02 August 2021
Treatment and reuse of wastewater from the fragrance and essential oils industry
1. Fragrances and Essential Oils Industry
The sector of the Fragrances and Essential Oils industry can be included within the cosmetic industry, but with characteristics that make it different. The substances used in this industry are mainly solvents, alcohols and what stands out as a characteristic substance: Essential Oils.
Given the great growth in the demand for perfumery products, it is very important to introduce this industry and the effects on the environment within the current main pollution problems for the environment.
For the manufacture of perfumes, essential oils are used combined with fixatives and solvents (mainly alcohols).
Essential oils are substances that are obtained from the various parts of a plant (flowers, fruits, leaves, barks, roots ...) and have a complex chemical composition where aromatic compounds predominate.
They volatilize easily and due to their nature and high concentration they are a highly important polluting factor for the environment, especially for the water, if they are not treated properly.
The main composition of the oils is distributed as follows:
- Terpenic hydrocarbons (in a higher proportion)
- Aromatic components characteristic of each oil (to a lesser extent)
- Other components with preservative, antibiotic and aroma fixing functions.
The drying and crushing processes are applied to extract the Essential Oils from the different parts of the plants. This process requires the use of a large amount of raw material given the low extraction performance of the oils. In addition, it requires the use of enormous amounts of water.
In the manufacture of fragrances, the most widely applied process for the distillation of essential oils is steam distillation. This process is commonly applied because the essences to be extracted have the ability to be entrained by water vapour at boiling temperature.
Water heated to its boiling point, around 100ºC, produces vapours that secrete and separate the compounds responsible for the aroma, which are embedded and integrated into the steam stream.
This steam loaded with odorous substances is introduced into a refrigeration cabinet where it condenses, generating the “hydrolate”.
The hydrolate is subsequently decanted and the aromatic essences are separated from its aqueous phase and extracted for the final elaboration of the perfume.
Due to these special characteristics of the wastewater and the type of pollutant coming from the Fragrances and Essential Oils industry, if this water were discharged into the sanitation network, the municipal plant would quickly be saturated, so a decentralized treatment is what more suitable, both to treat water and to allow its immediate reuse.
2. Wastewater characteristics
The steam distillation process requires a high demand on water, and consequently generates a large amount of wastewater.
As described above, the part of the hydrolate that remains after the extraction of the aromatic essences is what is considered as wastewater.
It is mainly composed of:
- Fatty acids.
- Aromatic or closed ring structures (main pollutant, derived from the terpenes present in essential oil): esters, ethers, ketones, aldehydes, alkenes and alcohols.
Their structure is shown in Figure 1. These compounds, in a high concentration, have adverse effects on the environment and human health.
Figure 1. Main aromatic compounds present in wastewater from the Fragrances and Essential Oils industry.
This means that the wastewater from the Fragrances and Essential Oils industry is characterized from a physical-chemical point of view by its high content of organic load (plant remains, starch and organic structures of closed ring and double bonds. which implies great difficulty for its biological degradation that accentuates its refractory character), conductivity (due to the high concentration of salts) and oils and fats.
Table 1 shows the parameters of a typical wastewater from the Fragrances and Essential Oils industry:
Table 1. Typical characterization of wastewater from the Fragrances and Essential Oils industry.
Typical wastewater values
5000 - 20000
10000 - 20000
1000 - 4000
Oils and fats
2000 - 4000
3. Treatment and reuse of wastewater
The main objective when designing a wastewater treatment process from the Fragrances and Essential Oils industry is the elimination of organic load, salts, oils and fats.
But this industry has such a high demand for water that the trend is not only to treat the water but to polish it for reuse. Therefore, a suitable selection of the technologies to apply is a key point in the development of a plant
The process that has so far proven most effective in producing very high quality treated effluents is described below.
As indicated in the previous section, the great difficulty for the biological elimination of the organic load does not allow the direct application of conventional technologies through bioreactors, but rather makes the incorporation of a highly effective pre-treatment for the elimination of part of the organic matter and its transformation into easily separable compounds, in addition to the elimination of oils and fats.
In this way, the wastewater is conditioned to be treated by biological processes.
It is extremely important to maintain a close control of pH, phosphates and nitrogen to avoid the malfunction of the biological process.
Figure 2. Pre-treatment process and biological treatment effectively applied in wastewater from the Fragrances and Essential Oils industry.
Table 2. shows the achievable yields in the elimination of the parameters shown in Table 1 through the proposed sequence of technologies:
Table 2. Achievable removal performances by means of a physical-chemical and DAF clarification pre-treatment followed by a biological treatment.
Oils and fats
This process allows the reuse of wastewater and also generates a negligible amount of sludge and minimizes the carbon footprint.
A sequence of physicochemical treatment by coagulation, flocculation and pH adjustment followed by a clarification stage is generally and effectively applied.
For this clarification stage, a highly efficient process is dissolved air flotation or DAF.
The purpose of coagulation is to destabilize colloidal matter. The reaction occurs by adding a coagulant, for example iron salts, poly aluminium chloride, organic coagulants, etc.
The function of neutralization is to adjust the pH by adding bases or acids.
Flocculation is the addition of a polyelectrolyte of specific polarity for each specific case (anionic, cationic or non-ionic) destined to add the clots formed in the previous process to have flocs of sufficient size for the separation of water from them (clarification) is carried out efficiently and quickly in the subsequent flotation equipment.
To know the types and necessary doses of coagulants, flocculants and pH adjustment products, it is necessary to carry out tests on wastewater. At SIGMA we can carry out these tests known as Jar - Test in our SIGMALAB facilities.
SIGMA has two types of coagulation technology, pH adjustment and flocculation: stirred tank system where reactions take place or special continuous plug flow system SIGMA PFL.
The technology is selected and designed based on the flow to be treated and the required product dosages.
Figure 3. Physicochemical processes designed and installed by SIGMA. Left: process in tanks and right: SIGMA PFL flocculation unit.
The flocs formed in the coagulation-flocculation process are of an ideal size to be separated from the water in a DAF dissolved air flotation unit. The DAF technology developed by SIGMA combines the principles of dissolved air flotation and sedimentation with optimal equipment design.
DAF technology is an efficient and robust separation process for oils, fats, colloids, ions, macromolecules, microorganisms and fibres.
During DAF treatment, compressed air is introduced into a recirculating clarification stream, dissolves in the liquid medium, and subsequently generates bubbles of 30 to 50 µm when released through a dispersion head into the flotation chamber. The coagulated and flocculated particles adhere to the bubbles and float to the top of the DAF unit, where they are removed mechanically.
The settleable matter descends into the sediment compartment at the bottom of the DAF unit and is discharged by a sludge extraction system, usually worm gear.
The clarified water leaves the DAF unit via an adjustable supernatant system. Part of this stream of clarified water will be redirected by the recirculation pump to enter the compression and air saturation system.
The coagulation-flocculation sequence followed by DAF is a very common and widely used concept in the treatment of wastewater from the Fragrances and Essential Oils industry and has proven over the years to be efficient in performance and costs, both operational as well as chemical and energy consumption when properly designed. It is an effective and robust pre-treatment for general industrial wastewater treatment.
SIGMA offers a wide range of DAF equipment, specially designed according to the flow to be treated and space requirements, from equipment that can treat flow rates of 5 m3/h to equipment that can treat 1,000 m3/h, compact equipment is also offered. The treatment capacity of SIGMA DAF equipment covers pollutant load ranges of up to 40 kg of solids per flotation surface.
We have a wide range of high-performance equipment suitable for different flows, each equipment is specially designed depending on the flow to be treated and its characteristics, for more information we share the technical specifications of each of these equipment:
Advantages of SIGMA DAF systems:
- High and constant clarification quality.
- Quick commissioning.
- Minimal sludge production (sludge concentrations of up to 5%, much higher than the achieved by conventional settlers)
- Easy to operate with simple, adaptable and effective control systems.
- Known technology, flexible to each case and robust.
3.2. Biological treatment
The main objective of a biological process is the elimination of the organic load of the residual water through the action of microorganisms in biological reactors.
Generally, conventional activated sludge reactors with anoxic and aerobic zones are used to also achieve the elimination of nutrients, but a more efficient biological system are membrane bioreactors or MBR.
MBR reactors combine the biological treatment process with Ultrafiltration membranes as a separation technology for water and sludge.
The biological processes can be aerobic, anoxic or anaerobic, for the treatment of wastewater from the Fragrances and Essential Oils industry, an aerobic treatment is commonly applied.
The application of Ultrafiltration membranes as clarification technology allows reaching very high concentrations of biomass within the reactor, between 6000 and 12000 mg/L MLSS (mixed liquor suspended solids), which entails a high performance of the biological process at the same time as a production of sludge in minimal excess, therefore, the volumes of this type of reactors are much smaller than those used in conventional biological processes.
MBR processes can be designed so that the membrane zone or tank is located outside the reaction tank or inside.
Figure 4. Scheme of the MBR biological wastewater treatment process: a) external membrane module and b) internal or submerged membrane module. Adapted from Artiga 2005
At the outlet of the MBR biological reactor, very clean water of remarkably high quality is obtained to be able to be reused as service or process water.
A detailed description of the SIGMA MBR systems can be found in the following article, which describes the process designed and applied by SIGMA to the treatment and reuse of water from the cosmetic industry, an industry closely related to Fragrances and Essential Oils: Application of CAF, DAF, MBR y Reverse Osmosis processes in the treatment and reutilization of wastewater in the cosmetic industry.
Advantages of the SIGMA MBR plants:
- Continuous discharge of clarified effluent.
- Full separation (100%) of the sludge and presence of no solids in suspension or particles in the clarification.
- Very high organic load reduction performance (> 90% COD and BOD5 removal).
- Very high concentration of BIOMASS inside the reactor: between 6000 and 12000 mg/L MLSS.
- Low reaction volumes and space saving.
- High resistance to oxidizing agents.
- Very high and CONSTANT quality of the water discharged with the possibility of REUSE.
- Minimal sludge production.
In addition to the implementation of modules attached to an MBR system, SIGMA designs, builds and installs compact MBR plants that incorporate the reaction zone (includes anoxic zone and aeration zone) and filtration in the same equipment. The equipment SIGMA SMBR offer the following advantages:
- PLUG&LAY solution.
- Maximum reliability and durability.
- Constant quality of the effluent.
- Compact plant that allows for the modular addition of UF membranes.
- Operation and control are simple and robust.
- High resistance to oxidizing agents.
SIGMA DAF SMBR plants are specifically designed for each wastewater stream to be treated. The range of capacities is between 20 - 100 m3/day.
Although the water treated by these technologies is of high enough quality for reuse, there are treatment alternatives that can be applied:
Treatment using advanced oxidation processes such as Fenton (these alternatives are installed in extreme cases where the COD is so refractory that it cannot be completely removed by the process described above).
Reverse Osmosis as a tertiary treatment to reinforce the quality of reuse water.
However, these technologies involve a more complex installation, as well as higher energy consumption, with the only advantage that the facilities are smaller than the main process proposed and can be used as support.
4. Example of SIGMA Case Study
SIGMA's experience in treating wastewater from the Fragrances and Essential Oils industry is extensive. Below is an example of a Case Study.
To obtain more information about the processes offered by SIGMA, for this industry and any other type of industry in general, do not hesitate to contact us in the form on the right, or at the email email@example.com, or by calling us at +34 972 223 481.
Aceites Especiales del Mediterráneo S.A. (AEMEDSA) is a world leader in the manufacture and marketing of white mineral oils and natural sulfonates. Its industrial activity is combined with the fulfilment of the Environmental Responsibility commitments.
The AEMEDSA wastewater treatment installed by SIGMA allows to comply with the current requirements for the discharge of industrial wastewater and offers the possibility of reusing the water in the process.
SIGMA installed a complete pre-treatment consisting of a physical-chemical process and DAF clarification. For the biological treatment, the previously existing reactor in the old plant was reconfigured, which consisted of an SBR ‘sequencing batch reactor’ system with poor performance, by a continuous aeration process accompanied by a secondary DAF clarifier.
Project location: Valle de Escombreras, Cartagena, Murcia.
Objectives: Modify the current wastewater treatment system, which is not being effective, to comply with current discharge requirements and the possibility of water reuse.
Figure 5. Wastewater treatment plant of an Essential Oils industry designed and installed by SIGMA, case of AEMEDSA.
Installed equipment and technologies:
- Homogenization tank with JET aeration system.
- Sigma PFL system for in-line coagulation-flocculation.
- Clarifier SIGMADAF FPAC model CPL15.
- JET aeration system as new configuration of the biological reactor.
- Secondary clarification system SIGMADAF FPAC model CPL20.
Capacity: 100 m3/day.
Table 3. Characteristics and performance of the SIGMA Case Study in the treatment of wastewater from the Essential Oils industry. AEMEDSA case.
fluctuant, average of 5500 mg/L
The wastewater is homogenized in a tank provided with aeration and is pumped to a SIGMA PFL system in which coagulation, flocculation and pH adjustment are carried out. The DAF FPAC-CPL15 primary clarifier allows the separation of the flocs generated, eliminating fats, oils, solids in suspension and part of the organic matter.
In the biological reactor, the removal of all organic matter and nutrients is carried out, a DAF FPAC-CPL20 is installed as a secondary clarifier. The discharged water has very high quality and, in addition to being discharged into the sanitation network, it can be reused in the process. The sludge generated in the process is thickened and dewatered by a centrifuge equipment.
Figure 6. Process diagram of the wastewater treatment plant of an Essential Oils industry designed and installed by SIGMA for discharge and possible reuse as process water, in the case of AEMEDSA.
Ortuño M. 2006. Manual práctico de aceites esenciales, aromas y perfumes. 2006. Aiyana Ediciones.
Poch J. 2007. La perfumería. Casa Editorial Bailly - Bailliere.