River Wastewater Research Articles

Chromate ion as a reference toxicant for aquatic phytotoxicity tests

AbstractTo conduct toxicity tests, it is essential to include controls to ascertain the health of the test organisms. The common practice is to include negative controls in every test. That positive controls are not used is perhaps because there is no consensus about the reference toxicant. The objective of this study was to test chromate ion as a candidate for reference toxicant. Two aquatic phytotoxicity tests were performed: a millet root elongation test and a duckweed test.To the same test species, the Cr(VI) toxic effect was very consistent in repeated experiments. The toxic effects to millet were nearly identical in both deionized water and sewage effluent samples. The toxic effect to duckweed was also highly repeatable in 59 water samples from 18 sample stations. The results suggest that the Cr(VI) ion can be used as a general reference toxicant in river water, lake water or wastewater samples. The concentration‐effect relationships, however, are different, depending on the test organisms.

Water Resources Planning – A Research Program

A research project on “Methodologies for Water Resources Policy Analysis” is under current development at the National Laboratory for Civil Engineering, Portugal. Its main objectives are to develop and test techniques, computational tools and procedures which may help in the design of water resources plans, in the comparison and evaluation of alternative strategies and in real time drainage basin management and operation. In order to achieve these objectives the technical activity of the project has tackled such water resources problems as the assessment of water availability and demands, the characterization of river water quality and wastewater, water pollution control and river water quality modeling. Also, effective technology transfer from technicians to local, regional and national managers and decision-makers has been tried. In this paper, the main project activities are summarized, some of the achievements are pointed out and its most significant results are presented.

Water for Las Vegas Metropolitan Area

The Las Vegas area is one of the most arid parts of the driest state in the nation. It is among the fastest growing areas in the nation, and water supplies must be sought and managed to meet the demands of this growth. This paper describes a long range plan of action to ensure adequate water supplies for the next fifty years. Water supplies currently available include groundwater, Colorado River water, and wastewater reuse. The paper describes water supply and water demand alternatives available to conjunctively use groundwater, Colorado River water, wastewater, and water conservation to meet demand considering uncertainties on available supplies and competing demand. Water demand functions were developed by different user classes including residential, commercial, industrial, civic, agricultural and non‐agricultural irrigation, and system losses. These functions can assist other planners in determining water use in arid climates.

Sign-of-charge of species of Cu, Cd and Zn extracted from sewage sludge, and effect of plants

Sewage sludge, obtained from the Back River Wastewater Treatment Plant, Baltimore, Maryland, in 1970, was stored either moist or air-dried for 5 years. Aqueous extracts of sludge were obtained and leached through columns containing either cation, anion, or mixed resins, with the pH adjusted to equal that of the extract. Analysis of the column leachates for Zn, Cd, and Cu was used to calculate concentrations of the various charged metal species. For Zn, between 84 and 92% of the species were cationic regardless of moisture conditions during storage; for Cd, moist storage yielded 83% amphoteric, and air dry storage 87% cationic species; for Cu, moist storage yielded 50% cationic and 30% amphoteric species, while air-dry storage yielded 16% cationic and 72% amphoteric species.