Bulletin Spring‧Summer 2001

Yet none o f these me t h o ds is ideal. Physical methods require high energy input, while the effectiveness of chemical methods and whether these processes generate further wastes are s t i l l q u e s t i o ns t h a t r ema i n unanswered. B i o l og i c a l methods involve the use of microorganisms such as bacteria to t u r n p o l l u t a n t s i n t o n o n - t o x i c , h a r m l e ss substances. Prof. Wo n g p o i n t ed out tha t b i o d e g r a d a t i o n is the most e n v i r o nme n t friendly as it does not require large amounts o f energ y a n d does n o t generate t o x ic substances. He has been using b i o s o r p t i on to remove heavy metals f r om contaminated waste water and biodegradation to treat such metals successfully since the late 1980s. Can the same methods be used for azo dyes? T h e drawback o f using biosorption to r emo v e s y n t h e t ic dyes f r o m i n d u s t r i al effluents is t ha t there is no s a t i s f a c t o ry treatment for the microorganisms that have ab s o r bed the dye. It's n ot p r a c t i c al f o r t r e a t i ng large volumes o f c o n t am i n a t ed water,' Prof. Wong said. He further pointed out that researchers had tried to degrade azo dyes anaerobically u s i n g m i c r o o r g a n i sms . Howe v er i t only t u r ned the water colourless, and failed to degrade the toxic and mutagenic aromatic amines therein. Some other researchers also discovered that azo dyes could be degraded aerobically using bacteria and fungi , but the method has yet to be improved . Figure 1 Structure of (a) methyl red (MR) and (b) procion red Mx-5B Drawing dye-contaminated water samples from a dyeing factory for research I n Search of an Ideal Me t hod Prof. Wong was determined to overcome these obstacles to f i n d the perfect treatment method. His research projec t was allocated a total o f HK$1 . 29 m i l l i on by the Research Grants Council i n 1991 and 1999. First he contacted some dyeing factories in Ho ng K o ng to request them to supply dye- contaminated water samples for the project. However, as most of them had moved north , he c ou ld on ly lay his hands o n a l i m i t ed n u m b e r o f samples a n d t h a t , in t u r n , n a r r owed d ow n the scope o f his research. A m o n g the l i m i t ed samples , Prof. Wo n g picked methyl red ( M R , see Figure l a) and procion red M X - 5 B (PR, see Figure l b ) for his study because thei r structures are the simplest. Prof. Wong isolated a bacteriu m called Pseudomonas sp. K - 1 (Figure 2) f r o m dye- c o n t am i n a t e d sludge and c u l t u r e d large amounts o f it. Pseudomonas sp. K - 1 c ou ld absorb large quantities of M R and PR very quickly, yet it could not degrade the toxi c substances i n these dyes , n o t even given time. Figure 2 Colonies of Pseudomonas sp. K-1 stained by procion red MX-5B Chinese Universit y Bulletin S p r i n g • Summer 2 0 00 34