Significance of physicochemical factors in the transmission of Escherichia coli and chloride

Background: Organic manures are the source of many pathogenic bacteria which could be dangerous for human health. Bacterial transmission and retention in soil is important for processes ranging from contaminant degradation during in situ bioremediation to transport of pathogenic bacteria into groundwater. Methods: The aim of this study was to evaluate the transport of Escherichia coli and chloride (Cl) in the soil saturation conditions, considering the importance of preferential flow using synthetic macrospores (different diameters of macrospores including 0, 1 and 2 cm) and HYDRUS-2D model. Also, the effect of different salinity levels of water (including electrical conductivity of 1, 2 and 4 dSm-1) on the transmission of E. coli was investigated. The preferential flow system was prepared and designed using two sand sizes including fine sand and coarse sands in the columns. Results: The results showed that the retention of E. coli increased with the ionic strength of the solution, while the effect of E. coli in the fine sand was greater than that of the coarse sand. This bacterial transfer behavior was well described by numerical simulations. The importance of preferential flow in bacterial transfer showed that it increases at higher ionic strength, even if overall transmission is reduced. Although the bacterial transmission is facilitated in salinity, the results of this study showed that with increase of ionic strength of the soil solution, the amount of bacterial purification was increased that could be effective in controlling groundwater contamination with saline water management. Conclusion: According to the results, with increase of ionic strength of the soil solution, the amount of bacterial purification was increased that could be effective in controlling groundwater contamination with saline water management, so that the least transition has taken place and the conditions for the use of unconventional water sources were also created, without the environmental problem of the risk of groundwater pollution. Keywords: Escherichia coli, Soil, Water pollutio

Investigation of Nitrate Removal from Zarjoub River Water of Rasht Using a Hybrid Wetland System

With the influx of agricultural, industrial and hospital pollutants into surface and groundwater, human health and other living organisms are facing a serious threat. Zarjoub River is one of the most polluted rivers in the country, which passes through the center of Rasht and all kinds of dangerous pollutants such as nitrate, phosphate and dangerous heavy metals flow into it. Artificial wetlands are one of the low-cost and environmentally friendly wastewater treatment methods that have received a lot of attention today. In this study, the use of artificial wetlands in sequential using three different plant species of phragmites, lemna and vetiver with two different arrangements to remove nitrate in autumn of 2019 and summer of 2020 has been investigated. The results showed that the average percentage of nitrate reduction by two plant treatments was 73% and 68%, and for the control treatment it was 35%, which indicates the effect of plants in wetlands. Also, the result showed that the amount of nitrate reduction from the effluent was directly related to temperature changes and growth status of plants. The results showed that the use of hybrid wetlands can have a good removal efficiency for pollutants compared to their individual use, but the difference in plant arrangement in wetlands, although statistically significant at a probability level of 1%, had little effect on the nitrate removal process on effluent

Simulation of 1D surface and 2D subsurface water flow and nitrate transport in alternate and conventional furrow fertigation

48 Pags., 3 Tabls., 11 Figs. The definitive version is available at: http://link.springer.com/journal/271Increasing water and fertilizer productivity stands as a relevant challenge for sustainable agriculture. Alternate furrow irrigation and surface fertigation have long been identified as water and fertilizer conserving techniques in agricultural lands. The objective of this study was to simulate water flow and fertilizer transport in the soil surface and in the soil profile for variable and fixed alternate furrow fertigation and for conventional furrow fertigation. An experimental data set was used to calibrate and validate two simulation models: a 1D surface fertigation model and the 2D subsurface water and solute transfer model HYDRUS-2D. Both models were combined to simulate the fertigation process in furrow irrigation. The surface fertigation model could successfully simulate runoff discharge and nitrate concentration for all irrigation treatments. Six soil hydraulic and solute transport parameters were inversely estimated using the Levenberg–Marquardt optimization technique. The outcome of this process calibrated HYDRUS-2D to the observed field data. HYDRUS-2D was run in validation mode, simulating water content and nitrate concentration in the soil profiles of the wet furrows, ridges and dry furrows at the upstream, middle and downstream parts of the experimental field. This model produced adequate agreement between measured and predicted soil water content and nitrate concentration. The combined model stands as a valuable tool to better design and manage fertigation in alternate and conventional furrow irrigation.This research was funded by The Center of Excellence for Evaluation and Rehabilitation of Irrigation and Drainage Networks of the University of Tehran.Peer reviewe

Optimum design of alternate and conventional furrow fertigation to minimize nitrate loss

47 Pags., 5 Tabls., 3 Figs. The definitive version is available at: http://ascelibrary.org/loi/jidedhAlternate-furrow fertigation has shown potential to improve water and fertilizer application efficiency in irrigated areas. A combination of simulation and optimization approaches permits researchers to identify optimum design and management practices in furrow fertigation, resulting in optimum cost, irrigation performance, or environmental impact. The objective of this paper is to apply one-dimensional (1D) surface and two-dimensional (2D) subsurface simulation-optimization models to the minimization of nitrate losses in two types of alternate-furrow fertigation, as follows: (1) variable alternate-furrow irrigation, and (2) fixed alternate-furrow irrigation. For comparison purposes, optimizations are also reported for conventional furrow irrigation. The model uses numerical surface fertigation and soil-water models to simulate water flow and nitrate transport in the soil surface and subsurface, respectively. A genetic algorithm is used to solve the optimization problem. Four decision variables (inflow discharge, cutoff time, start time, and duration of fertilizer solution injection) were optimized to minimize the selected objective function (nitrate loss) for two fertigation events performed during a maize-growing season. The simulation-optimization model succeeded in substantially reducing the value of the objective function as compared with the field conditions for all irrigation treatments. In the experimental conditions, optimization led to decreased inflow discharge and fertilizer injection during the first half of the irrigation event. This was because of the high potential of the field experiment to lose water and nitrate through runoff. In the optimum conditions, alternate-furrow fertigation strongly reduced water and nitrate losses compared with conventional furrow irrigation. The simulation-optimization model is a valuable tool for alleviation of the environmental impact of furrow irrigation.This research was funded by the Center of Excellence for Evaluation and Rehabilitation of Irrigation and Drainage Networks in University of Tehran.Peer reviewe

Development of an Automated Structural Health Monitoring System Based on Wireless Sensor Network for Civil Structures

Generally, Structural Health Monitoring (SHM) is used to identify damage and deterioration in civil structures during their regular lifetime as well as after earthquakes. A complete SHM system incorporates different components, such as sensing system, data management, data transmission, and data analysis for reliable decision-making purposes. During this research, a new vibration-based SHM system has been developed for condition assessment of large-scale civil structures. This structural health monitoring system consists of three significant components; a new wireless smart sensor network, a new MATLAB-based data management and data analysis platform compatible with the sensor network, and a new vibration-based nonlinearity identification technique for early damage identification purposes. The wireless smart sensor network has been designed to meet the requirements for low-amplitude ambient vibration measurement and sudden event monitoring of civil structures. The designed wireless smart sensor network can record both ambient and earthquake-induced vibrations from structures using two periodic and event-triggered sampling modes. A data management and data analysis toolbox has been also developed in MATLAB Graphical User Interface Layout Toolbox. Various time-domain and frequency-domain system identification techniques have been implemented into the toolbox to extract modal parameters from the vibration measurements. In addition, a vibration-based nonlinearity identification technique has been proposed to identify nonlinearities in a dynamic system. This technique combines vibration measurements with Autoregressive Moving Average with eXogenous inputs (ARMAX) model and Fuzzy C-means clustering (FCM) algorithm to categorise the linear and nonlinear behaviours of a structure, when it is subjected to various levels of earthquake excitation. To verify the reliability of different components of the developed SHM system, a series of shaking table tests was conducted on a steel truss bridge model at AUT structural laboratory. In addition, one span of a full-scale bridge, Newmarket viaduct located in Auckland, was instrumented using the developed wireless-based SHM system to investigate the system performance in an outdoor environment. The results obtained from the laboratory and field experiments showed that the developed vibration-based SHM system has a reliable performance in terms of hardware and software for condition monitoring of large-scale structures

Structural Health Monitoring of a Post-tensioned Concrete Bridge Using Wireless Sensor Network: Deployment and Evaluation

In this paper, a new developed wireless sensor unit is introduced and utilised to extract dynamic characteristics of a post-tensioned concrete bridge in New Zealand. The system includes 20 wireless senor nodes and one base station unit. The sensor nodes use wireless mesh network to transfer the measurements including temperature, humidity and 3-axis acceleration. The advantages of the sensor nodes are its high resolution and sensitivity, low cost and power consumption to record both ambient and earthquake-induced vibrations using two time-triggered and event- triggered modes. To assess the condition of the superstructure over time, the bridge dynamic characteristics obtained using the vibration recorded from the structure are compared with the counterparts measured several years ago using standalone MEMS accelerometers. The dynamic characteristics of the bridge show a constant performance of the full-scale structure over its lifetime. Also, the results indicate a reliable performance of the developed wireless sensor system for monitoring of large-scale structures