Yang Peiling

Biofilm structure and its influence on clogging in drip irrigation emitters distributing reclaimed wastewater.

Using reclaimed wastewater for crop irrigation is a practical alternative to discharge wastewater treatment plant effluents into surface waters. However, biofouling has been identified as a major contributor to emitter clogging in drip irrigation systems distributing reclaimed wastewater. Little is known about the biofilm structure and its influence on clogging in the drip emitter flow path. This study was first to investigate the microbial characteristics of mature biofilms present in the emitters and the effect of flow path structures on the biofilm microbial communities. The analysis of biofilm matrix structure using a scanning electron microscopy (SEM) revealed that particles in the matrix of the biofilm coupled extracellular polysaccharides (EPS) and formed sediment in the emitter flow path. Analysis of biofilm mass including protein, polysaccharide, and phospholipid fatty acids (PLFAs) showed that emitter flow path style influenced biofilm community structure and diversity. The correlations of biofilm biomass and discharge reduction after 360 h irrigation were computed and suggest that PFLAs provide the best correlation coefficient. Comparatively, the emitter with the unsymmetrical dentate structure and shorter flow path (Emitter C) had the best anti-clogging capability. By optimizing the dentate structure, the internal flow pattern within the flow path could be enhanced as an important method to control the biofilm within emitter flow path. This study established electron microscope techniques and biochemical microbial analysis methods that may provide a framework for future emitter biofilm studies.

Multifractal analysis of soil structure under long‐term wastewater irrigation based on digital image technology

Abstract Soil structure exerts important influences on edaphic conditions and the environment. It constitutes a fundamental soil property correlated to many other soil properties. In this study, generalised dimensions of soil structure are computed from data obtained by 2D image analysis of soil samples irrigated with wastewater for 30 and 50 years. The samples analysed show suitable scaling properties. The generalised dimensions Dq appear defined with R2 greater than 0.89 in the range of moment order (q) between ‐10 and +10. The variation of Dq with respect to q and the shape of the multifractal generalised spectrum reveal that soil structure has properties close to multifractal self‐similar measures. These results show that multifractal analysis is an appropriate tool for characterising soil structure and thus may be used as an indicator of soil structure as well as for deriving important soil physical properties.

Numerical study on flow property in dentate path of drip emitters

Abstract The hydraulic property of drip emitters is primarily reflected in steady dissipation of pressure energy by flow resistance. The dentate path helps in dissipating energy as water travels to the emitter opening and maintains a turbulent flow condition that facilitates movement of particulate material out of system to avoid clogging. In this study, emitters were designed using variable geometric parameters. The visualisation characteristics of computational fluid dynamics (CFD) was utilised for analysing the law of impact on flow movement by the path width (1.6, 1.3, 1.0, 0.6 mm), dentate height (1.0, 1.3, 1.6, 2.0 mm) and dentate angle (32°, 41°, 53°, 63°) and revealed the correlation relationship between the dentate structure of flow path of emitters and energy dissipation. Meanwhile, an anti‐clogging analysis was conducted. The simulation results indicated that the selected turbulent model and the numerical algorithm were suitable for the hydraulic calculation in flow paths. The rear of dentations and dentate tips were the primary regions for energy dissipation. The flow exponent with both dentate height and path width being 1.3 mm was minimum and the boundary flow velocity was maximum, i.e., there was good hydraulic performance and sound anti‐clogging capacity. Larger dentate angles had an active role in enhancing hydraulic performance but with a poor anti‐clogging property. Adjusting dentate jet effect by modifying the boundary structure of dentate flow paths could improve the inner flow pattern, enhance pressure energy dissipation, and improve boundary flow velocity, which was the key to enhancing hydraulic property and anti‐clogging property within flow path of emitters.

Structural and fractal characteristics of biofilm attached on the surfaces of aquatic plants and gravels in the rivers and lakes reusing reclaimed wastewater

Reusing reclaimed wastewater from lakes has become one of the most effective measures to relieve the urban ecological crisis. However, reclaimed wastewater still contains large amounts of nutrient salts, trace organic pollutants, suspended solid particles and microorganisms, which may significantly affect the aquatic ecosystems. The health of aquatic ecosystems can be directly and effectively monitored by evaluating the biofilms in them, because the structures of biofilms are directly affected by multiple environmental factors. Therefore, it is important to study the structures of biofilms attached on multiple medium surfaces in river-lake systems that contain reclaimed wastewater. In this study, the paper applied scanning electron microscope (SEM) technology and fractal theory to quantitatively describe the structural characteristics of biofilms attached on the medium surfaces of aquatic plants and gravels in the Lianshi Lake of Beijing Yongding River and other two kinds of reclaimed water of the river-lakes, whose sewage treatment processes were the combined process of deposit and sand filtration and UF membrane filtration, plus anaerobic-anoxic-oxic process, respectively. The paper found that these two types of biofilms were typical porous media and their basic skeletons were mainly composed of inorganic particles, microorganisms, and algae. Furthermore, most areas between the particles were filled with extracellular polymers (EPS) secreted by bacteria. At the same time, these biofilms showed obvious fractal and multifractal characteristics, but the fractal dimensions alone failed to effectively describe the complexity of biofilm structures. The multifractal spectra were able to quantitatively characterize the biofilms’ heterogeneity. In addition, the number of microorganism species, the quantity and the heterogeneity of aquatic plants’ surface biofilms were all higher than those of gravel surface biofilms, most likely due to the effects of light. In addition, the heterogeneity of biofilms in reclaimed water treated by the combined process of deposit and sand filtration and UF membrane filtration plus anaerobic-anoxic-oxic process was higher than that of biofilms in reclaimed water treated by traditionally activated sludge process (Lianshi Lake’s water). Besides, the non-uniformity of biofilms in reclaimed water treated by combined process of deposit and sand filtration was higher than that of biofilms in reclaimed water treated by UF membrane filtration plus anaerobic-anoxic-oxic process.

A backward propagation neural network for predicting daily transpiration of poplar

Abstract In this study, a supervised artificial neural network (ANN) trained by back propagation (BP) algorithm s was developed to predict the transpiration of poplar based on six input variables. Based on the transpiration characteristics of trees, a three‐layer BP network was constructed with six input units and one output unit. Daily average temperature, relative humidity, photosynthetic affective radiation, wind speed, sunlight duration and the soil water content 50 cm below the soil surface were considered as the six input variables of the network, which primarily affected the transpiration of poplar. The prediction of daily transpiration of poplar in Heilonggang region, Hebei province was conducted. The research results indicated that R 2 equalled 0.9534 between measured values and predicted values. The maximum relative error, the minimum relative error and the average relative error were 16.85, 1.49, and 4.2%, respectively. The proposed model could describe the relationship between the daily transpiration of poplar, the meteorological factors and soil moisture conditions with a relatively high accuracy. The research results had potential values for the production and management in this polar stand.

Quantitative Assessment of Heterogeneity of Loamy Soil Particle Size Distribution: A Multifractal Approach

Particle size distribution (PSD) constitutes a fundamental soil property correlated to many other soil properties. In this paper, we describe a multifractal approach to characterize particle-size distribution of loamy soil and use the information obtained to quantify the soil heterogeneity. Particle size distributions of the experimental samples were characterized by multifractal techniques, six loamy soil samples were analyzed routinely for particle size distribution by laser diffraction in the range of scales, varying from 0.02 to 2000µm. The generalized multifractal spectrum, Dq was calculated in the range of moment order (q) between-10 and 10. Samples showed heterogeneity in their multifractal behavior, D1 and the coefficients of determination of D1 presented 0.82 0.82

The Experimental Researches on the Technology of High Utility of Rainwater on Sloping Farmland

The experimental research on soil moisture preservation on sloping farmland was carried out by artificial rainfall simulation. The character of soil moisture movement in rain and after rain on sloping farmland was discussed by artificial rainfall simulation in the condition of wheat straw mulch. A better mulch way that is benefit to germination is proposed according to experimental results. . The infiltration law on sloping farmland in rainfall was studied. The technology of soil moisture preservation with wheat straw mulch is one of available measures of high utility of rainwater. Based on the principles of soil water dynamics, a numerical model to simulate soil moisture on sloping farmland under rainfall condition was proposed in the paper. A simple computational method is given to analyze the process of rainfall, infiltration and runoff.