EFFECT OF NICKEL(II) ON THE BIOMASS YIELD OF THE ACTIVATED-SLUDGE

Biomass yield of microorganisms is important in applied microbiology s ince it is the ultimate factor determining the amount of product produ ced regardless of whether product is growth-linked or not. In the case of environmental microbiology the opposite is true and minimizing the biomass produced, or the sludge in the relevant jargon, often is the prime goal. In this paper, a unique means of manipulating the microbia l biomass yield of a heterogeneous culture to fulfil either of the two goals is presented. 5.0 mgl(-1) Ni(II) in the feed composition to a c ompletely mixed, once- through, activated sludge was found to induce t he observed biomass yield of the microbial culture developed from sewa ge. As compared with the base-line study without Ni(LI), where the rea ctor received synthetic wastewater only, true biomass yield was found to have increased along with the increased decay constant with the net effect of lowering observed biomass yield drastically at lower diluti on rates and increasing it over that observed in the base-line study a t higher dilution rates. At 10.0 mgl(-1) influent Ni(II) concentration the culture conditions almost reverted back to the base- line study a nd at 25 mgl(-1) Ni(II) concentration a truly steady-state condition c ould not be attained. Copyright (C) 1996 IAWQ.