Application of CAF, DAF, MBR y Reverse Osmosis processes in the treatment and reutilization of wastewater in the cosmetic industry

1. Introduction: wastewater of the cosmetic industry

The cosmetic industry evolves as a function of technological advances, the demand for products and the increasingly restrictive environmental limitations of the emission of industrial waste. In addition, the cosmetic industry is a type of industry that consumes a large amount of water, which is why treatments are increasingly being proposed for the reuse of wastewater and not only to comply with the limits of discharge to the sewage network.

The concept of wastewater reuse finds its place within the CIRCULAR ECONOMY AND ENVIRONMENTAL SUSTAINABILITY, an ideology on the rise and that more and more industries apply to its principles and procedures.

The wastewater generated in the cosmetic industry is characterized by its high content of suspended solids, chemical oxygen demand (COD), oils and fats (colorants, oils and emulsions). The traditional treatments of this wastewater have been based on physical-chemical coagulation-flocculation processes for the separation of suspended solids and the organic matter associated with them.

However, given the tightening of discharge limits and the increasing need for water reuse, more and more intensive and efficient treatment processes are applied that include advanced technologies to meet the quality requirements of reuse.

In recent years, various technologies of physical, chemical and biological nature have been tested. One of the most efficient processes is the application of MBR membrane bioreactors preceded by a carefully designed physical-chemical pre-treatment. In addition, with the incorporation of advanced filtration treatments with Reverse Osmosis membranes, much higher qualities can be achieved.

2. Technologies for wastewater treatment and reuse in the cosmetic industry. Proposed process by SIGMA.

The treatment of wastewater from the cosmetic industry, in order to comply with discharge laws and obtain water of sufficient quality for reuse, must be efficient and allow future expansion of its capacity given the growing demand and production of this sector.

The most efficient configuration is the combination of processes for separating oils, fats and suspended solids (physical-chemical pre-treatment), followed by an advanced biological treatment and a tertiary treatment through the application of reverse osmosis membrane technologies.

SIGMA's experience and knowledge in water treatment engineering allow us to propose the following process for the treatment and reuse of wastewater from the cosmetic industry. This treatment can be modified and adapted for each case and type of water, however, maintaining the principles of each stage.

Pre-treatment: removal of oils, fats and suspended solids.

Cavitation air flotation CAF for the separation of oils and fats and large solids.

Coagulation – flocculation and neutralization to agglomerate suspended solids.

Dissolved air flotation DAF for the separation of suspended solids (previously agglomerated) and part of the organic matter.

Biological treatment: removal of COD and nutrients.

Membrane bio-reactor MBR with aeration system and Ultrafiltration.

Tertiary treatment: maximal quality of the effluent.

Application of Reverse Osmosis (RO) membranes to reach extraordinary water quality.

Sludge treatment.

The generated sludge, both in the pre-treatment and in the MBR and RO must be correctly managed and treated. An effective treatment for typical water sludge from the cosmetic industry is stabilization by digestion (it can be aerobic or anaerobic) and subsequent dehydration and thickening by means of a centrifuge.

Figure 1 shows a simplified scheme of the complete treatment of wastewater from the cosmetic industry for its reuse and/or discharge to the sanitation network.

2.1. Oils and fats separation: CAF equipment

Cavitation air flotation CAF separation systems are generally simple, direct-operating systems.

The SIGMA ACAF System is extremely simple to operate. It does not contain complex mechanical equipment and does not require manual intervention. The mechanical equipment consists of only two pieces and does not require air compressors, pumps or compression tanks.

It is an extremely efficient grease and oil separator with 99% yields, with a very low maintenance cost. These CAF systems allow treating water of highly variable flow and concentration with excellent results in all cases.

The wastewater enters a small aeration section in which the cavitation aerator is installed, rises through the aeration section, where it mixes with the micro bubbles produced by the cavitation aerator.

This aerator is a device to transfer air from the upper area of the surface to the lower area through a suction tube. The aerator works based on the principle of creating a vacuum in the swirls of the air discharge tubes that rotate submerged in the liquid.

Air flows through the machine shaft from the top of the surface to fill the void and form micro bubbles. The bubbles rise to the surface in a helix. The oxygen contained in the air is transferred to the liquid.

The density imbalance between the air and the water mass creates an updraft that draws the fat particles and suspended solids to the surface. The micro bubbles adhere to the particles and, upon reaching the surface, the particle is supported and kept floating by the micro bubbles. At the surface the air moves radially pushing the oils and solids.

The floated material is periodically and automatically swept by a skimmer mechanism that pushes the surface layer from the inlet of the flotation tank towards the outlet end and is conducted to the discharge channel.

The clarified water, through a submerged outlet, is led to an overflow chamber before passing to the discharge. The overflow controls the depth of the liquid in the flotation tank, preventing the oil sheet from flowing into the solids discharge channel.

Recirculation pipes are arranged along the bottom of the flotation chamber which ensure a continuous flotation of the tank contents, even in the event that the supply is interrupted.

SIGMA offers a wide range of SIGMA ACAF equipment that can be consulted at the following links:

ACAF Flotation System

ACAF data sheet

Advantages of the SIGMA ACAF systems:

• Simple operation: it does not contain complex mechanical equipment and does not require manual intervention.

• Wide range of treatment capacity: there are SIGMA ACAF equipment that allows treating up to 500 m³/h, and can even be adapted to the treatment of higher flows through special systems.

• Excellent results: oil and grease removal in a SIGMA ACAF system is 99%.

• In addition to the elimination of oils and fats, these equipments support the rest of the treatment since they allow the separation of a high percentage of suspended solids.

2.2. Physical – Chemical treatment and DAF equipment

The physical-chemical treatment consists of the coagulation, pH adjustment and flocculation processes for the agglomeration of the suspended solids and the installation of a clarification system via dissolved air flotation DAF for the effective separation of the solids and clarified water.

The purpose of coagulation is to destabilize colloidal matters. The reaction takes place by adding a coagulant, (poly aluminium chloride, organic coagulants, etc.)

The function of neutralization is to adjust the pH resulting from the coagulation process to a pH of around 7 by adding bases or acids, the dosage is controlled by a pH meter.

Flocculation is the addition of a polyelectrolyte of specific polarity for each specific case (anionic or cationic) destined to add together the clots formed in the previous process to have flocs of sufficient size for the separation of the water from them (clarification). perform efficiently and quickly in 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: a system through stirred tanks where reactions take place or a special system in plug-flow flocculation device SIGMA PFL. The technology is selected and designed based on the flow to be treated and the required product dosages.

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 fibers.

The coagulation-flocculation sequence followed by DAF is a very common and widely used concept in the treatment of wastewater from the cosmetic industry and has proven over the years to be efficient in performance and costs, both operational and consumption of chemicals and energy when properly designed. It is an effective and robust pre-treatment for general industrial wastewater treatment.

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 sedimentable 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 skimmers system. Part of this stream of clarified water will be redirected by the recirculation pump to enter the compression and air saturation system.

SIGMA offers a wide range of DAF flotation 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 1000 m3/h, compact equipment are 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 flow rates, each equipment is specially designed depending on the flow to be treated and its characteristics:

• SIGMA DAF FPAC: for flow rates between 5 and 160 m3/h with a very high solid load. It is a high-performance cross-flow system

DAF-FPAC datasheet

• SIGMA DAF FPBC: for flow rates between 10 and 250 m3/h of low to medium solid loads. The equipment applies counter current flow with high performance.

DAF FPBC datasheet

• SIGMA DAF FPHF: for flow rates between 200 and 1000 m3/h and high content of suspended solids. A combination of counter flow and cross flow is used for optimal performance.

DAF-FPHF datasheet

• COMPACT DAF: compact equipment installed in skids, in which the coagulation-flocculation system and the DAF are unified, allowing space savings and energy consumption.

DAF-FPAC COMPACT datasheet

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 usually achieved by conventional settlers).
• Easy to operate with simple, adaptable and effective control systems.
• Known technology, flexible to each case and robust.

2.3. Membrane bio-reactor MBR with Ultrafiltration membranes

For the treatment of wastewater from the cosmetic industry, an aerobic biological process of activated sludge is commonly and effectively applied in a membrane bio-reactor MBR.

MBR reactors combine the biological treatment process with Ultrafiltration membranes as a separation technology for water and sludge. The biological process can be aerobic, anoxic or anaerobic, for the treatment of wastewater from the cosmetic 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 minimum production of excess sludge, 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.

The aerobic biological process consists of the degradation of the organic matter contained in the wastewater to be treated through the action of microorganisms in the presence of oxygen. During the process, oxygen is injected into the reaction medium (made up of waste water and microorganisms) through aeration systems.

For typical wastewater from the cosmetic industry, it is recommended to apply special fine bubble aeration diffusers and the use of a rigorous control of dissolved oxygen for optimal and reduced energy consumption.

When an aerobic process is applied and therefore aerators are installed inside the reactor medium, it is recommended to use the configuration a) of Figure 13 of an external membrane module so as not to hinder the transfer of oxygen to the reaction medium.

The following conditions must be met in the reaction media for a correct development of the process:

• Control the pH between 6.5 y 8.5.
• Temperature must be kept between 10 y 40ºC. Optimal performance is reached at 20 - 35ºC.
• The absence of toxic substances or inhibitors of the process, such as heavy metals, excessive salinity, etc.

The mixed liquor from the biological reactor, with a very high content of MLSS, passes to the Ultrafiltration membrane zone where the filtration takes place.

The membranes separate the solid part and the liquid (denominated "permeate") is sent to a storage tank while the solids are sent back through a recirculation circuit to the biological reactor.

One of the most important aspects of an MBR reactor (and of any technology that applies membranes) is the cleaning system since they are susceptible to fouling and clogging that reduces their efficiency and life cycle. The submerged membranes are periodically cleaned by washing by running water in the opposite direction using the permeate itself and air used as the driving force.

Occasionally, the membrane modules will be submerged in a cleaning solution applying chemicals (usually acids).

Sludge in excess of the biological process that needs to be purged to maintain a constant biomass concentration, coming from cleaning, are sent to the sludge treatment described in 2.5.

SIGMA, in collaboration with KOCH, designs its MBR plants to optimize the performance of the membranes through the specific design of the hydraulic systems of this section in order to control and optimize the flow rates through the membranes, reducing the energy required to achieve longer filtration cycles and achieve a longer membrane life.

MBR reactors for wastewater from the cosmetic industry designed by SIGMA use hollow fiber membranes with outside-inside flow, all joined in bundles or modules that are immersed in the biomass in the membrane zone. They have a high mechanical resistance. The membranes are arranged in series of bundles mounted on multiple stainless steel structures with supports. Ultrafiltration membranes allow to retain and eliminate from the clarified water the following pollutants:

• Suspended solids
• Bacteria
• Virus
• Proteins
• Colloids

Figure 15. Surface area of hollow fiber ultrafiltration membranes, zoomed 10000x.

The key aspects of Ultrafiltration membranes and their modular design are as follows:

• Special design of the ends eliminates fouling problems.
• Integral support of the membranes, allows the circulation of air, permeate and counter current washing actions without the need to modify the configuration and with energy savings.
• Manufactured in an integral and robust assembly for easy installation and maintenance.
• The membranes are reinforced by braiding to achieve a very high mechanical resistance essential for their durability, especially in harsh biological environments and which ensures a low susceptibility to breakage and fouling. This gives the process high operational safety.
• The modules present great flexibility to be able to vary, according to each case, the following elements: number of rows per module, number of elements per row, fiber length (module height), packing density to achieve different filtering surface areas. Thus allowing a total adaptation of the dimensions of the module according to the needs of the application.

The effluent from a properly designed MBR process for the treatment of wastewater from the cosmetic industry has sufficient quality to reuse the water in some processes, the limits of which are established by local authorities.

Advantages of the SIGMA MBR plants:

• Continuous discharge of the clarified water.
• Total separation (100%) of the sludge and absence of suspended solids nor particles in the clarified water.
• Very high organic load removal performance (> 90% removal of COD and BOD₅).
• Very high concentration of BIOMASS inside the reactor: between 6,000 and 12,000 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.
• Minimum generation of sludge.

In addition, 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 SIGMA SMBR units offer the following advantages:

• They are a PLUG&LAY solution.
• They offer maximum reliability and durability.
• They allow to obtain a constant quality of the effluent.
• It is a compact plant that allows the modular addition of Ultrafiltration membranes.
• Its operation and control are simple and the equipment is robust.
• They have high resistance to oxidizing agents.

SMBR Datasheet

SIGMA DAF SMBR plants are specifically designed for each wastewater stream to be treated. The range of capacities is between 20 - 100 m³/day.

2.4. Reverse Osmosis

Although the clarification of the previous MBR process has a very high quality to be applied as reuse water in certain processes, not all the destinations of this reuse are admissible by local legislation.

In order to expand the possibilities of reuse, an even more polished quality of the effluent is required, for this, Reverse Osmosis (RO) technologies are used as the final stage (polishing) of the treatment to obtain water for reuse.

The RO membranes allow to remove from the water, in addition to the pollutants already eliminated by Ultrafiltration, the following:

• Traces of high, medium and low molecular weight organic compounds.
• Bivalent and monovalent ions.

The rejected effluent of a RO system can be treated together with the rest of the sludge or it can even be dumped into the sewage network.

The flow fed to the RO is divided into two streams: permeate or fresh water suitable for reuse and concentrate or rejection.

The most efficient RO membranes work with cross flow: clarification is generated perpendicular to the inflow of the water.

With these membranes a recovery of reuse water of up to 75% of the treated stream can be achieved. Module configuration uses spiral membranes, a maximum filtration efficiency configuration.

The RO systems designed by SIGMA allow up to 15% fouling of the membranes or a decrease in flow due to this fouling without losing the fresh water production capacity of the system. The RO units have a control system that provides them with autonomy and automatic operation capacity with the minimum intervention of operating personnel.

These membranes incorporate safety and alert systems and equipment in order to protect the system and its components from failures caused by clogging, fouling, breakage, excessive mechanical stress, uncontrolled pressure, etc.

A common practice is the installation of two or more RO steps to achieve the best quality of clarified water.

The elimination yields of the RO processes applied to wastewater from the cosmetic industry are shown in Table 1. The yields are shown based on the effluent from the MBR process and the final clarification of the RO:

Table 1. Yields of Reverse Osmosis applied to the effluent of an MBR.

Advantages of the RO processes by SIGMA:

• Obtaining a clarification with the highest quality for reuse.
• Possibility of discharge the rejection into the sanitation network or recirculating it to the treatment plant.
• Recovery of up to 75% of the influent as clarified water.
• Modules installed on easy-to-attach brackets.
• Simple operation and maintenance.
• Robust equipment with high mechanical resistance.

2.5. Sludge treatment

The sludge generated in the physical-chemical process and the surpluses from the biological process are treated in a SLUDGE DIGESTOR. RO concentrate flow could also be included. Sludge digesters can be aerobic or anaerobic depending on the nature of the sludge and energy availability.

When subjected to a digestion process, the sludge will reduce its volume due to the partial transformation of the volatile compounds into water and due to an increase in the concentration of the dry matter present. Likewise, once digested, especially the physical-chemical sludge, they offer better dehydration and treatment conditions in the selected dehydration system (filter-press, centrifugal decanter, etc.).

3. SIGMA Case Study: Beiersdorf Manufacturing Tres Cantos S.L. - Madrid

Wastewater from the cosmetic industry is characterized by a high content of suspended solids, COD, oils and fats. Given the legal requirements of discharge limits and the increasing need for water reuse, more and more intensive and efficient treatment processes are being applied that include advanced technologies to meet the quality requirements of reuse.

In the case of Beiersdorf Manufacturing Tres Cantos S.L., SIGMA designs and builds a complete wastewater reuse plant, based on a physical-chemical process (CAF, coagulation - flocculation, DAF) followed by a biological MBR process.

Year: 2011

Project location:  Beiersdorf Manufacturing Tres Cantos – Madrid, Spain.

Objectives: Design and installation of a wastewater treatment plant to obtain very high quality water for reuse in the process. Treatment of the sludge generated in the plant.

Installed equipment:

• Oils and fats separator SIGMACELL ACAF.
• Equalization tank with aeration by diffusers AQUA-JET.
• Coagulation, flocculation and pH adjustment system (includes reagent preparation tanks and reaction tanks).
• Flotation system SIGMA DAF FPBC-PWF.
• Biological reactor MBR with external module of Ultrafiltration membranes.
• Aerobic sludge digestion reactor.
• Sludge dewatering with centrifuge

Capacity:  600 m³/day, with capacity for 900 m³/day in future manufacturing plant extension.

Table 2. Characteristics and performances of the SIGMA Case Study in the treatment of wastewater from the cosmetic industry for its reuse. Case of Beiersdorf Manufacturing Tres Cantos S.L.

Fats and oils are eliminated in the SIGMACELL ACAF equipment. The water is then homogenized and subjected to a carefully studied coagulation-flocculation process, for this, Jar-Test tests were carried out to determine the type and optimal dosage of coagulant (PAC with polyamide) and flocculant (cationic polyelectrolyte). The flocculated solids are separated in a SIGMADAF FPBC-PWF equipment that allows obtaining a very high-quality clarification. For the elimination of biodegradable organic matter, an MBR biological treatment system is installed with advanced Ultrafiltration membrane technology. This allows to obtain a very high quality of water that is recirculated and reused in the production process of the cosmetic manufacturing plant.

Figure 25. Process diagram of the wastewater treatment plant of a cosmetic industry designed and installed by SIGMA for reuse as process water, case of Beiersdorf Manufacturing Tres Cantos S.L.

Download case study

4. References

Artiga P. 2005. Contribución a la mejora del tratamiento biológico de aguas residuales de la industria de curtidos. PhD Thesis. Universidad de Santiago de Compostela, Chemical Engineering department.

Mohedano A.F., Monsalvo V.M., López J., Rodríguez J.J. Tratamiento de aguas residuales de la industria cosmética en un reactor biológico de membranas. Publications of Chemical Engineering Section, Universidad Autónoma de Madrid.