The Des Moines Wastewater Reclamation Authority operates a 97-million gallon per day regional wastewater reclamation facility (WRF) largely constructed in the mid 1980s to serve the greater Des Moines, Iowa metropolitan area. Originally constructed in a largely rural area, current plans for the area around the WRF establish a need for emissions control to reduce offsite odor impacts, in addition to reducing odor emissions to the surrounding neighborhoods. Plans for the surrounding area include a major “Agrimergent Technology Park” targeting value-added agricultural research and production companies, major roadway improvements making the road past the reclamation facility a primary corridor into the downtown area, and extension of the Des Moines River trail system past the WRF.
The Emission Reduction Study presents a plan to strategically abate WRF emissions to economically avoid future issues. The plan is based on the following:
- Comprehensive monitoring, sampling, and assessment of over 30 emissions sources at the WRF.
- Prioritization of emission sources based on relative contribution to offsite odor levels.
- Consideration of multiple technologies to control priority emissions.
- Progressive control of WRF emissions to achieve short- and then long-term goals as warranted by development of the surrounding area.
This Study provides a template for other treatment plants to systematically identify and quantify odorous emissions, predict offsite odor levels and assess the relative contributions of individual emissions, establish short and long term goals for offsite odor levels, and develop a cost effective control plan using the appropriate technology to progressively target emissions focusing initially on those with the lowest cost to control. It also shares the findings and results achieved using this template for the Des Moines WRF.
The Des Moines Wastewater Reclamation Authority operates a 97-million gallon per day regional wastewater treatment facility (WRF) in southeast Des Moines as indicated in Figure 1. The WRF was largely constructed in the mid 1980s to serve the greater Des Moines metropolitan area. It incorporates rock trickling filters constructed in the 1960s as part of a two-stage roughing filter, activated sludge treatment process. Figure 1 – WRF Facility
The liquid treatment train also includes mechanical screens, sewage pumps, aerated grit chambers, primary clarifiers, final clarifiers, and seasonal chlorine disinfection. Significant quantities of hauled liquid waste are also treated at the WRF; some through the entire liquid treatment train, and some directly through the anaerobic digesters.
Solids handling consists of rotary drum thickeners for thickening waste activated sludge, anaerobic digesters for stabilization of blended primary and waste activated sludge, and belt filter presses for dewatering digested sludge. An onsite biosolids storage facility is used during inclement weather.
This Emissions Reduction Study presents a plan to strategically abate WRF emissions to economically avoid future issues. The plan is strategic in that it focuses on WRF emissions with the highest concentrations, lowest volumes, and/or lowest cost to control and avoids emissions with the lowest concentrations, highest volumes, and/or greatest cost to control. It will avoid future issues by controlling WRF emissions in advance of planned changes for the surrounding area that include a major Agrimergent Technology Park and major roadway improvements.