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671.
Louis A. Heifrich Mark Zimmerman Diana L. Weigmann 《Journal of the American Water Resources Association》1995,31(2):307-316
ABSTRACT: Filtering efficiency of the fathead minnow (Pimephales promelas), gizzard shad (Dorosoma cepedianum), carp (Cyprinus carpio), and a freshwater mussel (Elliptio coinpianata) was measured in field and laboratory trials to assess the ability of each species to control phytoplankton and suspended solid densities. All fish species tested were ineffective filterers and generally increased, rather than suppressed, algal and suspended solid concentrations. Filtering efficiencies of fish varied between -354 and 84 percent, depending on the size, shape, abundance, palatability, composition, and resistance to digestion of the particles. Because of poor filtering abilities, unpredictable feeding habits, and sensitivity to stress, the fish species examined are not effective biological controls in waste lagoons. In contrast, the freshwater mussel Elliptio was a highly effective control organism, averaging 66 percent filtering efficiency over a wide size range of algal and suspended particles. Filtration efficiency was positively correlated with mussel density. Elliptio was efficient at filtering small particles, which are particularly difficult to remove. Mean filtration rates ranged from 53 to 134 ml/mussel/h depending on the algal species consumed and algal densities (range 50–180,000 cells/ml) and 3 mg/L/mussel/h on suspended solids (range 14 to 112 mg/L). Water clarification was facilitated by both direct consumption and pseudofeces deposition. Elliptio and probably other mussel species can effectively control algae and suspended solids in wastewater lagoons and eutrophic lakes, if environmental conditions, especially dissolved oxygen levels, are suitable (>5 mg/L) for their survival. 相似文献
672.
Yun-Sheng Yu Manoutchehr Heidari Wang Guang-Te 《Journal of the American Water Resources Association》1989,25(2):295-300
ABSTRACT: Finite element and finite difference representations of the convective-dispersive equation have been widely used in determining contaminant transport in ground water. Due to inherent uncertainties of the transport process, those representations are inexact and contain errors. Errors in field measurements are unavoidable. By combining a numerical model, a measurement equation, and the Kalman filter, optimal estimates of the state variable (contaminant concentration) can be obtained. This paper describes the algorithm and gives a numerical example of contaminant transport in a two-dimensional ground water flow. The results show significant improvement in the estimated concentration distribution by using the filtering technique. 相似文献
673.
An efficient linear Kalman filter has been combined with a coupled atmospheric transport and soil–air exchange model to determine organochlorine pesticides emissions on the regional scale. In this study, results of -HCH emissions from the Great Lakes–St. Lawrence ecosystem, estimated from the coupled model, are presented and discussed. A source receptor technique is used to identify a priori the locations of emission sources of -HCH, the emissions are then updated through a Kalman filtering procedure which minimizes the weighted difference between the predicted mixing ratios from the coupled model and the measured concentrations over the Great Lakes–St. Lawrence river region. Two experiments using the inverse algorithm are carried out. In the first experiment, the coupled atmospheric transport and soil–air exchange model is implemented to predict -HCH air and soil concentrations. Emissions are then updated every 12 days using the updated soil concentrations and emission factors. However, the updated emissions are not input into the coupled atmospheric transport and soil–air exchange model. On the other hand, in the second experiment the updated emissions are fed back to the coupled model, so that the model is reinitialized in each 12 days. The results from the inverse technique for the year 1995 have been compared with grided -HCH emission inventory in Canada, generated by emission factors. It is shown that the estimated emissions of -HCH are consistent with the measured emissions. It is found that the St. Lawrence valley has larger emissions of -HCH than the Great Lakes region, indicating an opposite distribution to the emission usage inventory, but in agreement with the measured -HCH concentration. 相似文献
674.
Operational and Design Considerations of a Trickling Filter for Ammonia Removal from Potable Water 总被引:1,自引:0,他引:1
We studied the steady-state behavior of a mathematical model of a nitrifying trickling filter. In particular, we studied the effect of the operating conditions of the filter on the complete and safe nitrification. We presented the results with the help of the operating diagram of the system and we determined the range of operating conditions resulting in optimal operation. We also computed biofilm thickness along the filter depth and concentration profiles inside the biofilm, and compared them with experimental results found in the literature. The comparison shows very good qualitative agreement between model predictions and experimental data. 相似文献
675.
新型厌氧反应器处理生活污水的研究进展 总被引:4,自引:0,他引:4
新型高速厌氧反应器的发生使生活污水的厌氧处理成功可能,介绍了几种厌氧反应器的特点及其在生活污水处理中的研究现状。 相似文献
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677.
The united membrane biological reactor(UMBR) was studied for the treatment of some simulate and municipal wastewater. The removal efficiency for COD and turbidity are greater than 80% and 99% respectively. Effluent COD is less than 100 mg/L while turbidity less than 5. The removal of LAS in bath wastewater is greater than 70%. In treatment of dinning-hall wastewater, removal of fatty oil is greater than 90%, and its concentration in effluent is less than 5 mg/L. The match of biological reactor and the membrane separation component were calculated. The stable performance of wastewater treatment can be maintained by the optimization of operation conditions and the eleanout of membranes. 相似文献
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采用沉淀-SBR-活性炭过滤复合工艺对城市垃圾渗滤液进行处理,确定混凝、SBR和活性炭过滤的最佳参数。结果表明,当进水CODcr 2500mg/L、氨氮在900mg/L的条件下,经该系统处理后,出水CODcr均在300mg/L以下,氨氮在20mg/L以下。CODcr去除率达90%以上,氨氮去除率达98%以上,达到去除有机物和氨氮的较好效果。 相似文献