几种曝气器应用性能比较与分析

目前冀东油田有四座污水生化处理站,先后使用过普通管式曝气器、刚玉曝气器、动态曝气器和PE微孔曝气器。这四种曝气器都是通过微小空气通道对气流进行扩散,提高氧利用率。空气通道孔径越小,氧利用率越高,但同时通道也越容易堵塞,使运行稳定性变差。综合考虑这两方面因素带来的利弊,在氧利用率与运行稳定性之间找到最佳平衡点,在保证运行稳定性的情况下尽量提高氧利用率,降低能耗。分析各种曝气器的使用情况,为后续使用者提供技术参考。     

REAPPRAISAL OF WATER SUPPLY RESOURCES IN DELAWARE RIVER BASIN USING SYNTHETIC HYDROLOGY1

ABSTRACT The 60's drought (1961 1966) which hit the Northeastern United States, had its center over the Delaware River Basin and caused water supply shortages to New York City, Philadelphia, and many other towns and industries in the Basin. Until this event occurred, the existing water supply sources and those planned for the future had been considered adequate, as they were designed for the worst drought of record (usually the 1930-31 drought). In view of this “change in hydrology,” the Delaware River Basin Commission authorized a study (DRBC Resolution 67-4) to re-evaluate the adequacy of existing and planned water supply sources of the Delaware River Basin and its Service Area (New York City and northern New Jersey). Synthetic hydrology is a tool which can be used to overcome many of the limitations of the traditional approach. By analyzing generated streamflow traces in this study, it has been determined that there is a definite relationship between the accumulated rainfall deficiency during the drought and the return periods associated with various durations of runoff in the drought. This indicated that generated traces can be used to standardize the hydrology over an area where the intensity of drought varied. This represented an important facet in the study, because it provided a means to equalize the effects of this drought over the study area, and gave the Delaware River Basin Commission more information so that it could better plan and manage its water resources equitably, not only for the people within the Basin, but for the New York City and northern New Jersey areas as well. Synthetic hydrology was used to determine yield-probability relationships for 50-year periods, and storage-yield-frequency relationships for existing and planned water-supply reservoirs. It was also used to determine yield-probability relationships for reservoir systems within the Basin. In the study, it was determined that monthly streamflow traces and uniform draft rates could be used in yield analysis because of the magnitude of the reservoirs and because seasonal variations of draft rate are small in the study area. Although it was found that with the streamflow generating models (first order Markov) in common use today, it is not possible to definitely determine the actual frequency of a very severe historic drought, it is possible to place a drought in perspective by using synthetic hydrology. The study showed that it is a useful tool in determining water availability over a basin and is useful in studying water management problems such as interbasin transfers, and reservoir systems operations.     

Movement patterns of American eels (Anguilla rostrata) between salt- and freshwater in a coastal watershed, based on otolith microchemistry

Otolith strontium:calcium ratios were used to trace lifetime movements of American eels (Anguilla rostrata) captured in salt-water bays and adjoining freshwater ponds in Prince Edward Island, Canada. Eels were classified into migratory contingents based on their movement patterns. A pond with a pool-and-weir salmonid fishway and a pond drained by a low-gradient channel contained eels that had entered freshwater at all ages, but a pond with a 2.2 m vertical spillway contained only eels that had entered freshwater in the elver year. Salt-water residents were the dominant migratory contingent in salt-water bays (85% of 39), which overturns the paradigm of obligate catadromy for this species. Freshwater residency was the sole pattern found in the pond with the vertical spillway (100% of 12) and the majority contingent in the pond with the low-gradient channel (54% of 24). Inter-habitat shifting was the dominant migratory contingent in eels sampled from the pond with the pool-and-weir fishway (85% of 20). Resident eels were established in salt- and freshwater habitats by the year after their arrival in continental waters. Eels that shifted between habitats increased their rate of inter-habitat shifting with age. The high degree of plasticity in habitat use found in this study is consistent with worldwide Anguillid patterns as revealed by Sr:Ca.An erratum to this article can be found at     

Long-term evaluation of activated carbon as an adsorbent for biogas desulfurization

ABSTRACT

In this study, granular activated carbon (GAC) was used as an adsorbent for biogas desulfurization. Biogas containing 932–2,350 ppm of H₂S was collected from an anaerobic digester to treat the wastewater from a dairy farm with about 200 cows. An adsorption test was performed by introducing the biogas to a column that was packed with approximately 50 L of commercial GAC. The operation ceased if the effluent gas had an H₂S concentration of over 100 ppm. The GAC was replaced by a given weight of new GAC in a subsequent test. According to the results, for H₂S concentrations in the range of 932–1,560 ppm (average±SD = 1,260 ± 256 ppm), 1 kg of the GAC yielded biogas treatment capacities of 568 ± 112 m³ and H₂S adsorption capacities of 979 ± 235 g. For the higher influent H₂S concentrations of 2,110 ± 219 ppm, the biogas treatment and H₂S-adsorption capacities decreased to 229 ± 18 m³ and 668 ± 47 g, respectively. An estimation indicated a requisite cost of US$16.5 for the purification of 1,000 m³ of biogas containing 2,110 ppm of H₂S. This cost is approximately 5% of US$330, the value of 1,000 m³ of biogas.