Understanding Oxidation Ponds. Is Dissolved Oxygen Profiling the Key?

Three-dimensional dissolved oxygen (DO) profiling was undertaken at several Oxidation Pond-based wastewater treatment plants (WwTPs) throughout New Zealand. This profiling identified that significant variations in DO can occur within an Oxidation Pond. These variations are not limited to the diurnal variations commonly reported, but can also include significant variations through both the vertical and horizontal profiles. In some ponds profiled, the aerobic layer was restricted to the surface layers, while other ponds remained aerobic throughout the vertical profile. These findings have implications for Oxidation Pond efficacy, with the rate of removal of both BOD and ammonia being influenced by oxygen availability.

The results of three-dimensional profiling undertaken at two of these WwTPs are presented in this paper. This paper also discusses the implications of these measured vertical and horizontal variations in DO, not only with respect to performance, but also as a potential tool to understand when sludge accumulation may be impacting on pond performance.