Simultaneous heterotrophic and sulfur-oxidizing autotrophic denitrification process for drinking water treatment: control of sulfate production

A long-term performance of a packed-bed bioreactor containing sulfur and limestone was evaluated for the denitrification of drinking water. Autotrophic denitrification rate was limited by the slow dissolution rate of sulfur and limestone. Dissolution of limestone for alkalinity supplementation increased hardness due to release of Ca²⁺. Sulfate production is the main disadvantage of the sulfur autotrophic denitrification process. The effluent sulfate concentration was reduced to values below drinking water guidelines by stimulating the simultaneous heterotrophic and autotrophic denitrification with methanol supplementation. Complete removal of 75 mg/L NO₃-N with effluent sulfate concentration of around 225 mg/L was achieved when methanol was supplemented at methanol/NO₃-N ratio of 1.67 (mg/mg), which was much lower than the theoretical value of 2.47 for heterotrophic denitrification. Batch studies showed that sulfur-based autotrophic NO₂-N reduction rate was around three times lower than the reduction rate of NO₃-N, which led to NO₂-N accumulation at high loadings.     

Sorption Process for Copper Recovery from Effluents of Mining Enterprises by Granulated Pyrite-Bearing Wastes

The sorption process is proposed for copper recovery from waste effluents of mining enterprises by applying the old condensed granulated pyrite-bearing concentrates with obtaining sulfide product of 4.5% in copper content, amenable to pyrometallurgical processing. Copper is precipitated on pyrite particles as a low-temperature modification of -chalcosine. The sorption parameters are determined, the process flowsheet is developed, as well as technical and economical factors of underdump water treatment in the Sibai open pit are calculated.__________Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 92–97, 2004.     

Changes in concentration of aflatoxin M1 during manufacture and storage of skim milk powder

In this study, skim milk powder was produced from cow's milk contaminated artificially with aflatoxin M1 (AFM1) at two different levels, 1.5 and 3.5 microg/liter (ppb), and the effects of process stages on the AFM1 contents were investigated. Pasteurization, concentration, and spray drying caused losses of about 16, 40, and 68%, respectively, in AFM1 content of the milk contaminated with 1.5 microg/liter AFM1, and losses of 12, 35, and 59%, respectively, in the milk contaminated with 3.5 microg/liter AFM1. These losses were found to be statisticially significant at the level of P < 0.01. After 3- and 6-month storage periods, AFM1 content of the skim milk powder produced from milk with 1.5 microg/liter AFM1 decreased by 2 and 5%, respectively, whereas these rates were 2 and 4%, respectively, for the skim milk powders made from milk with 3.5 microg/liter AFM1 (after adjustment for sample weight). Changes in AFM1 content of milk powder samples were found statistically insignificant (P > 0.05 and P > 0.01) for 3- and 6-month storage periods.     

The impact of fat content and charcoal types on quality and the development of carcinogenic polycyclic aromatic hydrocarbons and heterocyclic aromatic amines formation of barbecued fish

The effects of fat content and charcoal types on the formation of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HAAs) in various barbecued fish (trout, sea bream, seabass, salmon and shad) were investigated. Fish samples were also analysed in terms of fat content and fatty acid profile. Total saturated fatty acids (∑SFA) contents reduced while the total polyunsaturated fatty acids (∑PUFA) contents increased after barbecuing. Both fat content and charcoal type had an effect on the amount of PAHs and HAAs. The amounts of ∑PAHs ranged between 6.95 and 99.03 ng g⁻¹ in barbecued fish. Notably, the highest amount of ∑PAHs was found in shad as well. The amounts of ∑HAAs ranged from non-detectable levels to 2.29 ng g⁻¹. The amounts of ∑PAHs and ∑HAAs were higher in samples barbecued with charcoal briquette compared to those barbecued with wood charcoal. Hence, we would suggest the use of wood charcoal in barbecuing.