MBRs – getting to the roots

As a relatively new technology, membrane bioreactors (MBRs) have often been disregarded in favour of conventional biotreatment plants. However, analyst reports show that the MBR market is seeing accelerated growth, which is expected to be sustained over the next decade.

In 2004, the European MBR market was worth £32.7M. Future projections expect this to rise annually by 6.7%, with the market set to more than double in size over the next seven years.

The cumulative capacity of both Zenon and Kubota has increased exponentially since the immersed products were introduced (see Fig 2). Both systems dominate the MBR market today, with a very large number of small-scale Kubota systems and the largest MBR systems tending to be Zenon. The largest MBR worldwide is at Kaarst in Germany (50 MLD), though there is a larger membrane wastewater recycling facility in Kuwait (the Sulaibiya plant), which has a design capacity of 375MLD.

Other MBR products have been marketed with varying degrees of success. The installation of in-building wastewater recycling plants in Japan based on the Novasep Orelis (formerly Rhodia Orelis and before this Rhône Poulenc) Pleiade FS sMBR system, actually pre-dates that of the Kubota plants for this duty. The Pleiade system was trialled in France in the 1970s, and by 1999 there were 125 small-scale systems (all below 0.200 MLD) worldwide, the majority of these being in Japan and around 12 in France.

Dorr-Oliver

The Dorr-Oliver Membrane Sewage Treatment system was similarly more successful in Japan than in North America in the 1970s and 80s.

Wehrle Environmental, part of Wehrle Werk AG, has a track record in multitube (MT) sidestream MBRs (predominantly employing Norit polymeric MT membrane modules) which dates back to the late 1980s. Wehrle Environmental’s MBRs have been used for landfill leachate treatment since 1990.

Development of the sidestream Degremont system began in the mid-1990s, this system being based on a ceramic membrane. These sidestream systems all tend to be employed for niche industrial effluent treatment applications involving low flows, such that their market penetration compared with the immersed systems, particularly in the municipal water sector, has been limited. Other commercial sMBR systems include the Dyna-Lift MBR (Dynatec) in the US, and the AMBR system (Aquabio), the latter also being based on MT membrane modules.

Alternative immersed FS and HF membrane systems or products have generally been marginalised by the success of the Kubota and Zenon products, but have nonetheless been able to enter the market successfully. Ultrafiltration HF

membrane modules include the well-established Mitsubishi Rayon Sterapore(tm) SUN(tm) module or the more recent SADF(tm) product. FS systems include the Toray membrane, a company better known for reverse osmosis membranes, and the Huber VRM technology.

Whereas the Toray product is a classic immersed rectangular FS membrane, the Huber technology is based on an immersed rotating hexagonal/ octagonal membrane element and has attracted interest particularly within Germany. Sidestream airlift technologies have also been developed by some membrane and/or process suppliers which would seem to provide some of the advantages of an immersed system in a sidestream configuration. However, the majority of the newer products are vertically-oriented HFs, mostly fabricated from the same base polymer (polyvinylidene difluoride, PVDF). Acquisitions, partnerships and licensing agreements have complicated the MBR market. A comprehensive review of these is beyond the scope of this brief précis, but a few salient points can be made.

Whereas Zenon is a single global company supplying both membranes and turnkey plants for both water and wastewater treatment duties, Kubota, Mitsubishi Rayon and Norit (who acquired X-flow and Stork in the 1990s) are primarily membrane suppliers offering licensing agreements for their products. The Kubota MBR process is provided by a series of generally geographically limited process firms, including Enviroquip in the US, Copa in the UK, Stereau in France and Hera in Spain. The UK licence was formerly held by Aquator, formed through a management buy-out from Wessex Water in 2001, which Copa bought in February 2004. Copa has reverted to the original name of MBR

Technology for its MBR-related activities. Mitsubishi Rayon has licensees in the UK and the US, the latter being Ionics (now part of GE Water), but its operations are largely restricted to the South-east Asian markets and Japan in particular. In Europe, Zenon has had licensing agreements with OTV (part of French giant Vivendi, now Veolia), Ondeo Degrémont and VA Tech Wabag.

There have been several recent acquisitions within the membrane municipal sector. Of special significance are the acquisition of PCI by ITT, of Puron by Koch and of USFilter/Memcor by Siemens. PCI Membranes, acquired from the Thames Water Group (itself now part of the German company RWE), developed the FYNE process in the early 1980s. This is an MT nanofiltration (NF) membrane based process for removing organic matter from upland surface waters.

PCI had no direct involvement with membrane bioreactors prior to the acquisition. ITT also acquired Sanitaire, market leader in diffused aeration systems, in 1999. There is an obvious synergy in MBR process development.

Puron was a small spin-out company from the University of Aachen. It developed an HF membrane which has undergone extensive demonstration as an iMBR at pilot scale. The acquisition of Puron by Koch in 2005 – Koch being a major membrane and membrane systems supplier and owner of Fluid Systems (acquired from another UK water utility, Anglian Water Group) – signals a strategic move into the MBR technology by a company normally associated with pure water membrane systems.

Memcor is a long-established HF microfiltration membrane supplier (formed as Memtec in 1982). It was acquired by USFilter in 1997 and was part of the Veolia group, until sold to Siemens in 2004. In 1998, it launched an immersed membrane process and introduced the MemJet iMBR in 2003. Memcor is a very significant player in the MBR market and is already on a par with Zenon in potable water treatment.

In North America, the MBR market is currently dominated by Zenon, and the company also has the significant share of installed capacity in many countries where it operates.

According to a recently published review of the North American market, 182 of the 258 installations (i.e. 71%) provided by the four leading MBR suppliers in the US, Canada and Mexico are Zenon plants.

Worldwide, however, there appear to be as many Mitsubishi Rayon plant as Zenon plants, but only two of these are in the US and the plants are generally smaller. Indeed, as of 2005, nine of the ten biggest MBR plants worldwide were Zenon plants.

On the other hand, in South-east Asia and in Japan in particular, the market is dominated by the Japanese membrane suppliers and Kubota specifically. Mitsubishi Rayon also has a significant presence in this region, particularly for industrial effluent treatment.

In the UK – the EU country with the largest number of MBRs for sewage treatment – all but three of the 21 municipal wastewater MBRs are Kubota (as of 2005). This trend is not repeated across mainland Europe, where Zenon again tends to dominate. For small flows, and in particular for more challenging high-strength industrial wastes, the dominance of Kubota and Zenon is much less pronounced. Wehrle held 10% of the total European MBR market in 2002, compared with 17% for Zenon at that time, which gives an indication of the significance of the industrial effluent treatment market.

Immature

Although commercial products have developed substantially since the late 1960s, MBR technology is still seen as being immature. And it is only since the introduction of the immersed configuration in 1990 that significant market penetration has taken place.

The market is still dominated by Zenon and Kubota but there is a wide range of products available for both industrial and municipal applications, with still more at developmental stage.

Confidence in MBR technology is growing, as capital and operational costs have decreased over the past 15 years, and as reference sites increase in number and maturity. As such, it is expected that MBR technology – as well as the market itself – will continue to develop at a significant paceSimon Judd is professor in membrane technology and director of water sciences at Cranfield University. www.cranfield.ac.uk/sims/water