Cooling water use patterns at US nonutility electric generating facilities

Cooling water is used by many industrial facilities. The largest user of cooling water is the electric power industry, although other significant users include the pulp and paper, chemical, iron and steel, aluminum, and petroleum refining industries. The US Environmental Protection Agency (EPA) is currently developing regulations to implement section 316(b) of the Clean Water Act, which deals with cooling water intake structures. The EPA will examine cooling water use patterns at various industries. Data pertaining to cooling water use patterns at utility plants are readily available; however, no information has been assembled for cooling water use at electric power generating facilities owned or operated by entities other than utilities (nonutilities). This paper presents data concerning cooling water use from two subsets of the nonutility sector and focuses on plants using once-through cooling systems. The first subset includes 123 nonutility plants that each generate at least 150 MW of power. Collectively, they represent 41,494 MW of generating capacity, or about 56% of the total nonutility generating capacity. Approximately 17% of the installations within that subset utilize once-through cooling water. The second subset includes 58 waste-to-energy facilities, which individually produce less than 80 MW but collectively generate about 2200 MW. Only 11% of this subset of plants uses once-through cooling water. The total 15,372 MW generated by once-through nonutilities is equivalent to only 6% of the 258,906 MW generated by utilities utilizing once-through cooling. From a national perspective this share may appear relatively insignificant. However, in some states, the nonutility once-through total is equivalent to a more significant percentage of the utility once-through total.     

Fish protection technologies: a status report

Section 316(b) of the Clean Water Act has required that “best technology available” (BTA) be used to minimize adverse environmental impacts resulting from operation of the cooling water intake structure (CWIS). The primary effects of CWIS operations are the entrainment of small aquatic organisms through the cooling water system and the impingement of larger life stages on traveling water screens. Extensive research has been conducted since the early 1970s in attempts to develop technologies that will minimize entrainment and impingement. As a result, a suite of technologies is available that can be considered for application as the BTA at the CWIS. Available technologies include fish collection systems, fish diversion systems, physical barriers and behavioral barriers. The ability of a given technology to meet BTA requirements is influenced by a wide variety of biological, environmental and engineering factors that must be evaluated on a site-specific basis. The status of systems and devices in each category of fish protection alternatives is presented.     

Assessment of 316(b) impacts on Ohio River fish populations

Cooling water intake systems have the potential to adversely impact aquatic organisms though entrainment and impingement (impacts referenced under 316(b) of the Clean Water Act), yet the loss of individual fish does not necessarily mean that a population will suffer a significant decrease in number. The results of utility sponsored studies on Ohio River fish populations provide strong evidence of positive changes in the fishery due to water quality improvements. Despite these improvements, a simulation is needed to determine if a reduction in 316(b) fish losses would result in higher or similar fish population levels. Electrofishing data collected at seven power plant locations from 1981 to 1998 will be used for the population assessments. Potential 316(b) impacts on Ohio River fish populations will be modeled using site specific 316(b) data and a Leslie matrix model. The theoretical maximum population for various fish species, with and without 316(b) impacts, will be compared and the probabilistic risk that fish populations will fall below the threshold for species survival will be assessed. Historically, EPA has allowed 316(b) to be implemented on a case-by-case basis, however, the utilities believe that the first step in assessing potential adverse environmental impacts is to assess the condition of the affected fish populations.     

Impacts of power-plant cooling systems on estuarine fish populations: the Hudson River after 25 years

In the early 1970s, impacts of power-plant cooling systems on fish populations were a major source of controversy. The most thoroughly studied and controversial power plants were the Indian Point, Bowline, and Roseton generating stations on the Hudson River. The assessments performed for these three plants were unique in employing river-wide sampling data and mathematical models designed to predict the effects of cooling-water withdrawals on the short- and long-term abundance of striped bass and other important fish populations. A Settlement Agreement in 1981 led to the establishment of a long-term monitoring program that continues to generate valuable information concerning the impacts of power-plant cooling systems on estuarine ecosystems. This paper evaluates the results generated by the past quarter century of Hudson River, with the objective of evaluating the utility of the information for future 316(b) assessments. Specific recommendations are made concerning: (1) methods for quantitative assessment of cooling-system impacts at new vs operating facilities; (2) research that would improve the efficiency and accuracy of assessments; and (3) the need to integrate cooling system impact studies into a general framework for management of aquatic ecosystems.     

A comparative review of entrainment survival studies at power plants in estuarine environments

Steam-electric power plants drawing cooling water from surface waters entrain a variety of plankton and weak-swimming nekton. These small organisms pass through the intake screens and are carried along with the cooling water through the plant and are subjected to thermal, physical, and chemical (biocide) stresses. In once-through cooling systems, entrained organisms are returned to the source water body, where they are subjected to rapidly decreasing temperatures as cooling waters are mixed into receiving waters. With 4316(b) of the Clean Water Act as the impetus, studies were conducted at many power plants to quantify the number of entrained organisms. Early studies focused on simple abundance, and assumed total mortality. By the late 1970s and early 1980s, advances in sampling technology demonstrated that many entrained organisms survived. Continuing refinement of sampling techniques revealed impressive survival statistics for many species (>90% in some cases), with concomitant reductions in perceived impacts. This paper reviews state-of-the-art sampling methods and results of field entrainment studies at seven power plants. This review demonstrates that high entrainment survival of a variety of aquatic organisms does, in fact, occur and specifies the plant-operating and environmental conditions under which high survival occurs.     

Multiattribute utility analysis for addressing Section 316(b) of the Clean Water Act

We believe that the fundamental issues associated with implementing Section 316(b) of the Clean Water Act are whether or not it requires a balancing of objectives and if it does, how that balancing should be done. If balancing is required, we recommend the use of multiattribute utility analysis (MUA). MUA is a formal, analytic approach for evaluating and comparing options for decisions with multiple objectives. It differentiates the two types of judgments needed for public policy decisions: (1) value judgments, which indicate what people want to happen as the result of a decision and their willingness to make tradeoffs, and (2) scientific judgments, which indicate what scientists or other technical specialists think is likely to happen based on the option that is chosen. MUA provides an approach for deciding what is an ‘adverse environmental impact’ and what is ‘best technology available’ based on site-specific considerations that can be consistently applied to all cooling water intakes. To illustrate the first step of a collaborative MUA process, we present a preliminary hierarchy of objectives constructed during a 1-day meeting held with regulators, electric utilities, and environmental groups to address the renewal of SPDES permits for four power plants operating on the Hudson River.     

Entrainment and impingement studies at two power plants on the Wabash River in Indiana

Fish entrainment and impingement studies were conducted at Cayuga and Wabash River generating Stations in 1987 and 1988, respectively. Concurrent river samplings were conducted upstream from the stations to assess adult fish and ichthyoplankton populations. The original 316(b) studies at these stations were conducted in 1976–1977 and concluded that the stations were having minimal adverse impact on the Wabash River fish community. The state regulatory agency did not agree with this interpretation and requested the subsequent 1987 and 1988 studies. The major issue at these once-through cooling power plants was the large water withdrawals at Cayuga and Wabash River Stations [1318 and 1096 cubic feet per second (cfs) maximum plant flows, respectively], in contrast to the relatively low average annual Wabash River flows (10,070 and 11,110 cfs, respectively). The close proximity of the stations (35 river miles apart) together with the high percentage of water withdrawn suggest that the potential risk of unacceptable impacts is high.The six-month impingement estimates for Cayuga and Wabash River Stations were 15,086 and 11,401 fish, respectively. Impingement catches at both stations were dominated by young-of-the-year (YOY) channel catfish and gizzard shad. In addition, small minnows (primarily bullhead minnow and emerald shiners) were commonly impinged at Cayuga Station. Minnows (predominantly spotfin shiner, bullhead minnow and emerald shiner) were also the dominant species in the river samplings upstream from the stations. In the entrainment samplings, an estimated 26,920,382 and 107,503,876 fish eggs and larvae were entrained each year at Cayuga and Wabash River Stations, respectively. Ictiobinae (buffaloes and carpsuckers) and Cyprinidae (minnows and shiners) were the dominant ichthyoplankton in the river. Approximately 3.5 and 23% of the total river ichthyoplankton were entrained at Cayuga and Wabash River Stations, respectively. Gizzard shad at Cayuga Station, and Ictiobinae and Cyprinidae at Wabash River Station (WRS) were the dominant taxa entrained by the stations. Unusually low river flows during the spring and summer of 1987 and 1988 provided worst-case conditions for entrainment and impingement at the stations. However, the relatively low impingement and entrainment numbers during these worst-case conditions indicated that these stations were not adversely affecting the Wabash River fish community.     

Evaluation of multi-metric bioassessment as an approach for assessing impacts of entrainment and impingement under Section 316(b) of the Clean Water Act

Over the past two decades, biological assessment has been widely adopted as a tool for comprehensive monitoring of ambient water quality, and increasingly it is used for management and regulation. Presently, biocriteria are central to the pre-decisional draft regulatory framework the US Environmental Protection Agency is developing under a consent decree to implement Section 316(b) of the Clean Water Act. With the increasing integration of multi-metric bioassessment and biocriteria into environmental regulation, it becomes important to critically review the performance of the methods to ensure they are robust and reliable tools for determining water body impairment. This paper examines the strengths and weaknesses of current approaches to bioassessment, focusing on issues that derive from recent advances in theoretical and applied ecology. Two critically important insights into the structure and function of ecosystems are: (1) the dynamic character of ecosystems; and (2) the significance of context and scale. Ecological dynamics produce spatio-temporal variability, which presents significant challenges to the development of biological criteria. This challenge is highlighted by the large percentage of sites potentially affected by arbitrary decisions sometimes made in setting biocriteria thresholds. Multi-metric bioassessment has not taken adequate account of the multi-scaled nature of ecological systems. Consideration of spatial scale will be especially important as multi-metric bioassessment methods originally developed in streams are adapted to larger, more open systems such as large rivers, estuaries, and coastal waters, and for regulation of cooling water intake structures.     

A perspective on power generation impacts and compensation in fish populations

Renewed interest in the topic of compensation in fish populations has been stimulated by new EPA 316(b) regulations relating to entrainment and impingement looming on the horizon. The purpose of this paper is to revisit the topic of population compensation for fish populations in the context of assessing power generation impacts. I define compensation as the net population-level outcome of changes in growth, survival, and reproduction at the individual fish level that offsets decreases or increases in population density. Potential mechanisms of compensation have been well document in laboratory and field experiments. The process underlying all these mechanisms is that changes in population density can change per capita availability of essential resources such as food and space. The state of science in this area is constrained both retrospectively and prospectively by five technical stumbling blocks. Technological advances have improved our ability to bound the phenotypic plasticity of a species and to assess the potential effects of power generation impacts through a combination of monitoring, special studies, and simulation modeling. Four generalizations concerning compensation are mentioned. Progress has been made over the past three decades, but this topic remains scientifically challenging and politically controversial.     

Heavy metal distribution of natural and reclaimed tidal riparian wetlands in south estuary, China

The characteristics of heavy metals in water, soils and plants of NRWs are significantly different from those in the RTRWs which are strongly affected by human activities.     

Experimentally-derived upper thermal tolerances for redhorse suckers: revised 316(A) variance conditions at two generating facilities in Ohio

American Electric Power’s Conseville Station and Muskingum River Plant, located on the Muskingum River in southeastern Ohio, utilize once-through cooling for seven (combined) generating units. Both facilities had approved 316(a) variances that required maintenance of a baseline fully-mixed downstream temperature of 31.6°C (88.9°F). Fish sampling conducted during critical conditions in Summer 1993 indicated the presence of thermally-sensitive redhorse suckers (Moxostoma sp.) at river temperatures >32.2°C (90.0°F). Because the assumed upper tolerance limit for redhorse suckers (31.6°C) was extrapolated from field observations, we determined the actual thermal tolerance of suckers using fish collected locally. During September 1996 golden and shorthead redhorses were collected from the nearby Walhonding River. The short-term upper thermal tolerances were determined by the ultimate upper incipient lethal temperature (UUILT) and the critical thermal maximum (CTM) endpoints. For shorthead redhorse the calculated UUILT was 33.3°C (91.9°F), and the CTM was 35.1°C (95.2°F). For golden redhorse a similar CTM was obtained; however, a reliable UUILT could not be extrapolated due to procedural problems. The results of these tests played a role in Ohio EPA approving a higher fully-mixed downstream limit. This study demonstrates the value of obtaining thermal tolerances experimentally when assumed tolerance values are considered suspect.     

A retrospective evaluation of 316(b) mitigation options using a decision analysis framework

Choosing the best 316(b) mitigation option is a daunting task. Decision analysis (DA) provides an objective framework that can be used to choose among several mitigation strategies where there are multiple objectives and numerous uncertainties. This paper has two objectives: (1) to illustrate the use of the DA framework for making a 316(b) decision (using the Chalk Point Power Station as a case study); and (2) to show that DA is also useful for quantifying the benefits of a previous decision. The Chalk Point case, resolved in 1990, centered around the mitigation of adverse environmental impacts of a cooling water intake structure (CWIS) as a result of fish and blue crab losses associated with impingement and entrainment. Barrier nets and fishery enhancement programs were used to mitigate the losses. We compare the costs and benefits of the mitigation options actually employed to those of other options. The costs and benefits were estimated numerically using standard DA methods. Valuations and probabilities were derived largely by professional judgment based upon the original Chalk Point 316(b) studies and ongoing monitoring. DA indicated that the optimal strategy and expected utility were functions of the weighting of environmental benefits relative to cost.     

美国溶解氧基准标准及其对我国的启示

近年来我国水质量整体改善,但全国采用统一的溶解氧标准易导致不同地区水体欠保护或过保护.美国拥有相对完善的溶解氧标准体系,在综述了美国溶解氧基准标准制定体系的基础上,初步分析了我国溶解氧标准现存的不足及美国溶解氧标准制定对我国的启示.美国国家环境保护局通过分析不同溶解氧暴露情况对水生生物的影响,针对淡水和海水2种栖息地环境,对冷水和温水物种及其不同生活史阶段分别制定溶解氧基准值.美国各州参照溶解氧基准,考虑社会经济、反降级政策等因素,在不同时间和地点分别制定了保护指定水体功能的溶解氧标准值.我国现行的溶解氧标准值,主要参考国外发达国家标准制定,缺少对我国溶解氧背景浓度和水生生物溶解氧敏感性的基础研究.为制定符合我国国情的溶解氧基准标准,需在综合考虑我国气候、地理条件等自然因素对溶解氧影响基础上,开展水生生物对溶解氧敏感性、栖息地环境对物种及溶解氧浓度影响的相关研究工作,并综合考虑反降级政策,防止水质进一步恶化.      

Cost effective environmental control technology for utilities

On September 24, 1998, new regulations announced by the US EPA require 22 eastern states plus the District of Columbia to develop state implementation plans to reduce ground-level ozone through the reduction of nitrogen oxide (NOx) emissions (Cooper, 1998). This plan calls for a 28% NOx cut in the summer time (1.2 million tons) by 2007. This calls for utilities to develop new, efficient, and robust post-combustion NOx control technologies. A new environmental control technology called low temperature oxidation (LTO) system, which can reduce NOx emissions below measurable levels (i.e. 2 ppm using process analyzers) at low temperature (125-325 °F), was awarded the best available control technology and the lowest available emission reduction technology by the US EPA in April 1998. Ozone is employed to oxidize nitric oxide (NO) to dinitrogen pentoxide (N₂O₅) at a low temperature in an oxidizer, which is then easily absorbed by water in a scrubber. Bench scale and pilot plant tests have shown that the LTO process can almost completely remove the NOx emissions (i.e. NOx emissions are below levels measurable using process analyzers). This proved that the LTO system is an attractive process to meet the stricter NOx regulations. There are multiple benefits of the LTO system besides removal of NOx emissions, includes reduction of SOx and CO emissions, and no secondary air emissions (NH₃, N₂O). In order to obtain minimum NOx emissions, extra ozone needs to be supplied. The cost of the process also increases nonlinearly as emissions decrease. This poses a challenging multiobjective optimization problem where emissions like NOx and SOx need to be minimized, while minimizing the system cost as well as extra ozone. This problem is addressed using a new and efficient multiobjective optimization framework. This framework will provide designs that are cost effective as well as environmentally friendly.     

从意愿到行动:中国地方环保局的机构能力研究

越来越多的研究将中国的环境问题归因于执法不严.但是,很少有人探索环保机构能力和环境管制以及执法之间的关系.在前人对国家能力研究的基础上,发展了一套指标体系对中国地方环保局的机构能力进行评价,并分析了环保机构能力和污染物减排之间的关系.研究表明:具有较好人力资本(而不是预算更多)的地方环保局能够更好地从事环境监管工作,地方环保局的机构能力提升对污染物减排产生显著正面效果;另外,严格的环境监管却不一定会改善环境状况.那些工业治理环境能力强的地区通常工业较发达,污染物排放量大,抵消了环保局监管执法所产生的正面收益.由此可见,要缩小环境法律法规规定的目标和环境现状之间的差距,仅靠监管手段创新和增强地方环保局的机构能力是不够的,中国还需要努力开展全社会监管环境的制度建设.     

The impact of climate change mitigation on water demand for energy and food: An integrated analysis based on the Shared Socioeconomic Pathways

Climate change mitigation, in the context of growing population and ever increasing economic activity, will require a transformation of energy and agricultural systems, posing significant challenges to global water resources. We use an integrated modelling framework of the water-energy-land-climate systems to assess how changes in electricity and land use, induced by climate change mitigation, impact on water demand under alternative socioeconomic (Shared Socioeconomic Pathways) and water policy assumptions (irrigation of bioenergy crops, cooling technologies for electricity generation). The impacts of climate change mitigation on cumulated global water demand across the century are highly uncertain, and depending on socioeconomic and water policy conditions, they range from a reduction of 15,000 km³ to an increase of more than 160,000 km³. The impact of irrigation of bioenergy crops is the most prominent factor, leading to significantly higher water requirements under climate change mitigation if bioenergy crops are irrigated. Differences in socioeconomic drivers and fossil fuel availability result in significant differences in electricity and bioenergy demands, in the associated electricity and primary energy mixes, and consequently in water demand. Economic affluence and abundance of fossil fuels aggravate pressures on water resources due to higher energy demand and greater deployment of water intensive technologies such as bioenergy and nuclear power. The evolution of future cooling systems is also identified as an important determinant of electricity water demand. Climate policy can result in a reduction of water demand if combined with policies on irrigation of bioenergy, and the deployment of non-water-intensive electricity sources and cooling types.     

气候变暖对中国夏热冬冷地区居住建筑采暖降温年耗电量的影响

20世纪80年代中期以来的气候变暖,尤其是90年代中期以来的气候显著变暖带给社会经济发展的利与弊,一直以来受到广泛关注。气候变暖对于建筑耗能,尤其是对采暖和降温总耗能的影响很值得研究。论文以主要使用电能进行空间调节的中国夏热冬冷地区为对象,以《夏热冬冷地区居住建筑节能设计标准JCJ134-2001》中所规定的采暖、降温耗电量限值为依据,研究了气候变暖对该区居住建筑单位面积采暖年耗电量、降温年耗电量及采暖降温年耗电总量的影响。结果表明,1986年以来的气候变暖,尤其是1996年以来的气候显著变暖,理论上使夏热冬冷地区居住建筑单位面积采暖年耗电量降低;同时增加了相当一部分地区居住建筑单位面积降温年耗电量;除个别地区外,气候变暖理论上使中国夏热冬冷地区居住建筑单位面积采暖降温耗电总量普遍下降。     

On the use of expert judgment to characterize uncertainties in the health benefits of regulatory controls of particulate matter

Health benefits assessment is an analytic tool used extensively by the U.S. Environmental Protection Agency (EPA) in characterizing the costs and benefits of air quality regulations. In a 2002 review of EPA methods, the U.S. National Research Council (NRC) called on EPA to more fully account for and communicate uncertainties in estimates of the health benefits of air pollution regulations. In particular, the NRC recommended that EPA use expert judgment to quantify uncertainties in cases where empirical estimates are lacking. In response, EPA developed and carried out an expert elicitation (EE) study to quantify uncertainties in the effects of fine particulate matter (PM_2.5) on mortality in the U.S. This work has yielded new estimates of the uncertainty distribution of a key relationship – the concentration–response (C–R) function – used around the world in benefits analyses for air quality regulations. This paper discusses the ways in which the EE results have informed and influenced recent regulatory impact analyses (RIAs) carried out by EPA to characterize and communicate the health benefits of regulations affecting ambient PM_2.5 concentrations. Given the growing importance of PM benefits analysis across the globe, recent developments pioneered by EPA could have widespread relevance.     

Wisconsin Electric’s experience with fish impingement and entrainment studies

Since 1975, Wisconsin Electric has conducted impingement studies at seven steam electric, once-through cooling-equipped power plants, as well as at one closed-cycle cooling system-equipped plant. Entrainment studies were also conducted at all seven once-through cooling-equipped plants. All eight plants are located on the Great Lakes or on major tributaries to them. Two of the eight plants have since been retired, while portions of two remaining multi-unit plants have been retired.As part of the study reports ultimately filed with the state agencies overseeing the studies, companies were also required to provide information on: intake design, capacity, and operation; whether biocides were used at the plants to control biofouling; and what ice control measures were employed during the winter season. Companies were also asked to provide brief assessments of available intake design alternatives that could be reasonably expected to reduce entrainment or impingement, as well as order of magnitude cost estimates for retrofiting plants with feasible alternative technologies.The studies concluded that since the vast majority of fish impinged during the 1975–1976 period were alewife and rainbow smelt (the then most abundant species in Lakes Michigan and Superior) and since the historic commercial harvests of these two species greatly exceeded annual impingement estimates, the impact of these incremental losses to lake-wide populations was inconsequential. With respect to the entrainment results, the studies detected few fish eggs or larvae that were not alewife or smelt.As a consequence of these findings, the company did not believe that any structural modifications to the intakes were necessary, since any one of the feasible alternatives would have been very costly. The state agencies concurred with these findings.