Membrane bioreactor plants

Membrane bioreactor plants are much smaller than CAS-TF plants. This is shown by comparing the total hydraulic retention time (HRT) in Figure 7.5 and the total plant surface area... 

Clara M, Strenn B, Cans O, Martinez E, Kreuzinger N, Kroiss H (2005) Removal of selected pharmaceuticals, fragrances and endocrine disrupting compounds in a membrane bioreactor and conventional wastewater treatment plants. Water Res 39 4797 807... 

Clara M, Strenn B, Ausserleitner M, Kreuzinger N (2004) Comparison of the behaviour of selected micropollutants in a membrane bioreactor and a conventional wastewater treatment plant. Water Sci Technol 50 29-36... 

Generally, a distinction can be made between membrane bioreactors based on cells performing a desired conversion and processes based on enzymes. In ceU-based processes, bacteria, plant and mammalian cells are used for the production of (fine) chemicals, pharmaceuticals and food additives or for the treatment of waste streams. Enzyme-based membrane bioreactors are typically used for the degradation of natural polymeric materials Hke starch, cellulose or proteins or for the resolution of optically active components in the pharmaceutical, agrochemical, food and chemical industry [50, 51]. In general, only ultrafiltration (UF) or microfiltration (MF)-based processes have been reported and little is known on the application of reverse osmosis (RO) or nanofiltration (NF) in membrane bioreactors. Additionally, membrane contactor systems have been developed, based on micro-porous polyolefin or teflon membranes [52-55]. 

Petrovic M, de Alda MJ, Diaz-Cruz S et al (2009) Pate and removal of pharmaceuticals and illicit drugs in conventional and membrane bioreactor waste water treatment plants and by riverbank filtration. Philos Transact A Math Phys Eng Sci 367(1904) 3979-4003... 

Some of the largest plants for seawater desalination, wastewater treatment and gas separation are already based on membrane engineering. For example, the Ashkelon Desalination Plant for seawater reverse osmosis (SWRO), in Israel, has been fully operational since December 2005 and produces more than 100 million m3 of desalinated water per year. One of the largest submerged membrane bioreactor unit in the world was recently built in Porto Marghera (Italy) to treat tertiary water. The growth in membrane installations for water treatment in the past decade has resulted in a decreased cost of desalination facilities, with the consequence that the cost of the reclaimed water for membrane plants has also been reduced. 

Membrane technology may become essential if zero-discharge mills become a requirement or legislation on water use becomes very restrictive. The type of membrane fractionation required varies according to the use that is to be made of the treated water. This issue is addressed in Chapter 35, which describes the apphcation of membrane processes in the pulp and paper industry for treatment of the effluent generated. Chapter 36 focuses on the apphcation of membrane bioreactors in wastewater treatment. Chapter 37 describes the apphcations of hollow fiber contactors in membrane-assisted solvent extraction for the recovery of metallic pollutants. The apphcations of membrane contactors in the treatment of gaseous waste streams are presented in Chapter 38. Chapter 39 deals with an important development in the strip dispersion technique for actinide recovery/metal separation. Chapter 40 focuses on electrically enhanced membrane separation and catalysis. Chapter 41 contains important case studies on the treatment of effluent in the leather industry. The case studies cover the work carried out at pilot plant level with membrane bioreactors and reverse osmosis. Development in nanofiltration and a case study on the recovery of impurity-free sodium thiocyanate in the acrylic industry are described in Chapter 42. 

The waters in question are pumped to a membrane bioreactor equipped with an air injection system, where part of the feed is recycled, making it move across a membrane ultrafiltration system, to prevent the presence of suspended microelements in the later phase of reverse osmosis. From the ultrafiltration process, two streams are obtained a concentrated stream of salts and microbial mass, which is recycled to the bioreactor, and a permeate stream that passes to the reverse osmosis plant. 

FIGURE 41.2 Flow diagram of the membrane bioreactor pilot plant. 

Operational Data of the Membrane Bioreactor Pilot Plant ... 

From the results obtained in the ultrafiltration membrane bioreactor and reverse osmosis pilot smdies, the industrial plant was designed with the following general characteristics. 

In the membrane bioreactor, there is a reduction of 81% COD, 97.5% BOD5, 93% suspended solids, and 80% sulfides. In the reverse osmosis plant, there is a reduction of 96.2% COD, 97% BOD5, 80% sulpides, and 93% suspended solids. The conductivity decreased by 98%. 

An example of an industrial membrane bioreactor is the hollow-fiber membrane system for the production of (-)-MPGM (1), which is an important intermediate for the production of diltiazem hydrochloride [130, 131]. For the enantiospecific hydrolysis of MPGM a hoUow-fiber ultrafiltration membrane with immobilized lipase from Serratia marcescens is used. (-i-)-MPGM is selectively converted into (2S,3R)-(-i-)-3-(4-methoxy-phenyl)glycidic acid and methanol. The reactant is dissolved in toluene, whereas the hydrophilic product is removed via the aqueous phase at the permeate side of the membrane (see Fig. 5.17). Enantiomerically pure (-)-MPGM is obtained from the toluene phase by a crystallization step. In cooperation with Sepracor Inc., a pilot-plant membrane reactor has been developed, which produces annually about 40 kg (-)-MPGM per m of membrane surface. 

Microfiltration plants are also being installed in membrane bioreactors to treat municipal and industrial sewage water. Two types of systems that can be used are illustrated in Fig. 7.6. The design shown in Fig. 7.6(a), using a crossflow filtration module, was developed as early as 1966 by Okey and Stavenger at Dorr-Oliver [17]. The process was not commercialized for another 30 years for lack of suitable membrane technology. In the 1990s, workers at Zenon [15,16] in Canada and... 

Membrane processes for this analysis include SWRO, BWRO, low-pressure RO (LPRO), brine recovery RO (BRO), pressurised MF/UF (pMF/UF), immersed membrane bioreactor (iMBR), cross-flow membrane filtration (XMF) and electrodeionisation (EDI). Membrane process characteristics for water treatment are detailed in Table 5.1. Typical process flow schematics of RO membrane plants are shown in Figures 5.1 and 5.2. RO/NF systems are typically multi-stage and single-pass or multi-stage and double-pass, as shown in Figures 2.21-2.23. 

Figure 5.3 Process flow schematics of membrane plants. Process A is single-pass RO process B is double-pass RO process C is high-recovery RO process D is pressurised MFAJF-RO integrated plant process E is membrane bioreactor-RO integrated plant process F is cross-flow MF-RO integrated plant and processes G and HI are RO-EDI integrated high-purity water plants. In process H2, second-pass RO replaces EDI, and no post-treatment after MBIX is required.

Consequently, membrane bioreactors are an example of the combination of two unit operations in one step for example, membrane filtration with the chemical reaction. In a typical membrane bioreactor, as weU as acting as a support for the biocatalyst, the membrane can be a very effective separation system for undesirable reactions or products. The removal of a reaction product from the reaction environment can be easily achieved thanks to the membrane selective permeability, and this is of great advantage in thermodynamically unfavourable conditions, such as reversible reactions or product-inhibited enzyme reactions. A very interesting example of a membrane bioreactor is the combination of a membrane process, such as microfiltration or ultrafiltration (UF), with a suspended growth bioreactor. Such a set up is now widely used for municipal and industrial wastewater treatment, with some plants capable of treating waste from populations of up to 80 000 people (Judd, 2006). 

---