Wastewater reuse and exposure to Legionella organisms

Eight hundred and fifty-two (852) blood sera were drawn in 1980 and 1981 from populations residing in 30 agricultural settlements (having a total population of 16,240). These sera were tested for the presence of antibodies against 15 different antigens of Legionella species (L. pneumophila serogroups 1–8 and seven other Legionella, i.e. bozemanii, gormanii, micdadei, jordanis, dumoffii, longbeacheae and oakridgensis). The results indicate a significant (P < 0.02) excess in the percentage of sera positive for L. pneumophila (serogroups 1–8) among sewage and non-sewage irrigation and fish pond workers as compared to the control group (4.5% vs 1.5%). For the other Legionella species, there was no difference among the above groups. The isolation of L. pneumophila serogroup 4 and five organisms resembling Legionella spp from one oxidation pond used for irrigation strengthens the seroepidemiological findings.     

Factors Affecting 1-Octen-3-ol in Mushrooms at Harvest and During Postharvest Storage

Harvesting experiments revealed that immature whole mushrooms with closed veils had higher 1-octen-3-0l levels than more mature whole mushrooms with open veils. The l-octen-3-01 content of the gills was higher in immature mushrooms with closed veils, gradually decreased with maturity as the veil opened, and finally increased after the gills were well exposed. Postharvest experiments demonstrated that storage temperature influenced the activity of lipoxygenase-hydroperoxide lyase, but no differences in 1-octen-3-01 content were observed. Enzyme activity as well as 1-octen-3-01 content decreased during storage. Addition of calcium chloride to irrigation water, employed to improve quality and shelf life of fresh mushrooms, increased the amount of l-octen-3-01 immediately after harvest.     

景电高扬程灌区水价改革实践及思考

水价是水商品价值的体现。由于多方面的原因，水价改革的进程与水商品生产经营的市场化供求关系还不相适应，致使现行水价不能体现水资源的市场需求价值。回顾总结景电灌区水价调整改革的实践，可以为西北高扬程灌区水价改革提供借鉴。     

滴灌系统叠片过滤器离散型流道结构水力性能试验及内部流场模拟

为获得叠片流道内部水流流动特性,解决叠片过滤器水头损失较大的弊端,通过室内试验对比了传统叠片过滤器和具有离散型流道结构的叠片过滤器在不同流量下的水头损失,并采用Fluent19.0对清水条件下2种不同流道结构叠片过滤器内部流场分布规律进行数值模拟。结果表明:流道内部流量模拟值与试验设定值最大相对误差为4.8%;随着流量的增大,传统叠片过滤器产生的水头损失更为明显,与传统叠片过滤器相比,离散型流道叠片过滤器产生的水头损失在最大流量下降幅为20.8%;对不同流道进行内部流场分析,得出同一流量下离散型流道的平均过流断面面积大于直线型流道,过流断面面积越大,则流速越小,水头损失也越小,离散型流道内部局部水头损失占主导地位,凸台的离散排列降低了沿程水头损失。研究结果可为叠片流道的设计和结构优化提供参考。     

宁夏汉延渠灌区灌溉水利用系数测算分析与评价

农田灌溉水利用系数表示从水源引水被农作物吸收利用的过程,是反应灌区灌溉用水效率的一项指标。本文以汉延渠灌区为例,综合考虑宁夏的气候环境、土壤类型、灌溉制度及作物种植结构等因素,选取典型渠段和样点灌区,分别采用"连乘法"和"首尾法"计算宁夏汉延渠灌区2018—2019年的灌溉水利用系数,并对其进行对比分析评价,从而确定灌区适宜的计算方法。     

Screening model for assessing ‘cost’ of minimum flow requirements in the Svartå River,Sweden

The minimum flow requirements in the Svartå River in Sweden are directed at maintaining fishlife and providing suitable dilution for waste flows. The implications of varying the minimum flow requirements in the river are examined using a mixed integer optimisation model. The model is formulated as a modified method-of-weights technique with the economic issues of hydro-electricity generation, irrigation and urban water supply placed in the objective function and the minimum flows specified within the constraint set. The integer component of the model is required to model the operating policy at the major flow regulation facility in the system and the restricted validity of the irrigation permits. Application of the model shows that in dry years where competition between minimum flow levels and the other economic uses, is most intense, the levels achieved by the various economic objectives are only slightly reduced even with significant increases in the minimum flow requirements. Variations in minimum flow requirements of up to 45% only produce changes of 10% or less in the economic objectives. The lack of sensitivity of the objective levels is due primarily to the level of control exerted indirectly on the whole system in dry years by the release regulation policy and the restricted validity of the irrigation permits. In normal to wet years these policies are not as restrictive and more choice is available. In such years, however, there is generally sufficient water to satisfy all requirements and allocation is not a critical issue. The model itself is formulated generally so that a range of scenarios beyond those examined specifically in the paper can be considered.     

Water-saving strategies for irrigation agriculture in Saudi Arabia

Agriculture policy changes in Saudi Arabia are investigated by water footprint (WF) assessment. WF is calculated with the model SPARE:WATER for 3758 irrigated sites. The WF of agriculture areas (WF_area, km³ yr^?1) has decreased (–17%) since the year 2000 to 13.84 km³ yr^?1 (2011), which is mainly caused by the reduction of cropland by –33%. Nevertheless, water consumption per field has increased about 16%, which can be attributed to the cultivation of fodder crops (+12%). A scenario analysis revealed that a shifting cropping pattern towards less fodder crops reduces WF_area by –15%, and implementing improved irrigation technology leads to a combined reduction of up to 32%     

Has water-saving irrigation recovered groundwater in the Hebei Province plains of China?

This study performed a quantitative evaluation of the impact of water-saving irrigation on the groundwater regime in the Hebei Province plains area. In this work, the change in groundwater regime and the contributions of precipitation and water-saving irrigation development were investigated. The results indicate that the groundwater overdraft has been mitigated to some extent, mainly due to changes in precipitation and the implementation of water-saving irrigation, with contributions of 64.3% and 35.7%, respectively, when considering only these two factors. Water-saving irrigation is accepted as an important means for reducing groundwater depletion, but should be used in conjunction with other measures.     

含水量对渠道保温板保温耐久性的影响及保温板厚度设计

北方渠道大多使用保温板防止混凝土衬砌受冻胀破坏。在计算保温板厚度时为了降低成本,容易忽略保温板使用过程中受各种因素的影响导致保温效果变差的情况,使混凝土衬砌达不到设计使用年限便提前被破坏。内蒙古河套灌区试验结果表明,由于受酸雨、冻融作用、含水量等因素的影响,保温板保温效果平均每年降低0.9℃,其中受含水量变化的影响最大。经试验测得:聚苯乙烯保温板(EPS)含水量每增加1%,会导致导热系数增大5%。基于多层材料串联热阻叠加原理和热阻等效原理,对保温板厚度计算公式进行完善,并提出相应的铺设方法和施工技术要求。该设计对保温板在季节性冻土区的推广应用具有一定参考价值。     

Theory and application of Agricultural Innovation Platforms for improved irrigation scheme management in Southern Africa

Abstract

Many small-scale irrigation systems are characterized by low yields and deteriorating infrastructure. Interventions often erroneously focus on increasing yields and rehabilitating infrastructure. Small-scale irrigation systems have many of the characteristics of complex socio-ecological systems, with many different actors and numerous interconnected subsystems. However, the limited interaction between the different subsystems and their agents prevents learning and the emergence of more beneficial outcomes. This article reports on using Agricultural Innovation Platforms to create an environment in which irrigation scheme actors can engage, experiment, learn and build adaptive capacity to increase market-related offtake and move out of poverty.