Comparing Contaminant Removal Costs for Aquifer Recharge with Wastewater with Water Supply Benefits

The use of waters of impaired quality has been suggested as a means to expand available water resources supply for water‐limited communities. An ongoing concern is the safety of supplies that use wastewater because of the potential for introduction of emerging contaminants such as pharmaceuticals into drinking water supplies. Prior research into contaminants of emerging concerns (CECs) have included a variety of methods, but the only consistent removal is with reverse osmosis (RO) membranes, ultraviolet light (UV), and advanced oxidation processes (AOP). However, few of these prior studies have measurable quantities of these contaminants in the influent wastewater, so determining actual removal percentages is difficult. This project was designed to evaluate the removal of CECs to verify that a 3‐log removal of common constituents was realized. Spike testing was used to compare to prior research and to evaluate whether the project costs were competitive with other forms of reuse or other water supplies. The combination of RO/UV/AOP was effective at obtaining a 3‐log removal of CECs, but the RO and UV/AOP processes alone were not capable of removing all substances. However, despite the extensive treatment, the proposed process was both competitive cost‐wise and met the water quality goals.     

Local extinction of a foundation species in a hypoxic estuary: integrating individuals to ecosystem

We integrated across individual, population, community, and ecosystem levels to understand the impact of environmental stress by tracking the foundation species Mytilus edulis in the hypoxic estuary Narragansett Bay, Rhode Island, USA. Our initial surveys revealed that the mussels occurred in nine extensive (2-28 ha) dense (814-9943 individuals/m2) subtidal reefs that attracted a diverse suite of predators (sea stars, crabs, gastropods). Hypoxia occurred in the summer of 2001, and a mussel transplant experiment revealed overall reduced growth rates of individuals, and higher mortality rates among larger mussels. At the population level, large decreases in densities and cover of mussels were correlated with dissolved oxygen concentrations, leading to extinction at one site and reductions of over an order of magnitude at others. Within one year, seven of the eight remaining populations were edged to extinction, and the previously extinct population was recolonized. At the community level, a predator exclusion experiment indicated that predation was an unimportant source of mussel mortality during the hypoxic period, in part due to the emigration of sea stars, as predicted by the Consumer Stress Model. However, mussels were too intolerant to hypoxia to have a net benefit from the predation refuge. The seasonal (summer) occurrence of hypoxia allowed sea stars to return following a lag, as predicted by a stress return time model, and the resumption of predation contributed to the subsequent extinction of mussel populations. At the ecosystem level, the initial filtration rate of the mussel reefs was estimated at 134.6 x 10(6) m3/d, equivalent to filtering the volume of the bay 1.3 times during the 26-d average residence time. That function was reduced by >75% following hypoxia. The effect of hypoxia on each level of organization had consequences at others. For example, size-specific mortality and decreased growth of individuals, and reduced filtration capacity of reefs, indicated a loss of the ability of mussels to entrain planktonic productivity and potential to control future eutrophication and hypoxia. Our study quantified patterns of loss and identified pathways within an integrative framework of feedbacks, summarized in a conceptual model that is applicable to similar foundation species subjected to environmental stress.     

Assessment of the environmental contamination with long-lived radionuclides around an operating RBMK reactor station

The presence of man-made gamma emitting radionuclides in the region within 32km radius of the Ignalina NPP/Lithuania has been investigated during the period 2001-2004, prior to the closure of the first of the two operating RBMK 1500-type reactors. Gamma spectrometric measurements of various terrestrial and aquatic plants as well as of soil samples showed moderate environmental contamination with the fission product (137)Cs and with the neutron activation products (60)Co and (54)Mn. Traces of the activation products (65)Zn and (110m)Ag were found in the nearest vicinity of the NPP. Activity concentrations were inhomogeneously distributed in the area of interest. Moss and algae samples showed the highest uptake of radionuclides. In addition to the gamma spectrometric measurements, the levels of (14)C were determined in the same bio-indicator samples using accelerator mass spectrometry.