Effects of nitrogen and phosphorus limitation on the activated sludge biomass in a kraft mill biotreatment system.

Unlike wastewater, pulp and paper mill effluents are generally severely deficient in bioavailable nitrogen and phosphorus. The influence of nitrogen and phosphorus limitations on steady-state or typical pulp and paper mill activated sludge floc properties and performance was studied using a bioreactor-fed synthetic raw mill effluent and seeded with mill activated sludge. Limitation of either nitrogen or phosphorus decreased growth, five-day biochemical oxygen demand, and suspended solids removal. Nitrogen limitation greatly enhanced activated sludge floc poly-beta3-hydroxybutyrate (PHB), but not carbohydrate or extracellular polymeric substances (EPS). In contrast, phosphorus limitation increased total floc carbohydrate and EPS, but not PHB. The flocs showed little ability to store either nitrogen or phosphorus. Nitrogen limitation, but not phosphorus limitation, produced much more negative net floc surface charge, increasing fines, while phosphorus limitation, but not nitrogen limitation, increased the floc bound water content and surface hydrophobicity and decreased fines.     

The Southeastern Aerosol Research and Characterization Study: part 1--Overview

This paper presents an overview of a major, long-term program for tropospheric gas and aerosol research in the southeastern United States. Building on three existing ozone (O3)-focused research sites begun in mid-1992, the Southeastern Aerosol Research and Characterization Study (SEARCH) was initiated in mid-1998 as a 7-year observation and research program with a broader focus including aerosols and an expanded geographical coverage in the Southeast. The monitoring network comprises four urban-rural (or urban-suburban) site pairs at locations along the coast of the Gulf of Mexico and inland, including two moderately sized and two major urban areas (Pensacola, FL; Gulfport, MS; Atlanta, GA; and Birmingham, AL). The sites are equipped with an extensive suite of instruments for measuring particulate matter (PM), gases relevant to secondary O3 and the production of secondary aerosol particles, and surface meteorology. The measurements taken to date have added substantially to the knowledge about the temporal behavior and geographic variability of tropospheric aerosols in the Southeast. Details are presented in four papers to follow.     

An examination of the physical properties,fate, ecotoxicity and potential environmental risks for a series of propylene glycol ethers

Propylene glycol ethers (PGEs) are comprised of mono-, di- and tri-PGEs and several of their acetate esters. The nature of the range of applications that use PGEs suggests that there is a potential for both intentional and unintentional entry of the materials into the environment. Selected physical/chemical properties, fate characteristics, aquatic toxicity data and calculated environmental concentrations were used to assess potential risks from the manufacture, handling, use, and disposal of PGEs. In general, the PGEs are low to moderately volatile, have high aqueous solubilities, low octanol-water partition coefficients (Kow), and bioconcentration factor values of <10, which indicate they are unlikely to accumulate in aquatic food chains. Both abiotic and biological degradation processes reduce environmental concentrations of PGEs. In air, vapor-phase PGEs react with photo-chemically produced hydroxyl radicals and have half-lives ranging from 5.5 to 34.4 h. A variety of ready and inherent biodegradation test methods, as well as tests that simulate biodegradation in wastewater treatment plants, surface water and soil have been conducted on PGEs. Significant aerobic biodegradation was generally observed, with a range of biodegradation half-lives on the order of 5-25 d. Acute aquatic toxicity studies with PGEs resulted in LC50 values ranging from approximately >100 to >20,000 mg/l for freshwater fish, the pelagic invertebrate Daphnia magna, green algae Selenastrum capricornutum (now called Pseudokirchneriella capricornutum) and bacteria. Level 3 multi-media modeling (EQC model of Mackay) was used to simulate regional-scale concentrations of PGEs in air, soil, water, and sediment. Toxicity thresholds were then compared with regional-scale water, soil and sediment concentrations to determine hazard quotients. Based upon this analysis, concentrations of PGEs are unlikely to pose adverse risks to the environment.     

A reproducible approach to the reporting of organochlorine compounds in epidemiologic studies

A growing body of research indicates that the most biologically active PCB congeners and organochlorines are not the most abundant components in human and wildlife samples. As researchers attempt measurement on a wider pool of less abundant compounds, they inevitably face quantification problems. To address this problem and enhance comparability across studies, we propose a standardized approach to report organochlorines that is based on a reproducible method to determine the limit of quantification (LQ). Two statistical methods are incorporated into our approach, one by Gibbons termed the Alternative Minimum Level (AML), and one based on determining a region of stable relativestandard deviation in instrument response (RSD). We illustrate our approach using historical samples collected during the 1960s from a cohort of pregnant women enrolled in the Child Health and Development Study. The results are applicable to determining the LQ of any method, and are of utmost importance to environmental scientists conducting trace organic analyses of complex mixtures. Our results demonstrate that: (1) precision as measured by RSD is the most important criterion in determining LQ; (2) the AML routinely isolates a region of constant RSD; and (3) the precision of the instrument detector response as measured with pure standards locates the LQ applicable for real samples - that is, the true limits of quantification reside in the detector, not the matrix effects or analyte recoveries associated with real samples. A corollary of these findings is that bias due to matrix effects and analyte recoveries can be assessed separately from precision and LQdetermination. Previous approaches involved spiking matrix blanks to determine LQ, a problematic strategy for real world, complex matrices. We have now validated the use of pure standards in LQ determination, an approach that is practical and accessible to most analysts.     

The midlatitude North American background aerosol and global aerosol variation

Protocols for the particulate matter (PM) National Ambient Air Quality Standards (NAAQS), and the Regional Haze Rule (RHR) give two complementary definitions for "natural" background airborne particle concentrations in the United States. The definition for the NAAQS derives largely from reported annual averages, whereas the definition for the RHR takes into account the frequency of occurrence of a range of visibility conditions estimated using fine particle composition. These definitions are simple, static representations of background or "unmanageable" aerosol conditions in the United States. An accumulation of data from rural-remote sites representing global conditions indicates that the airborne particle concentrations are highly variable. Observational campaigns show weather-related variations, including incidents of regional or intercontinental transport of pollution that influence background aerosol levels over midlatitude North America. Defining a background in North America based on long-term observations relies mainly on the remote-rural IMPROVE network in the United States, with a few additional measurements from Canada. Examination of the frequency of occurrence of mass concentrations and particle components provides insight not only about annual median conditions but also the variability of apparent background conditions. The results of this analysis suggest that a more elaborate approach to defining an unmanageable background could improve the present approach taken for information input into the U.S. regulatory process. An approach interpreting the continental gradients in fine PM (PM2.5) concentrations and composition may be warranted.     

Explicit and implicit coupling during solute transport through clay membrane barriers

Simulations of salt (KCl) flux through a 1-m-thick clay membrane barrier (CMB) based on coupled solute transport theory are compared to simulated fluxes based on traditional advective-dispersive transport theory. The simulations are based on measured values for the effective salt-diffusion coefficient (Ds*) and chemico-osmotic efficiency coefficient (omega) for a bentonite-based barrier material subjected to KCl solutions. The results indicate that the exit salt flux is reduced due to both explicit coupling (hyperfiltration and chemico-osmotic counter-advection) and an implicit coupling effect resulting from the decrease in Ds* due to a decrease in the apparent tortuosity factor, tau a, with an increase in omega. Implicit coupling is shown to be more significant than explicit coupling for reducing and retarding salt flux through a CMB under diffusion-dominated conditions. Failure to account for the implicit coupling effect may result in unrealistic results, such as the existence of salt flux through a perfect (ideal) clay membrane (i.e., omega=1).     

The influence of untreated wastewater to aquatic communities in the Balatuin River,The Philippines

A risk assessment of chemical constituents in rivers that receive untreated wastewater should take into account the adverse effects of increased biological oxygen demand (BOD), ammonia and reduced dissolved oxygen (DO). This concept was tested via a field study in the Balatuin River, The Philippines, where the influence of physical and chemical factors, including the consumer product chemical linear alkylbenezene sulfonate (LAS), to aquatic communities (algae, invertebrates, fish) was determined. Periphytic algae were found to be insensitive to high BOD (>10 mg/l) and ammonia (>0.01 mg unionized NH(3)/l), concentrations from organically enriched untreated wastewater discharges. However, taxa richness and abundance of macroinvertebrates were influenced greatly by the discharges. Where BOD and ammonia concentrations were elevated, the dominant taxa were oligochaete worms and chironominds. Fish and crustaceans (freshwater crabs and prawns) were found only in sites with the least BOD concentrations (furthest upstream and downstream). The maximum concentration of LAS (0.122 mg/l) was less than that expected to affect 5% of taxa (0.245 mg/l), whereas exceedences of DO and ammonia criteria were observed in several sites. The lack of recovery observed was attributed to influences of low DO, high ammonia and poor colonization from upstream and downstream reaches due to organically-enriched discharges