This paper assesses the potential impacts of climate change on the mid-Atlantic coastal (MAC) region of the United States. In order of increasing uncertainty, it is projected that sea level, temperature and streamflow will increase in the MAC region in response to higher levels of atmospheric CO 2 . A case study for Delaware based on digital elevation models suggests that, by the end of the 21st century, 1.6% of its land area and 21% of its wetlands will be lost to an encroaching sea. Sea-level rise will also result in higher storm surges, causing 100 yr floods to occur 3 or 4 times more frequently by the end of the 21st century. Increased accretion in coastal wetlands, however, which may occur in response to increases in CO 2 , temperature, and streamflow, could mitigate some of the flooding effect of sea-level rise. Warming alone will result in northward displacements of some mobile estuarine species and will exacerbate the already low summer oxygen levels in mid-Atlantic estuaries because of increased oxygen demand and decreased oxygen solubility. Streamflow increases could substantially degrade water quality, with significant negative consequences for submerged aquatic vegetation and birds. Though climate change may have some positive impacts on the MAC region, such as increased coastal tourism due to warming and some ecological benefits from less-frequent harsh winters, most impacts are expected to be negative. Policies designed to minimize adverse ecological impacts of human activities on coastal ecosystems in the mid-Atlantic, such as decreases in nutrient loading of watersheds, could help mitigate some of the risks associated with future climate variability and change in this region.

Electrical grid-powered aeration is used in most pond-based systems and equalization basins at activated sludge wastewater treatment plants to provide the mixing and oxygenation that enables bacteria to digest organicmatter. Oxygen also is needed in the near-surface water of all ponds and basins to provide an ''odor cap'' by oxidizing malodorous sulfur compounds, preventing their release to air. Much more aeration typically is needed to mix than oxygenate the wastewater. This imbalance causes an operational inefficiency in that grid-power is used to supply more oxygen than needed. The U.S. Environmental Protection Agency concluded that the use of solar-powered circulation (SPC) technology reduces the need to aerate, operational costs, and greenhouse gas emissions associated with electrical power generation. However, the Agency did not quantify electrical, water quality, or other parameters. The New Hampshire Department of Environmental Services directed a 3-site study to quantify the ability of SPC to replace some or all aeration while maintaining good effluent water quality. Water quantity and quality, odor event, and kilowatt-hour consumption and expenditure data were collected 1 year prior to, and 2 years during, SPC treatment at pond-based treatment plants in Pittsfield and Exeter, and at the activated sludge treatment plant in Rochester. Final effluent water quality was maintained, no effluent violations or odor events occurred, and sludge buildup was minimal during the SPC study period. Electricity usage and costs declined by about 38% in Pittsfield and Exeter, and by about 87% in Rochester, resulting in carbon dioxide emission reductions of 273,161, 918,183, and 1,082,509 kg, respectively. Payback periods ranged from 1.9 to 3.7 years. SPC improved operational efficiency at the plants by reducing grid-power consumption while operational objectives were met. The 25-year expected lifetime of SPC units with minimal maintenance requirements indicated long-term reductions in operational expenses and greenhouse gas emissions.

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The Eden, NC, wastewater utility investigated alternatives to electrical-grid powered aeration in reactor basins to improve operational and processing efficiencies. Surface aeration mixes inefficiently and produces more oxygen than needed, causing excessive electricity usage, operational costs, and greenhouse gas emissions. A single solar-powered circulator (SPC) was installed in a basin of 7,041.5 m 2 and 7.0 MG operating volume. Three of 12, 20-HP aerators were deactivated immediately, and up to six aerators were deactivated over time. Water quality, electricity usage, and cost was monitored for 1 year during SPC, and compared with comparable data collected the previous year. Statistically significant decreases in effluent total-suspended solids, total nitrogen, total phosphorus, and fecal coliform were observed during SPC. Electricity usage and expenditures declined by 42% and 31%, respectively, resulting in a carbon footprint reduction of 1,029,188.4 kg CO 2 (2,268,972 lbs) and a 10.7-month payback period. SPC significantly improved operational and processing efficiencies.