Batch Studies on the Biological Denitrification of Wastewater.

Abstract

<p> This dissertation examines the influence of the process variables, organic carbon concentration, nitrate concentration, pH, organism concentration, and temperature, on the rate of denitrification of dominant batch cultures of Pseudomonas denitrificans. The aim of the work was to determine which of the first four variables were important in controlling rate, and whether significant interactions existed between variables. As well, the ability of these typical bacterial denitrifiers to operate at low temperature conditions was to be ascertained. </p> <p> The experimental procedure indicated that pH and carbon concentration are the major influences on the unit denitrification rate a well as the overriding factor temperature which profoundly influences any bacterial process. Organic carbon concentration controls the rate up to the point where the stoichiometric requirements for nitrate reduction and the carbon needs for new cell growth are satisfied. A broad pH optimum within the normal range experienced in most wastewater treatment conditions was demonstrated. The temperature dependancy of the unit denitrification rate was shown to follow an Arrhenius relationship between 3ºC and 27ºC. As well, for the simplified system investigated the unit rate was independent of nitrate concentration. </p> <p> The dominant culture was related to mixed cultures of activated sludge to provide an estimate of the denitrifying rate of activated sludge on a similar simple batch system. </p>