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PubMed1990

Decontamination of landfill leachate by soils with different textures.

Soils with different textures (sandy, loamy, and clay soils) were used as filters to attenuate leachate from the Gin Drinkers' Bay landfill. They were used to pack columns of different depths: 0.2, 0.6, and 1.0 m. Eight millimeters of leachate was drained into the soil columns each day for 56 days. The percolated leachates were collected weekly and their properties analyzed. It was revealed that the properties became rather stable at Day 28 and therefore only the data from Day 28 are presented. The effluents from the loamy and clay columns with depths of 0.6 and 1.0 m contained significantly lower (P less than 0.05) ammonia contents and had lower chemical oxygen demand than those from sandy soil columns. Moreover, the depth of the columns of loam and clay did not show a significant difference (P greater than 0.05). Sandy soil was the least effective in attenuating the leachate. The efficiency of all the soil columns decrease as the soil depth decreased. It was also noted that growing of tree seedings (Acacia confusa) could further improve the efficiency of the loamy soil, especially for the removal of Na. The phytotoxicity of the raw and percolated leachate was evaluated using seed germination of two plant species (Brassica chinensis and Lolium perenne) and the growth of an uncellular green alga (Chlorella pyrenoidosa). In general, the raw leachate was toxic and inhibited seed germination and root growth of the two plant species and the growth rate of the unicellular green alga. The toxicity was due to the high levels of ammonia-nitrogen. COD, iron, manganese, and sodium ions. Percolated leachate, especially from loamy and clay soil columns, exhibited a decrease in phytotoxicity. Clay or loamy soil columns of 0.6-m soil depth seemed to be sufficient to remove the phytotoxic substances in landfill leachate.

Decontamination↗
PubMed1989

Decontamination of landfill leachate by soil infiltration.

A soil column study was conducted to evaluate the efficiency of soil to attenuate pollutants in landfill leachate. It was found that more than 60% of the initial alkalinity, COD, and total nitrogen was removed after the leachate had percolated through the soil column. Lower efficiencies were observed for the removal of dissolved cations, ammonia nitrogen, and nitrate nitrogen. When previously percolated leachate was recirculated through the soil column, significant removal (93.6%) of ammonia nitrogen was achieved. Moreover, a further reduction in COD, total nitrogen, nitrate nitrogen, and potassium was evident. Bioassay tests of seed germination and root growth of Brassica chinensis were performed to compare the phytotoxicities of untreated, percolated, and recirculated leachates. The phytotoxicity was reduced by both treatments, with the greatest detoxification observed in the leachate recirculation treatment. The values of pH and Olsen phosphorus were significantly reduced (P less than 0.01) in the treated column soil, whereas significant increases (P less than 0.05) in electrical conductivity (EC), various forms of nitrogen, exchangeable sodium percentage (ESP), potassium, magnesium, zinc, and iron were observed. EC, ESP, potassium, magnesium, sodium, iron, and various forms of nitrogen accumulated at the soil surface (10 cm). On the other hand, manganese was deposited at 20 to 50 cm below the soil surface of the treated column.

Biological Assay↗
PubMedDate not supplied

[Low-temperature regimens for the decontamination of fish of the larvae of Opisthorchis].

It has been established experimentally that the Opisthorchis metacercaria in fish muscles were killed at -28 degrees S in 15-20 h., at -35 degrees C in 8 h. and at -40 degrees C in 2 h. The period of fish freezing becomes much longer when it is stored in snow-covered heaps, which may be the cause of Opisthorchis invasion of wild and domestic carnivorous animals.

Animals↗