The process of generating electricity at thermal power stations involves the usage of vast quantities of water for steam generation, condensing, cooling, air pollution control, waste transport and other purposes. The input water may need treatment prior to its use and, once used, will require treatment to remove impurities introduced in the process, prior to release back to receiving waters. Water and power production are so inextricably linked that the term “Water-Energy Nexus” has come into common usage.
Water availability and restrictions on the introduction of pollutants to water bodies have placed greater emphasis on water reuse, rather than once through and done. Innovation in cooling water cycles, water re-use and intermediate treatment methods have enable power generation facilities to become much more efficient in their usage of water to achieve the goal of “zero liquid discharge.” In order to achieve such efficiencies, technical expertise in areas including process design, industrial water treatment, environmental sciences and air pollution control technologies must be combined.
Effective management of water used in the power generation process can be broken into three categories:
There have been various regulations adopted in the US under the Clean Water Act to address these three objectives in various combinations.
Water intake and discharge CWA §316(a) and (b)
Power plants and heavy industrial facilities often use significant amounts of water from adjacent rivers, oceans and lakes to cool and condense steam used in the electricity production process and for other cooling needs. Cooling water intake structures (CWIS) and cooling system devices (e.g. intake screens) can adversely affect fish and other aquatic life by drawing organisms (including eggs and larvae) into the cooling system (entrainment) and trapping organisms against intake screens (impingement). On May 19, 2014, the US Environmental Protection Agency (EPA) issued the 316(b) final rule. The EPA regulates CWIS under this provision of the Clean Water Act (CWA). In addition, the EPA under 316(a) addresses the regulation of thermal variances resulting from impacts of cooling water discharges through the National Pollutant Discharge Elimination System (NPDES) permit renewal process.
Cooling water intake and discharge services
Water quality CWA §423 effluent limitation guidelines
According to the EPA, steam electric power plants contribute over half of all toxic pollutants discharged to surface waters by all industrial categories currently regulated in the United States under the Clean Water Act. Some examples of toxic pollutants discharged are lead, mercury, arsenic, selenium and aluminum. There are numerous documented instances of environmental impacts associated with these discharges including aquatic life impacts and toxic metal bioaccumulation in wildlife.
The proposed national standards will reduce pollutant discharges by placing greater emphasis on treating dissolved pollutants versus a focus on setting out particulates. This challenge is made even greater the new Coal Combustion Residuals (CCR) Rules which will require closure of many the surface impoundments used to collect CCR as well as liquid waste streams from various plant processes.
Amec Foster Wheeler has experienced personnel, who can assist clients with the consulting, engineering and program/construction management required to develop cost-effective solutions to this wastewater challenge. Since part of our business involves the design and fabrication of combustion and air pollution control equipment, we are extremely familiar with the solid and liquid pollutants produced by this advanced equipment. Our engineering, procurement, construction (EPC) capabilities enable us to first develop accurate estimates of costs for treatment options and then to implement the chosen solution.
Minimization of consumptive water usage
According to a US Geological Survey (USGS) report, in 2010 water used for thermal power generation accounted for 45% of all withdrawals in the US. Global concern over availability of adequate levels of fresh water has put additional pressure on the power generation industry to control the quantity of water it consumes. Amec Foster Wheeler has deep experience in water management issues, not only within the power generation industry, but also in other process-related industries such as petrochemicals, oil refining and paper and pulp production.
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