College of Engineering Unit:
Facultative ponds followed by constructed wetlands provide adequate, relatively low-cost, and moderately low maintenance wastewater treatment for small communities such as Monroe, Oregon. Various alternative design options were analyzed for implementation at this site. The overall redesign of the existing facilities attempts to utilize the previously constructed facultative pond series to decrease overhead costs. The overall design includes a primary facultative pond followed in series by free water surface (FWS) constructed wetlands. Chlorine disinfection and dichlorination takes place before discharge to the Long Tom River. Retrofitting the current ponds for this design involves building two parallel facultative ponds with increased surface area to decrease the aerial BOD5 and TSS loading rates to appropriate levels for constructed wetlands that will further treat and polish the wastewater before discharge. The FWS wetlands are divided into alternating emergent vegetation zones and open surface zones with submerged vegetation. This layout of the wetlands will provide the necessary environment for ammonia nitrification and a small amount of denitrification treatment to account for future nitrogen regulation. By designing the system into two parallel treatment trains, redundancy addresses emergencies and maintenance needs. The design has improved the efficiency of removing BOD5 and total suspended solids present in the influent of the wastewater treatment facility with considerations for industrial and population growth expectations to the year 2040 to meet the EPA wastewater effluent quality requirements outlined in the NPDES permit for Monroe. This updated version of the wastewater treatment system includes basic design recommendations and discusses the expected outcomes of the design. Additionally, this design project addresses the capital cost of design, operation, and maintenance and potential funding benefits found in Public Law 117-58 for infrastructure projects.
The City of Monroe's current wastewater treatment facility consists of 3 facultative ponds: a primary pond, secondary pond, and a polishing pond in series. Facultative oxidation ponds are a common concept for small rural communities where land is not a limiting factor. Facultative ponds can be used to treat raw, screened, or primarily settled municipal wastewater. The current facility often violates biochemical oxygen demand discharge limitations. This project will describe an alternate proposal for treating the wastewater pollutant loading from the City of Monroe through upgrades of the existing system with redesign to incorporate constructed wetlands while considering the projected population and industrial growth expectation. In addition to BOD and suspended solids, this project will address ammonia, thermal, and funding concerns to meet current and potential discharge requirements.