Emerging Water Management Challenges at Coal-Fired Power Stations using Flue Gas Desulfurization - Requirements to Address New USEPA Regulations

摘要

In September 2015, the U.S. Environmental Protection Agency (EPA) promulgated changes to the wastewater discharge regulations for the Steam and Electric Power Generating industry. A key feature of the new regulations established revised limits on the levels of the inorganic constituents As, Se, and Hg, as well as nitrate present in wastewater discharges from a range of process and industrial operations byproducts, including Flue Gas Desulfurization (FGD) wastewater. These regulation changes were in response to the implementation of new technologies and air pollution controls within coal-fired power stations over the last 30 years, which has impacted on wastewater characteristics. The changes to discharge criteria present a number of new challenges to the Steam and Electric Power Generating sector - some obvious, such as the need for new infrastructure to meet these new regulations; some less obvious, such as the need to enhance operational capabilities to meet the needs of technologies that may be new to power station operators.. Both opportunities and risks are inherent with these changes, being both a great opportunity for power generators to review their site water balances and make improvements in the way they manage their water cycle, with the clear risk of implementing new technologies or approaches that complicate site operations and potentially distract from core operational activities. The new regulations will require existing federal and state discharge permits to be renegotiated, such that permit renewals demonstrate an approach to meeting the new discharge limits. In turn, this will require that many operations will need to install new or improved pollution control technologies on FGD wastewater streams, such as enhanced physico-chemical treatment systems, ion exchange and membrane technologies, and biological treatment processes that have applicability to inorganic treatment. Alternatively, there will be a need to consider different approaches to wastewater management and disposal, such as deep well injection, water recycling, and/or establishing zero liquid discharge (ZLD) arrangements. The best value approach for any particular facility will be dependent on site-specific factors and needs to be considered on a case-by-case basis. An important consideration also relates to the potential for routine analytical procedures to not accurately reflect true constituent values for As, Se, and Hg. As a result, USEPA has identified modified analytical test procedures in order to overcome observed matrix affects. Composite samples were collected and submitted for analytical testing using the routine ICP-MS technique, as well as alternate techniques devised to address possible matrix interference affects. The audience will be given a brief summary of new USEPA regulations, with a focus on the key issues identified that coal-fired power stations must address and outline suggested approaches to best manage these issues in a way that minimizes the impact to both the financial performance and operational integrity of the facility. Recent analytical results from FGD wastewater testing using multiple laboratory techniques will be presented and discussed as it relates to accurate representation of As, Se, and Hg concentrations in order to evaluate the most appropriate wastewater management approach. This will allow for decisions to obtain the lowest life-cycle Capex/Opex values. This discussion will include firsthand experience obtained from power stations already addressing similar challenges.