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In South Asia and Africa, an estimated 88.5 million diarrhea episodes are attributed to Shigella infections annually (1). Shigellosis occurs most often in children < 5 years of age (2,3). [...]

The objective of this study was to assess the effectiveness of alkaline hydrolysis as an alternative ex situ technology for remediating groundwater contaminated with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Treatment in both batch reactor and continuous stirred tank reactor (CSTR) was investigated. RDX reactivity was strongly dependent on the reaction pH investigated (11-13). The batch system achieved pseudo-first-order RDX reaction rates in the range of (0.8-27.7) x [10.sup.-3] [min.sup.-1], corresponding to half-life periods of 17.9 to 0.5 h, respectively. In the CSTR system operated at the initial RDX concentration of 4.5 x [10.sup.-3] mM, 99% RDX removal was achieved with the hydraulic retention time of 2 days and the reaction pH of 11.9. Formate and nitrite were produced as the major hydrolysates in the CSTR system, indicating a simultaneous reaction mechanism involving RDX ring cleavage and elimination of the ring nitrogen. The net OH- demand used only for RDX removal in the CSTR was found to be 1.5, 390, and 130 M O[H.sup.-]/M RD[X.sub.removed] at pH values of 11.9, 11.5, and 11.0, respectively. A conceptual cost analysis indicated that the expense of alkaline treatment may be comparable to the expense of granular activated carbon treatment for long treatment periods (30 years or more), due to the potentially lower annual operational cost of alkali treatment. DOI: 10.1061/(ASCE)0733-9372(2006)132:2(256) CE Database subject headings: Alkalinity; Reactors; Costs; Water treatment; Remedial action; Ground-water pollution.

Analysis of ester-linked phospholipid fatty acids, multiplex PCR of microbial genes, and radiorespiratory techniques can be used to determine whether sediments containing polyaromatic hydrocarbons also contain the that can degrade PAHs. The sediments can then be bioremediated and used again.

A previous study has shown that cell size and cell-solid interactions influence bacterial deposition in coarse grain media. Herein, it is shown that physicochemical factors affect bacterial transport through the clean bed collision efficiency and the area blocked by an attached cell. Analysis of the deposition of seven bacterial strains revealed that cell-cell repulsion enhances blocking and that interactions between the cell and solids are influenced by properties such as cell coating, hydrophobicity of the substratum and the ionic strength of the aqueous phase.

A collision-blocking model was developed to represent deposition of Pseudomonas putida mt2 and Rhodococcus strain C125 during their transport in coarse grain media such a sand columns. Measurements of clean bed collision efficiency and the surface area blocked by attached cells provided evidence showing that cell size and cell-solid interactions influence bacterial deposition.

Bacterial adhesion is enhanced as a result of an increase in hydrophobicity of cells and substrates producing greater attractive forces. On negatively charged surfaces of glass and Teflon, the deposition of different pseudomonads and coryneform bacteria with varying hydrophobicities and negative cell surface charges is examined. For static batch systems the level of deposition is 5 times 10 to the 4th power and 3.6 times 10 to the 7th power cells per square centimeter, while for dynamic column, the level of deposition is 5 times 10 to the 4th power and 1.6 times 10 times 7 cells per centimeter squared.

Bacterial depositions in porous media can have a considerable impact on the supply of water, the contamination of groundwater and the treatment of wastewater. Filtration theory was used to describe bacterial-cell deposition in clean porous media. An equation was developed to illustrate how a one-dimensional clean-bed filter removes suspended particles. It was hypothesized that the interaction of diffuse layers with similar charges can impede bacterial deposition. The research showed that bacteria can be analyzed through mechanistic models of particle transport.

A new approach for deriving the sediment quality criteria for dioxin is presented. The move is based on growing concern among environmental regulatory agencies on the effects on aquatic life and human health resulting from exposure to contaminated sediments. Studies have shown that a biota-to-sediment accumulation factor is a suitable criterium to reassess dioxin levels in fish tissue.