3 Environmental Impacts
The major problem met by the vegetable oil industry is wastewater, both quantitatively and qualitatively. Wastewater generation in an edible oil industry can be
divided into two categories:
• Wastewater generated directly from processes, e.g., neutralization, washings, etc.
• Wastewater generated from auxiliary systems, e.g., cooling and vacuum
systems, etc.
Wastewater generated from both sources varies significantly in pollution load and
concentration. Process wastewater contains high amounts of BOD, COD, oil and
grease, TSS, TDS, and nickel while wastewater generated from the auxiliary systems
is huge in quantity and relatively higher in temperature. It sometimes contains traces
of VOCs. Boiler condensate recovery system is not efficient in some and practically
non-existent in most.
Most of the water used for neutralization and deodorization in vegetable oil
processing facilities ends up as wastewater with a high organic load. The complexity
of wastewater sources makes such wastewater hard to treat. The sources of wastewater can be listed as cleaning of greasy floors and equipment, leakages, heat
exchangers, gas scrubbers, barometric condensers, process water from the refining
plant, and soap-stock splitting effluents. Typically, vegetable oil refinery wastewater
contains used chemicals including alkalis such as caustic soda and sodium carbonate; heavy metals from bleaching earth; acids such as phosphoric acid, citric acid,
and sulfuric acid; Ni catalysts; and methylates. Also, pesticides used during the
growth of vegetable oilseed have been found in vegetable oil processing industrial
wastes. Additionally, vegetable oil refinery wastewater contains chemical compounds like phenol, heavy metals from bleaching earth, catalysts used in the
hydrogenation process, oxidizable substances, and fats and oils to lesser degree.
Because of quantity and characteristic variations and complexity, wastewater treatment to meet the desired effluent standards is complicated, and the selection of
wastewater treatment method depends on many local conditions and, therefore,
cannot be standardized.
Solvents such as acetone, ethanol, and methanol are sometimes used instead of, or
to supplement, hexane in the extraction process. Hexane can cause health problems
in relatively low concentrations and other dangerous chemicals, including strong
acids and bases, present significant health and safety hazards.
Besides liquid waste, solid waste and air emissions are also generated. Solid
wastes include spent earth, filter cloth, and spent catalyst. Spent earth and spent
catalyst are in slurry form and are combined together to extract before their final
disposal. Also, during production of vegetable oil, some by-products, such as oils for
animal feed or pharmaceutical products, are often produced by further processing of
residues. This processing can reduce solid waste production, including fractions like
spent bleaching earth that can be reused for energy production through direct
incineration or biogas production either on-site or at another location. Citric acid
8 Vegetable Oil Refining Wastes
333
The major problem met by the vegetable oil industry is wastewater, both quantitatively and qualitatively. Wastewater generation in an edible oil industry can be
divided into two categories:
• Wastewater generated directly from processes, e.g., neutralization, washings, etc.
• Wastewater generated from auxiliary systems, e.g., cooling and vacuum
systems, etc.
Wastewater generated from both sources varies significantly in pollution load and
concentration. Process wastewater contains high amounts of BOD, COD, oil and
grease, TSS, TDS, and nickel while wastewater generated from the auxiliary systems
is huge in quantity and relatively higher in temperature. It sometimes contains traces
of VOCs. Boiler condensate recovery system is not efficient in some and practically
non-existent in most.
Most of the water used for neutralization and deodorization in vegetable oil
processing facilities ends up as wastewater with a high organic load. The complexity
of wastewater sources makes such wastewater hard to treat. The sources of wastewater can be listed as cleaning of greasy floors and equipment, leakages, heat
exchangers, gas scrubbers, barometric condensers, process water from the refining
plant, and soap-stock splitting effluents. Typically, vegetable oil refinery wastewater
contains used chemicals including alkalis such as caustic soda and sodium carbonate; heavy metals from bleaching earth; acids such as phosphoric acid, citric acid,
and sulfuric acid; Ni catalysts; and methylates. Also, pesticides used during the
growth of vegetable oilseed have been found in vegetable oil processing industrial
wastes. Additionally, vegetable oil refinery wastewater contains chemical compounds like phenol, heavy metals from bleaching earth, catalysts used in the
hydrogenation process, oxidizable substances, and fats and oils to lesser degree.
Because of quantity and characteristic variations and complexity, wastewater treatment to meet the desired effluent standards is complicated, and the selection of
wastewater treatment method depends on many local conditions and, therefore,
cannot be standardized.
Solvents such as acetone, ethanol, and methanol are sometimes used instead of, or
to supplement, hexane in the extraction process. Hexane can cause health problems
in relatively low concentrations and other dangerous chemicals, including strong
acids and bases, present significant health and safety hazards.
Besides liquid waste, solid waste and air emissions are also generated. Solid
wastes include spent earth, filter cloth, and spent catalyst. Spent earth and spent
catalyst are in slurry form and are combined together to extract before their final
disposal. Also, during production of vegetable oil, some by-products, such as oils for
animal feed or pharmaceutical products, are often produced by further processing of
residues. This processing can reduce solid waste production, including fractions like
spent bleaching earth that can be reused for energy production through direct
incineration or biogas production either on-site or at another location. Citric acid
8 Vegetable Oil Refining Wastes
333