Xinhua Zhao

Effects of aeration position on organics, nitrogen and phosphorus removal in combined oxidation pond-constructed wetland systems.

Given that few studies investigated the effects of aeration position (AP) on the performance of aerated constructed wetlands, the aim of this study was to evaluate the effects of AP on organics, nitrogen and phosphorus removal in lab-scale combined oxidation pond-constructed wetland (OP-CW) systems. Results showed that middle aeration allowed the CW to possess more uniform oxygen distribution and to achieve greater removals of COD and NH3-N, while the CW under bottom aeration and surface aeration demonstrated more distinct stratification of oxygen distribution and surface aeration brought about better TN removal capacity for the OP-CW system. However, no significant influence of artificial aeration or AP on TP removal was observed. Overall, AP could significantly affect the spatial distribution of dissolved oxygen by influencing the oxygen diffusion paths in aerated CWs, thereby influencing the removal of pollutants, especially organics and nitrogen, which offers a reference for the design of aerated CWs.

The influence of dual-substrate-layer extensive green roofs on rainwater runoff quantity and quality

This study investigates the ability of dual-substrate-layer extensive green roofs to retain rainwater and reduce pollutant leaching. The substrates in dual-substrate-layer green roofs consist of an upper organic nutrition layer for plant growth and a lower inorganic adsorption layer for water retention and pollutant reduction. One traditional single-substrate-layer extensive green roof was built for comparison with dual-substrate-layer green roofs. During the experimental period, dual-substrate-layer green roofs supported better natural vegetation growth, with coverage exceeding 90%, while the coverage in single-substrate-layer green roof was over 80%. Based on the average retention value of the total rainfall for four types of simulated rains (the total rainfall depth (mm) was 43.2, 54.6, 76.2 and 86.4, respectively), the dual-substrate-layer green roofs, which used the mixture of activated charcoal with perlite and vermiculite as the adsorption substrate, possessed better rainfall retention performance (65.9% and 55.4%) than the single-substrate-layer green roof (52.5%). All of the dual-substrate-layer green roofs appeared to be sinks for organics, heavy metals and all forms of nitrogen in all cases, while acted as sources of phosphorus contaminants in the case of heavy rains. In consideration of the factors of water retention, pollution reduction and service life of the green roof, a mixture of activated charcoal and/or pumice with perlite and vermiculite is recommended as the adsorption substrate. The green roofs were able to mitigate mild acid rain, raising the pH from approximately 5.6 in rainfall to 6.5-7.6 in green roof runoff. No signs of a first flush effect for phosphate, total phosphorus, ammonia nitrogen, nitrate nitrogen, total nitrogen, organics, zinc, lead, chromium, manganese, copper, pH or turbidity were found in the green roof runoff. Cost analysis further proved the practicability of dual-substrate-layer green roofs in retaining rainwater, and their long-term rainwater runoff quantity and quality performance in urban environments merit further investigation.

Notice of Retraction Hydraulic and water quality reliability analysis of water distribution system

On the basis of previous studies, the water quality and hydraulic reliability of water distribution system was analyzed. Then the calculation models of the hydraulic and water quality reliability are established. Finally, a simulated municipal water distribution system is taken as the example to validate the rationality and feasibility of the models. The results show that the models established in this paper is reasonably and feasibly to be used into practice.

Study of NH 3 -N prediction based on nonstationary time series in a sewage River

Using the deterministic analysis of non-stationary time series, this paper focuses on the prediction of NH3-N in a sewage River. Considering environmental hazards of indiscriminate discharge of sewage, the experiment was performed on a sewage river of selected area. NH3-N was measured at selected seven sampling locations from Aug 2007 to Aug. 2008. We conducted a total of nine samples. During the experiment, the sampling time is basically the same and time intervals of sampling are also consistent, therefore the sampled data (seven samples) can be looked on as a sequence of time. According to the requirements of time series analysis, manipulate the data and test the stationarity of the series. By time series analysis, an exponential smoothing of NH3-N is developed. As long as we know the actual value and predicted value of NH3-N concentration in last period, we can predict the next NH3-N concentration. Significant test of model parameters and adaptive testing of the model show that the exponential smoothing of NH3-N was significant. Using the data from water quality testing department of the city to test the model, which indicates that the veracity of the model was 82.9%, which meets the precision requirement of the mode1.

Study on prediction of COD in a southern sewage river of certain coastal city

This paper focuses on the prediction of Chemical Oxygen Consumption (COD) in a sewage River. Considering environmental hazards of indiscriminate discharge of sewage, the experiment was performed on a sewage river of selected area. COD was measured at selected sampling locations from Aug 2007 to Aug. 2008. We conducted a total of nine samples. During the experiment, the sampling time is basically the same and time intervals of sampling are also consistent, therefore the sampled data (seven samples) can be looked on as a sequence of time. According to the requirements of time series analysis, manipulate the data and test the stationarity of the series. By time series analysis, an ARIMA (1, 0, 2) model is developed. Significant test of model parameters and adaptive testing of the model show that the ARIMA (1, 0, 2) model of COD was significant. Using the data from water quality testing department of the city to test the model. The results indicates that the veracity of the ARIMA model was 84.9%, which meets the precision requirement of the model. The model is conducive to the rational utilization of environmental capacity and can provide scientific foundation for general regulation and management of rivers.

Study on regional water supply system plan model of a new district in North China

City water demand of new area in 2020 is forecasted on the basis of water resources optimized allocation. According to the real situation, regional water supply system is fixed on new area. Optimized path of the main pipes spanning different areas of new area is confirmed and optimized mathematical model of new area is set up. Finally, Methods of Matlab GA Toolbox are used to solve the model and results are analysed.

Simulation of urban storm system based on situations of different return periods

A hydraulic model based on case is built using InfoWorks Collection System software and verified using pump station records. Model reactions under different return periods using different real time control plans are discussed. The longer return periods are, the more influence the storm system is suffered. Different pump control plans make great influence on urban storm system.