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h a s a resis t ivi ty of 1 megaohm per cm. Regenerat ion of the ca t ion a n d an ion co lumns is s imul taneous , p roduc ing eff luents tha t a re largely se l f -neutra l is ing t hus min imis ing the envi ronmenta l impact .

After deionisat ion, the water is fed into two holding t a n k s and p u m p e d cons tan t ly a r o u n d a r ing-main which suppl ies p rocess water to mixing t anks in the p roduc t ion a r ea via take-off points . The tanks , mixing vessels and d i s t r ibu t ion pipework are all cons t ruc ted from s ta in less steel. Microfilters and an ul traviolet l amp are incorpora ted into the d i s t r ibu t ion loop to ensu re tha t the bac te r ia l count is kept below 10 colony-formlng un i t s per mL (CFU/mL).

The labora tory water purif icat ion sys tem features reverse osmosis , deionisat ion, microfl l t rat ion and UV irradiat ion. As in the case of the p rocess system, the purif ied water is cont inua l ly rec i rcu la ted a round a d i s t r ibu t ion loop which feeds take-off points in the labora tor ies .

Further Informatlon from: Elga Ltd, High Street, Lane End, High Wycombe, Buckinghamshire, HP14 3JH, UK. Tel: +44 (0)494 881393. Fax: +44 (0)494 881007.

Liquid m e m b r a n e r e m o v a l o f H2S The appl ica t ion of a l iquid m e m b r a n e for selective removal of H2S from gases also conta in ing CO2 has been invest igated b y r e sea rche r s in The Nether lands (J. Membrane Sci., 82, 1993, pp 185-197).

The l iquid m e m b r a n e was filled with pu re methy l -d l -e thano l -amine (MDEA) which showed no react ion with CO2. A theoret ical model was used to descr ibe the chemical equi l ibr ium between the dissolved gas and MDEA in the membrane , and the phys ica l equi l ibr ium between the solute in the gas and the l iquid phase . H2S and CO2 fluxes were determined, a n d in te rpre ted with the theoret ical model.

To a l imited degree, reac t ion was observed between H2S a n d the amine, which resu l t s in a higher selectivity t han can be expected on the bas i s of the phys ica l solubi l i ty of CO2 and H2S. To fur ther increase selectivity, it was d i scus sed tha t a solvent with higher H2S solubi l i ty could be used, or a combina t ion of ter t iary amine and a co-solvent which allows a fur ther d issoc ia t ion of the physica l ly dissolved H2S.

Further Informatlon from: G.F. Versteeg, Faculty of Chemical Technology, University of Twente, P.O. Box 21 7, 7500 AE Enschede, The Netherlands.

Call for papers The 7th In te rna t iona l Sympos ium on Synthet ic Membranes in Science and Indus t ry will be held from Augus t 29 -Sep tember 2 1994 in Tubingen, Germany.

The scientific p rogramme inc ludes invited lectures on var ious topics, focused especial ly on funct ional m e m b r a n e s and ca r r i e r - a s s i s t ed m e m b r a n e processes . Papers for oral a n d pos ter p resen ta t ions are solicited on the following topics:

• f undamen ta l s of m e m b r a n e processes ;

• p repa ra t ion and charac te r iza t ion of new synthet ic membranes ;

• chemical engineering aspec t s of m e m b r a n e separa t ion processes;

• m e m b r a n e s and m e m b r a n e processes in indus t r ia l appl icat ions;

• m e m b r a n e s in biomedical sys t ems and analytic, diagnost ic and sensor ic devices;

• m e m b r a n e s in energy conversion and storage systems; and

• new appl ica t ions of m e m b r a n e s and processes . Authors who wish to submi t a pape r for oral

p resen ta t ion or a s a pos ter should submi t the title and an abs t rac t of abou t 300 words (in English) before 31 October 1993.

Further Information from: DECHEMA e.V., Exhibitions and Congresses, P.O. Box 15 01 04, D-60061 Frankfurt am Main, Germany. Tel: +69 75 64 2 4 1 / 2 4 2 / 2 4 3 . Fax: +69 75 64 201.

High r overy c o n c e n t r a t o r Amlcon, Inc has re leased a new version of its Centr iprep concent ra tors with a 50 000 molecular weight cut-off, for concentra t ing, purifying or desa l t ing samples of u p to 15 ml. The non-fouling design is especial ly su i ted to concent ra t ing a n d desal t ing par t ic le - laden samples . It is ideal for recovery of biomolecules from cell cu l ture supe rna t an t s , lysates, ext rac ts or o ther biological samples .

Samples of up to 15 ml can be rapid ly concen t ra ted to a s little as 0.65 ml in 20--45 minutes . Integral deads top pro tec t ion prevents fi l tration of sample to dryness . The un i t ' s low-adsorpt ive m e m b r a n e provides over 90% prote in recovery and complete desa l t ing with min imal dena tu ra t ion or shear.

4 M e m b r a n e Techno logy No. 3 6

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Centr iprep concen t ra to r s can be used in mos t s t a n d a r d centr i fuges with f ixed-angle or swlnging-bucket ro tors and 50 ml tube adapter . They are also avai lable in 3000, 10 000, 30 000 and 100 000 MW cut-offs.

Further information from: Amlcon, Inc, 72 Cherry Hill Drive, Beverly, MA 01915, USA. Tel: +1 508 777 3622. Fax: +1 506 777 6294.

Rapid E. co l i . t e s t ing us ing m e m b r a n e d iscs Domnick h u n t e r Process Division h a s worked in close al l iance with major food m a n u f a c t u r e r s to identify a specific oppor tun i ty for i ts ASYPOR membrane .

The m e m b r a n e has proven to be very successfu l for the enumera t ion of Escherlchla coll in foods and raw

mater ia ls . The pe r fo rmance of the 0.45 Ore, 85 m m discs, is sa id to be derived from the asymmet r i c pore size d is t r ibu t ion of the ASYPOR membrane .

The membrane , made from mixed es ters of cellulose, ha s pores graded th roughou t the dep th of the membrane . The pores on the u p s t r e a m surface, the open side, are larger t han the pores on the down s t ream side, the t ight side. When used as pa r t of the Tryptone Bile Agar Direct Plate Method (DPM), this m e m b r a n e encourages bac te r ia l growth as a resu l t of i ts propert ies .

DPM is used by m a n y food m a n u f a c t u r e r s because resu l t s can be ob ta ined in 24 hours , a n d with less effort t han the Most Probable Number Test.

Further Information from: Elaine Robinson, Marketing Services Assistant, domnlck hunter Ltd, Process Division, Durham Road, Birtley, Co. Durham DH3 2SF, UK. Tel: +44 (0)91 410 5121. Fax: +44 (0)91 410 5312.

RO leachate t r e a t m e n t s y s t e m s distr ibuted by US Filter Rochem Separa t ion Systems, a subs id i a ry of the In te rna t iona l Rochem Group, h a s a n n o u n c e d the gran t ing of exclusive US d is t r ibu t ion r ights for the company ' s reverse osmosis l eacha te t r ea tmen t equ ipment to US Filter Corp, a leading suppl ie r of l eacha te t r ea tmen t sys tems.

Rochem's reverse osmosis l eacha te t r ea tmen t equ ipment u se s the pa t en ted Disc Tube TM m e m b r a n e module technology, in t roduced in the USA about 2 years ago. Rochem is cur ren t ly p rocess ing over 1 mill ion gal lons of landflU leacha te per day in Europe.

The pa ten ted Disc Tube m e m b r a n e modules - - compr ised of u l t rasonica l ly welded octagonal m e m b r a n e cushions , hydraul ic carr ier discs, end f langes and t ubu l a r p r e s s u r e vessels m are capable of process ing large volumes of raw leacha te a n d recovering pure water, which can be r eused or r e tu rned to the environment . The modu les remove inorganic mate r i a l s from the leachate; inorganic sa l ts are normal ly r educed 99% a n d heavy meta l s can be removed to below detect ion levels.

Organic mate r i a l s such as pes t ic ides and herbicides , are also removed. The modu les prevent the passage of biological mater ia l , fea ture au tomat ic opera t ion and require min imal opera tor at tent ion.

Further information from: Stan Karrs, US Filter, 181 Thorn Hill Road, Warrendale, PA 15086-0627, USA. Tel: +1 412 772 0044.

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