Removal of micropollutants and ecotoxicity during combined biological activated carbon and ozone (BO3) treatment.

Ozonation is a viable option to improve the removal of micropollutants (MPs) in wastewater treatment plants (WWTPs). Nevertheless, the application of ozonation is hindered by its high energy requirements and by the uncertainties regarding the formation of toxic transformation products in the process. Energy requirements of ozonation can be reduced with a pre-ozone treatment, such as a biological activated carbon (BAC) filter, that removes part of the effluent organic matter before ozonation. This study investigated a combination of BAC filtration followed by ozonation (the BO3 process) to remove MPs at low ozone doses and low energy input, and focused on the formation of toxic organic and inorganic products during ozonation. Effluent from a WWTP was collected, spiked with MPs (approximately 1 µg/L) and treated with the BO3 process. Different flowrates (0.25-4 L/h) and specific ozone doses (0.2-0.6 g O3/g TOC) were tested and MPs, ecotoxicity and bromate were analyzed. For ecotoxicity assessment, three in vivo (daphnia, algae and bacteria) and six in vitro CALUX assays (Era, GR, PAH, P53, PR, andNrf2 CALUX) were used. Results show that the combination of BAC filtration and ozonation has higher MP removal and higher ecotoxicity removal than only BAC filtration and only ozonation. The in vivo assays show a low ecotoxicity in the initial WWTP effluent samples and no clear trend with increasing ozone doses, while most of the in vitro assays show a decrease in ecotoxicity with increasing ozone dose. This suggests that for the tested bioassays, feed water and ozone doses, the overall ecotoxicity of the formed transformation products during ozonation was lower than the overall ecotoxicity of the parent compounds. In the experiments with bromide spiking, relevant formation of bromate was observed above specific ozone doses of approximately 0.4 O3/g TOC and more bromate was formed for the samples with BAC pre-treatment. This indirectly indicates the effectivity of the pre-treatment in removing organic matter and making ozone more available to react with other compounds (such as MPs, but also bromide), but also underlines the importance of controlling the ozone dose to be below the threshold to avoid formation of bromate. It was concluded that treatment of the tested WWTP effluent in the BO3 process at a specific ozone dose of 0.2 g O3/g TOC, results in high MP removal at limited energy input while no increase in ecotoxicity, nor formation of bromate was observed under this condition. This indicates that the hybrid BO3 process can be implemented to remove MPs and improve the ecological quality of this WWTP effluent with a lower energy demand than conventional MP removal processes such as standalone ozonation.

The effect of organic matter fractions on micropollutant ozonation in wastewater effluents.

Organic matter (OM) is the most important factor influencing the effectivity and efficiency of micropollutant (MP) ozonation in wastewater effluents. The importance of the quantity of OM is known, because of this, total organic carbon (TOC) is generally used to determine the required ozone dose for any water sample. Still, the effect of OM type on MP ozonation is not well understood. In this study, effluents from five wastewater treatment plants were collected and the organic matter in these effluents was fractionated using membranes (F1-4) and resin (HI, HOA, HON and HOB). Fractions were diluted to the same TOC concentration, spiked with MPs and ozonated at three ozone doses. Our results show that all five effluents had comparable OM compositions and similar MP removal, confirming the suitability of OM quantity (TOC) to compare the ozone requirements for wastewater effluents. From the 19 analysed MPs, three groups were identified that showed similar removal behaviour. The strongest differences between the groups were observed around MP ozone reactivities of 102, 104 and 106 M-1 s-1. This indicates the presence of three OM groups in the samples that interfere with the removal of different MPs. MP removal in the resin fraction HON were higher for MPs with high and medium ozone reactivity, indicating a low interference of OM in this fraction with MP ozonation. OM in the resin fractions HOA and HI showed higher interference with MP ozonation. Therefore, removing the HOA and HI fractions prior to ozonation would result in a lower required ozone dose and a more efficient removal of the MPs. MP removal correlated with the OM characteristics A300, SR and fluorescence component comp 2. These characteristics can be used as inline tools to predict the required ozone dose in water treatment plants.

A Merkel cell carcinoma presenting as a solitary lymph node metastasis without a primary lesion. Report of a case and review of the literature.

Merkel cell carcinoma is an uncommon, aggressive neuroendocrine tumour of the skin. At presentation regional lymph nodes are involved in approximately one third of the patients. In this report a patient is presented in whom Merkel cell carcinoma presented as a solitary lymph node metastasis with an unknown primary skin lesion. The diagnosis of unknown primary merkel cell carcinoma including the use of immunohistochemical markers and treatment options based on data from the literature are discussed.

Alanine umbilical uptake, disposal rate, and decarboxylation rate in the fetal lamb.

Fetal plasma alanine disposal rate (DR) and decarboxylation rate were measured at 132 +/- 1 days gestation in nine fetal lambs infused with L-[1-14C]alanine via a brachial vein. In five experiments, L-[1-13C]alanine was added to the infusate. Using L-[1-14C]alanine, we found mean DR to be 15.5 +/- 1.8 mumol.min-1 . kg-1. DR was significantly correlated to both arterial plasma alanine and whole blood lactate concentrations. Placental uptake of fetal plasma alanine accounted for 19 +/- 4% of DR. Fetal and placental production of CO2 from the first carbon of alanine were 61 +/- 2 and 16 +/- 2% of DR, respectively, for a total uterine excretion of 77 +/- 3%. Net alanine flux from placenta to fetus was 5.2 +/- 0.5 mumol.min-1 x kg-1, which was less than fetal plasma alanine decarboxylation (9.4 +/- 1.2 mumol.min-1 x kg-1) plus fetal alanine accretion (2.4 mumol.min-1 x kg-1). Utilizing L-[1-13C]alanine, we found DR to be 14.2 +/- 0.8 mumol.min-1 x kg-1, not significantly different from the 14C data. We conclude that both the umbilical uptake of alanine from the placenta and fetal alanine synthesis contribute to fetal alanine supply and that oxidation is the main route of fetal plasma alanine disposal.

Recurrent inguinal hernia treated by classical hernioplasty.

The treatment of recurrent inguinal hernia by classical hernioplasty, ie, via the anterior approach and using endogenous tissue for repair, was evaluated in 163 patients operated on between 1980 and 1987. One hundred fifteen patients had a first recurrence and 48 had a multiple recurrence; 58% were of the direct type; 30% were of the indirect type; 7% were of the combined type; and 5% were not defined. In 1989 a questionnaire was sent to all patients; those indicating symptoms of recurrence underwent further examination. There was a mean follow-up of 52 months and a total follow-up period of 706 years. Thirty-seven patients had a repeated recurrence with a cumulative recurrence rate of 16%, 21%, and 23%, after 1, 2, and 5 years, respectively. Increase of age and time passed since the last repair reduced the recurrence rate. Increased abdominal pressure, type of anesthesia or surgical technique, and wound hematoma had no effect. It is concluded that the technique of classical hernioplasty as such may be unsuitable for repair of recurrent inguinal hernias.

Mass-transfer effects on the rate of isomerization of D-glucose into D-fructose, catalyzed by whole-cell immobilized glucose isomerase.

The investigated catalyst system consists of immobilized Arthrobacter cells containing the enzyme glucose isomerase, which catalyzes the isomerization of glucose into fructose. The internal structure of the catalyst was determined from electrom microscope photographs of replicas of freeze-etched catalyst. On the basis of the photographs a model for the internal structure of the catalyst was proposed. This structure was subsequently used to describe the reaction including mass-transfer effects. It appeared that under normal operating conditions the external mass-transfer rate does not influence the overall rate of reaction. The effect of internal mass-transfer resistances on the overall reaction rate can well be accounted for by the so-called porous sphere model. The intrinsic kinetics of the isomerization catalyzed by the present catalyst system can be represented by a modified Michaelis-Menten equation for a reversible one-substrate reaction.

Combined external and internal mass transfer effects in heterogeneous (enzyme) catalysis.

A graphical method is outlined in order to calculate the conversion under combined intra- and extraparticle transport limitations using the existing effectiveness factor charts for intraparticle diffusion. This method is applied to the case of an immobilized enzyme, assuming that the kinetics are of the Michaelis-Menten type.