ARC is in the process of developing research lines on strategic topics in order to utilize synergies among the ARC members and with partnering universities. Also these research lines should assist in making connections with utilities and other stakeholders. One of the first research lines to be developed is Membrane Technology. To explore opportunities for collaboration and develop the Membrane Technology research line, a workshop was held on January 12 and 13, 2011.
The ARC Membrane Technology (MT) partners will concentrate on membrane processes, particularly on hybrid technologies, and contribute to better water quality (e.g., by rejecting organic micro pollutants and enhancing biological stability) and to improved membrane process operation (e.g., by reducing waste streams and energy requirements). This research collaboration will focus on innovative issues and address conditions that are relevant to end users – for instance, climate change, water resource shortages, emerging pathogens and contaminants, and sustainable water treatment.
Membrane technology was developed in the second half of the 20th century thanks to the invention, by Loeb and Sourarijan, of thin-film composite membranes for seawater desalination. The development of membranes has accelerated ever since and resulted in the worldwide application of membranes in wastewater, drinking water and industrial water treatment. The market for high pressure membranes (nanofiltration and reverse osmosis) currently amounts to a staggering $ 450 million for desalination and $ 300 million for industrial processes — according to Global Water Intelligence, the overall Water Technology Markets reports, the total market is expected to double by 2016. In fact, membranes – including ultrafiltration and microfiltration membranes – are the fastest growing water equipment category.
Water companies are legally obligated – within the limits of their economic capabilities – to optimize the supply of drinking water in order to comply with public health requirements. This optimization is achieved by improving water quality and by operating water treatment processes more cost-efficiently. Membrane technology plays a key role in improving water quality by removing particles, pathogens (viruses and bacteria), natural organic matter, emerging substances (e.g., pesticides, endocrine hormone disruptors, pharmaceuticals, cyanotoxins), and other dissolved matter from sources of drinking water. Moreover, membrane technology is used to improve the biological stability of drinking water in the distribution network.
The ARC MT consortium focuses on the improvement of water quality through the use of membrane technology. The main thrusts of this effort involve: (i) improving membrane operation by cost-effective methods; (ii) reducing problems with waste streams, such as concentrates; and (iii) cutting the energy requirements of membrane technology. The approach involves the application of innovative hybrid membrane processes, using a synergistic combination of different treatment processes.
The ARC MT consortium’s research and development work focuses on improving the performance of membrane processes in drinking water treatment, by improving water quality, reducing operational problems, decreasing waste streams and minimizing energy requirements for membrane processes. Its research topics encompass the challenges of water resource shortages, increased urbanization, climate change, emerging pathogens and contaminants, and sustainable water treatment. Concretely, the consortium’s research is subdivided into the themes below.
Hybrid Membrane Processes
These processes combine membrane technology with another treatment process in order to synergistically enhance both processes. More specifically, pressure-driven membrane processes – microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) – can be combined with state-of-the-art and innovative adsorptive, oxidative and biological processes. Examples of state-of-the-art processes being investigated by the ARC MT partners are: (i) powdered activated carbon (PAC) to enhance the performance of micro- and ultrafiltration; (ii) coagulation/flocculation to remove natural organic matter (NOM) thus improving MF/UF process operation; and (iii) oxidation (e.g., ozone, UV/peroxide) of feed water for drinking water treatment preceding NF processes. Examples of more innovative processes include the use of sub-micron PAC, alternative adsorbents or ion exchange to enhance membrane process performance.
Innovative Membrane Products and Processes
Developed over the last decade, these products and processes result from the R&D drivers of the ARC MT partners: namely, enhancing water quality, reducing operational problems, reducing concentrates and cutting energy demand. What follows are some examples of innovative membrane products and processes being studied by ARC MT partners. Forward osmosis (FO), which is driven by an osmotic pressure difference over the membrane, and results in lower energy needs, low fouling and high rejection levels for most micro pollutants. Membranes based on nano-materials, which show a high performance in terms of the quantity and quality of the water produced, and a low fouling propensity. Ceramic membranes, which are robust and can withstand extreme conditions (e.g., during cleaning), and perform better than some commercial polymeric membranes. New types of membrane operation, including in hybrid (adsorptive, oxidative or biological) processes. And, finally, membrane bioreactors (MBR), which are being developed to improve the water quality of the effluent, while reducing the installation’s footprint.
Membrane Process Modeling
The purpose of this modeling is to optimize membrane process operation, including risk minimization (prediction of passage of emerging substances), or to obtain a fouling prediction tool. This tool, which predicts the rejection of organic micro pollutants by NF and RO, is based on a quantitative structure activity relationship (QSAR) approach, including steric hindrance, physico-chemical interaction and electrostatic repulsion models. Furthermore, stochastic artificial neural networks (ANN) and mechanistic models are used by the ARC MT partners to optimize process operation of full-scale membrane installations. Finally, fouling prediction models are under development to predict the particulate, organic and biological fouling of membranes.
Monitoring Water Quality in Membrane Processes
Specifically, the ARC MT partners focus on the development of fouling indicators to predict fouling behavior in membrane processes. Membrane fouling can be subdivided into organic fouling, biofouling, particulate fouling and scaling, and different fouling indicators can be developed for each type. Other topics here include: (i) risk assessment of water quality in relation to membrane performance, such as the presence of chlorine, which can deteriorate the rejection of NF/RO membranes; and (ii) real-time monitoring and prediction of membrane rejection properties in full-scale installations over time.
New Sources for Water Production
The search for new conventional and alternative water sources for the production of drinking or process water, using membrane filtration, is of growing interest to utilities, industrial end users and suppliers. The traditional sources for drinking water production are surface water and groundwater. Global challenges, particularly climate change, are exerting increased pressure on these sources, and problems are arising in the form of the very rapid degradation of raw water quality (e.g., water salinity and toxic algal blooms) and of water scarcity. Alternative sources for production of high quality water (e.g., drinking water) are seawater, rainwater and (reclaimed) wastewater. These challenges demand advanced, flexible and safe treatment processes, such as those offered by membranes.
Reduction of cost and energy consumption of membrane processes
This is an ongoing interest of utilities and end users, and therefore concerns the ARC MT consortium as well. Membrane technologies are generally regarded as involving high energy consumption and thus a considerable carbon footprint. New membrane products and processes attempt to lower this energy use. Furthermore, membrane performance – i.e., the quantity and quality of the water produced – decreases as the membranes become fouled. Membrane fouling can be controlled by intensive pretreatment and by regular membrane cleaning, both of which impact the installation’s costs and energy use. An optimal system selection will depend on many factors, and can be made on the basis of the combined experience of the ARC MT partners.
New membrane technology markets
These markets include the application of membrane technology in the treatment of concentrate and of wastewater from oil production, as well as in fish farming. These new markets are being explored by the ARC MT consortium.
The ARC MT partners are currently, or have recently been, involved in several national and international membrane technology projects (e.g., TOXIC, TECHNEAU, MEDINA, TRUST). As a result, the consortium possesses a solid core of knowledge on the application of this technology in drinking water and wastewater treatment. The joint expertise of the ARC MT partners covers a wide range of relevant issues in the field of membrane technology, including different membrane products and processes, membrane applications, scales of operation, and innovative processes and trends. The consortium offers utilities and end users in Europe (and worldwide) the advantage of an extensive network in the field of membrane research and development. This includes the possibility of capitalizing on experiences between end users and the ARC MT partners for capacity building and knowledge transfer. The consortium partners offer an extensive experience in the water and membrane market – an experience developed in a variety of institutional contexts, ranging from public to private, from municipal to industrial, from local to regional, from large to small, and from universities to end users. Their experience in existing treatment plants and in the advanced treatment options also constitutes an added value for the successful application of membrane technology, be it for rehabilitation works or for new investments.