Biosorption of zinc ions from aqueous solution by the microalga Scenedesmus obliquus

Aquatic environments are often exposed to toxic heavy metals, which gain access to the food chain via microalgae and may cause severe problems at higher trophic levels. However, such a metabolic specificity can be taken advantage of in bioremediation strategies. The potential of a novel wild strain of Scenedesmus obliquus, previously isolated from a heavy metal-contaminated site in northern Portugal, to remove Zn from aqueous solutions was thus studied, using several initial concentrations. The removal extent reached its maximum by 1 day: 836.5 mg Zn/g biomass, at the initial concentration of 75 mg/L, mainly by adsorption onto the cell surface. Comparative studies encompassing a commercially available strain of the same microalgal species led to a maximum removal extent of only 429.6 mg Zn/g biomass, under identical conditions. Heat-inactivated cells permitted a maximum removal of 209.6 mg Zn/g biomass, at an initial concentration of 50 mg Zn/L. The maximum adsorption capacity of Zn, estimated via Langmuir’s isotherm, was 330 mg Zn/g biomass. Finally, Zn removal was highest at pH 6.0–7.0. It was proven, for the first time, that such a wild microalga can uptake and adsorb Zn very efficiently, which unfolds a particularly good potential for bioremediation. Its performance is far better than similar (reference) species, especially near neutrality, and even following heat-treatment.     

Vacuum pyrolysis process for remediation of hydrocarbon-contaminated soils

A vacuum pyrolysis process was used for the remediation of hydrocarbon–contaminated soils from “Les Vidangeurs de Montréal” site in Mascouche in the province of Québec, near Montréal. Ten samples were tested on a laboratory scale batch reactor, and one sample was tested on a prototype process development unit. The process is simple, efficient, reliable, and economically competitive with other existing technologies. The vacuum pyrolysis process efficiently treated soils contaminated with a variety of pollution levels and types, irrespective of the soil matrix, providing treated soils meeting the A criterion (noncontaminated, residential level) of the Ministry of Environment Québec (MENVIQ). The pyrolytic oil and the noncondensable pyrolytic gases can be used as makeup fuel in the process, because they have a high calorific value and their combustion should not pose any emission problems. The waterphase effluent must be treated before discharge.     

The carajas iron ore project: The strategy of a third world state- owned enterprise in a depressed market

This paper describes how the Carajas iron ore project was set up in February 1985 at a time of deep recession in the iron ore and steel industries. Development of the project was met with much criticism, mainly from North American steel makers, who argued that the project would only be successful through the support of a Third World government, highly dependent on foreign exchange, without any consideration being given to its economic feasibility or to the fundamentals of the market. The authors explain why the World Bank took the step of setting up the project and how its development can be partly explained by the interests of the Japanese and European steel makers. The role of the Brazilian government is explained and the authors conclude that the relatively low rate of investment anticipated by the project will be overshadowed by the high gains in foreign exchange.     

Operating Experience with Biogas Plants in Sri Lanka

Three hundred and three biogas plants, representing a majority of the units installed in Sri Lanka up to 1984, were inspected, and it was found that 280 of these had been put into commission at some time prior to the study. Of the 280 commissioned plants, 170 (61%) were functioning satisfactorily providing biogas for cooking and/or lighting. The remaining 110 (39%) were either not functioning or were supplying very little gas owing to gas leaks, inadequate input of dung, or poor plant management. The most common plant was the 6 m³, fixed dome, household plant, and the most common raw material used was cattle dung. In the majority of household plants the cost of construction was partly or wholly subsidized.     

Structure-biodegradation relationships of polymeric materials. 1. Effect of degree of oxidation on biodegradability of carbohydrate polymers

The biodegradability of oxidized starch and inulin has been studied in relation to the degree of periodate oxidation to dialdehyde derivatives, by measuring oxygen consumption and mineralization to carbon dioxide. A higher degree of oxidation of dialdehyde starch and dialdchyde inulin results in a lower rate at which the polymers are biodegraded. It is demonstrated that the biodegradation rate of dialdehyde inulin derivatives decreases more than that of equivalent starch derivatives. The differences in biodegradation behavior between dialdehyde starch and dialdehyde inulin, resulting from comparable modifications, are discussed in terms of conformational structure.