Stephan J. Nix

Urban Wastewater Management in the United States: Past, Present, and Future

as either centralized, where all the wastewater is collected and conveyed to a central location for treatment or disposal, or decentralized, where the wastewater is primarily treated or disposed of on-site or near the source. Historically, municipalities, consulting engineers, and individuals have had the option of centralized or decentralized wastewater management and could have chosen from a variety of collection and disposal technologies to implement the management strategy. Although these options were available, the majority of engineers, public health officials, policy makers, and members of the public typically preferred one management strategy and one technology to the others. The reasons for a particular preference were based on a combination of cost, urban development patterns, accepted scientific theories, tradition, religious attitudes, prevailing public opinion on sanitation, the contemporary political environment, and many other factors. The development of urban wastewater management strategies and technologies from the early nineteenth century to the present

Analysis of the Long-Term Performance of Storage / Release Systems Using Linked Watershed-Water Body Modeling

This paper presents a method to analyze the long-term performance of storage/release systems using continuous simulation. The method follows previous efforts that packaged the storage/release problem into a two-input, one-output production function analysis. The two inputs are the storage capacity and the release/treatment rate. The output of the production function typically has been in terms of some measure of pollution control provided by the system (e.g., percent suspended solids removal). We take the analysis one step further by developing the production function with the output in terms of some measure of receiving-water impact. For this paper, we develop the production function in terms of the percent of time the in-stream flow rate exceeds a critical flow rate marking the point where sediment in the receiving water would be eroded. The modeling framework uses several blocks of the U.S. EPA Storm Water Management Model (SWMM) to simulate an urban catchment, the storage/release system, and a stream. The analysis involves performing long-term simulations using SWMM, systematically altering the simulated storage capacity and release/treatment rate between simulations, and deriving the production function using spatial interpolation. After the production function is established a cost optimization procedure is applied to determine the storage capacity and release rate combination that meets the receiving water goals while minimizing cost. Application of the analysis method is demonstrated using a hypothetical storage/release system and receiving water body.