COST REDUCTIONS DUE TO SEASONAL VARIATION IN MUNICIPAL WASTE WATER TREATMENT LEVELS1

ABSTRACT: Varying treatment levels to meet seasonal variation in assimilative capacity of streams can reduce total costs of treatment. A mathematical model of a Pennsylvania stream based on a theoretically sound approximation of the physical relationships underlying the distribution of DO in a river system was used to determine discharge constraints for an economic optimization model which produced estimates of sewage treatment cost savings. Increasing the number of flow periods during the year enhances cost reducing opportunities even when land application processes are considered. Also, the least cost treatment process for year around operation may not be the least costly under multiple flow period management.     

STOCHASTIC MODELING OF MONTHLY AND DAILY RAINFALL SEQUENCES1

ABSTRACT: A monthly model and two daily models (I and II) are presented for the purpose of generating monthly and daily rainfall sequences in the Quae Yai river basin in Thailand. Performance of the models are evaluated by comparing the statistical parameters of the generated sequences with those from historical data. For monthly generation, Thomas-Fiering model worked satisfactorily in spite of the monthly correlations being weak, if any. Daily Model I, which assumes no persistence between daily rainfall amounts within the wet spells, could not preserve some important parameters regardless of the simplicity in model construction. Application of multi-state transition probability matrix model gave good results, although the user has to modify some parameters looking at the performance of the model for each historical record.     

MULTICOMPONENT GEOCHEMICAL TRANSPORT MODELING USING HYDRUS-1D AND HP11

Abstract: The transport of reactive contaminants in the subsurface is generally affected by a large number of nonlinear and often interactive physical, chemical, and biological processes. Simulating these processes requires a comprehensive reactive transport code that couples the physical processes of water flow and advective-dispersive transport with a range of biogeochemical processes. Two recently developed coupled geochemical models that are both based on the HYDRUS-1D software package for variably saturated flow and transport are summarized in this paper. One model resulted from coupling HYDRUS-1D with the UNSATCHEM module. While restricted to major ion chemistry, this program enables quantitative predictions of such problems as analyzing the effects of salinity on plant growth and the amount of water and amendments required to reclaim salt-affected soil profiles. The second model, HPI, resulted from coupling HYDRUS-1D with the PHREEQC biogeochemical code. The latter program accounts for a wide range of instantaneous or kinetic chemical and biological reactions, including complexation, cation exchange, surface complexation, precipitation dissolution and/or redox reactions. The versatility of HP1 is illustrated in this paper by means of two examples: the leaching of toxic trace elements and the transport of the explosive TNT and its degradation products.     

定费用时尿素热解脱硝系统的可靠性研究

针对费用最小化理论在可靠性分配中的局限性,建立更切合实际的固定费用下可靠度极大化思想。将该思想运用到尿素热解脱硝系统中,针对系统结构功能特征及运行特点,深入分析各系统间逻辑功能关系,提出了完整的尿素热解脱硝系统可靠性分配模型。并引入可靠性成本预估函数,以固定费用为约束,建立数学模型,实现了系统可靠性指标的最优化分配。最后以脱硝系统为例,获得具有实际意义的数值解,证明了该方法的可用性及正确性。     

三种综合评价数学模型优选旅游区发展影响因素比较

以优选旅游区发展影响因素为例,阐明3种综合评价数学模型的特点及选择数学模型的原则,同时介绍了如何加强综合评价的科学性和合理性。     

Water Quality Modeling of Municipal Discharges from Sea Outfalls,Mumbai

The island city of Mumbai with a population of about 10 million generates about 2000 million liters per day (mld) of sewage from the seven service areas of the city sewerage network and discharges it into the adjoining west coast and the two creeks in the Arabian Sea. This has resulted in degradation of coastal water quality, contamination of the adjoining beaches and seafronts. The Municipal Corporation of Greater Mumbai has therefore, undertaken the task of delineating appropriate sewage disposal system to achieve cleaner marine ecosystem through marine outfalls at specific locations. This paper presents the results of the mathematical simulations on the impacts of discharge is-a-vis the length of the outfall and level of land treatment apriori. The results of the simulation indicate the level of bacterial pollution to be higher near the diffuser locations as compared to nearshore regions. 48 hsimulation result analysis shows that FC counts nearthe diffuser location will be in the range of 2000–8000 counts per 100 ml.     

ECOLOGICAL MODELS AND ENVIRONMENTAL STUDIES1

The recent world-wide trend towards centralization of all environmental management functions into one regulatory agency has illustrated the necessity for resources management agencies to adopt a total systems viewpoint. Environmental systems are typically complex and multi-dimensional in nature. Mathematical models for the management of air, water and land resources have found wide acceptance among planners and decision-makers. Ecological models of life processes have not reached the same state of development or acceptance. A general review of ecological systems theory and examples of the types of ecological models that have been developed to date arc presented in this paper. With this material as a background and given the vast literature on engineering and economic models, a conceptual framework for an approach to environmental studies and the analysis of polluted environmental systems is presented.     

Evolving Expectations of Dam Removal Outcomes: Downstream Geomorphic Effects Following Removal of a Small,Gravel‐Filled Dam1

Kibler, Kelly, Desiree Tullos, and Mathias Kondolf, 2011. Evolving Expectations of Dam Removal Outcomes: Downstream Geomorphic Effects Following Removal of a Small, Gravel‐Filled Dam. Journal of the American Water Resources Association (JAWRA) 1‐16. DOI: 10.1111/j.1752‐1688.2011.00523.x Abstract: Dam removal is a promising river restoration technique, particularly for the vast number of rivers impounded by small dams that no longer fulfill their intended function. As the decommissioning of small dams becomes increasingly commonplace in the future, it is essential that decisions regarding how and when to remove these structures are informed by appropriate conceptual ideas outlining potential outcomes. To refine predictions, it is necessary to utilize information from ongoing dam removal monitoring to evolve predictive tools, including conceptual models. Following removal of the Brownsville Dam from the Calapooia River, Oregon, aquatic habitats directly below the dam became more heterogeneous over the short term, whereas changes further downstream were virtually undetectable. One year after dam removal, substrates of bars and riffles within 400 m downstream of the dam coarsened and a dominance of gravel and cobble sediments replaced previously hardpan substrate. New bars formed and existing bars grew such that bar area and volume increased substantially, and a pool‐riffle structure formed where plane‐bed glide formations had previously dominated. As the Brownsville Dam stored coarse rather than fine sediments, outcomes following removal differ from results of many prior dam removal studies. Therefore, we propose a refined conceptual model describing downstream geomorphic processes following small dam removal when upstream fill is dominated by coarse sediments.     

Climatic Change, Wildfire, and Conservation

Abstract:  Climatic variability is a dominant factor affecting large wildfires in the western United States, an observation supported by palaeoecological data on charcoal in lake sediments and reconstructions from fire-scarred trees. Although current fire management focuses on fuel reductions to bring fuel loadings back to their historical ranges, at the regional scale extreme fire weather is still the dominant influence on area burned and fire severity. Current forecasting tools are limited to short-term predictions of fire weather, but increased understanding of large-scale oceanic and atmospheric patterns in the Pacific Ocean (e.g., El Niño Southern Oscillation, Pacific Decadal Oscillation) may improve our ability to predict climatic variability at seasonal to annual leads. Associations between these quasi-periodic patterns and fire occurrence, though evident in some regions, have been difficult to establish in others. Increased temperature in the future will likely extend fire seasons throughout the western United States, with more fires occurring earlier and later than is currently typical, and will increase the total area burned in some regions. If climatic change increases the amplitude and duration of extreme fire weather, we can expect significant changes in the distribution and abundance of dominant plant species in some ecosystems, which would thus affect habitat of some sensitive plant and animal species. Some species that are sensitive to fire may decline, whereas the distribution and abundance of species favored by fire may be enhanced. The effects of climatic change will partially depend on the extent to which resource management modifies vegetation structure and fuels.