The chemical sector plays a significant role in the European economy, contributing with a 30% of the world’s total chemical production, employing 1.2 million people and generating around €550 billion in sales. By adopting measures to increase resources and energy efficiency, and developing improved production processes, the European chemical industry is significantly reducing its overall environmental impact. In addition, innovation and new technologies are enabling chemical companies to develop sustainable solutions for society as a whole.
The chemical and pharmaceutical industries are very diverse businesses. Even though the total amount of different substances produced in the chemical and pharmaceutical industry might be big, the amount of unit processes and unit operations for the chemical reactions and processing and refining of products are typically limited. Water is essential in most chemical and pharmaceutical production units. It occurs as a medium, a product stream to refine or a waste water. For a specific production, the choice of unit processes and operations together with the choice of raw material and process equipment define the required water quality and quantity, which can vary in a wide range. A major part of the overall water consumption is used for steam generation and cooling.
In terms of water treatment, the chemical sector has historically focused on:
• the treatment of strongly polluted effluents,
• removal of trace elements,
• and the treatment of water, especially for cooling, with a strong emphasis on corrosion problems and chemical conditioning.
Water loop closure received limited attention. However, the chemical and pharmaceutical industries in Europe are aware of the importance to reduce their water use and emissions. Most companies have a commitment to reduce the amount of water used per unit of product produced. However, in some branches of the sector, e.g. the pharmaceutical industry, this might not be possible due to present regulations by the authorities.
Two chemical companies have joint forces in close collaboration with leading water treatment suppliers and RTO within AquaFit4Use with the aim to investigate several local and global water reuse scenarios.
Activities in AQUAFIT4USE
Objective: to reduce fresh water consumption by investigating various global and local water reuse scenarios and by testing selected technologies for total effluent treatment or removal of trace organics.
Topic 1: Membrane bioreactor technology as a core treatment step in water reuse
Membrane bioreactors (MBRs) have been evaluated for many municipal and industrial cases as an advanced treatment technology. Although some references already exist for chemical wastewater treatment plants, the question remains how well MBR technology can cope with the high variability and specific product streams appearing in the final effluent. In Aquafit4use, the application limits with regard to process reliability, stability and membrane lifetime are thus evaluated. MBRs are typically considered an excellent pre treatment for lifetime are thus evaluated. MBRs are typically considered an excellent pre treatment for further effluent polishing with e.g. reverse osmosis (RO). This aspect is also included in the evaluation.
MBR pilot trials have been performed at 2 test sites.
On one hand, the integrated production site of BASF in Antwerp, Belgium, was selected as the worst case scenario. It combines 54 production units in 4 production sectors, i.e. agricultural chemicals, plastics and fibres, finishing products and other chemicals. Three different MBR technologies were linked to the full-scale treatment plant and tested in parallel for 1 year (Figure 1). General conclusions are that stable operation was typically possible at fluxes between 10 and 15 l/m².h. Considering the whole test period, the required cleaning frequencies were quite high and recovery of the membranes sometimes unpredictable. The test results underachieved the expectations for a stable and reliable long-term full-scale application at this test site.
Simulations at various recoveries and with or without the addition of antiscalants confirmed that many ions were present in too high concentrations in the MBR permeates to allow a RO post-treatment. Thus, (part of) the hazardous scalants must be removed before the MBR permeates can be fed to a RO installation.
MBR pilot trials at BASF Antwerp
The second test site was located in Sweden (Perstorp Specialty Chemicals AB). Here, the experimental programme encompassed parallel treatments of the industrial wastewater in a pilot scale MBR unit including anoxic and aerobic process tanks and in the existing conventional activated sludge (CAS) treatment plant. The results showed that while the effluent from the MBR pilot was not improved as compared to the CAS facility with respect to conventional dissolved wastewater parameters, the biogrowth potential of the MBR effluent was significantly lower. The low biogrowth potential being a highly important quality improvement for most reuse options, it could be concluded that the effluent from MBR is significantly better suited than CAS effluent for reuse purposes at Perstorp.
Topic 2: Treatment trains for total effluent reuse or local reuse options
Experimental investigations at Perstorp not only focussed on comparing MBR treatment with CAS. Various treatment trains were tested for further polishing of both effluents. The objectives were to investigate the technical and economic feasibility for an improvement of the final effluent quality to a degree that allowed water reuse at the industrial complex. Reuse options might be considered directly based on the MBR effluent or on reuse of effluent after further upgrading.
Effluents from the CAS and the MBR were in trial runs post-treated in Denutritor for removal of biological growth potential, or with advanced oxidation technology (AOP) based on ozone or ozone/hydrogen peroxide to test the feasibility for further improvement of the effluent quality. Finally, the effluents from CAS/Denutritor and MBR, respectively, were treated in a RO pilot unit.
As mentioned before, the results showed that the biogrowth potential of the MBR effluent was significantly lower than for the CAS effluent and comparable to the effluent from the combination CAS/Denutritor. Therefore the effluents from MBR or from CAS/Denutritor are significantly better suited than CAS effluent for reuse purposes at Perstorp. The most attractive reuse option for the upgraded centralized effluent was identified as intake water for the water treatment to the boiler feed supply. Upgrading of the MBR-treated centralized effluent (or CAS/Denutritor with ultrafiltration) with RO is needed to remove the salts and it is also essential to reduce bio-growth potential before the RO treatment. Based on economic feasibility the suggested reuse scheme looks reasonably attractive for Perstorp as a step towards increasing production capacity without increasing the effluent discharge volume. This is important for Perstorp Specialty Chemicals AB as the effluent discharge volume today is the bottle-neck once production capacity increase is needed.
Technologies used in various treatment trains tested at Perstorp: Denutritor (top left), Advanced Oxidation Processes (top right), MBR (bottom left), RO (bottom right)
: MBR fouling measurements and potential of fouling reducing additives
VITO has adapted and tested the MBR-VFM (VITO Fouling Measurement) monitoring sensor for tests on chemical wastewater,. The concept of the MBR-VFM was developed within FP6 project AMEDEUS (contract 018328), funded by the European Commission. Where AMEDEUS targeted treatment of municipal wastewater, it was now the aim within AquaFit4Use to upgrade and validate the fouling measurement for harsh chemical wastewater and use it to evaluate the effectiveness and mode of action of various additives aiming at fouling reduction.
The MBR pilot testing at BASF Antwerp was complemented with fouling measurements and analyses, which consisted among others of filterability parameters, evaluation of reversible and irreversible fouling propensity and characterization of the mixed liquor properties. For most parameters monitored, the relation between mixed liquor characteristics or fouling indicators and on-line permeability was limited, absent or differed between the pilot units for unclear reasons, pointing to complex fouling phenomena in this matrix.
Because fouling in MBRs on chemical wastewater was mostly linked to variability in the wastewater composition, it seemed promising to test various fouling reducing additives to counter the negative impact of substances in the wastewater on fouling propensity. Out of 8 tested fouling reducers, the cationic polymers Nalco MPE50 and Adifloc KD452 and 2 novel cationic polymers were found to have a positive effect and high effectiveness on mixed liquor filterability. This positive impact was confirmed during parallel laboratory-scale MBR trials where one of the novel products was added.
- sustainable water management
- sustainable water use in chemical, paper, textile and food industries
- seventh framework programme theme 6 - environment