Randhir P. Deo

Surface Complexation of Neptunium(V) onto Whole Cells and Cell Components of Shewanella alga: Modeling and Experimental Study

We systematically quantified surface complexation of Np(V) onto whole cells, cell wall, and extracellular polymeric substances (EPS) of Shewanella alga strain BrY. We first performed acid and base titrations and used the mathematical model FITEQL to estimate the concentrations and deprotonation constants of specific surface functional groups. Deprotonation constants most likely corresponded to a carboxyl group not associated with amino acids (pK(a) approximately 5), a phosphoryl site (pK(a) approximately 7.2), and an amine site (pK(a) > 10). We then carried out batch sorption experiments with Np(V) and each of the S. alga components as a function of pH. Since significant Np(V) sorption was observed on S. alga whole cells and its components in the pH range 2-5, we assumed the existence of a fourth site: a low-pK(a) carboxyl site (pK(a) approximately 2.4) that is associated with amino acids. We used the SPECIATE submodel of the biogeochemical model CCBATCH to compute the stability constants for Np(V) complexation to each surface functional group. The stability constants were similar for each functional group on S. alga bacterial whole cells, cell walls, and EPS, and they explain the complicated sorption patterns when they are combined with the aqueous-phase speciation of Np(V). For pH < 8, the aquo NpO(2)(+) species was the dominant form of Np(V), and its log K values for the low-pK(a) carboxyl, mid-pK(a) carboxyl, and phosphoryl groups were 1.8, 1.8, and 2.5-3.1, respectively. For pH greater than 8, the key surface ligand was amine >XNH(3)(+), which complexed with NpO(2)(CO(3))(3)(5-). The log K for NpO(2)(CO(3))(3)(5-) complexed onto the amine groups was 3.1-3.9. All of the log K values are similar to those of Np(V) complexes with aqueous carboxyl and N-containing carboxyl ligands. These results help quantify the role of surface complexation in defining actinide-microbiological interactions in the subsurface.

Pharmaceuticals in the Surface Water of the USA: A Review

This review investigates the occurrence of pharmaceuticals in the surface waters (including rivers, lakes, oceans, and aquifers) of the USA, discusses various pathways of pharmaceutical contamination from different point sources, assesses the potential risk of pharmaceutical contamination for aquatic organisms, and provides a discussion on the opportunities for a sustainable management of pharmaceutical contamination. We found a total of 93 pharmaceuticals that have been reported to contaminate the surface water, including: 27 antibiotics; 15 antidepressants; 9 antihypertensives; 7 analgesics; 7 anticonvulsants; 6 antilipidemics; 3 contraceptives; 3 stimulants; and 2 each of antihistamines, blood thinners, disinfectants, antacids, antitussives, anti-anxiety, anti-inflammatory, and diuretic agents. The pharmaceuticals that are assessed to be at high risk (risk quotient RQ ≥1.0) include acetaminophen (analgesic), caffeine (stimulant), sulfadimethoxine (antibiotic), as well as triclocarban and triclosan (both used in disinfectants). Such drugs require detailed evaluation as to the frequency of their occurrence and the risks for aquatic organisms and humans. Opportunities for sustainable control of pharmaceutical contamination include source control (proper disposal of leftover pharmaceuticals; careful monitoring of hospital wastes), and improvements to treatment facilities for the efficient removal and safe transformation of pharmaceutical contaminants.

Effect of sample filtration on the quality of monitoring data reported for organic compounds during wastewater treatment

Accurate quantification of organic wastewater compounds (OWCs) is essential for assessing their removal efficiency in wastewater treatment plants (WWTPs) and for calculating discharge rates into effluent-receiving surface waters. In this study, we undertook a theoretical evaluation of the effect of sorption and sample filtration on data quality. Filtration of samples, while commonly practiced, may preclude a potentially significant fraction of chemical mass from both chemical measurements and mass flow analyses for WWTPs. Sorption theory dictates that analyte losses from sample filtration are notable for hydrophobic organic compounds (HOCs) featuring a pH-dependent logarithmically transformed organic carbon-water distribution coefficient (log D(OC)) of > or =3.0. Among a total of 33 organic wastewater compounds considered, the extent of sorption to filterable materials ranged from 22% for bisphenol A diglycidyl ether (BADGE) to 99% for di-(2-ethylhexyl)phthalate (DEHP). Sample filtration also was demonstrated to have a profound impact on the outcome of chemical fate and behavior studies. When the chemical mass residing on filterable particulates was considered, the concentration spread (range) doubled between maximum and minimum concentrations reported for raw wastewater. Furthermore, removal efficiencies of WWTPs calculated for HOCs increased by as much as 62% just by changing the method of accounting. We conclude that some of the data spread reported in the literature concerning chemical mass loadings, contaminant concentrations in raw sewage, and removal efficiencies of similarly designed WWTPs is driven not by actual differences in sewage composition, geographic locations and treatment units but by sample processing protocols and the method of mass accounting.

Subsurface Interactions of Actinide Species with Microorganisms

Subsurface microbiological processes have an important role in defining the speciation and mobility of actinide contaminants in groundwater. The relative importance of these processes, especially when groundwater conditions support high microbiological activity, has, however, only been recognized by researchers in the field since the early 1990s. The need to mechanistically understand the key interactions between actinide species and microbial processes becomes greater as we increasingly rely on more passive, long-term containment strategies, such as natural attenuation, where microbial processes are likely to predominate (NRC, 2000a).

In silico screening for unmonitored, potentially problematic high production volume (HPV) chemicals prone to sequestration in biosolids.

Thousands of high production volume (HPV) chemicals are used in the US at rates exceeding 450,000 kg (1 million pounds) per year, yet little is known about their fates during wastewater treatment and upon release into the environment. We utilized a recently introduced empirical model to predict the fraction of the mass loading (in raw sewage) that is expected to persist in digested sludge following conventional municipal treatment of chemical-laden sewage. The model requires only two readily available input parameters, a compounds log K(OW) value and a dimensionless curve fitting parameter (p(fit)). Following refinement of the fitting parameter and cross-validation of the model using the Jackknife method, we predicted the mass fractions of 207 hydrophobic HPV chemicals (log K(OW) of ≥ 4.0) that are expected to accumulate in digested municipal sludge during conventional wastewater treatment. Using this screening approach in conjunction with information from toxicity databases, we identified 11 HPV chemicals that are of potential concern due to (i) their propensity to accumulate and persist in sludge (>50% of mass loading), (ii) unfavorable ecotoxicity threshold values, and (iii) structural characteristics suggestive of environmental persistence following release of these HPV chemicals on land during biosolids recycling. The in silico screening approach taken in this study highlights existing environmental monitoring needs and may guide risk management strategies for biosolids disposal.

Empirical Model for Predicting Concentrations of Refractory Hydrophobic Organic Compounds in Digested Sludge from Municipal Wastewater Treatment Plants

An empirical model is presented allowing for the prediction of concentrations of hydrophobic organic compounds (HOCs) prone to accumulate and persist in digested sludge (biosolids) generated during conventional municipal wastewater treatment. The sole input requirements of the model are the concentrations of the individual HOCs entering the wastewater treatment plant in raw sewage, the compounds respective pH-dependent octanol-water partitioning coefficient (D(OW)), and an empirically determined fitting parameter (p(fit)) that reflects persistence of compounds in biosolids after accounting for all potential removal mechanisms during wastewater treatment. The accuracy of the model was successfully confirmed at the 99% confidence level in a paired t test that compared predicted concentrations in biosolids to empirical measurements reported in the literature. After successful validation, the resultant model was applied to predict levels of various HOCs for which occurrence data in biosolids thus far are lacking.

Comment on “the removal of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs during wastewater treatment and its impact on the quality of receiving waters” by Barbara Kasprzyk-Hordern, Richard M. Dinsdale, and Alan J. Guwy

* Corresponding author. The Biodesign Instit Avenue, P.O. Box 875701, Tempe, AZ 85287, E-mail address: halden@asu.edu (R.U. Ha 0043-1354/

Pharmaceuticals in the Built and Natural Water Environment of the United States

– see front matter a 2009 Elsevi doi:10.1016/j.watres.2009.11.040 In a recent comprehensive study, Kasprzyk-Hordern et al. compounds bound to suspended solids (Pavlovic et al., 2007; (2009) reported on the fates of 55 organic contaminants in two contrasting wastewater treatment plants (WWTPs), and assessed the impact of treated wastewater effluent on the quality of receiving waters. Concentrations of pharmaceuticals and personal care products (PPCPs) were determined in filtered samples of raw sewage and in filtered effluent to characterize the mass loading and removal efficiencies of two different sewage treatment technologies. The sample processing strategy chosen by Kasprzyk-Hordern et al. (2009) is robust for polar compounds but potentially problematic for nonpolar organics. Prior to spiking with internal standards, Kasprzyk-Hordern’s team acidified wastewater samples to pH 2 and performed vacuum filtration, using two glass fiber filters featuring pore sizes of 2.7 and 0.7 mm. This filtration step removes suspended solids and frequently is employed to avoid clogging of extraction resins and analytical capillaries. However, sample filtration also precludes from chemical analysis the mass fraction of hydrophobic organic