Coal Ash Leachate: Evaluating the Impact of Adding a Prominent Significant Industrial User
- Mary Sadler PE, Victor Czar PE, Paul Weeks PE, Tim Devine PE
In the wake of highly publicized coal ash pond spills, the fate of coal ash waste has become a passionate topic of public interest. In 2015, a potential new significant industrial user (SIU) applied to discharge coal ash leachate to the Big Buffalo Wastewater Treatment Plant (WWTP), a facility owned and operated by the City of Sanford, North Carolina. An evaluation of the potential impacts of this potential waste stream was required to assess Sanford’s ability to meet current and anticipated future effluent permit limits. The evaluation included addressing public concerns regarding a broad array of environmental impacts, such as source water protection, the impact to the City’s biosolids land application program, analytical methods, and radioactivity.
The technical evaluation included a waste stream characterization, a site-specific metals removal study, and an update of the City’s headworks analysis using several scenarios. The waste stream characterization was developed using leachate data from North Carolina coal ash ponds and available literature values. The site-specific metals removal study was conducted for 14 metals to update the headworks analysis with current removal efficiency data. The Big Buffalo WWTP was recently expanded from 6 to 12 mgd. The expansion project also included a biological nutrient removal upgrade. Several headworks analysis scenarios were then evaluated to determine waste load allocations available to new industry. The headworks analysis scenarios considered the new metals removal efficiencies as well as future regulatory issues. A relative metals evaluation was also conducted to demonstrate to the public the amount of water a person would need to consume to exceed a health reference dose and the mass of discharged metal in effluent expressed as teaspoons per day.
This paper will present the regulatory and technical analysis, the challenges of communicating to the public, and addressing public concerns regarding a high-profile industry and a controversial issue.
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