Ben Koopman

Effect of temperature and ph on the effective maximum specific growth rate of nitrifying bacteria

For modeling nitrification in wastewater treatment processes it is necessary to determine the dependence of the maximum specific growth rate (μA) of nitrifying bacteria on temperature and pH. A functional relationship for the simultaneous dependence of the effective maximum specific growth rate (μA) minus the decay coefficient, bA) on temperature and pH, obtained from theoretical arguments, was verified via batch experiments with sludge from a local wastewater treatment plant. The parameters for the functional relationship were determined from the experimental data using a nonlinear regression scheme. An optimum pH of approx. 7.8 was determined and the effective maximum specific growth rate was found to be a monotonically increasing function of temperature in the range of 15–25°C.

Removal of nitrogen and phosphate from wastewater by addition of bittern

Removal of nitrogen and phosphate through crystallization of struvite (MgNH(4)PO(4).6H(2)O) has gained increasing interest. Since wastewaters tend to be low in magnesium relative to ammonia and phosphates, addition of this mineral is usually required to effect the struvite crystallization process. The present study evaluated the feasibility of using bittern, a byproduct of salt manufacture, as a low-cost source of magnesium ions. High reaction rates were observed; the extent of nitrogen and phosphorus removals did not change beyond 10 min. Phosphorus removals from pure solutions with bittern added were equivalent to those obtained with MgCl(2) or seawater. Nitrogen removals with bittern were somewhat lower than with the alternate Mg(2+) sources, however. Application of bittern to biologically treated wastewater from a swine farm achieved high phosphate removal, but ammonia removals were limited by imbalance in the nitrogen:phosphorus ratio.

Evaluation of a microplate assay specific for heavy metal toxicity

A rapid, quantitative microbial assay, which is specific for heavy metal toxicity, has been developed. The assay (MetPLATE™) is in a 96-well microtitration plate format and is suitable for determining toxicity characteristics such as median inhibitory concentrations. The sensitivity of MetPLATE™ to heavy metals [Cu, Zn, Cd, Pb, Hg, Cr(III)] was generally higher than Microtox and was of the same order as or better than Daphnia and fish bioassay. MetPLATE was insensitive to organic compounds at concentrations higher than those found in the environment. Six out of 10 industrial wastewaters or process waters surveyed were toxic. Heavy metal analysis of these waters confirmed the presence of heavy metals in the toxic samples. MetPLATE can be run concurrently with other assays for general toxicity to help determine the nature of chemicals causing toxicity.

Influence of Suwannee River humic acid on particle properties and toxicity of silver nanoparticles

Adsorption of natural organic matter (NOM) on nanoparticles can have dramatic impacts on particle dispersion resulting in altered fate and transport as well as bioavailability and toxicity. In this study, the adsorption of Suwannee River humic acid (SRHA) on silver nanoparticles (nano-Ag) was determined and showed a Langmuir adsorption at pH 7 with an adsorption maximum of 28.6 mg g(-1) nano-Ag. It was also revealed that addition of <10 mg L(-1) total organic carbon (TOC) increased the total Ag content suspended in the aquatic system, likely due to increased dispersion. Total silver content decreased with concentrations of NOM greater than 10mg TOCL(-1) indicating an increase in nanoparticle agglomeration and settling above this concentration. However, SRHA did not have any significant effect on the equilibrium concentration of ionic Ag dissolved in solution. Exposure of Daphnia to nano-Ag particles (50 μg L(-1) and pH 7) produced a linear decrease in toxicity with increasing NOM. These results clearly indicate the importance of water chemistry on the fate and toxicity of nanoparticulates.

Bacterial and Enzymatic Bioassays for Toxicity Testing in the Environment

Microbioassays using bacteria or enzymes are increasingly applied to measure chemical toxicity in the environment. Attractive features of these assays may include low cost, rapid response to toxicants, high sample throughput, modest laboratory equipment and space requirements, low sample volume, portability, and reproducible responses. Enzymatic tests rely on measurement of either enzyme activity or enzyme biosynthesis. Dehydrogenases are the enzymes most used in toxicity testing. Assay of dehydrogenase activity is conveniently carried out using oxidoreduction dyes such as tetrazolium salts. Other enzyme activity tests utilize ATPases, esterases, phosphatases, urease, luciferase, beta-galactosidase, protease, amylase, or beta-glucosidase. Recently, the inhibition of enzyme (beta-galactosidase, tryptophanase, alpha-glucosidase) biosynthesis has been explored as a basis for toxicity testing. Enzyme biosynthesis was found to be generally more sensitive to organic chemicals than enzyme activity. Bacterial toxicity tests are based on bioluminescence, motility, growth, viability, ATP, oxygen uptake, nitrification, or heat production. An important aspect of bacterial tests is the permeability of cells to environmental toxicants, particularly organic chemicals of hydrophobic nature. Physical, chemical, and genetic alterations of the outer membrane of E. coli have been found to affect test sensitivity to organic toxicants. Several microbioassays are now commercially available. The names of the assays and their basis are: Microtox (bioluminescence), Polytox (respiration), ECHA Biocide Monitor (dehydrogenase activity), Toxi-Chromotest (enzyme biosynthesis), and MetPAD (enzyme activity). An important feature common to these tests is the provision of standardized cultures of bacteria in freeze-dried form. Two of the more recent applications of microbioassays are in sediment toxicity testing and toxicity reduction evaluation. Sediment pore water may be assayed directly or solvents may be used to extract the toxicants. Some of the solvents used for extraction of organic chemicals are themselves toxic to bacteria (e.g., dichloromethane), requiring exchange with a less toxic solvent (e.g., ethanol, methanol, DMSO). A modification of the Microtox test allows direct assay of solid-phase samples such as sediments. The toxicity reduction evaluation (TRE) must be carried out at wastewater treatment plants whose effluents fail toxicity standards. The TREs require numerous and repeated toxicity assays, thus favoring application of microbioassays. Presently, no single microbioassay can detect all categories of environmental toxicants with equal sensitivity. Therefore, a battery of tests approach is recommended. The differential sensitivity of alternative tests may, in fact, be exploited. Further research is needed to construct strains of genetically engineered microorganisms or isolate microorganisms or enzymes that respond to specific classes of toxicants. These can be combined into batteries appropriate for different environments or test objectives.

TOXICITY TESTING USING IMMOBILIZED ALGAE

Abstract Alginate-immobilized and free Selenastrum capricornutum Printz cells were compared for use in algal toxicity assays. Chemicals investigated were cadmium, copper, Glyphosate, Hydrothol, Paraquat, pentachlorophenol, and sodium dodecyl sulfate. Toxicity was characterized in terms of growth inhibition, with growth measured by in vitro chlorophyll fluorescence. Sensitivity of the immobilized and free algal assays to copper, cadmium and pentachlorophenol was similar. However, immobilization substantially reduced the toxicity of Hydrothol, Paraquat, and Glyphosate to the algae. Sodium dodecyl sulfate disrupted the alginate matrix and therefore its toxicity could not be determined successfully with the immobilized algal assay.

Effect of fermented swine wastes on biological nutrient removal in sequencing batch reactors

Fermented swine waste was compared to acetate for supplementation of bench-scale sequencing batch reactors (SBRs) to improve nutrient removal. Swine waste solids were fermented at room temperature for 10 days. The SBRs were fed diluted swine wastewater and operated on a cycle consisting of the following phases: 10-min anoxic fill, 13-h oxic, 7-h anoxic, 3-h oxic, 40-min settling, 10-min draw. Supplemental organic matter was added at the beginning of the anoxic phase. There was essentially no difference in performance of the reactors supplemented with either acetate or fermented swine waste: both achieved a total nitrogen removal of 90% and a total phosphorus removal of 89%. In comparison, a control reactor (receiving no supplementation) achieved total nitrogen and total phosphorus removals of 76 and 15%, respectively. Sludge phosphorus contents of the supplemented reactors were above 7% of volatile suspended solids, compared to sludge phosphorus content of less than 1% for the control reactor.

Polyhydroxy fullerenes for non-invasive cancer imaging and therapy.

DOI: 10.1002/smll.201000847 Nanoparticle-mediated, image-guided cancer therapy has tremendous promise for increasing the effi cacy of cancer treatment while reducing toxic side effects traditionally associated with treatment. Carbon nanotubes and metal-based nanomaterials are leading candidates for image-guided therapy in cancer nanotechnology. [ 1–5 ] However, limited solvent compatibility, non-biodegradability and concerns over the safety of these nanomaterials may hinder their commercialization. Here, we show that the photothermal and photoacoustic properties of polyhydroxy fullerenes [ 6 ] (PHF)—which are water-soluble, biodegradable, [ 7 ] antioxidant, [ 8–10 ] and rapidly excreted [ 11 ] —can be applied for imaging and therapy of cancer. Biodegradable PHF-containing chitosan nanoparticles provided excellent photoacoustic contrast. Tumors injected with PHF nanoparticles and exposed to near infrared laser decreased in cross-sectional area by an average of 32% within two hours of treatment, with only a blister visible 20 hours post-treatment. We anticipate that photoacoustic and photothermal properties of PHF along with their other therapeutic properties [ 12–15 ] will enable safe, non-invasive image-guided therapy of cancer with minimal side-effects. Polyhydroxy Fullerenes for Non-Invasive Cancer Imaging and Therapy

ATP, oxygen uptake rate and INT-dehydrogenase activity of actinomycete foams

Abstract The purpose of this study was to establish the validity of the INT-dehydrogenase test for determining the biochemical activity of actinomycete foams. Parallel measurements of INT-dehydrogenase activity, adenosine triphosphate and oxygen uptake rate were made on foam samples collected from three different activated sludge plants over a period of several months. Activity levels of actinomycete foams measured in this study were found to be comparable to those of activated sludge as reported in the literature. Good-to-excellent correlations (r2 > 0.87) were found between INT-dehydrogenase activity and the alternative parameters. Precision of all assays tested was comparable. The INT-dehydrogenase test can therefore be used in lieu of ATP or oxygen uptake rate assays without sacrifice in either the reliability or reproducibility of results obtained.

Heavy Metal Toxicity Testing in Environmental Samples

The toxicity of heavy metals in the environment depends on a number of physicochemical and biological factors. The complexity of these relationships has encouraged the use of bioassays for direct measurement of the [table: see text] impact of toxic metals on selected test species. Fish and daphnid bioassays are well accepted by the scientific and regulatory communities, but their length (48 h or more) and the considerable time and effort needed to culture the test organisms make their application to sample screening problematical. Microbial and biochemical assays based on the inhibition of bioluminescence, enzyme activity, enzyme biosynthesis, growth, respiration, and heat production are typically faster and less expensive than the traditional and fish bioassays. Some of these tests approach or equal the sensitivity of daphnids to heavy metals. Since the soil acts as a sink for airborne and waste-applied metals, the uptake of metals by plants and the associated toxic impacts are important. Growth inhibition, enzyme induction, and production of stress proteins have been considered as toxicity end points. Enzymatic tests have been developed that are specific for heavy metal toxicity. Such tests can facilitate toxicity reduction evaluations. Detection of individual metals in the environment may eventually be possible using biosensors consisting of genetically engineered microorganisms. Direct solid-phase tests for soil, sediment, or sludge toxicity, using bacterial bioluminescence or enzyme activity as end points, have been developed. Such tests may complement traditional solid-phase toxicity tests using nematodes or earthworms as indicator organisms. Based on the work reviewed, we draw the following conclusions: 1. The Microtox assay is sensitive to mercury but would fail to detect the toxicity of certain metals, such as cadmium. Among all the microbial assays reviewed, the bioassay based on growth inhibition of the alga Selenastrum capricornutum appears to give the lowest EC50s, similar to those seen for daphnid bioassays. 2. Biosensors, using genetically engineered microorganisms, offer an elegant means of detecting the presence of specific heavy metals in environmental samples. However, at the present time, they are not designed for assessing heavy metal toxicity. 3. The use of bioassays specific for heavy metal toxicity can be useful for directly assessing the bioavailability of these toxicants in environmental samples, thus avoiding the need for fractionation.+4