液氨泄漏事故模式比较研究

泄漏、扩散、点火这3个因素,在液氨泄漏源附近一定的时空范围内,按不同时序可以演变成BLEVE、喷射火、闪火、蒸气云爆炸和大气中扩散等5种事故后果模式。该文针对液氨的独特理化性质,对液氨泄漏及其在大气中扩散物理过程进行了分析,并通过算例对比研究了5种液氨事故模式的危害范围和程度,为预防液氨泄漏事故发生和液氨泄漏事故预警提供参考。     

厌氧氨氧化反应器的启动及运行

采用污泥混合接种的方法 ,成功地启动了实验室规模的厌氧氨氧化反应器 ,启动后含氨模拟废水运行的进水氨浓度和进水亚硝基氮浓度均为 2 0mmol/L ,氨氮、亚硝基氮和总氮的容积负荷率为 10 6 9mmol/L .d、12 2 6mmol/L .d和 394 5 5mg/L .d ,氨氮、亚硝基氮和总氮的去除率保持在 90 %、99%和 95 %以上。对运行条件研究表明 ,厌氧氨氧化反应的最适pH为 7～ 7 5 ,最适温度约在30± 1℃。厌氧氨氧化随亚硝酸盐浓度的升高而下降 ,氨的厌氧转化随COD浓度的增加也呈抑制型曲线 ,当COD浓度为 80 0±5 0mg/L时 ,厌氧氨氧化速率达到最大。     

氮肥工业中氨氮废水治理技术进展

介绍了氮肥厂对合成氨低温变换工艺冷凝液和尿素解吸废水的回收处理方法。认为选用热力水解法处理尿素吸废水是可行的。     

碱解工艺预处理DMF废水

N,N-二甲基甲酰胺(DMF)及其分解产物二甲胺(DMA)对生物硝化具有强烈的抑制作用,致使含DMF废水的生物处理系统出水的氨氮质量浓度难以达到排放标准。为此,采用碱解预处理方法去除废水中的DMF和DMA。借助实验室小试装置优化了过程控制参数,再将此预处理方法运用到某DMF废水处理工程。小试结果表明,在加碱量为n(NaOH)∶n(DMF)=1.2∶1、反应压力为0.04 MPa、反应温度为76.0℃、反应时间为60 min的条件下,模拟废水的DMF质量浓度由10 000 mg/L降至35 mg/L,DMA质量浓度降至28 mg/L。DMF实际废水处理工程结果表明,经碱解预处理后,生物处理系统进水中DMF稳定在1.0 mg/L以下,DMA稳定在10 mg/L以下,出水氨氮质量浓度降至2.0 mg/L以下,生物硝化过程得以恢复。     

RUNOFF POLLUTION FROM MULTIPLE FAMILY HOUSING1

ABSTRACT: Increasingly, residential development in urbanizing areas is accomplished by large housing projects, composed of clusters of townhouses or garden partments. It is hypothesized that the runoff from such developments should carry more pollution than that from the same number of housing units on separate plots, because the runoff is conveyed directly to drainage channels rather than being drained across lawns and gardens, which may absorb part of the pollutants. In order to evaluate this effect, storm event data were obtained from a planned unit development near Hightstown, N. J., using samples taken every 10 minutes throughout the storm at two different storm sewers. Results show heavy metals pollution about what had been anticipated, in accordance with the hypothesis given above, and BOD ammonia and phosphates higher than predicted. The results are significant for areawide water quality planning in metropolitan areas, where projections of future pollution loadings depends upon the land use.     

AMMONIA IN TEXAS STREAMS DURING LOW FLOW FROM MUNICIPAL WASTEWATER1

ABSTRACT: An investigation of treated municipal wastewaters discharged into Texas streams was conducted to determine the probable effect of concentrations of ammonia in receiving waters, based on existing data on ammonia levels which are lethal to various species of fish. Recorded data for most Texas cities were analyzed. Based on existing toxicity criteria for ammonia of 1/10 TL_m= 0.31 mg/1 NH₃-N, employing known discharge flow rates, and 7-day, 5-year or 7-day, 10-year low flows in Texas streams, appreciable numbers of sites were found to pose a threat to various species of fish. Using the bluegill (Lepomis macrochirus) as a median tolerance limit species, data from 65 cities which met the aforecited requirements, were analyzed. Those included a total of 92 wastewater effluents. Sixty-nine percent of those cities and 70% of their effluents exceeded the 0.31 mg/1 NH₃-N limit in the stream below the discharge point. Thirty-seven percent of the cities equaled or exceeded the 96-hour TL_m concentration limit of 3.1 mg/1 ammonia. Based on the 10 mg/1 NO₃-N standard for intake water for potable supplies, 32% of the effluents resulted in a stream concentration which exceeded 10 mg/1, assuming a straight conversion of NH₃-N to NO₃-N.     

INVESTIGATIONS ON NUTRIENT FACTORS LIMITING PHYTOPLANKTON PRODUCTIVITY IN TWO CENTRAL VIRGINIA PONDS1

ABSTRACT. Laboratory and field studies were initiated to evaluate at regular intervals by ¹⁴C and chlorophyll enrichment bioassay some of the nutrients, particularly ammonia, that might limit phytoplankton photosynthesis in two central Virginia ponds. Preliminary comparisons of the phytoplankton, their production, and the chemical characteristics of the water were determined. Ammonia, phosphate, nitrate, iron, carbon dioxide, silica and chloride differed most markedly among the various nutrients analyzed. Investigations were continued to compare the validity of using field and laboratory ecosystem work to predict changes in trophic levels resulting from nutrient enrichment, i.e., eutrophication. Laboratory experiments using aquatic microecosystems and field experiments employing in situ plastic cylinders and battery jars support the view that ammonia is a key factor regulating “trophic” features in these two ponds.     

pH对亚硝化、厌氧氨氧化反应及联合工艺氮素转化的影响

利用具有pH调节功能的序批式反应器,分别接种好氧生物膜和厌氧颗粒污泥,研究了不同pH对自养生物脱氮工艺氮素转化的影响。结果表明:当pH为8.18时,亚硝氮累积速率较高,为0.79 kg/(m3·d)。当pH为7.85时,厌氧氨氧化菌脱氮效能达到最大,为1.52 kg/(m3·d)。联合工艺进水pH为7.7±0.1时,优先控制好氧段pH为7.5左右,厌氧段pH为7.6,氮去除速率高达0.98 kg/(m3·d)。     

总氨氮在餐厨垃圾厌氧消化系统中的积累及其抑制作用

为研究总氨氮(TAN)在餐厨垃圾中温干式厌氧消化系统内的积累及抑制作用,在单相完全搅拌式(CSTR)反应器内进行餐厨垃圾中温厌氧消化,反应器在3 g·L-1·d-1(以VS计)的负荷下连续运行230余天,期间不断监测TAN及其余物化指标的变化.试验结果表明,TAN在系统内的积累呈现先快后慢的趋势,且不会持续积累,而是积累到一定程度后会保持稳定.游离氨(FAN)是氨抑制中起主导作用的因素,FAN大于150 mg·L-1时就会影响到系统效率;大于200 mg·L-1时会影响系统稳定性;大于300 mg·L-1后会产生强烈抑制,引发稳态型抑制,甚至导致系统出现泡沫.此外,氨抑制会影响系统产气动力学,导致产气速率降低,产气量减少.寻找合理的措施消除氨抑制对保障系统稳定运行具有重要意义.     

人工湿地生物沸石快速吸附-再生性能与再生机理研究

在填充生物沸石和石灰石的强化硝化模拟人工湿地中,考察了生物沸石快速吸附-再生动态平衡性能和生物沸石再生的机理.研究结果表明,生物沸石模拟人工湿地中硝化作用明显,产生的氧化态氮主要为硝氮,平均浓度为106.31 mg·L~(-1)(大于吸附去除的氨氮浓度).模拟人工湿地出水中的金属阳离子主要为Na+和Ca~(2+),30 d后Ca~(2+)浓度大于Na+浓度.生物沸石的再生是离子交换释放氨氮和微生物协同作用的结果.石灰石缓慢释放的Ca~(2+)可促进生物沸石再生,生物沸石与石灰石投加量的最佳质量比为5∶1.生物沸石再生过程中,微生物起主导作用.