Implications of municipal wastewater irrigation on soil health from a study in Bangladesh

This study evaluated soil health in fields of wheat (Triticum aestivum L. cv Shatabdi) and potatoes (Solanum tuberosum L.) irrigated by different blends of municipal wastewater (hereafter called wastewater). The crops were grown with and without added fertilizers over three consecutive years. The wastewater contained high concentrations of organic carbon (C), nitrogen (N), phosphorus (P), sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), zinc (Zn) and boron (B). It also contained negligible concentrations of a few heavy metals. Irrigation by wastewater resulted in an increase in the porosity of the surface soil and thus a reduced bulk density. Wastewater enhanced the saturated hydraulic conductivity and water retention capacity of the soils. The organic carbon, total N, available P and S, and exchangeable Na, K, Ca and Mg of the soils increased proportionately with the quantity of applied wastewater. C, N and K increased significantly (α = 0.05) when fields were irrigated using raw wastewater after applied fertilizers; the other elements accumulated in the soil insignificantly under both fertility levels. Electrical conductivity (EC) and pH of the upper 0–20 and 20–40 cm soil layers increased with the application of wastewater; the increase was significant only under raw wastewater irrigation. In the 40–60 cm soil layer, both EC and pH remained unchanged. The applied inorganic fertilizers raised EC but reduced soil pH. The wastewater contained large counts of total coliform (TC: 17.2 × 10⁶ cfu/100 mL) and faecal coliform (FC: 13.4 × 10³ cfu/100 mL). Irrigation using municipal wastewater is proposed for improving soil fertility as well as for alleviating water scarcity with the exception of some crops whose edible parts come in direct contact with wastewater and/or are eaten uncooked.     

再生水灌溉对4类土壤Cd生物有效性的影响

根据国家土壤环境质量标准,选取重金属Cd含量为二级水平的4类土壤（红壤、 潮土、 土、 黑土）进行土培试验,研究再生水灌溉与小白菜生物量及Cd含量、 土壤有效态Cd含量、 pH、 微生物群落的关系,以及不同类型土壤间的差异性。结果表明, 再生水灌溉在不同类型土壤上对小白菜生物量及Cd含量、 土壤有效态Cd含量、 土壤pH和微生物数量的影响不同: 1）红壤、 潮土、 土上小白菜生物量增加显著,分别增加9.09%、 16.08%、 9.92%,黑土上增加不显著; 2）小白菜Cd含量在红壤上显著降低,由对照的0.29 mg/kg降低到0.22 mg/kg,在黑土上比对照增加了18.75%,在潮土和土上影响不大; 3）有效态Cd含量在红壤没有变化,但在潮土、 土、 黑土上增加显著; 4） 4类土壤微生物数量增加显著; 5）潮土、 土、 黑土的pH值有所降低。     

Effects of municipal wastewater on soil chemical properties in cultivating turfgrass using subsurface drip irrigation

Knowing the concentrations of the nutrient elements in soils is important due to their toxic effect on humans and the environment. The aims of this study were to assess the effects of water quality, depths, and distances of lateral installation on soil chemical properties during turfgrass cultivation. A field experiment was conducted using a Split-Split-Plot design based on the randomized complete block (RCB) design with two treatments (well water and wastewater) and eight sub-treatments (45 and 60 cm distance of the laterals and 15, 20, 25, and 30 cm depths of laterals) in three replicates on a sandy loam soil, in Shahrekord, Iran. Soil samples were collected from 0 to 30 and 30 to 60 cm depth for measuring nitrate (NO₃^?), electrical conductivity (EC), and pH at the end of the experiment. During the experiment, fecal coliform was also measured at the soil surface. Results indicated that by increasing lateral distance, NO₃^? level increased in both layers. With installing laterals in deeper levels, NO₃^? concentration decreased at the beginning, then increased in the first layer, whereas in the second layer, NO₃^? concentration decreased. In addition, installing laterals in deeper depth caused an increase in soil EC in the top layer, but a decrease in the lower layer. However, the results showed that there was no significant effect of the treatments (well water and wastewater) and the sub-treatments (distance and depths of laterals) on soil pH. The results also show that with increasing laterals depth, fecal coliform level decreased at the soil surface.     

柑橘园低功耗滴灌控制器的设计与实现

为提高偏远山区柑橘园滴灌的管理效率,降低劳力投入,节约生产成本,利用低功耗设计技术研制了一个以干电池供电的滴灌控制器。控制器主要由ATMega88V单片机、电源电路、人机交互单元、双稳态脉冲电磁阀及其驱动电路组成。以可调数字电源提供0～10 V直流电压,分别在0～0.9 MPa管道水压条件下,测试了控制器的耗电情况,试验结果表明,控制器能驱动电磁阀开关动作的最低工作电压为3 V,电磁阀开关动作的电流随电压的升高而增大,水压条件对电磁阀开关动作电流影响不显著,当电压＞5 V时控制器的静态电流为50 μA,当电压从5 V下降至3 V的过程中,静态电流逐渐上升至最大值149.2 μA。采用型号为6LR61的9 V碱性电池作为电源,并使控制器每休眠5 s则驱动电磁阀开或关动作一次,以测试控制器连续工作于大负载下时的电池使用寿命,试验结果表明,电池可工作364 h,共驱动电磁阀开关动作272 160次。根据试验结果估算出,一节额定容量为2 500?mA·h的9 V电池可使控制器工作5 a以上。该控制器成本低,操作简单,适合于中小面积柑橘园的滴灌自动控制。     

Mercury pathways in municipal wastewater treatment plants

A nine-week sampling and analysis program was completed at a large municipal wastewater treatment plant to characterize the fate of Hg entering the plant. Mercury removal in primary treatment averaged 79%, and the average Hg removal across the entire plant was approximately 96%. Mercury loadings on the secondary (activated sludge) treatment process were elevated to near plant influent levels due to the recycle of spent scrubber water from sewage sludge incinerator emissions control equipment. This internal recycle of spent incinerator scrubber water resulted in elevated Hg loadings to the incinerators, and effectively reduced the Hg control efficiency of the emissions control equipment to near zero. Measurements indicate that approximately 95% of the Hg mass entering the plant is discharged to the atmosphere via sludge incinerator emissions. These results indicate that municipal wastewater treatment facilities can remove Hg from wastewater quite effectively; however, where wastewater sludge is incinerated, almost the entire mass of Hg removed from the wastewater can be discharged to the atmosphere.     

城市污水土地处理系统的工艺创新及其在中国东北的实践

On the basis of ecological principles including holistic optimization, cycling and regeneration, and regional differentiation, land treatment systems （LTSs） for municipal wastewater were continuously explored and updated in the western Shenyang area and the Huolinhe area, China. Intensified pretreatment, addition of a man-made soil filtration layer, and use of an ecologically diversified secondary plant cover were proved to be technically feasible. Hydraulic loading was determined according to the assimilation capacity of soil ecosystems, thus ensuring safe operation of wastewater treatment. This modernized and alternative approach to wastewater treatment had been widely applied in middle-sized and small cities and towns of Northeast China, and these innovative systems in some areas had indicated favorable ecological, social, and economic benefits.     

再生水滴灌系统滴头抗堵塞性能试验研究

为了得到再生水灌溉对滴灌流量的影响规律及滴头抗堵塞性能,该文通过试验对再生水灌溉条件下11种不同滴头流道的流量变化进行了研究。结果表明：再生水灌溉条件下滴头流量的降幅与流道长度、流道截面积呈现正相关关系,具有反冲洗功能的滴头可以有效防止堵塞。田间试验表明,再生水处理滴头流量与地下水处理相比明显下降,流道沉积物富集是导致滴头流量衰减的主要原因。建议再生水滴灌系统选择具有反冲洗功能的滴头或者滴头流道较短、流道截面积较小的滴头,可有效降低堵塞的发生,为再生水灌溉系统科学选型与配套提供依据。     

Some characteristics of organic soils irrigated with municipal wastewater

Soil irrigation with wastewater (WW) gives the opportunity to solve the problems of its disposal, final purification or reuse. Many studies have examined mineral soils upon continued WW application. The aim of this paper was to examine the properties of organic soils 3 years after WW application was discontinued. Peat‐muck soil planted with Populus spp. or Salix spp., and mineral‐muck soil under grasses were irrigated for 4 years with municipal WW at a low (comparable with intensive NPK fertilization) and high WW rate (600 and 1200 mm yearly, respectively). Soils were analysed for organic matter (OM), pH, bulk density (BD), water holding capacity (WHC), P₂O₅, Fe₂O₃, Al₂O₃, MnO, Zn, Pb, Cu, Cr, magnetic susceptibility (MS) and dehydrogenase and catalase activities. The results were compared with control soils which have never received WW. The study showed that only P₂O₅, MnO and catalase activity (CA) were significantly affected by former WW application. On average, P₂O₅ increased by 30 per cent, whereas MnO decreased by 35 per cent with no differences between the two WW rates. CA decreased by 18 per cent at the high WW rate. Most of tested characteristics were determined by soil type. The peat‐muck soil showed higher OM, WHC, P₂O₅, MnO, Pb and CA than mineral‐muck soil and lower BD, MS, Fe₂O₃, Al₂O₃ and Cr. Soil depth influenced Fe₂O₃, MnO, Zn, MS and enzyme activities, while basic soil properties (OM, pH, BD, WHC and P₂O₅) were not changed by soil depth. Heavy metals (Zn, Cr, Cu and Pb) were below upper permissible limits. Copyright © 2010 John Wiley & Sons, Ltd.     

基于语义本体的柑橘肥水管理决策支持系统

利用信息技术实现柑橘精准生产管理是果树信息化管理的重点和难点。该文针对山地果园肥水信息化精准管理问题,研发了基于语义本体的柑橘肥水管理决策支持系统。柑橘肥水语义本体是决策支持系统的核心,它以资源描述框架三元组整合涉农信息。系统实现了施肥、生理病害防治和排灌监测3个功能。系统验证结果表明:1)施肥查询模块能够根据树龄、施肥时期、土壤质地、地形和产量5个因素计算氮、磷、钾施肥量,经216组数据验证其输出正确率100%;2)经100组涵盖12种营养素缺乏和过剩生理病害数据验证,病症查询模块能够根据输入病症正确判断生理病害;3)排灌检测模块能根据不同土壤质地对排灌实时监测,经小型气象站获取的土壤含水率数据验证,系统正确预警率达100%。经361组性能测试数据结果表明系统平均响应时间在0.23 s(浏览器端应用)和0.58 s(手机端应用)内,具备较优性能。该研究为农业领域知识建模和异构多源数据整合等问题提供了可行方案。     

柑橘肥水智能决策支持系统的变化预测方法及应用效果

本体是农业智能信息系统的核心,是实现精准农业信息服务的关键.本体的维护和管理过程将导致本体发生各种变化,从而对其支撑的应用程序产生不同程度的影响.如何有效地分析本体元素的变化对应用程序的影响是农业智能信息系统维护和管理的难题.该文提出一种基于界面组件依赖矩阵、本体概念依赖矩阵及本体概念-界面组件依赖矩阵的系统变化预测方法,实现了避免代码层分析而较准确预测本体概念的变化对应用程序用户界面组件的影响.以包含22个本体概念和6个界面组件的柑橘肥水智能决策支持系统为案例分析,验证结果表明:该变化预测方法能够达到85％的平均准确率和98％的平均召回率.该变化预测方法对解决以本体为核心的农业智能信息系统的变化管理难题可提供有效的解决方案.     

柑橘园水肥一体化滴灌自动控制装置的研制

为实现建设有独立水池和独立液肥池的柑橘园的水肥滴灌的自动控制,研制了一个干电池供电的水肥一体化滴灌定时控制装置。该装置通过2个电磁阀的开关操作分别控制2个池中的清水和液肥进入滴灌管网的顺序和时间,实现水肥一体化滴灌的自动控制。充分利用了休眠机制和电源管理技术,其静态电流小于11.2A。经连续6个月的实际应用试验表明,装置运行稳定可靠,其电池电压仅从初始值9.35V下降为8.50V。该装置操作简单,既可以进行水肥一体化滴灌,又可以进行清水滴灌,还可以将多套装置进行组合实现轮灌以控制更大的灌溉面积,具有推广应用前景。     

土霉素处理废水作农业灌溉用水的研究

以土霉素处理废水灌溉玉米和谷子试验结果表明 ,农作物适量灌溉土霉素处理废水可缓解农业用水短缺 ,增加作物产量 ,且土霉素处理废水污灌未对种植土壤造成污染 ,并具改良土壤和增加肥效的作用。     

生活污水灌溉小白菜的盆栽试验研究

污水水质及灌溉制度是影响污水灌溉安全性的主要因素.盆栽试验设置了两种水质(清水和污水)和4个灌水下限(60?,70?,80?,90?),共8个处理,研究了污灌条件下不同灌水下限对小白菜生长及品质的影响.试验结果表明:生活污水灌溉会造成小白菜轻度减产,植株的硝酸盐含量和叶片叶绿素含量增加,植株重金属累积增加;灌水下限对小白菜生长状况和品质均有较大影响,污水灌溉条件下各项指标随灌水下限变化的变化规律不同于清水灌溉条件,表明污水灌溉的灌水下限不能直接移用清水灌溉的控制指标.综合分析表明污水灌溉80? 灌水下限条件下小白菜有较高的产量、水分利用效率和叶绿素含量,较低的硝酸盐含量和重金属富集,因此选择土壤相对含水率80?以及与此相对应的叶片细胞液浓度9.3%作为污水灌溉的灌水下限指标.     

再生水滴灌条件下滴头堵塞特性评估

针对再生水水质复杂,污染物众多,其在农业滴灌上的应用对滴灌系统的抗堵塞能力要求更高的特点,采用6种滴头进行约360h的再生水滴灌试验,测定了再生水滴灌条件下滴头堵塞规律,探讨了滴头流道尺寸参数对于堵塞规律的影响,并采用环境扫描电子显微镜技术分析了滴头堵塞物质的组成结构。试验结果表明：不同流道结构的滴头抗堵塞能力明显不同,各类滴头流量下降的幅度范围为14.4%～72.2%;流道水力直径、流道长度、锯齿高度和锯齿间距等参数都影响着堵塞的发生,其中以水力直径代表性最好,分区域地呈负相关关系;微生物、胞外多聚物以及颗粒物质混合形成的絮状结构,构成了滴头流道内的主要沉积物;堵塞过程的发生往往是以微生物富集开始的。试验结果有助于进一步提高再生水滴灌的应用水平。     

养殖池塘废水灌溉下稻田减量施肥试验研究

采用田间试验,以当地常规施肥和灌溉为对照(CK),研究了减量施用氮、磷肥条件下,稻田湿地生态系统对池塘养殖废水中氮、磷的消纳效果,池塘养殖废水灌溉后对稻田田面水和渗漏水水质、水稻养分吸收和产量的影响。结果表明,稻田系统可有效消除池塘养殖废水中铵态氮(NH_4~+-N)、硝态氮(NO-3-N)、总氮(TN)、可溶性磷(DP)、颗粒态磷(PP)、总磷(TP),其去除率随着施肥量的减少而增加,在常规施肥量、减量施肥20%和减量施肥40%情况下对池塘养殖废水TN的去除率平均分别为25.1%、38.9%和50.5%,对TP的去除率平均分别为56.4%、71.2%和76.2%,对氮、磷的去除以NH_4~+-N、NO-3-N和PP为主;池塘养殖废水灌溉后,稻田田面水和渗漏水中NH_4~+-N、NO-3-N、TN、DP、PP、TP质量浓度会随着施肥量减少呈现下降趋势,减量施肥20%和减量施肥40%下,田面水中TN、TP的质量浓度平均分别较CK降低5.8%和23.4%、20.8%和35.5%;渗漏水中TN、TP的质量浓度平均分别较CK降低18.3%和27.5%、23.1%和45.8%。在水稻养分吸收和产量构成方面,减量施肥20%后,池塘养殖废水中的营养物质能满足水稻的养分需求;池塘养殖废水灌溉时,水稻产量以常规施肥量处理最高(较CK增产2.3%),常规施肥量80%的处理其产量与CK相似,而常规施肥量60%的处理其产量较CK显著降低。综合考虑水稻种植的经济效益和环境效益,建议池塘养殖废水灌溉条件下施肥水平应在常规施肥量的80%左右。     

Predicting crop-water production functions for long-term effects of deficit irrigation on citrus productivity (SW Spain)

Crop-water production functions (CWPFs) constitute a suitable tool for irrigation management in water-scarcity situations, and for estimating the yield response when a crop is subjected to long-term water stress. This work examines the long-term effects of different strategies of sustained deficit irrigation in mature sweet orange trees (Citrus sinensis L. Osb. cv. Salustiana). The trial was conducted from 2004 to 2010, with three deficit treatments imposed as a function of the water-stress index, which is defined as the ratio between the actual volume of water supply and the crop evapotranspiration rate. Crop-water production functions were evaluated for each year. Additionally, different yield-loss functions were defined on the basis of the impact of deficit irrigation for the entire study period. According to the findings, the crop response to water stress followed a clear trend over successive years, in which the time course of the yield loss showed an attenuated oscillation. Thus, the calculated yield-loss functions could be provided as an alternative tool for programming a long-term strategy of deficit irrigation under a water-scarcity situation.     

Utilization of created wetlands to upgrade small municipal wastewater treatment systems

Created wetlands offer a low cost, low maintenance, and practical alternative for upgrading secondary municipal wastewater treatment systems. The removal efficiencies, effects of seasonal temperature variations, and effects of increased loading rates on contaminant removal within such a system was studied by Auburn University researchers at a created wetland site in Hurtsboro, Alabama. The 0.16 ha system consisted of a two cell wetlands planted with cattails (Typha latifolia), bulrush (Scirpus validus), arrow duck potatoes (Sagitaria latifolis), burr reeds (Spargaminum eurycarpun), water pennywort (Hydrocotyl ranunculoides), and parrotfeather (Myriophyllum brasiliense). Testing occurred from January through September of 1988 at hydraulic loading rates of 169, 289, and 345 m³ ha^?1 d^?1. The monthly average total suspended solids influent: effluent mg L^?1 concentration ratio during the study period was 135:19 while the monthly average total BOD₅ influent: effluent mg L^?1 concentration ratio was 38:8. Once the system stabilized, the monthly average total BOD₅ effluent concentration remained essentially constant over the range of average BOD₅ loading rates employed in this study. Total Kjeldahl N removal was more effective at loading rates of 2.6 kg ha^?1 d^?1. The monthly average influent: effluent TKN mg L^?1 concentration ratio was 15:4.     

城市污水再生水灌溉对黑麦草生长及土壤磷素转化的影响

为了进一步明确城市污水再生水的农业利用价值,在温室条件下采用盆栽试验方法种植黑麦草,以自来水(clean water,CW)灌溉为对照,分别进行全再生水(reclaimed municipal wastewater,RW)和混合再生水(自来水+再生水,CW+RW,1∶1)灌溉处理,研究了再生水灌溉对黑麦草生长和土壤磷素的转化特征。结果表明,城市污水再生水灌溉显著增加了黑麦草地上部和根系的生物量,CW+RW处理黑麦草地上部和根系生物量在播种55 d后分别较对照(CW)增加18.92%和6.42%,RW处理分别增加26.79%和10.55%;黑麦草地上部磷含量分别显著增加8.48%和10.93%。再生水灌溉土壤全磷含量变化不大并有减少趋势,但土壤速效磷含量CW+RW和RW处理分别较对照(CW)增加29.15%和43.80%;CW+RW和RW处理显著增加了土壤有机磷组分中的活性有机磷和中活性有机磷,与对照CW相比,其中活性有机磷增幅分别为50.30%和81.57%,中活性有机磷增幅分别为7.66%和13.68%;也显著增加了无机磷组分中的Ca2-P和Ca8-P,CW+RW和RW处理Ca2-P含量由对照的12.90 mg·kg-1分别增加到16.42 mg·kg-1和15.49 mg·kg-1,与对照相比,增幅分别为27.29%和19.38%,Ca8-P增幅分别为19.94%和16.03%。再生水灌溉显著降低了土壤pH并显著增加了土壤有机质含量,这可能是增加土壤磷活性的原因之一。再生水灌溉对提高土壤磷素利用率有促进作用。     

Regenerant wastewater irrigation and ion uptake in five turfgrass species

The effects of wastewater and high concentrations of chloride (Cl), magnesium (Mg²⁺), calcium (Ca²⁺), and potassium (K⁺) on ion uptake and growth of turfgrass species were studied. Simulated water softener regenerated wastewater was prepared based on 1.8 kg KC1 regeneration rate to attain ion concentrations of 30 mM of K⁺, 100 mM of Ca²⁺, 100 mM of Mg²⁺, and 420 mM of Cl^‐. It was diluted to 1/5, 1/10, and 1/20 concentrations with tap water for the irrigation studies. Wastewater irrigation did not affect the growth rates of the turfgrass. No significant increase of Ca²⁺, K⁺, and Mg²⁺ uptake was detected under the wastewater irrigation treatment. However, the Cl^‐uptake was significantly different between irrigation treatments. It was found that in the spring, in the turf plots irrigated by 1/20 concentration wastewater, an amount equivalent to 60% of the applied Cl^‐ was taken up and removed in the Kentucky bluegrass and perennial ryegrass clippings, and more than 80% was taken up by tall fescue, bermudagrass, and zoysiagrass. A lower percentage of the applied Cl^‐ was removed by the clippings when the turf was irrigated with higher wastewater concentrations. Soil exchangeable Mg²⁺ and Cl^‐ concentrations were slightly, but significantly, higher under the wastewater irrigation treatments. Soil salinity measured by electrical conductivity (EC) was not significantly affected by the 1/20 wastewater irrigation. The soil EC values of the turf plots irrigated with 1/10 and 1/5 wastewater were highest in the summer (10 and 14 dS m^‐1) and lowest in the winter (2 to 4 dS‐m^‐1). This study suggests that the turfgrass species are relatively tolerant to high Cl^‐ concentrations, and under appropriate management, regenerant wastewater can be used for turfgrass irrigation with minimal environmental impact.