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The effect of oxidative and thermo-oxidative co-treatment of excess municipal sludge was investigated. A mixture of primary and waste activated sludge was anaerobically treated using two different configurations: i) two stages and ii) a single stage with recycling. Oxidative or thermo-oxidative co-treatment placed in between the reactor or in the recycle line was studied. A two-stage configuration with no co-treatment served as a control and resulted in 50.1% overall solids removal. Compared to the control, an increase in solids removal of 10.8 and 2.7% was observed when oxidative co-treatment was placed between reactors and in the recycle line respectively. When thermo-oxidative co-treatment was placed between the two stages or in the recycle line an increase in solids removal of 25.1 and 26.9% respectively was observed. The performances of the different configurations were also evaluated with parameters such as COD, TKN, ammonia, and fecal coliform concentration.

A new photocleavable linker, 4,4'-bis(alkoxymethyl-3,3'-dinitro)biphenyl, is reported that undergoes photolysis at two positions to release two equivalents of primary, secondary, or benzylic alcohol in yields that are higher than those obtained from the analogous monomeric o-nitrobenzyl ethers.

Suspended Particulate Matter (SPM), surface (bed sediments) and short length cores of sediments collected from the largest tributary of the river Ganges, namely the river Yamuna, were analysed for total mercury as well as its fractionation in various size and chemical sites in the sediments following standard procedures. Also, attempts were made to determine the vertical distribution in sediments in relation to the recent timescale of a few decades. Our observations indicate that the SPM in general showed higher levels of total mercury compared to the surface sediments while at places the enhancement could be by a factor of 10, say around 25 microg g(-1) in the downstream region that integrates the industrial midstream and agricultural downstream terrain near its confluence with the Ganges. Surface sediments in the upstream direction near the Himalayan foothills and SPM in the lower reaches showed significant high Index of Geoaccumulation (Igeo) as defined by Müller. Size fractionation studies indicate that the finer fraction preferentially showed higher levels of mercury while in the lower reaches of the river, the total mercury is equitably distributed among all size fractions. The proportion of the residual fraction of mercury in relation to mobile fractions, in general decreases downstream towards its confluence with the Ganges river. In sediment cores, the vertical distribution show systematic peaks of mercury indicating that addition of this toxic metal to the aquatic system is in direct proportion to the increase in various types of human activities such as thermal power plants, land use changes (urbanisation) in the midstream region and intensive fertiliser application in lower reaches of this vast river basin.

The natural abundance of fluoride in soils of the Ajmer distict, Rajasthan was examined. From undisturbed soil, the top 15 cm of the profile was examined and the soil split into fractions based on sand, silt and clay particle size. Clay contained a high amount of fluoride, whereas sand and silts are enriched with much less fluoride. The relation between the soil fractions in observed clay fraction fluoride content matched groundwater fluoride variation. However, the enrichment of fluoride material extracted from the largest soil fraction had considerably lower amounts of clay relative to that from the smaller fractions.

Peroxidase (Donor: H(2)O(2)oxidoreductase EC 1.11.1.7) from human term placentae of non-smokers was purified to homogeneity by a combination of NH(4)Cl extraction, affinity chromatography, (NH(4))(2)SO(4)precipitation, ion-exchange and gel filtration chromatography. The homogeneity of purified human placental peroxidase (HTPP) was confirmed by gel filtration, reverse phase high performance liquid chromatography (HPLC) and SDS-PAGE. Peroxidase was found to be a membrane bound enzyme. A high concentration of NH(4)Cl (1.2 m) was needed to extract and solublize the enzyme. Removal of the salt resulted in irreversible precipitation of the enzyme. The protein exhibited a molecular mass of 126 000 kDa according to gel filtration and approximately 60 000 kDa by SDS-PAGE, indicating that the peroxidase is a homodimer. The purified peroxidase showed an optimum pH range of 7 to 8.5 and the K(m)for H(2)O(2)and guaiacol were found to be 0.08 m m and 10.0 m m, respectively. The purified peroxidase oxidized several substrates, namely potassium iodide, tetramethyl benzidine, guaiacol, ortho dianisidne and tyrosine. The enzyme was resistant to thermal denaturation up to 70 degrees C and also to chaotropic agents, guanidinium chloride and urea. Spectral properties indicated the presence of Soret band at 433 which shifted to 451 nm on complexation with cyanide. The circular dichroism studies showed that HTPP has a predominantly helical secondary structure. The enzyme showed similarities to the myeloperoxidase with regard to spectral and catalytical properties but differed significantly in amino acid composition, the R(z)value and molecular mass. Purified HTPP differed from eosinophil peroxidase in all physico-chemical properties indicating that it is not of eosinophil origin, but may represent a distinct, constitutive peroxidase in human placenta. Further, purified peroxidase catalyzed oxidation of benzo(a)pyrene-7, 8-dihydrodiol in presence of tyrosine and hydrogen peroxide to BP-tetrols, the hydrolytic products of BP-diol-epoxides, demonstrating the ability of peroxidase in bioactivation of benzo(a)pyrene in human placenta., (Copyright 2000 Harcourt Publishers Ltd.)

Human placenta, umbilical cord blood, maternal blood and breast milk samples from mothers were analysed for the presence of selected polycyclic aromatic hydrocarbons (PAHs). Benzo(a) pyrene (B(a)P), dibenzo(a,c)anthracene (DBA) and chrysene (Chy) were detected in all the four types of sample. Levels of dibenzo(a,c)anthracene were higher in the above samples compared with the other two PAHs. Umbilical cord blood and breast milk samples showed relatively high concentrations of all the three PAHs and thus demonstrated that the developing foetus/new born were exposed to these carcinogenic environmental contaminants. The possible implications of PAHs in relation to human health are discussed.