDS. Most of the dissolved solids are
undesirable in the receiving water. Dissolved minerals and
organic constituents may produce aesthetically displeasing
colour, tastes and odour. Some chemicals may be toxic and
some of the dissolved organic constituents are known to be
carcinogens. Quite often two or more dissolved substances
combine to form a compound whose characteristics are
more objectionable than those of the original matter.
Oil and Grease
The concentration of oil and grease in process effluent ismany times higher than allowable limits of NEQS. High
amount of oil present in the wastewater may reduceabsorption of oxygen by the receiving water body, hence
resulting in the depletion of dissolved oxygen. This may
endanger aquatic life as discussed earlier.
Also, oil films on the surface of water result in reduction of
light transmission through surface water, thereby reducing
photosynthesis by aquatic plants. Oils may also form
suspension or emulsion in the water, which could be
harmful for fish and other aquatic life.
Nickel
Nickel is a heavy metal and is used as a catalyst in the
hydrogenation process of ghee manufacturing. Some of the
nickel is discharged into the effluent while most of the
spent nickel is disposed off as solid waste. Nickel is anessential element in animal nutrition in trace quantities but
toxic and carcinogenic in higher concentration.
4.2 Impacts Associated with Solid Waste
Dumping of rubbish and waste inside the plant causes
unhygienic conditions.
The sludge that is formed at the water ponds decreases the
ponds capacity, its recycling capability, and the quality of
water.
Having large amounts of sludge in the fat traps affect the
treatment capacity, as the water flows from one basin to the
next underneath the concrete baffles.
Burning spent nickel in kilns may result in the emission of
nickel compounds in the air. As nickel dust is a possible
carcinogen, producing respiratory cancer, hence its entry
into the air can pose a problem to the population living near
the kilns.
Burning spent oil and lubricants without any control about
the composition of the oil and the flue gases from
combustion is a source of air pollution.
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4.3 Impacts Associated with SoilContamination
Soil contamination can cause ground water pollution that
may afterwards affect surface water.Soil contamination nowadays is an important issue in
industrialised countries, and companies are very concernedabout its grave environmental impacts. In the past,
industries did not take into account the importance of soilcontamination, but this has drastically changed in the last
few years, as the price of land can decrease, or evenbecome nil, when the soil where the industry is located is
polluted.
4.4 Impacts Associated with Air Emissions
Impacts associated with possible air emissions from edibleoil industries are given in the following sections.
Oxides of NitrogenOxides of Nitrogen are emitted from boiler stack and thegenerator exhaust.
Continuous or intermittent exposure of humans to NOxmay cause certain illnesses, such as irritation in the
respiratory tract and abnormal accumulation of fluid in thelungs leading to pulmonary edema. Direct exposure of NOxto soil causes necrosis, causing vegetation loss and may
lead to inhibition of plant growth.
NOx undergo various photochemical and chemicalreactions in the atmosphere leading to the formation of
photochemical smog and acid rain. Although, emissions ofNOx from generator are for short period of time, still the
cumulative effects of NOx at global scenario should not beignored. Depletion of ozone at stratosphere level, formation
of photochemical smog and acid rain may occur due to this.
Oxides of SulphurOxides of Sulphur are emitted in oil mills due to the
burning of fuels in the generator, and also from gas
cracking. Direct exposure to these oxides can be veryharmful to human health, plants and vegetation. Theharmful effects are dependent on the concentration andexposure duration. Indirectly SOx reacts in the atmosphere
to form photochemical smog and acid rain.
Carbon MonoxideCarbon monoxide is a colourless non-irritating gas, whichis generated due to incomplete combustion.
At high concentrations exceeding 5000 ppm with an
exposure of few minutes, this gas can be fatal for human oranimal lives, by reacting with haemoglobin to form
carboxyheamoglobin.At much lesser concentrations, buut with a high duration ofexposure, this gas may still be dangerous for human beings,
as it may cause damages to visual perception, manualdexterity and the ability to learn.
Concentration of CO from the methane cracking plants andthe generator exhausts of the audited mills are very high.
Therefore its long-term impacts can not be ignored.
Particulate Matter (PM)Particulate matter covers a large variety of particles,varying in size and chemical composition, however in this
report, the fine particles of carbon from burning fuel are
considered.
Adverse effects of the particulate matter on human healthare reported in relation to the diseases of the respiratory
system. Lowering of the aesthetics value of a place and lossof general visibility may also be attributed to PM at high
concentration.
The general corrosion reactions on building materials, dueto the presence of NOx and SOx in the air, may also get
catalysed due to the presence of particulate matter.
Carbon Dioxide (CO2)Carbon dioxide is generated in large quantities duringnatural gas cracking in edible oil mills. In some mills this is
collected and sold to beverage industry. While in others thisgas is exhausted into the atmosphere. Laboratory results of
gas cracking plant exhaust show that the concentration ofCO2 in the exhaust is about 500 times of its concentration
in clean air.
CO2 is a green house gas and its higher concentration in theatmosphere is responsible for the phenomenon of global
warming.
4.5 Impacts Associated with Noise
Noise is considered as an interference to and impositionupon comfort, health and the quality of life. Given the
conditions like exposure limit and time, noise may haveboth physiological as well as psychological effects on
human health.
Physiological effects include dizziness, nausea, unusual
blood pressure variation, physical fatigue, loss of hearing,etc. While reduced mental capability and irritations may
attribute to psychological effects.
Very high noise levels were observed in the surrounding ofthe generator room and the boiler house. As these
operations require almost full attention from the workers allthe time, therefore each worker is expected to be exposed
to high noise for at least 8 hours in 24 hours. This conditionmay lead to a permanent hearing loss for workers as well as
physical and mental fatigue, which consequently may lowertheir manual and mental dexterity.
4.6 Implications Associated with Occupational Health and Safety (OH&S)
In edible oil refineries major issues related to OH&S are
handling of chemicals, improper ventilation in process
building, slippery floors and exposure to high noise.
Workers in Pakistan are habitually prone to work with barehands and feet. This puts them at the high risk of
contracting skin disease, such as chemical burns, irritations,
ulcers, etc. Handling of hazardous chemicals such as
caustic soda, sulphuric acids, nickel oxides, etc. without
protective gears poses serious health as well as safetyhazard.
In some industries fumes and exhaust gases emitted from
different processes stay in the process building because of
improper ventilation These cause discomfort to workersand also reduces their output. Some processes also emit
VOCs which may be carcinogenic.
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Slippery floor of the process building due to oil spills onthe floor, always poses risks of injuries to employees.
4.7 Impacts Associated with Energy Wastage
Environment is nowadays understood as a wide andcomprehensive field that includes not only avoidance of
pollution, but also efficient use of energy and natural
resources. Inefficient usage of energy has the following
disadvantages:
Wastage of money, as more natural gas or electricity isconsumed.
Wastage of non-renewable natural resources, as the fuelsrequired to produce the energy are limited natural
resources.
Higher emissions of air pollutants such as carbon dioxides,
as more natural gas and fuel are burnt.
5. Recommendations
A number of recommendations, aimed at the improvement of
environmental conditions of edible oil industries, have beenformulated on the basis of the findings of the three audits by
ETPI, and information available through various secondarysources. Each recommendation has been developed and
worked out on the basis of the present state of information.For further development and cost estimation of each
recommendation, more specific data would be necessary. Thiscan be undertaken at the implementation stage.
5.1 Wastewater Reduction & TreatmentIn the following sections, the detailed description for the
relevant recommendations formulated for wastewaterreduction and treatment is given.
5.1.1 Size Optimisation of Separation Chambers
Due to the small size of separation chambers beneath the pre-and post neutralisation vessels, a proper retention time is not
being given to the washing effluent containing the soapstockand oil etc. This results in incomplete separation of soapstock,
oil, and wastewater. It is recommended that the size of thesechambers be optimised. This would give the following
advantages:
Oil losses would be minimised and the recovery of goodoil would be enhanced at this stage, leading to economic
benefits.
The pollution load in the outgoing water would beminimised, leading to size optimisation of the end-of-
pipe treatment.
5.1.2 Recycling of Washing Water after NeutralisationUsually six to seven washes of about 1 m3 each are applied
after pre-neutralisation and four washes of 1 m3 each afterpost-neutralisation to remove soapstock from oil.
The pollution load transferred to washing water decreasesfrom the first wash to the last wash. Therefore, it seemsfeasible to reuse the water coming from the last wash in the
first wash of the oil. In this sense, it is recommended to makesome trials to check the possibility of using a counter current
washing scheme after post-neutralisation. If the resultsachieved in post-neutralisation are encouraging enough, thesame trial could be made for pre-neutralisation. Countercurrent washing is a normal practice in many industrial
processes.
The importance of decreasing the amount of water used for
washing after neutralisation is not based on the intake watersavings, but on the reduction of the wastewater treatment
plant size. Since pre- and post-neutralisation are the two
main sources of process wastewater and a future treatment
plant would be meant mainly for treating process water, areduction on pre- and post-neutralisation wastewater means
a reduction in the investment and operational cost of such aplant.
5.1.3 Replacement of Gravity Settling by Centrifuge after NeutralisationSoapstock and washing water are separated from the oil, after
pre- and post-neutralisation, by means of gravity settling.
The separation of soapstock and water from oil can be
improved by means of centrifugal separators, in whichcentrifugal force is applied to separate fractions as it forces the
heavier particles towards the periphery, while the light phaseflows toward the centre of the separator.
The separation efficiency of centrifugal separators is much
higher than of gravity settling. This results in the followingpositive effects:
Reduction in oil l ossesBecause of better separation caused by the centrifugal force,less oil is lost with soapstock and washing water. It has been
reported that the use of centrifugal separators instead ofgravity settling can reduce the loss of oil during
neutralisation to more than 25%.
Reduction of washing waterWhen centrifugal separators are used, only 2 washes (with anamount of water of about 10% of the oil weight each) are
required. According to the information received fromequipment supplier, normal process water consumption when
using centrifugal separator is about 50% of presentconsumption. Also it will mean a reduction in the investment
and operational cost of the treatment plant.
Reduction of water content in oi lThe use of centrifugal separators will also reduce the amountof water that remains in the oil after neutralisation by 50%. As
this water must be evaporated before bleaching, the decreaseof water content of the oil will mean a reduction in the amount
of steam required and the time used for this purpose.
Improvement of oil quali ty:Another benefit of using centrifugal separators is theimprovement of the oil quality after neutralisation. The
following oil quality can be achieved after neutralisation ifcentrifugation is applied:
Switching from gravity settling to centrifugal separation
means a drastic change in the neutralisation process. It is notpossible to carry out this step by means of some new
equipment and some small modifications to the present
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process. First of all, it means a change from batch process to
continuous process. Secondly, a complete new installationhas to be purchased and installed.
Table 5.1: Oil Quality due to Centrifugation
Characteristics Incoming Oil Product
Max. FFA content 5 % 0.05%Max. Phosphatide content 200 ppm 5 ppmMax. soap content 100 ppm
Max. impurities content 0.1%Max. moisture content 0.5% 0.5 %
Source: Equipment suppliers
The investment cost of a new refining plant of 187 ton/day
capacity is estimated at Rs. 33,000,000.
Annual savings achievable due to process improvement can
be summarised as follows:
Decrease of oil losses: approx. Rs 4,100,000/year
Steam savings at bleaching: approx. Rs 160,000/year
Personnel cost savings: a modern continuous refiningprocess is fully automatic and needs minimum of
personnel attention. One worker, with a part-time job,can operate this installation (including necessary
cleaning and maintenance works).
Savings in chemicals: with high efficiency equipment(mixers, reactors, separators), reactive and chemicals
consumption is reduced when implementing a continuoscentrifugal separation system.
Increase in energy consumption: centrifugal separatorshave high electricity consumption. Thus, theimplementation of centrifugal separators will mean an
increase in the electricity demand of the mill. Aninstallation as described above, has a typical electricity
demand of 12 kWh per ton of oil.
Comparing the investment cost with estimated annualsavings, the payback period of implementing a centrifugalseparation system can be estimated to be about 5 years.
5.1.4 Use of Pressurised Water for Floor Cleaning
It is recommended to use hoses with automatic shut down and
pressurised water nozzles (water flow stops automaticallywhen the hose is left on the floor) to clean the floor, in order
to increase the efficiency of washing and save the water.
5.1.5 Improvement of Foam and Soap Removalfrom Fat Traps
Soap and foam is removed from the fat traps manually afterclosing the outlet of the last fat trap and raising the water
level. As outlet of the last fat trap is closed, the water rises andoverflows from the last trap to the drain. The skimming soap
and foam is, therefore, discharged in the drain.
It is rather simple to provide the fat trap with a mechanical ormanual system that can take out the fat from the traps without
the need of raising the water level. The simplest form is a pipeof about 6 diameter positioned across the water surface and
mounted at the ends in slip bearing. The pipe has a slot cut init lengthwise. The pipe is equipped with a means of rotatingand sliding arrangements so that the slot may be positioned atthe desired elevation and the pipe can be moved along the
chamber. The slot is left at the top normally. When it is
desired to skim fat, the pipe is turned until the slot is belowthe fat surface. The oil flows into the pipe to a sump at the
end.
The investment required is very low (about Rs.25,000) anddaily operation will benefit as well as the environment. Such
fat removers may be even fabricated locally at the industrys
own workshop.
5.1.6 Reorganisation of Water Systems
Total water consumption can be minimised by means ofreorganising the water scheme. This reorganisation consists
mainly in segregating the water according to its use and pre-treating, recirculating and finally treating/discharging each
separately. Though, there is a certain segregation of water inindustry, it could be improved, as some of the water types are
mixed up. This would result in a decrease in waterconsumption hence in a smaller size wastewater treatment
facility.
Recommendations on how to maintain the quality of each
type of water with the aim of keeping the cycles as close aspossible and with minimum addition of fresh water are
given below:
a) Process water :
The food industry is generally subjected to strict
requirements regarding quality of water that is in contactwith the product. In the previous sections, recommendations
to reuse and reduce the consumption of process water havealready been outlined. The final treatment for process water
is discussed in section 5.1.8.
b) Cooling and vacuum water:
Presently, edible oil mills either discharge the cooling water
into the drain or recirculate it in the vacuum system. It isrecommended to establish two separate semi-closed systems,
for cooling and vacuum water, providing both of them withcooling towers to dissipate heat. By maintaining proper water
quality it is possible to operate the cooling and vacuumsystems in a closed loop, requiring low make-up water
addition and decreasing the water consumption considerably.
For the vacuum water system an indirect cooling system is
recommended. Vacuum water should be cooled in a heatexchanger with cooling tower water before being recycled to
the vacuum system. Thus, there is no direct contact betweenthe two water systems, and the problem of odour and/or
presence of any organic compounds is avoided. The heatexchanger will need some cleaning, therefore it is advisable
to have two heat exchangers, one in operation while the otheris on stand-by.
For long lasting and smooth operation and efficiency of thecooling system it is necessary to avoid corrosion, scaleformation and micro-organism and bacteria development.
These problems are normally avoided by means of usingwater of an appropriate quality, applying some treatment
(such as filtration) and by dosing some additives.
Because of evaporation, there is an increase of salt content in
water, which results in the scale formation. This is normallymitigated with a continuous blowing down of certain amount
of water, which is replaced by fresh water.
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c) Recovery of steam condensate at boiler:Presently, edible oil industries recover only about 15-50% ofthe steam as condensate. The rest is drained as water or sentto the air at deodoriser.
Following are the advantages of recirculating the condensate:
Energy savings, as temperature of condensate is higherthan the intake water
Less water consumption Less cleaning cycles of the ion exchange resins Less chemicals consumption
With a good piping system, 80% recirculation rate ofcondensate is possible. A good piping system means highquality materials at heat exchangers and a good preventivemaintenance program (to avoid leakage and contamination ofwater with oil). 80% recovery of condensate means waterconsumption in the boiler will be less than half of presentconsumption.
Besides, much attention must be put on boiler water quality,as it influences directly the life, performance andmaintenance requirements of the boiler. Problems ofcorrosion and scale formation are also present in boiler waterwith even more influence on the system life. It is of high
importance to remove oxygen and CO2 from condensate inorder to avoid corrosion. This is normally done by injectingsteam at the degasifier and by dosing some additives.
5.1.7 Use of Flow Meters
Presently, none of the measuring system or device is in use inthe process and water systems. The use of flow meters tomeasure the quantities of various material and water streamscould prevent the unnecessary excessive dosing, therebysaving the resources.
5.1.8 Wastewater Treatment
After all in-process recommendations have been undertaken,the only way to improve the quality of the wastewaterdischarge is by means of an end-of-pipe treatment.
Knowing the potential and limitations of in-houseimprovements and cleaner technologies, ETPI has adopted anapproach based on both types (in-house and end-of-pipe) ofenvironmental solutions. The approach is two-phased. In thefirst phase, cleaner production technologies (CP) will beimplemented. Once the industrial unit has stabilised the
pollution and hydraulic loads, then end-of-pipe (EOP)treatment facilities will be designed and will be implementedin the second phase. It is anticipated that by adopting thisstrategy two benefits will be secured. These are: (a) duringimplementation of CP the understanding of the managementand technical teams about the environmental problems andsolutions will improve, and (b) the EOP environmentalsolutions will be much smaller and more cost effective.
In case of edible oil industries, end of pipe treatment will bedifferent for process wastewater and non-process wastewater.
Process Wastewater Treatment
Although process wastewater is small in quantity ascompared to non-process wastewater, but it is highly
polluted with oil and has high BOD, COD and suspendedsolid. After segregation, the estimated quantity of thisstream will be in the range of 500-800 litre/ton of
production. The average values of pollutants in processwater will be:
BOD 600 mg/LTSS 2400 mg/LOil 100 mg/L
The treatment will comprise of two main steps i.e. primary
treatment and secondary treatment.
Primary Treatment
The purpose of primary treatment is to remove the floatable
oil and grease and suspended solids. This will also reducethe BOD and COD concentration. This can be achieved
either by gravity settling or by dissolved air flotation. Both
options are discussed below, and the pertinent design dataand costs are given in Table 5-2 and Table 5.3:
Table 5.2: Design Data of Primary TreatmentSystem
Parameter
Gravity
Settling
Tank
Chemically
Enhanced
DAF
Units
Flow 100 100 m3/day
No of Tanks 1 1 No.Surface area 4 0.75 m2
Depth 2.5 1 mChemical
Mixing Tank
- 1 No.
Depth - 1 mArea - 0.5 m2
Capacity of airpump
- 1.5 bars
Removal EfficienciesBOD 35 35 %
TSS 65 65 %Oil up to 50 up to 30 ppm
Table 5.3: Cost Estimates for PrimaryTreatment System
Cost In Rs.Components
Option 1 Option 2
Screen 70,000 70,000Civil work 60,000 40,000
Piping, mechanical & electricalequipment
150,000 250,000
Contingencies @ 15 % 42,000 54,000
Total 322,000 414,000
Operational and maintenance
per annum
70,000 150,000
Option 1: Gravity Settling:The principle behind this process is the same as used by theindustry to separate water, oil and soapstock in soap pits.The objective of gravity sedimentation or flotation is toachieve a slow, smooth, tranquil and uniform passage ofthe liquid stream from the inlet end to effluent end. Duringthis process the oil particles rise to the surface because oflower density and are removed by skimming them from thetop. Suspended solids will settle at the bottom of the tankand will be removed in the form of sludge. The details withschematic diagram are shown in Figure 5.1. Option 2: Chemically Enhanced Dissolved Air
Flotation
In this process air is dissolved in the wastewater under apressure of several atmospheres. When the solution isdepressurised, the dissolved air is released as fine bubbles.Additives such as aluminium and ferric salts are used to
bind the oil droplets together and in doing so, create astructure (floc) that can easily entrap air bubbles. A few air
bubbles on a floc will rapidly buoy it to the surface.
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In principle DAF resembles gravity settling but the surfaceoverflow rates are four times or even more, as the rise rateof particles is greater with attached air bubbles. Also the oilremoval efficiency is very high in case of chemicallyenhanced air flotation. The details with schematic diagramare shown in Figure 5.2.
Secondary TreatmentThe remaining oil in wastewater after gravity settling or
dissolved air flotation is in a dispersed state or in solution.Removal of the dispersed oil and other biodegradableorganic compounds can be accomplished by biologicaltreatment such as activated sludge process or aeratedlagoons.
Both processes require high capital investment. Aeratedlagoons require a large area of land but operational costsare much lower than activated sludge.
Option 1 Aerated LagoonsAn aerated lagoon is a basin in which wastewater is
biologically treated on a flow-through basis. A largesurface area is required because of high retention time.Oxygen is supplied by means of surface aerators. In anaerobic lagoon most of the solids are maintained insuspension by mixing while some of the solids settle at the
bottom and decompose anaerobically. The soluble products
of the anaerobic decomposition would, in turn, oxidise inthe upper layer of the lagoon. If groundwater pollution isnot an issue than this method will be low-cost because ofmainly earthwork construction.
Option 2 Activated SludgeThe activated sludge process is an aerobic, biologicaloxidation process in which wastewater is aerated in the
presence of a flocculent, mixed microbial culture, known asactivated sludge.
Essential elements in this process are: the aeration tank inwhich the activated sludge and incoming wastewater arethoroughly mixed (the mixture is known as mixed liquor)and an abundant supply of dissolved oxygen is provided; afinal settling tank for separating the activated sludge fromthe treated effluent; a return sludge system to recycle thesettled activated sludge solids back to the influent; and a
sludge digester.
Operationally, biological waste treatment with the activatedsludge is typically accomplished using a flow diagram suchas that shown in Figure 5.3.
Table 5.4: Design Data of Secondary TreatmentSystem
Parameter Option 1 Option 2 UnitsFlow 100 100 m3/day
Aeration Tanks/LagoonsNo ofTanks/Lagoons
2 1 No.
Surface area 120 20 m2
Depth 2.5 3 mAir Requirement 47 47 CFM.Blower / SurfaceAerator Capacity
25 25 CFM
No of Blowers /Aerators
2 2 No
Secondary Sedimentation TanksNo of Tanks - 1 NoSurface area - 4 m2
Depth - 2.5 mSludge Digester
No of Tanks 1 No.Surface area 48 m2
Depth 6.5 mSludge Drying Beds
No of Tanks 2 2 No.Surface area 12 12 m2
Depth 1 1 m
Table 5.4: Cost Estimates for SecondaryTreatment System
Cost In Rs.Components
Option 1 Option 2
Civil work 1,660,000 900,000Piping, mechanical & electrical
equipment
250,000 430,000
Contingencies @ 15 % 300,000 200,000Total 2,210,000 1,530,000
Operational and maintenance
per annum
150,000 300,000
Non process wastewater
By observing good housekeeping this water can be keptfree of all pollutants, except for TDS. TDS can only be
removed by reverse osmosis (R.O), and the water can berecycled but R.O. treatment is very expensive.
5.2 Solid WasteMeasures, which could be taken to reduce and properly
handle the solid wastes, are given in the following sections:
5.2.1 Improvement of Waste Management and Land FillingThere are a number of possibilities available for improving
the present waste management system. The investmentinvolved in such improvements is limited, as many of them
are related to good working practices.
It is of the utmost importance for a food industry to offer aclean and hygienic surrounding. In order to guarantee this,
waste management procedures should be issued out andimplemented. Furthermore, the management should ensure
that the procedures are regularly followed by workers.
The behaviour of each type of waste and the potential risks to
environment and human health differ very much, therefore,they must be managed, stored and disposed off separately.
The control measures that can be implemented to improvethe present situation are stated below.
a) Domestic/General waste::
It is recommended that containers should be provided toavoid uncontrolled dumping of waste inside the plant. Closedcontainers should be used to prevent the spillage of waste
and to avoid odour nuisance. Furthermore, it isrecommended to increase the awareness of employees
regarding waste by arranging a certain number of short andinformal training sessions for all employees and by placing
posters in strategic places, such as: canteen, tea shop, near
the waste containers, etc.
The containers must be regularly collected and emptied at a
local landfill, to avoid over spillage and dumping of waste inthe containers surroundings.
b) T in scrap:
The management for tin waste can be improved to get moretidy and organised storage in the factory. In order to get a
better price for the recycled tin, it is recommended to avoidmixing it with other kind of waste and avoid longer storage
time.
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Figure 5.1: Gravity Settling Tank
Figure 5.2: Chemically Enhanced Dissolved Air Flotation
Figure 5.3: Process Flow Diagram of Activated Sludge System
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c) Sludge fr om water ponds, fat traps and raw oil tanks:
Water ponds: It is recommended to clean the waterponds once every two months, and to dispose offthis sludge in a municipal waste landfill.
Fat traps: It is recommended to clean the fat trapsregularly (once every 3 months). The sludge
generated as a result of this cleaning process can be
used in the soap section.
Raw Oil Tanks: It is recommended that raw oil tanksbe cleaned every 3 months, so that the layer of
sludge at the bottom of the tank is as thin aspossible. By keeping the sludge layer thin, the
degradation of oil is minimised and the formation ofsludge is, therefore, minimised.
d) Spent earth:Cleaning activity of the scraped earth from process buildingcan be simplified by installing an external vertical chute and
a storage area down the chute, so that the spent earth can bedischarged out of the building through a window and the
chute. It is recommended to cover the area where the spentearth is piled with a simple roof to avoid getting it wet during
rains and dispersion by wind and water.
e) Spent lubricants:
Spent oil and lubricants are considered hazardous waste and
should only be sold to an authorised waste dealer, who isresponsible for its correct treatment.
5.2.2 Use of Tankers with Internal Coils toMinimise Sludge
To avoid oil losses and to minimise sludge formation, the tank
trucks must be provided with proper insulation and internalheating coils. This could reduce the oil losses during storage
and handling by 50 %. This reduction can be estimated astotal oil loss savings of about 0.05% of the oil processed.
Providing internal coils to tank trucks would be a difficult task
to be performed by a single mill, and it is very difficult toforce the carrier to make the investment needed for that.
However, this is something that could be discussed and doneon a sectoral basis.
5.2.3 Increased Recycling of Nickel Catalysts
Nickel catalyst is presently being recycled at a ratio of 90%fresh to 10% recycled in some industries. This recycling ratio
is very low. Normally, edible oil mills reuse up to 80% ofrecycled catalyst. It is recommended to perform some trials
with increased catalyst recycling in order to see what is themaximum recycling ratio that can be achieved.
Another possibility for improving nickel catalyst recovery is
the use of centrifugal separators instead of filter press.
5.2.4 Recovery of Oil from Spent Earth
Oil mills are presently producing carbon oil from spent earth
by adding caustic soda and heating. This way the oil content
in spent earth is used to make a by-product, while at leastpart of this oil content can be recovered as a product, i.e.
edible oil. This can be done in