Groundwater contamination by microbiological and chemical substances released from hospital wastewater: Health risk assessment for drinking water consumers

Contamination of natural aquatic ecosystems by hospital wastewater is a major environmental and human health issue. Disinfectants, pharmaceuticals, radionuclides and solvents are widely used in hospitals for medical purposes and research. After application, some of these substances combine with hospital effluents and, in industrialised countries, reach the municipal sewer network. In certain developing countries, hospitals usually discharge their wastewater into septic tanks equipped with diffusion wells. The discharge of chemical compounds from hospital activities into the natural environment can lead to the pollution of water resources and risks for human health. The aim of this article is to present: (i) the steps of a procedure intended to evaluate risks to human health linked to hospital effluents discharged into a septic tank equipped with a diffusion well; and (ii) the results of its application on the effluents of a hospital in Port-au-Prince. The procedure is based on a scenario that describes the discharge of hospital effluents, via septic tanks, into a karstic formation where water resources are used for human consumption. COD, Chloroform, dichlomethane, dibromochloromethane, dichlorobromomethane and bromoform contents were measured. Furthermore, the presence of heavy metals (chrome, nickel and lead) and faecal coliforms were studied. Maximum concentrations were 700 NPP/100 ml for faecal coliforms and 112 mg/L for COD. A risk of infection of 10^? 5 infection per year was calculated. Major chemical risks, particularly for children, relating to Pb(II), Cr(III), Cr(VI) and Ni(II) contained in the ground water were also characterised. Certain aspects of the scenario studied require improvement, especially those relating to the characterisation of drugs in groundwater and the detection of other microbiological indicators such as protozoa, enterococcus and viruses.     

Carbon dioxide capture and recovery by means of TSA and/or VSA

Experimental work is performed with a 5A zeolite on a small laboratory column with heating from the wall. Carbon dioxide adsorption occurs at atmospheric pressure and different CO₂ concentrations in nitrogen. Comparisons of different methods of desorption by heating, purge and/or vacuum are studied. Desorption by heating only leads to almost pure CO₂ (around 99% purity) and a recovery nearly linear to the heating temperature, ranging from 45% at 130 °C to 79% at 210 °C. Recovery can be subsequently increased with a nitrogen purge to more than 98% but the recovered carbon dioxide is diluted due to the dispersive character of the desorption wave and the operation time is long. Increasing the flow rate decreases the desorption time but has no effect on the purity because the total purge volume remains about the same. Substitution of the purge step with a vacuum step leads to pure CO₂ and almost total recovery. Desorption under vacuum only without heating leads to pure CO₂ (around 99% purity) but limited recovery (85% in the present work).Desorption under vacuum seems to be more simple for large-scale applications. When using a water liquid ring pump, the temperature of the ring must be kept as low as possible to provide a high operating capacity.     

Modeling the carbon dynamics of the La Grande hydroelectric complex in northern Quebec

A mechanistic semi-empirical carbon cycle model of the La Grande reservoir complex in northern Quebec, Canada was conceived in order to investigate the climate impact of such a large alteration of the continental water cycle. The model includes inputs from the drainage basin, organic matter release from flooded soils, CO₂ emissions across the water-atmosphere interface and sedimentation. Most input data stems from previous research by our group on those ecosystems. The model includes the seven reservoirs of the La Grande complex and was run for periods of 50 and 100 years. Terrigeneous dissolved, particulate and suspended soil carbon fluxes and concentrations were computed. Over 100 years, 31.3 × 10¹² g C are released from flooded soils, equivalent to 28-29% of inputs from the drainage basin. 40-74% of dissolved organic carbon is mineralized. CO₂ fluxes over 100 years are 50.5-79.8 × 10¹² g C, 46.4-67.9 × 10¹² g C more than in the absence of reservoirs. The increase in mineralization of organic matter and in CO₂ emissions is a result of the increase in cumulated water residence time due to the creation of the reservoirs. Changes in other carbon sinks and sources likely offset a part of this additional carbon flux to the atmosphere. In the first years following flooding of the reservoir, organic carbon release from flooded soils exceeds CO₂ emissions, implying the downstream export of large quantities of eroded soil organic carbon. After this initial period, CO₂ emissions are fuelled by organic carbon originating from the drainage basin.     

Using penalty functions to evaluate aggregation models for environmental indices

The purpose of indices is to summarize a large volume of information into a single number that is easy to understand and interpret. Environmental indices provide a composite picture of an environmental condition derived from a series of observed measurements and parameters. They are used as communication tools by regulatory agencies to characterize the state of a specific environmental system (air, water, and sediments) and to study the impact of regulatory policies on various environmental management practices. In the development of environmental indices, a few issues and problems have been encountered arising as a result of the abstraction of information and data. These problems are referred to as characteristic properties that include ambiguity, eclipsing, compensation and rigidity. These characteristic properties have long been identified and interpreted in Boolean (e.g., Yes/No) or qualitative (e.g., low, medium, high) terms. In this paper, we propose a new approach to describe the above stated characteristic properties on a continuous scale to evaluate and compare the behavior of various aggregation models. Our approach is based on developing penalty functions for each characteristic property. A water quality index example by Swamee and Tyagi (2000) is used to explain our approach. A detailed case study for a developing microbial risk index is also provided to show how the proposed approach can be extended to complex hierarchical systems. Results show that it is possible to improve aggregation models for index development. Future research directions to improve index development are also discussed.     

DOMESTIC WASTEWATER TREATMENT BY PEATLANDS IN A NORTHERN CLIMATE: A WATER QUALITY STUDY1

ABSTRACT: The use of peatlands as the main form of wastewater treatment in a northern climate was studied for the James Bay Energy Society. The Fontanges campsite (70° 17′ 30″ W; 54° 34′ 00″ N) was chosen as the study site. In less than 1.5 km from the point of discharge BOD₅, COD, total hardness, inorganic carbon, orthophosphates, total phosphorus, ammonia and total nitrogen were reduced by at least 90 percent. The peatland treatment system studied is divided into four components, each having a specific function. The first part combines the action of microorganisms and adsorption on peat, thus reducing the organic content while increasing the inorganic constituents. The second part uses peat to adsorb the inorganic elements already present in the wastewater and those produced in the first part of the system. The third component acts as an aerator, increasing the dissolved oxygen and decreasing the BOD₅ levels of the water. The fourth part removes most of the remaining nutrients, thus acting like a tertiary treatment. Overall, peatlands seemed to be effective in treating domestic settled wastewater in a cold climate.     

Mineralisation of Monuron photoinduced by Fe(III) in aqueous solution

The degradation of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) photoinduced by Fe(III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe(OH)2+, the most photoreactive species in terms of *OH radical formation. These *OH radicals are able to degrade Monuron until total mineralisation. The primordial role of the speciation of Fe(III)-hydroxy complex in aqueous solution, for the efficiency of the elimination of pollutant, was shown and explained in detail. The formation of Fe(II) in the irradiated solution was monitored and correlated with the total organic carbon evolution. Degradation photoproducts were identified and a mechanism of degradation is proposed.     

Bioremediation of Chromate by Sulfate-Reducing Bacteria, Cytochromes c3 and hydrogenases

The treatment of soils and ground waters polluted by heavy metals is of economical and environmental interest. Reduction of Cr(VI) to the less toxic Cr(III) associated to its precipitation is a potentially useful process for bioremediation. In order to develop ecological processes using micro-organisms, we have compared various sulfate-reducing bacteria for enzymatic reduction of chromate. The best Cr(VI) reductase activity was obtained with Desulfomicrobium norvegicum. Despite morphological changes induced by the presence of chromate, this strain can grow in the presence of up to 500 M Cr(VI) and can decontaminate waters polluted by Cr(VI) when seeded in bioreactors. We have demonstrated the ability of several metalloenzymes (cytochromes c ₃ and hydrogenases) to reduce chromate. Biophysical investigations of the chromate/protein interaction in order to get further informations on the mechanism of metal reduction by cytochromes c ₃ are under the way.