Travel of microorganisms from a septic tile

An investigation was carried out to monitor the horizontal travel of indicator microorganism from the end of a septic tile in the direction of groundwater flow. The microorganism levels exhibited a declining trend with distance away from the tile end. This investigation also revealed that because the unsaturated depth of soil available for microorganism vertical travel was limited, relatively high levels of organisms were found in the groundwater even at a horizontal distance of 15.25 m from the end of the septic tile.     

Quantification of Shallow Groundwater Nutrient Dynamics in Septic Areas

Of all groundwater pollution sources, septic systems are the second largest source of groundwater nitrate contamination in USA. This study investigated shallow groundwater (SGW) nutrient dynamics in septic areas at the northern part of the Lower St. Johns River Basin, Florida, USA. Thirty-five SGW-monitoring wells, located at nine different urban areas served by septic systems, were used to collect the SGW samples seasonally and/or biweekly for a duration of 3?years from 2003 to 2006. Analytical results showed that there were 16 wells with nitrate concentrations exceeding the US Environmental Protection Agency's drinking water limit (10?mg?L^?1). There also were 11 and 14 wells with total Kjeldahl nitrogen (TKN) and total phosphorus (TP) concentrations, respectively, exceeding the ambient water quality criteria (0.9?mg?L^?1 for TKN and 0.04?mg?L^?1 for TP) recommended for rivers and streams in nutrient Ecoregion XII (Southeast USA). In general, site variations are much greater than seasonal variations in SGW nutrient concentrations. A negative correlation existed between nitrate/nitrite?Cnitrogen (NO_x?CN) and TKN as well as between NO_x?CN and ammonium ( $ NH_4^{ + } $ ), whereas a positive correlation occurred between TKN and $ NH_4^{ + } $ . Furthermore, a positive correlation was found between reduction and oxidation (redox) potential and water level, while no correlation was observed between potassium concentration and redox potential. This study demonstrates a need to investigate the potential adverse impacts of SGW nutrients from the septic areas upon the deeper groundwater quality due to the nutrient penetration and upon the surface water quality due to the nutrient discharge.     

Microbial contamination of alluvial gravel aquifers by septic tank effluent

The effects of two methods of septic tank effluent disposal on the microbial quality of alluvial gravel aquifers were investigated at an experimental site in the Canterbury Plains, New Zealand. The movement of faecal coliform bacteria 9 m from a 5.5 m deep soakage pit into an unconfined aquifer, and 42 m from an 18 m deep injection bore into a confined aquifer was recorded. Partial sealing of the soakage pit sidewalls was evident, but approximately 80% of the effluent appeared to percolate rapidly into the unconfined groundwater through a permeable pathway in the unsaturated zone. There was evidence of groundwater mounding beneath the soakage pit and around the injection bore and the consequent radial spread of leachate from both disposal structures. In both the confined and unconfined aquifers, the most heavily contaminated bores exhibited marked diurnal fluctuations in faecal coliform concentrations in response to periods of effluent discharge. First arrival velocities of a rifampycin-resistantEscherichia coli tracer of approximately 15 m day^?1 in the unconfined groundwater and 151 m day^?1 in the confined groundwater were recorded. Implications of the findings for the monitoring and management of groundwater quality beneath unsewered communities on alluvial gravel formations are briefly discussed.     

Quantitatively tracing bacterial transport in saturated soil systems

Three isolates of Escherichia coli were labeled by their resistance to sodium azide and, separately, to novobiocin, nalidixic acid, and tetracycline. The strains exhibited a high degree of persistence in the soil environment and were recoverable on strain specific media at levels within the 95% confidence interval of the numbers covered on nonselective media. The E. coli strains were subsequently used to evaluate the events which would occur when a septic tank drainfield became submerged in a perched water table and effluentborne bacteria escaped into the groundwater. Field experiments were conducted by introducing the strains into horizontal lines installed into the A, B, and C horizons of a soil profile and transport was evaluated by collecting groundwater samples from 5 rows of piezometers (sampling six separate depth zones/row) located downslope from the injection lines. The major portion of subsurface transport of the bacterial populations occurred in specific zones in the soil profile and at an apparent maximum velocity of 17.0 cm min^?1. The maximum bacterial density in the groundwater, observed at each sampling distance downslope, was used to produce a mathematical relationship which described the overall decrease in numbers of organisms with increased distance through the soil. The potential health hazards which could occur by the subsurface transport of fecal organisms in relation to these experiments are discussed.     

Identification of an Assemblage of Indicator Organisms to Assess Timing and Source of Bacterial Contamination in Groundwater

Bacterial contamination of drinking water wells is a commonproblem in many rural areas. Some of this contamination may berelated to manure spreading or housing of livestock; another source is on-site septic systems. Current indicator organisms are able to detect the presence of fecal contamination, but where there may be more than one potential source of fecal material, the current indicators are unable to ascertain the origin. This laboratory investigation was undertaken to determine the longevity and reliability of a selected suite of indicator organisms. Total coliform, fecal coliform, fecal streptococci and Clostridium perfringens were monitoredin a simulated contaminated groundwater environment for 6 months. All four indicator organisms were present at the end of6 months. The number of fecal streptococi bacteria decreased most noticeably, allowing assessment of relative age of contamination. C. perfringens was found to be a reliableindicator of contamination from animal manure. Fecal material from 28 different animals and three septic systems were assessed for the presence of the indicator organisms. Totalcoliform, fecal coliform and fecal streptococci were present in the fecal material of all animals tested including reptiles.C. perfringens was detected in feces from all but two of the animals assessed. Using an assemblage of indicator organisms provides more information regarding source and timingof contamination than just testing for total coliform and fecalcoliform bacteria.     

Movement of nitrogen and carbon from a septic system drainfield

A septic system drainfield that had been in use for 6 yr was instrumented to study the vertical and horizontal movement of N and C. The original system was designed so that the effluent from the septic tank could be deverted to either of two parallel leaching trenches. Each trench contained three precast leaching chambers (1.22 m×2.44 m×0.3 m) placed end to end at a depth of 1.4 m. Since installation each trench had been used alternately for 6 mo periods. In each of the 2 yr of this study, effluent began to pond in the leaching chamber within 24 h after the effluent was directed to that trench. Approximately 100 days were required to develop a quasi steady state with respect to the depth of ponding and concentrations of N and C in the soil solution. In both years of the study about 25% of the influent-N was mineralized. However, in the first year very little nitrification occurred while in the second year essentially all of the NH₄ in the soil profile was nitrified and moved without apparent loss to the groundwater. These differences in N transformation appeared to be indirectly controlled by rainfall with 50% less precipitation received in the second than in the first year.     

Bacterial pollution of groundwater: A review

Contamination of groundwater resources from bacterial laden wastewater and effluents poses a great threat to the potability and use of these water sources. Future planning, development and management schemes must consider this topic to avoid costly and sometimes untested corrective actions. Major factors affecting the quantity and velocity at which bacteria are able to migrate through soil can be classified as (1) soil factors including particle size distribution, structure, clay content, pore size distribution and moisture regime, and (2) biological factors responsible for bacterial die-off including pH, temperature, moisture content, and nutrient supply. Past bacterial pollution problems have been shown to be localized and restricted to wells utilizing near-surface waters. The following problem areas exist and must be given special consideration in planning and development: (1) use of septic disposal systems in unsuitable soils; (2) drainage waters from wastewater application areas utilizing artificial drainage systems; (3) waste application in areas underlain by fractured crystalline rock or channelized bedrock; and (4) bacterial contamination induced over great distances by groundwater pumping.     

Influence of temperature on the performance of septic tank systems

Air, liquid and soil temperatures are important environmental factors that influence the operation of septic tank-soil absorption systems. An investigation conducted near Ottawa on the efficiency of an experimental tile system did not show any specific trend between soil temperatures (depth dependent) and efficiency; this can be attributed to the fact that the depth factor carries with it other elements such as proximity to groundwater table, oxygen penetration that significantly influence the efficiency of the system. It is however observed that generally periods of higher air and soil temperatures (June to October) showed better efficiencies for most of the parameters studied.     

用分布式水循环模型与机器学习预测内蒙古河套灌区节水潜力

为探究内蒙古河套灌区真实节水潜力,该研究构建河套灌区分布式水循环模型与基于机器学习的盐分模型,设置节水方案集,定量分析各方案下的灌区引、耗水量、地下水埋深、积盐量变化等。结果表明：1）水面蒸发的纳什系数均不低于0.654,相对误差绝对值不高于分别为4.82%,相关关系为0.88,排水过程纳什系数均不低于0.600,相对误差绝对值不高于分别为5.11%,相关关系为0.82,地下水埋深的纳什系数均不低于0.628,相对误差绝对值不高于分别为5.12%,相关关系为0.86,满足灌区水循环满足精度要求。本文选择采用土壤盐分模型,得到土壤积盐量与实测值的纳什系数均不低于0.76,满足精度要求。2）渠道砌衬方案S1、田间节水调控方案S2、种植结构调整方案S3的耗水节水量分别为2.93亿、3.02亿和2.54亿m³。S1+S2+S3组合方案灌区耗水节水量最多,为9.11亿m³,S2+S3方案组合次之。3）渠系水利用系数提高,将引起地下水水位下降,不利于排盐,S1方案下地下水埋深大于3 m的面积比例较基准方案增加了7.59%,不利于灌区排盐。田间工程措施使得相应的农田入渗量减少,地下水位下降,有利于灌区脱盐,S2方案下地下水入渗补给量较基准方案减少2.57亿m³,灌区地下水位下降较为明显,S2方案有利于灌区脱盐。S3方案下地下水入渗补给量略微减少,地下水位变化不大,有利于灌区脱盐。不同方案组合,S1+S2、S1+S2+S3方案下对地下水埋深影响较大,尤其是S1+S2+S3方案在灌区西北部、山前、乌拉特前旗、乌梁素海东部的形成连片埋深高值区,影响区域生育期农田作物与林草地植被生长。S1S2方案下不利于灌区脱盐,自然植被生育期平均埋深超过2.5 m的比例较基准方案增加了5.46%。在综合考虑生态环境的约束下,推荐耗水节水量最大的方案S2+S3,即灌区适宜的耗水节水潜力为5.69亿m³。该方案下虽然也会引起地下水位略有下降、进乌梁素海排入水量略微减少,但最有有利于灌区排盐。研究可为引黄灌区节水方案制定与灌溉管理提供技术支撑。     

滹滏平原地下水资源脆弱性时变分析

采用灰色关联度法和BP神经网络法计算各指标权重,然后用综合指数法分别对滹滏平原1984年和2000年地下水资源脆弱性进行了评价。2000年相对于1984年,地下水资源脆弱性分布特征发生了明显的变化,而且脆弱性级别升高。地下水资源脆弱性具有时变性,制定地下水合理利用模式时应当结合现状实际地下水资源脆弱性。     

Heavy metal and volatile organic chemical removal and treatment in on-site wastewater infiltration systems

Solvents, greases, and rinse waters from routine vehicle maintenance contain heavy metals and volatile organic chemicals (VOCs). In Wisconsin, these fluids enter catch basins along with rinsing waters and are discharged to soil infiltration systems drainfields after mixing with domestic wastewaters in a septic tank. The purpose of this study was to monitor heavy metal and VOC removal and treatment in catch basins and septic tanks at four publicly-owned motor vehicle service stations (MVSS). Cadmium, chromium, and lead were found in catch basin wastewater, septic tank effluent, and septic tank sludge at concentrations ranging from 0.002–7.7 mg L^?1. Lead was found in the highest concentration. The highest concentrations of metals were in septic tank sludge. Of the >50 VOCs scanned for in catch basin wastewater, septic tank effluent, and septic tank sludge samples, 29 were found in concentrations that exceeded analytical detection limits. Concentrations of detected VOCs ranged from 1.0–15,800 µg L^?1 and the highest concentrations of VOCs were found in catch basin wastewater and septic tank sludge. Acetone, ethylbenzene, toluene, and xylenes were the most commonly found VOCs at all sampling locations. Thus, heavy metals and VOCs were not completely removed in catch basins and were discharged to septic tanks where removal occured possibly as these contaminants settled with solids in the sludge. The level of treatment was, however, inadequate and heavy metals and VOCs were discharged to drainfields.     

基于指示Kriging法的土壤盐渍化与地下水埋深关系研究

在北方干旱、半干旱的地下水浅埋区,土壤盐渍化是土地资源退化的主要原因,防治土壤盐渍化是农业和生态环境可持续发展的重要保障。该文以内蒙古河套灌区解放闸灌域为例,运用指示Kriging法绘制并比较了不同阈值下地下水位埋深和土壤表层含盐量的概率分布图,从概率空间分布的角度分析研究了土壤盐渍化与地下水位埋深之间的关系,从而将这方面的研究从通常的农田尺度扩大到灌域尺度。结果表明:1)土壤盐分和地下水位埋深空间变异强度均为中等,且具有中等的空间自相关性,球状模型拟合变异函数的效果较好;2)在灌域尺度上,解放闸灌域4月底土壤表层发生中度、轻度盐渍化时地下水位临界埋深分别为2.0、2.5m,西南及中东部地下水位埋深小于临界埋深的概率较大,是土壤返盐的高风险区;3)3月底地下水位埋深对土壤返盐的影响比4月底更大一些,这表明地下水位埋深对土壤返盐的影响具有一定滞后效应,只有地下水位埋深小于临界深度的状态维持一段时间,才会造成土壤中度或轻度盐渍化。     

塔里木盆地南缘绿洲地下水时空变异与监测点位优化——以策勒绿洲为例

[目的]揭示塔里木盆地南缘绿洲地下水时空变异特征,优化监测点位,为实现水资源的合理利用与绿洲可持续发展提供依据。[方法]基于2008—2014年地下水监测数据,首先利用地统计学方法,通过对球状、指数、高斯3种模型的系统分析,确定适宜该地区的最优模型;其次利用该模型定量分析区域地下水时空变异特征,并进行地下水监测点位优化;最后利用Thiessen多边形法计算地下水平均埋深,对绿洲地下水平均埋深变化特征进行分析。[结果]高斯模型为最优模型,并且地下水的空间异质性和连通性增强;在不影响监测精度前提下,将原有23个监测点有效减至12个,降低监测成本;绿洲地下水平均埋深变化趋于稳定。[结论]绿洲地下水尽管受绿洲扩张影响显著,但因径流补给,目前总体处于安全状况。为保障绿洲健康可持续发展,需在目前绿洲规模基础上适当控制绿洲扩张。     

天山北麓地下水基于生态水位的调控模拟分析

针对地下水资源可持续利用与表生生态协调发展的问题,在对天山北麓野外调查及已有研究结果分析的基础上得出细土平原区生态水位埋深为3～6 m。应用数值模拟技术对现状及调整开采布局后地下水位引起的表生生态效应进行对比,结果表明:现状地下水资源开发布局不仅易诱发表生生态负效应,而且造成了水资源浪费;通过调控地下水状态可以实现地下水资源可持续利用与表生生态协调发展的目的,并确定了不同地貌单元地下水开采阈值即山前戈壁带、细土平原区和沙漠边缘分别为7.3亿m³/a,16.4亿m³/a和2.4亿m³/a。     

Kontinuierliche Erfassung von Grundwasserständen mittels eines kostengünstigen Meßsensors nach dem Kompartimentprinzip

An inexpensive sensor for continuous measurement of shallow groundwater levels using the compartimentation principle An inexpensive, datalogger-compatible sensor for continuous measurement of groundwater levels has been developed and tested in constant strain under field conditions. The precision of the device has been compared to manual single-spot measurements.     

GM(1,1)模型改进技术在咸阳市地下水动态预测中的应用

针对地下水埋深变化离散性程度较大的咸阳市,采用GM（1,1）模型改进技术对其地下水动态进行预测研究,为地下水埋深的准确预测提供支持。以灰色理论GM（1,1）模型为基础,运用滑动平均法对离散性程度较大的原始序列进行改造,使原始数据的变化变得缓慢,再利用改造后的序列建立GM（1,1）^*模型,以咸阳市地下水埋深资料为研究对象,进行地下水动态预测,并与未改进的GM（1,1）模型的预测结果进行比较。咸阳市地下水动态的预测结果显示,该区地下水埋深有逐年减小的趋势,说明该区地下水资源得到了有效的保护与利用。利用2001-2007年的地下水埋深资料建立GM（1,1）^*模型进行预测,相较于实测数据,GM（1,1）^*模型的预测结果科学合理;相较于未改进的GM（1,1）模型的预测结果,改进后的GM（1,1）^*模型具有更高的预测精度和实用性。GM（1,1）模型改进技术的应用,减小了原始序列的离散性程度,提高了预测精度,为地下水动态预测提供一种新思路。     

退耕对滇池湖滨土壤理化性质与无机磷分布的影响

[目的]明晰退耕对滇池湖滨土壤理化性质和土壤磷素形态分布的影响,进而评价退耕的土壤恢复效应和环境效应。[方法]采用空间代替时间的研究方法,对比研究滇池湖滨缓冲带和设施农田剖面土壤理化性质以及无机磷剖面分布特征,并且以滇池湖滨3个区域(牛恋、海埂、兴隆)相同退耕方式为对照进行研究。[结果]退耕3a后,牛恋缓冲带浅表地下水埋深明显变浅,土壤有机碳和全氮含量明显增加,土壤全磷,Olsen-P,Al-P和Fe-P含量均明显降低,O-P含量明显增加。但是浅表地下水埋深较深的海埂缓冲带土壤理化性质和无机磷组分没有发生明显变化。兴隆缓冲带土壤有机碳和全氮含量明显降低。3a内退耕没有直接对土壤理化性质和无机磷组分产生明显影响,浅表地下水埋深改变是影响土壤恢复和无机磷组分变化的直接原因之一。[结论]滇池湖滨缓冲带和设施农田土壤磷素均存在淋失风险,退耕活动通过抬高浅表地下水位加速土壤磷素淋失从而降低土壤潜在淋失风险。     

半干旱地区草地生态系统的潜水依赖性模拟

针对半干旱地区复杂的水分条件,从水循环整体的角度出发,通过水循环模拟与植物生长模拟,探索地表植被与潜水的关系。以通辽市平原区的主要植被类型草地为研究对象,选取草地干物质产量作为反映草地植被生长状况的指标,通过分析该指标对降水和地下水变化的响应,阐明地表生态系统对地下水的依赖性。结果表明,枯水年草地生态系统稳定的适宜地下水埋深应在2.0～2.2 m之间;平水年草地干物质产量比枯水年增加13.0%～47.8%,说明降水是影响半干旱地区生态系统稳定的重要因素;无潜水支持条件下,枯水年的草地干物质产量比多年平均值减产11.0%～14.7%,而平水年仅减产3.8%～5.9%,可见降水的丰枯变化影响着草地的潜水依赖程度。     

Biosurfactant in Membrane Separation of Atrazine from Water

This study examines the effects of land use change on nitrate concentration and the abundances of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and narG-containing denitrifiers in shallow groundwater. The results reveal a general increase of nitrate in shallow groundwater following the change of land use from paddy fields to vegetable patches. Furthermore, a significant relationship between NO₃ ^?-N concentrations was observed both in groundwater and in soil at soil depths of 0–20, 20–40, 40–60, 60–80, and 80–100 cm. With regard to gene abundance in groundwater, the AOB amoA gene was most abundant and the AOA amoA gene copy numbers were lowest from the field with long-term paddy cultivation compared with the field under vegetable cultivation. The narG gene copy numbers were higher from the field under short-term vegetable cultivation compared with fields under long-term vegetable cultivation. The NO₃ ^?-N concentrations in groundwater correlated positively with AOA amoA gene copy numbers, negatively with the AOB amoA gene, but with no significant relationship with the narG gene. In conclusion, land use change from paddy fields to vegetable patches increases nitrate in groundwater, which is correlated significantly with nitrate in soil and the abundance of the amoA gene, but is not related to the narG gene in groundwater. This study also suggests that the removal of groundwater nitrate pollution is not feasible through biological denitrification without additional denitrifiers and that it might even become more aggravated because of the AOA.     

再生水灌区地下水防污性能区划模型的建立与验证

为促进地下水水资源保护和利用,根据研究区域的特点以及地下水防污性能的影响因素,基于DRASTIC模型,选用以下6个因子：地下水水位埋深、降雨入渗补给量、表层土壤类型、包气带岩性、含水水力传导度以及土地利用类型建立了再生水灌区地下水特殊防污性能区划模型。采用地理信息系统GIS技术和内梅罗指数法,绘制研究区域地下水综合污染指数分布空间图,并且探讨了防污性能区划的验证方法以及等级划分标准。结果表明：地下水综合污染指数与研究区域的防污性能具有很好的相关性（R2=0.9591）,采用DRASTIC模型评价地下水特殊防污性能是可行的,可为再生水灌区地下水的保护以及利用规划提供重要借鉴。