Measurement and Modelling of Ammonia Emissions at Waste Treatment Lagoon-Atmospheric Interface

Global emissions of ammonia are approximately 75 Tg N/yr (1 Tg =10¹²g). The major global source is excreta from domestic animals ( 32 Tg N ^-1yr^-1). Waste storage and treatment lagoonsare used to treat the excreta of hogs in North Carolina (NC). Proteins and nitrogen rich compounds in the lagoon are convertedto ammonia, through a series of biological and chemical transformations. The process of ammonia emission has been investigated using two different model approaches: (1) CoupledMass Transfer with Chemical Reaction Model (Model I), and (2)Mass Transport without Chemical Reaction Model (Model II). Asensitivity analysis is performed with the models, and the modelresults are compared with ammonia emission experiments at a swinewaste storage and treatment lagoon in NC using a dynamic emissionflux chamber.Results of model predictions of emission flux indicate an exponential increase in ammonia flux with increasing lagoontemperature and pH, a linear increase with increasing lagoontotal ammoniacal nitrogen (TAN), and a secondary degree increasewith the increasing wind speed. In addition, the fluxes predictedby Model I are consistently larger than fluxes predicted by Model II. Experimental values of flux agreed well with model predictions, with the experimental values lying in different positions between the two model predictions under different physical and chemical conditions. Further, when compared to diurnal and seasonal experimental flux values, Model I corroborates the results in calm meteorological conditions (windspeed U10 = 1.5 m s^-1). However, the observed results are better predicted by Model II during unstable conditions, when wind speeds are higher than 2.0 m s^-1 and physical transfer process functions dominate.     

Metal bioremediation through growing cells

Heavy-metal pollution represents an important environmental problem due to the toxic effects of metals, and their accumulation throughout the food chain leads to serious ecological and health problems. Metal remediation through common physico-chemical techniques is expensive and unsuitable in case of voluminous effluents containing complexing organic matter and low metal contamination. Biotechnological approaches that are designed to cover such niches have, therefore, received great deal of attention in the recent years. Biosorption studies involving low-cost and often dead/pretreated biomass have dominated the literature and, subsequently, extensive reviews focusing on equilibrium and kinetics of metal biosorption have also come up. However, the low binding capacity of biomass for certain recalcitrant metals such as Ni and failure to effectively remove metals from real industrial effluents due to presence of organic or inorganic ligands limit this approach. At times, when pure biosorptive metal removal is not feasible, application of a judicious consortium of growing metal-resistant cells can ensure better removal through a combination of bioprecipitation, biosorption and continuous metabolic uptake of metals after physical adsorption. Such approach may lead to simultaneous removal of toxic metals, organic loads and other inorganic impurities, as well as allow optimization through development of resistant species. However, sensitivity of living cells to extremes of pH or high metal concentration and need to furnish metabolic energy are some of the major constraints of employing growing cells for bioremediation. The efforts to meet such challenges via isolation of metal-resistant bacterial/fungal strains and exploitation of organic wastes as carbon substrates have began. Recent studies show that the strains (bacteria, yeast and fungi) isolated from contaminated sites possess excellent capability of metal scavenging. Some bacterial strains possess high tolerance to various metals and may be potential candidates for their simultaneous removal from wastes. Evidently, the stage has already been set for the application of metal-resistant growing microbial cells for metal harvesting. This review focuses on the applicability of growing bacterial/fungal/algal cells for metal removal and the efforts directed towards cell/process development to make this option technically/economically viable for the comprehensive treatment of metal-rich effluents.     

ECONOMIC INCENTIVES FOR AGRICULTURAL NONPOINT SOURCE POLLUTION CONTROL1

ABSTRACT. The limited success of command-and-control policies for reducing nonpoint source (NPS) water pollution mandated under the Federal Water Pollution Control Act (FWPCA) has prompted increased interest in economic incentive policies as an alternative control mechanism. A variety of measures have been proposed ranging from fairly minor modifications of existing policies to substantial revisions including watershed-wide polices that rely on economic incentives. While greater use of economic incentive policies, such as environmental bonds and point/nonpoint source trading is being advocated in the reauthorization of the CWA, the expected effects of individual proposals will be modest. The characteristics of NPS pollution, namely uncertainty and asymmetrical information, underscores that there is no single, ideal policy instrument for controlling the many types of agricultural NPS water pollution. Some of the usual incentive-based policies, such as effluent taxes, are not well suited to the task. Individual incentive policies proposed for the reauthorized CWA, such as pollution trading or deposit/refund systems, are not broadly applicable for heterogeneous pollution situations. Economic incentive policies may be appropriate in some cases, and command-and-control policies will be preferable in others and may in fact complement incentive policies.     

Water-induced erosion potentiality and vulnerability assessment in Kangsabati river basin,eastern India

Environment, Development and Sustainability - The large-scale water-induced erosion is one of the most determining elements on land degradation in subtropical monsoon-dominated region. From this...     

Catalyst assisted destruction of trichloro ethylene and toluene in corona discharges

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Destruction of VOCs by combination of corona discharge and catalysis techniques

The catalytic effect of alumina on the destruction of toluene, benzene, acetone and methanol, in DC pulsed corona discharge reactor was studied. In the presence of alumina the inlet concentration of the VOCs was varied from 5 x 10-6 mol/L to 80% x 10-6 mol/L, and their decomposition efficiency (conversion %) was found to be 99%-80% for toluene, 99%-97% for benzene, 95%-92% for acetone, and 72%-85% for methanol. Corresponding decomposition in the absence of alumina was 90%-38% for toluene, 89%-57% forbenzene, 42%-30% for acetone, and 47%-19% for methanol. Feed gas flow rate was 400 cm3/min and power reading from DC source was 7.4 W in all of the experiments. Alumina also shifted the CO/CO2 ratio in the by-products in favor of CO2. Ozone concentration at the reactor outlet was higher in the presence of alumina. Enhancement in VOCs decomposition by alumina was explained on the basis of higher concentration of ozone and its precursor atomic oxygen [O].Decomposition efficiency (conversion %) for individual compounds was found to be inversely proportional to the ionization potential of the compound, under identical conditions. Double DC high voltage sources pulse generator was tested and found to improve VOCs decomposition compared with the conventional single DC high voltage source.     

Evaporation behaviour of different organic effluents from open surfaces

Production of large quantities of effluents from different industrial units and the problems of their disposal necessitated this evaporation study. The evaporation of water, sewage water, oil refinery effluent, papermill effluent and liquor distillery effluent was observed in glass beakers when placed (i) in an oven at 60 degrees C and (ii) in screen house for 30 days, by periodically weighing of the beakers. In other experiments, the effect of increasing the frequency of stirring on increasing the evaporation efficiency of the liquor distillery effluent (ELD) was examined in detail. All of the organic effluents except ELD had similar evaporation behaviours as water, but formation of a self-forming film caused the evaporation of ELD to be considerably lower. Resistance to evaporation caused by this film was found to be a decreasing function of the frequency of stirring. This study has a bearing on improving the efficiency of evaporation lagoons, and three stirrings in a day with a manually drawn stirrer in a full-scale lagoon are proposed as a practical and economically viable technique to save 44% of lagoon land in arid and semi-arid regions of the world.     

Environmental challenge vis a vis opportunity: the case of water hyacinth

Water hyacinth (Eichhornia crassipes) is a noxious weed that has attracted worldwide attention due to its fast spread and congested growth, which lead to serious problems in navigation, irrigation, and power generation. On the other hand, when looked from a resource angle, it appears to be a valuable resource with several unique properties. As a result, research activity concerning control (especially biological control) and utilization (especially wastewater treatment or phytoremediation) of water hyacinth has boomed up in the last few decades. Investigations on biogas/compost production from water hyacinth have also come up very well mainly from few research groups in India. This review presents a comprehensive view of the research related to water hyacinth with special emphasis on the recent investigations on water hyacinth control and utilization technologies conducted in the last 2-3 decades. Based on these significant research achievements, now it is desirable to identify a management strategy so that the excessive growth can be controlled and the plant can be used in beneficial ways. In the rural areas, water hyacinth could be used in an integrated manner for decentralized wastewater treatment systems coupled to biogas and compost production from the resulting biomass. There is a need to work out the techno-economic viability of such integrated model systems.     

Health risk assessment of hexachlorocyclohexane in soil,water and plants in the agricultural area of Potohar region,Punjab, Pakistan

Environmental Geochemistry and Health - As the largest organ of the human body, the skin is the major exposure route of NO2. However, the evidence for a relationship between NO2 exposure and...