Experimental and Theoretical Studies of Sulfide Generation in Sewerage Systems

The measurement of sulfide generation rates from sewer slimes using a rotating-drum reactor is described. The practical utility of this procedure for assessing the contribution to sulfide production which arises from the admission of industrial wastes into domestic sewage is demonstrated. The use of the reactor for more theoretical purposes such as the determination of the zero-order rate constant for a particular sewage is also described.

The effect of flow velocity on sulfide generation rate was investigated by pumping sewage at controlled rates through a ‘model' sewer which ‘flowed full'. Under turbulent flow conditions (Re>4000) the rate of sulfide production (expressed as a mass flux g m⁻²day⁻¹) was relatively high and the effect of flow rate on the rate of production was positive but small. In the laminar region (Re<2100) the situation was reversed i.e. the sulfide mass flux was relatively low but the effect of flow rate on sulfide production was relatively large.

Theoretical studies of sulfide generation are outlined. The zero order rate constant, determined using the rotating drum reactor, was utilised to predict sulfide generation rates in the model sewer. Agreement between experiment and prediction was satisfactory for conditions of turbulent flow. For laminar flow the agreement was less satisfactory. However the predictions for laminar flow were qualitatively correct in as much that a significant drop in sulfide generation rate was observed on moving into the laminar flow region.

The results of the studies show that it is possible to develop a predictive design procedure for sulfide production based on established engineering principles rather than relying on empirical correlations.