INHIBITION OF ANAEROBIC-DIGESTION BY TEREPHTHALIC ACID AND ITS AROMATIC BY PRODUCTS

With 14.4 million tons produced in 1993, purified terephthalic acid (P TA) and dimethylterephthalate (DMT) are the main monomers used in the world polyester production. Even though there are ten industrial diges ters treating the effluents of both products, little is known about th e influence of their organic components, terephthalic (TA), p-toluic ( p-tol), benzoic (BA) and phthalic (PA) acids as well as 4-carboxybenza ldehyde (4-CBA) on methanogenesis. This study shows that the concentra tions of 4-CBA, p-tol and TA required to inhibit by 50% the hydrogenot rophic methanogenic activity are respectively 5.4, 34 and more than 10 0 mM. At the maximum concentration tested (10 mM), the inhibition of t he acetoclastic methanogenic activity by the same compounds was less t han 12%. The results indicate that at the concentration of TA, p-tol a nd 4-CBA found in PTA and DMT wastewater, no significant inhibition of the methanogenic activity should be observed for PTA but that the hyd rogenotrophic activity could be reduced by as much as 30% in the case of DMT. The degradation of TA was completely inhibited by the presence of BA and glucose while the presence of phthalate had no effect. Acco rding to these results, it is concluded that it is at least possible t o anaerobically treat the easily biodegradable compounds of these effl uents (acetic, benzoic and formic acid) as they would not be significa ntly inhibited by TA, p-tol or 4-CBA. (C) 1997 IAWQ. Published by Else vier Science Ltd.