Advanced Materials Research Vols. 1010-1012

Abstract: Anaerobic digestion and struvite precipitation were the two effective ways to treat excess sludge for recovering the bioenergy (biogas) and phosphorus. The total solids content played an important role in the biogas production and the phosphorus release. The experimental results showed that cumulative biogas decreased significantly with the increase of total solids content from 5% to 10% but increased subsequently with a further increase of total solids content, and the maximal cumulative biogas was achieved at 5% of total solids. The concentrations of PO₄³-P and total soluble P varied with total solids content, and the maximal concentrations were obtained under the condition of 20% of total solids, namely 1327 mg·L^-1 for PO₄³-P and 1288 mg·L^-1 for total soluble P. Pearson’s relationship analysis reflected that the released total soluble P was mainly composed of PO₄³-P during the anaerobic digestion. Furthermore, the maximal yield of PO₄³-P and the maximal solubilization ratio of total P were achieved at 15% of total solids, and they respectively reached 4.2 mg·g^-1 and 16.1% with 48% reduction of volatile solids and 40% reduction of total solids after anaerobic digestion.

Abstract: Three-stage countercurrent anaerobic digestion as a novel anaerobic fermentation process was applied to improve the biogas production and nitrogen and phosphorus release ratio from chicken manure. The digestion performance of each stage (H1, H2 and H3) for producing biogas, biomethane, NH₄⁺-N and PO₄^3--P was investigated. Results showed that the maximum biogas production ratio and cumulative biogas were achieved by H1, and their values reached 714 mL/d and 8636 mL, respectively. Compared with H2 and H3, the cumulative biogas from H1 increased by 45.6% or more. CH₄ content remained relatively stable in H1, and its average value was 68%, which was a little higher than that in H2 and H3. Moreover, NH₄⁺-N and PO₄^3--P levels which were released during anaerobic digestion of chicken manure arrived at 6.4 g/L and 230.6 mg/L in H1, and they were approximately 27% and 7% more than the other two stages, respectively. The results indicated that the three-stage countercurrent anaerobic digestion process could reduce the inhibitory effect of ammonia and VFAs on anaerobic microorganisms.

Abstract: The main purpose of this article is to develop an environmentally friendly and economically effective process to produce silica from rice husk ash. Sodium silicate solution was prepared by the reaction of rice husk ash and sodium hydroxide solution, and then the sodium silicate solution was used as the raw material for the preparation of silica with sodium bicarbonate. During the reaction, the by-product can be passed into CO₂ to prepare sodium bicarbonate what can be reutilized. Experimental route achieved resource recycling and environment-friendly, low energy consumption, zero emissions and so on. Meanwhile the microstructures of the silica powders were characterized by Transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Thermo gravimetric/Differential thermal analyzer (TG-DTA).The purity of silicon was up to 99.43% and the particle size was 200-300nm.

Abstract: Models of groundwater flow are widely used for a variety of purposes ranging from water supply studies to designing contaminant cleanup. In general, groundwater flow system can be divided into steady-state and transient. In the present work, we investigate the usefulness of finite element method in modelling of steady-state subsurface fluid flow and transient solute transport along a vertical cross section in an unconfined aquifer. Details are explained on numerical approximations leading to different numerical results. Extensions for pollutant transport are mentioned.

Abstract: The generalized model experiments were designed and conducted in the pressure pipeline to investigate the characteristic of sediment incipient motion. There were some differences between the measured sediment critical velocity and the predictive one which was calculated by traditional formulas. In this paper, the analyses of velocity distribution and its corresponding effect on the sediment incipient motion in the pressure pipeline are done. Then, a simple but available formula which is suitable for the prediction of sediment critical velocity in the pressure pipeline is proposed. Finally, this formula is verified by experimental data and good agreements are observed between the recorded data and predictions.

Abstract: In recent years, the Chinese government has adjust the implementation of national industrial structure and popularize water saving. However, agricultural water consumption still accounted for more than 60% of the total water content. With the rapid development of economy, the situation of water shortage is becoming increasingly serious. In agriculture production, developing accurate quantity water infrastructure projects can promote water saving on agricultural production and advance the process of water-saving agriculture. Based on the analysis of the current situation of agricultural development in China, this manuscript compared the development of the irrigation district management system since 1950s, and summarized the main factors restricting the construction of water-saving irrigation area. The results show that (1) Irrigation facilities coverage remains to be improved. (2) Low accuracy of measuring water facilities. (3) Lack of economic and practical equipment. In addition, this paper also put forward the research and development direction of quantity of water facilities in future. It can provide useful reference for water-saving agriculture development in China.

Abstract: Traditional reservoir scheduling guarantees efficient utilization of water resources and maximizes hydropower station operation efficiency. However it doesn’t consider the surrounding ecological environment demand. Ecological operation which is based on Traditional reservoir scheduling makes the reservoir achieve long-term, sustainable operation and reduce adverse impacts on the ecological environment. Xiangjiaba reservoir is the ties of the downstream of jinsha river and the Yangtze river which is located in jinsha river basin ecological sensitive area. So the completion of the Xiangjiaba reservoir must result in unhealthy ecological environment impact. With traditional genetic algorithm (GA) encoding complexity and being easy to fall into local convergence limitation, put forward a kind of improved convergence of genetic algorithm, the improved genetic algorithm with real number coding and fitness function which is converted into a nonlinear trigonometric function selection operator. Select the adaptive crossover probability and mutation probability adjust, in order to improve the convergence of the algorithm. RVA method is used to calculate the IHA index upper and lower threshold value and the upper and lower threshold could value as the constraint conditions of ecological scheduling objective function model. The results show that the improved genetic algorithm converge makes the global optimal solution ability stronger and faster; RVA method is suitable for the jinshajiang river and results are more comprehensive and more reasonable.

Abstract: Accurate prediction of water use efficiency is very important to water management.We proposed a hybrid autoregressive integrated moving average (ARIMA) and Back Propagation (BP) neural network model to predict industrial water use efficiency. The procedure of the hybrid model consisted three steps: linear modelling, nonlinear modelling and combining. Jiangsu province was selected as a case study area. Empirical results show good fitness of the hybrid model. Based on the empirical forecasting results, policy suggestions are provided to strengthen management of water resources.

Abstract: A graphing method is presented in this paper for estimating the parameters of solute transport in soils based on the convection-dispersion equation (CDE). The ratio of flux concentration change with time (dc/dt) is obtained on data of breakthrough curve (BTC) of solute transport in a semi-infinite soil column. Using graphing software, for example, the Microsoft Excel, can draw two curves of t^1.5dc/dt and dc/dt respect to time. Each curve has single peak. The two curves are used to estimate the retardation factor and dispersion coefficient in the CDE. Hypothetical examples and displacement experimental data of two soils were used to validate the new graphing method for its accuracy and stability for estimating the two parameters. The stability of parameter estimation is evaluated by the standard deviations of estimation parameters to their average value. The accuracy of the new method is assessed by comparing it with other two most used methods that are the CXTFIT and the slope methods. The results show that the method has both high accuracy and good stability. The new method is particularly good for the estimation of parameter R. The method is a deterministic method and it is simple in terms of calculations. It also has the advantages of uniqueness and no initial guess of the parameters over the CXTFIT method. The new method provides an alternative approach for estimating parameters of solute transport in soils. It is simple, accurate, stable, and saves time.

Abstract: Thermal dissipation sap flow rate probe was used to measure trunk sap flow dynamic of Poplar during the growing season from September 2011 to May 2012 in coastal region of China. The relationship of trunk sap flow rate and meteorological factors was analyzed. The results showed that the process of sap flow rate of Poplar presented an obvious day and night alternate phenomenon. The diurnal variation of sap flow was a single-peak curve in sunny day and a multi-peak curve in rainy day. According to Pearson correlation analysis, the diurnal sap flow rate of Poplar was positively correlated with solar radiation and atmospheric temperature, and negatively correlated with air relative humidity. The regression analysis showed that there was a significant correlation between multi-day sap flow rate and solar radiation, and the determination coefficient was 0.287 and 0.778 in summer and autumn, respectively. The linear regression model of multi-day sap flow with meteorological multi-factor was remarkable correlation, and the determination coefficient was 0.577 and 0.791 in summer and autumn, respectively. The regression model of multi-day sap flow with meteorological multi-factor was better than with single meteorological factor.