Nutrient Removal and the Water Environment

The inaugural WEF Nutrient Removal specialty conference was an unmitigated success, both well-attended and crammed full of interesting presentations. This high level of interest in nutrient removal practices is an indication of the increased attention accorded environmental quality and consequently evolving government regulations. We expect the current issue of Water Practice to serve as an important contribution to this closely followed field.

Nutrient removal is being given increasing attention as the effects of nutrient loading are observed in ecosystems throughout the world. Some of the greatest impacts are being borne by our most unique aquatic systems, such as the Chesapeake Bay and Long Island Sound of North America (see Brown et al., this issue) and the Baltic Sea off of Sweden (Sundin, this issue).  These affected waters have large drainage basins, typically including more populated areas. In an effort to restore water quality, regulators are tightening nutrient Total Maximum Daily Loads (TMDLs) in tons per year while the total loading to wastewater treatment plants has been increasing. The net result has been an increasing pressure on treatment plants to further increase their nutrient removal capabilities.

In order to comply with these ever more stringent discharge requirements, utilities have had to adapt new technologies and find better ways of operating their old technologies.  In many cases, total nitrogen concentrations of 3 mg/L and 0.3 mg/L effluent phosphorous or lower are required.  Often, aids to nutrient removal are required, such as the addition of a carbon source (Rusten & Odegaard, Motsch et al., this issue), effluent filtration (Brown et al.), or chemical precipitation (Rusten & Odegaard). Improvements to existing technologies such as Moving Bed BioReactor (MBBR) or Integrated Fixed Film Activated Sludge (IFAS) have been tested and implemented to achieve these low levels within a smaller footprint (Rusten & Odegaard, Motsch et al., Johnson et al.).  The use of computer modeling is also proving to be a useful tool to compare processes and predict how they will perform under varying loads (Sen et al.).

There are a number of newer approaches on the horizon as well. In this issue, Wett et al. discuss the necessary water quality parameters for deammonification using ammonia oxidizing bacteria. From a more acute operational perspective, Pinto et al. look at the impact of toxic shock events and note that corrective action may sometimes exacerbate the problem. As treatment operations are forced to bear more of the environmental burden and with a lower margin for error, unique strategies and unexpected scenarios such as these should also be explored.

Alan Scrivner, Issue Editor
AES Engineering

Dimitrios Katehis, Issue Editor
CH2M HILL