No abstract

This article discusses how advances in chemical feed equipment provide options for cost‐effective alkalinity addition. In the past, carbon dioxide systems required deep basins and a significant amount of reaction time to achieve stable water. Improved technology provides a more consistent lime feed rate and a faster‐reacting lime slurry, which can allow for addition of lime after filtration without significantly affecting finished water turbidity. The use of carbon dioxide and lime allows utilities to “dial in” finished water alkalinity and pH simultaneously.

Central Oklahoma has a diverse, complex climate with weather events ranging from extreme winter conditions to severe drought with exceptional temperatures to violent storms to destructive flooding. In order for Oklahoma City Water Utilities Trust (OCWUT) through the Utilities Department for the City of Oklahoma City to respond to system failures resulting from inclement and disasters, policies and procedures have been implemented to immediately address impacts to the water and wastewater system. Emergency construction contracts allow for the design, bidding and contract award within a period of a few days. Material pre-purchase provides for materials on-hand to eliminate lead times for manufacture and/or delivery of pipe and repair kits. Contracting of on-call services has allowed OCWUT to remain ready to respond while not increasing staff or while deferring capital expenditures. Lastly, resource flexibility has created the ability to reallocate assets as needed to other areas to enable OCWUT to address increased demands for a particular area while not increasing overall staffing levels.

The approach developed for Oklahoma City evaluates a total year of simulated rainfall based on historical precipitation patterns. The typical year time series rainfall was used by Oklahoma City to identify an acceptable level of protection and risk. It was also possible to define different levels of protection to different parts of the wastewater collection system and evaluate seasonal collection system performance. This is a robust analysis which uses local precipitation patterns and can be readily duplicated for any geographic location. Most importantly perhaps, it puts the decision of acceptable level of protection and risk firmly into the hands of the wastewater collection system owner.

The Oklahoma City Water Utilities Trust (OCWUT) reconciled several sanitary sewer overflow data sources and performed an informal condition assessment of their wastewater collection system in response to a Request for Information from the U.S. Environmental Protection Agency. Based on the assessment, staff implemented a targeted preventative maintenance program and developed several capital improvement projects for both rehabilitation and replacement and for increasing collection system and treatment capacity. From this process, OCWUT determined that an improved preventative maintenance program was necessary, better organization of the data would provide more accessible data for future analysis and a formalized, electronic method for condition assessment of the collection system would save valuable time and resources. Lastly, OCWUT realized that in-house staff could provide a quick and thorough response on time-constrained regulatory requests due to institutional knowledge of their systems.