MBR Performance

Brindle et al. [14] conducted a comprehensive review of MBR performance drawing on published data for installations ranging from laboratory scale to fuU commercial scale and for a variety of process variants. For the treatment of municipal wastewater, volumetric loading rates ranged between 0.45 and 

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An example of a membrane module for assembling in a MBR is reported in Fig. 23.5. It is evident that many factors could affect MBR performance, as summarized in Fig. 23.6 membrane properties, sludge characteristics and operating conditions that are related to capital and maintenance costs, materials and utUities costs as well as service costs. Their optimization is strictly related to the economics of the treatment systems, also compared with traditional ones. 

Factors affecting MBR performances and economics.TMP transmembrane pressure CF cross filtration SRT solids retention time HRT hydraulic retention time. 

Interactive relationships between the MBR performance attributes. MLSS, mixed liquor suspended solids. 

The MBR can accommodate distillation through an outlet tube connected to a port on the top flange. With that arrangement, a monodehydrobromination of 1,6-di-bromohexane was performed in which the product 6-bromohex-l-ene was removed from the mixture before a second molecule of HBr could be eliminated [26, 33]. 

Several workers have employed monomodal cavities for microwave chemistry on the sub-gram scale. In some cases in which monomodal cavities have been used7, special benefits of so-called focussed microwaves have been claimed. As mentioned earlier, the dielectric properties of a sample can alter substantially with temperature and/or with changing chemical composition. Hence, regardless of whether multi-modal or unimodal cavities are employed, frequent tuning may be necessary if heating efficiency is to be retained. This aspect has often been overlooked by proponents of focussed microwaves. The nett result is that transfer of microwave conditions between monomodal to multi-modal cavities is usually facile. With the MBR (which had a tunable multimodal cavity), Cablewski et al. performed five reactions that had been conducted earlier on the gram scale or below with focussed microwaves (T. Cablewski, B. Heilman, P. Pilotti, J. Thorn, and C.R. Strauss, personal communication see also Ref. 117 for conference poster). These were scaled-up between 40- and 60-fold and reaction conditions... 

Now we perform different substitutions in the first right-hand side contribution we put R = rx - R + mcr/M while for the second one we take R = r, - R- mbr/M. Then we arrive at the more simplified expression... 

Recent studies in the pharmaceutical field using MBR technology are related to optical resolution of racemic mixtures or esters synthesis. The kinetic resolution of (R,S)-naproxen methyl esters to produce (S)-naproxen in emulsion enzyme membrane reactors (E-EMRs) where emulsion is produced by crossflow membrane emulsification [38, 39], and of racemic ibuprofen ester [40] were developed. The esters synthesis, like for example butyl laurate, by a covalent attachment of Candida antarctica lipase B (CALB) onto a ceramic support previously coated by polymers was recently described [41]. An enzymatic membrane reactor based on the immobilization of lipase on a ceramic support was used to perform interesterification between castor oil triglycerides and methyl oleate, reducing the viscosity of the substrate by injecting supercritical CO2 [42],... 

The CMR and MBRs provided the basis for modern commercial microwave reactors, including robotically operated automated systems that are now widely employed in synthetic research and pilot-scale laboratories in academia and industry [13]. Since 2000, commercial microwave reactors have become available. Batch systems, produced by three major companies in Italy and Germany, Sweden and the United States, typically operate on a scale from 0.5 mL up to 2 L. Other companies based in Austria, Poland and Japan have also recently entered the market. Systems possessing either multimodal or monomodal cavities are produced with one recent addition being a single unit capable of performing in either mode as required. Microwave reactors are employed extensively in chemical discovery where successive reactions can be performed rapidly in parallel or sequentially. One manufacturer recently estimated that about 10000 reactions per week were performed in its systems alone. This indicates the extent to which microwave chemistry in closed vessels has dramatically influenced approaches to synthesis. 

Papeterie du Rhin, Paper Roll Mill, France. In 1999, Veolia Water STI installed an MBR with Zeeweed ultrafiltration membranes (pore size 0.04 p.m) in Papeterie du Rhin s paper roll mill in France (Table 35.1). Recycled (not deinked) paper is used as the raw material. The bioreactor (1500 m ) is operated at a mixed liquor suspended solids (MLSS) content of 12-16 g/L. Brockmann and Praderie [58] report an average flux of 15 L/(m h) at a pressure of 0.15 bar over a 1 year filtration period. The wastewater from the mill is first prescreened with dmm screens, then sent to an equalization basin, from which it is pumped directly into the bioreactor. Table 35.6 summarizes the performance of the MBR process. The pressure used to draw the water through the membrane is 7-55 kPa. The filtrate is partly recycled as process water [27,57,58]. 

The purpose of this chapter is to review the critical factors contributing to MBR process performance and to report recent advancements in key areas. Coverage is directed toward membrane separation bioreactors, although recent developments in membrane biofilm reactors will be briefly discussed. Much of the current MBR research effort is directed toward municipal wastewater applications however, substantial commonalities exist with respect to industrial wastewater appheation and where possible, reference is made to the specific aspects of the technology when applied to the treatment of industrial wastewater. 

Characteristics and Performance Data from Selected Published Studies of MBRs Applied to the Treatment of Industrial Wastewater... 

FIGURE 36.3 Schematic interrelationship between factors that determine process performance in MBRs. Wastewater characteristics are implicit in this outline. The term biological reactions includes exogenous and endogenous metabolism, extracellular enzymatic activity, and product formation (EPS). 

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