Optimisation of the design parameters in an activated sludge system for the wastewater treatment of a potato processing plant

Aerated biological reactors at a laboratory scale, fed continuously with a model wastewater system, were used to obtain design parameters of an activa ted sludge process for the wastewater treatment of a potato processing plan t. Experiments were performed using different dilution rates (D) ranging be tween 0.01 and 0.13 h(-1) to determine parameters such as: maximum specific microbial growth rate (mu(max)), saturation constant (K-s), coefficient of microbial decay (k(d)) and true biomass yield (Y-x/s) Design parameters we re calculated from the mass balances of substrate consumption and biomass p roduction under steady state, considering a Monod-type equation to represen t the effect of substrate concentration on biomass production rate. The val ues of Y-X/S and k(d) were obtained from the linear plot of q(s) (specific rate of substrate consumption) vs. D. Experimental data regression led to y (X/S) = 0.45 gVSS/g COD and k(d) = 0.024 h(-1). By non-linear regression of q(s) vs. substrate concentration (S-s) data the following values were obta ined mu(max) = 0.09 h(-1) and K-s = 0.006 g/l. Critical dilution rate was a lso calculated; it corresponds to the D value for which the cells of a reac tor operating under such conditions are destroyed or are eliminated from th e system at the same rate than they are produced. (C) 1999 Elsevier Science Ltd. All rights reserved.