Simulation of a subsurface vertical flow constructed wetland for CSO treatment.

Constructed wetlands (CWs) have proved to be a highly effective measure to reduce the ecological impact of combined sewer overflows (CSOs) on receiving waters. Due to the stochastic nature of the loading regime and the multitude of environmental influences, assessment of the performance of such plants requires detailed mathematical modelling. A multi-component reactive transport module (CW2D) was applied to simulate the flow, transport and degradation processes occurring in a CW for CSO treatment. CW2D was originally developed to simulate the treatment of municipal wastewater in subsurface flow CWs. Loading and operational conditions in CSO treatment differ fundamentally from the conditions occurring for wastewater treatment. Despite these differences, first results from the simulation of lab-scale experiments show, that the model is generally applicable to this type of plant. Modelling of adsorption, degradation processes, and influent fractionation, however, require further research.     

“新奥法“支护在南山隧洞的应用

南山隧洞局部地质条件复杂,围岩类别低,在施工过程中采用"新奥法"支护该隧洞Ⅲ-Ⅴ类围岩,即初期支护为锚喷,二次支护为模注混凝土和灌浆处理。"新奥法"技术在本工程中的成功应用再次证明了该技术在不良地质条件下隧洞施工的应用价值。     

Identification of sewer pipes to be cleaned for reduction of CSO pollutant load.

To reduce the CSO (Combined Sewer Overflow) pollutant discharge, one of the effective options is cleaning of sewer pipes before rainfall events. To maximize the efficiency, identification of pipes to be cleaned is necessary. In this study, we discussed the location of pipe deposit in dry weather in a combined sewer system using a distributed model and investigated the effect of pipe cleaning to reduce the pollutant load from the CSO. First we simulated the dry weather flow in a combined sewer system. The pipe deposit distribution in the network was estimated after 3 days of dry weather period. Several specific pipes with structural defect and upper end pipes tend to have an accumulation of deposit. Wet weather simulations were conducted with and without pipe cleaning in rainfall events with different patterns. The SS loads in CSO with and without the pipe cleaning were compared. The difference in the estimated loads was interpreted as the contribution of wash-off in the cleaned pipe. The effect of pipe cleaning on reduction of the CSO pollutant load was quantitatively evaluated (e.g. the cleaning of one specific pipe could reduce 22% of total CSO load). The CSO simulations containing pipe cleaning options revealed that identification of pipes with accumulated deposit using the distributed model is very useful and informative to evaluate the applicability of pipe cleaning option for CSO pollutant reduction.     

“新奥法”改进工艺在特大洞室开挖施工中的应用

利用传统新奥法进行隧洞开挖施工难以满足现代水电建设对工期的要求。采用流水作业方法对传统新奥法施工工艺进行了改进,该改进工法的核心是将原来的各层逐层开挖调整为同时开挖,并将改进的施工方法成功应用到某大型水电站特大调室的开挖中。结果表明,该工法不占用直线工期,且施工资源得到合理利用,闲置减少,经济效益显著,可在类似水电工程隧洞施工中推广。     

Constructed wetlands for CSO treatment: an overview of practice and research in Germany.

Vertical flow treatment wetlands have been developed as very useful tools for treatment of combined sewage overflow. Several systems have been in operation for over 15 years. Based on recent research work, new technical guidelines now recommend systems with a drained filter of sand 0/2 mm and a throttled outflow. COD, NH4-N and SS removal rates of 85-99% can be expected from this type of filter. SS loadings that are too high and very long or frequent inundation affect the performance adversely. Information for successful long-term operation were derived from various existing plants.     

An analysis of relay protection requirements for the purpose of estimating its effectiveness

Existing requirements, used to estimate the effectiveness of relay protection, are analyzed. The need to include in these requirements economic indicators of the functioning of relay-protection devices and automation or the reliability of the electric supply, taking into account the results of the functioning of these devices, is validated. This enables the effectiveness of the decisions taken when choosing relay protection and automation devices to be increased.     

Interaction of oxygen concentration and retention of pollutants in vertical flow constructed wetlands for CSO treatment.

The EU Water Framework Directive (WFD) calls for a good quality of all water bodies. Retention soil filters (RSF) have been developed to treat discharges from combined sewers systems. RSF have proved over the past 15 years to be the most effective measure to meet the EU WFD standards, especially for small or particularly sensitive receiving waters, which require an enhanced reduction of emissions from combined sewer overflows (CSOs). The paper presents results from laboratory-scale experiments, in which the oxygen measurement in the filter plays a main role. The results show remarkable differences in oxygen concentrations in different filter depths. The highest oxygen consumption takes place in the upper part of the filter. In the lower part the re-aeration of sewage from the soil air dominates. This indicates that the biological activity is limited to the upper part of the filter. The availability of oxygen in the filter is a sign for degradation of wastewater compounds (ammonium, COD) under certain conditions and already takes place during the filter operation. The removal of ammonium especially cannot be strictly divided into phases of sorption during the loading and oxidation during the dry period any more.     

Increase of River Base Flow by Hydropower Gate Operation for Mitigation of CSO Impacts – Potential and Limitations

In this paper the measure of increased river base flow is developed and evaluated. Aim is the temporal increase of flow in manmade low flow stretches for sufficient dilution of downstream acute pollution introduced by combined sewer overflows (CSOs). The increase of flow is done by operating upstream located retaining structures such as hydropower intakes. For implementation both energy producers and municipalities are required to cooperate. Thus the measure fits into a core aim of the Water Framework Directive of having basin wide approaches for improvements. Technically the focus of the measure is clearly on the mitigation of acute pollution, not addressing delayed or accumulate pollutants. The framework and implications are discussed for having an appropriate real time control (RTC) concept based on model based predictive control (MBPC). A specially development algorithm for the operation is presented and subsequently tested off-line with a semi-virtual catchment. The boundary conditions of the catchment are varied with regard to the connected catchment size, the river connected and the pollutant concentration originating from the catchment. Based on these scenarios and a review on uncertainties in rain forecasts, limits for the measure are derived. Costs for the measure were estimated as equivalent cost due to losses in energy production. It is shown that not only the costs for annual spilled water are to be considered but as well peak flows generated in the river system. The increase of CSO volume as an alternative measure was not found to be a suitable measure, leading to unrealistic high volumes and consequently to exorbitant costs.     

Model based hydropower gate operation for mitigation of CSO impacts by means of river base flow increase.

In river stretches being subjected to flow regulation, usually for the purpose of energy production (e.g. Hydropower) or flood protection (river barrage), a special measure can be taken against the effect of combined sewer overflows (CSOs). The basic idea is the temporal increase of the river base flow (during storm weather) as an in-stream measure for mitigation of CSO spilling. The focus is the mitigation of the negative effect of acute pollution of substances. The measure developed can be seen as an application of the classic real time control (RTC) concept onto the river system. Upstream gate operation is to be based on real time monitoring and forecasting of precipitation. The main objective is the development of a model based predictive control system for the gate operation, by modelling of the overall wastewater system (incl. the receiving water). The main emphasis is put on the operational strategy and the appropriate short-term forecast of spilling events. The potential of the measure is tested for the application of the operational strategy and its ecological and economic feasibility. The implementation of such an in-stream measure into the hydropower's operational scheme is unique. Advantages are (a) the additional in-stream dilution of acute pollutants entering the receiving water and (b) the resulting minimization of the required CSO storage volume.     

Assessment of CSO loads--based on UVIVIS-spectroscopy by means of different regression methods.

The use of UV/VIS-spectroscopy for water quality measurements is based on the solution of the correlation between the surrogate parameter absorbance and the resulting equivalence parameters. The coherence of absorbance and equivalence parameters (CODtot, CODsol, TSS) is solved in this paper with different regression methods. The correlation of absorbance and concentrations are analysed based on linear regression methods, model tree regressions, multivariate regression methods and support vector machines using sequential minimal optimisation algorithm. For this purpose the regression methods are calibrated on three 24hours measurement campaigns of a combined sewer measurement station situated in the combined sewer overflow chamber in Graz (Austria). The online measurement station has been conveying data for more than 2 1/2 years up to now. Finally, the load calculation based on the different regression methods and its comparison demonstrate that an apparently complex model does not inevitably lead to accurate concentration values due to possible model overfitting. Hence, the paper points out the possibilities and the drawbacks of spectroscopy measuring in sewers and the arising concentration values.     

水文序列的相关插补条件

引用统计学中有关统计检验的概念，分析作为插补资料的相关关系条件，并尽可能给出判别准则及判别式。在相关插补水文序列时，首先需要进行以下检验：（１）残差检验；（２）线性相关程度检验；（３）展延范围的确定。残差检验可论证随机误差是否服从正态分布及是否相互独立。线性相关程度检验可分析所假定的线性回归是否合理及相关程度是否满足插补要求。通过插补范围的估计可求出最大的外延幅度，使插补值的取值范围或误差控制在一     

Characterization of the potential impact of retention tank emptying on wastewater primary treatment: a new element for CSO management

Theoretical studies have shown that discharges from retention tanks could have a negative impact on the WWTP's (Wastewater Treatment Plant) effluent. Characterization of such discharges is necessary to better understand these impacts. This study aims at: (1) characterizing water quality during emptying of a tank; and (2) characterizing the temporal variation of settling velocities of the waters released to the WWTP. Two full-scale sampling campaigns (18 rain events) have been realized in Quebec City and laboratory analyses have shown a wide variability of total suspended solids (TSS) and Chemical Oxygen Demand (COD) concentrations in the water released from the tank. Suspended solids seem to settle quickly because they are only found in large amounts during the first 15 min of pumping to the WWTP. These solids are hypothesized to come from the pumping in which solids remained after a previous event. When these solids are evacuated, low TSS containing waters are pumped from the retention tank. A second concentration peak occurs at the end of the emptying period when the tank is cleaned with wash water. Finally, settling velocity studies allowed characterizing combined sewer wastewaters by separating three main fractions of pollutants which correspond to the beginning, middle and end of emptying. In most cases, it is noticed that particle settling velocities increase as the pollutant load increases.     

Energy requirements for waste water treatment

The actual mathematical models describing global climate closely link the detected increase in global temperature to anthropogenic activity. The only energy source we can rely on in a long perspective is solar irradiation which is in the order of 10,000 kW/inhabitant. The actual primary power consumption (mainly based on fossil resources) in the developed countries is in the range of 5 to 10 kW/inhabitant. The total power contained in our nutrition is in the range of 0.11 kW/inhabitant. The organic pollution of domestic waste water corresponds to approximately 0.018 kW/inhabitant. The nutrients contained in the waste water can also be converted into energy equivalents replacing market fertiliser production. This energy equivalent is in the range of 0.009 kW/inhabitant. Hence waste water will never be a relevant source of energy as long as our primary energy consumption is in the range of several kW/inhabitant. The annual mean primary power demand of conventional municipal waste water treatment with nutrient removal is in the range of 0.003-0.015 kW/inhabitant. In principle it is already possible to reduce this value for external energy supply to zero. Such plants should be connected to an electrical grid in order to keep investment costs low. Peak energy demand will be supported from the grid and surplus electric energy from the plant can be is fed to the grid. Zero 'carbon footprint' will not be affected by this solution. Energy minimisation must never negatively affect treatment efficiency because water quality conservation is more important for sustainable development than the possible reduction in energy demand. This argument is strongly supported by economical considerations as the fixed costs for waste water infrastructure are dominant.     

An application of linear programming to determine optimal systems for rainwater management: An economic view

Two decision models, one for determining optimal systems for rainwater management and the other for allocating additional water supplies from managed rainfall in conjunction with irrigation water, are formulated. The application of a rainwater management model to the command and to a watercourse, decides the minimum cost activities to manage rainwater. The output from the first model is used as the input in the second model which optimally allocates water to competing crops. It has been shown that 80% of rainwater could be managed economically in rice fields and in storage underground through artificial recharge. Optimal allocation of managed rainwater in conjunction with irrigation water increases the income of the project area to the extent of 14%.List of symbols AER Total available energy kWh - B _max Maximized value of the objective function, Rs - C _W Cost of canal water, Rs/10³ m³ - C _i Cost of managing rainwater through activityi, Rs/10³/m³ - C _min Minimized cost of managing surplus rainwater, Rs - C _RF Average cost of managed rainwater through activityi, Rs/10³ m³ - E _i Energy consumption in rainwater management activityi, kWh/10³ m³ (only energy required for pumping water is considered) - FLS Available capacity for fallow land storage, 10³ m³ - FPS Total storage in lined and unlined farm ponds, 10³ m³ - GWR Runoff diversion for artificial recharge through inverted tubewells, 10³ m³ - i A suffix for management activities having values 1,2,3,..., - j Crop index having values 1,2,3,..., - k Index for crop season, 1=kharif (summer) and 2=rabi(winter) - MRF Maximum rainfall surplus (runoff) available for management. (Runoff value at a 5-year return period was adopted) - P _j Income from crop activityj, Rs/ha - RFL Storage in fallow alkali land, 10³ m³ - RFS Storage in rice fields up to various depths, 10³ m³ - RWM _i Volume of rainwater managed through activityi, 10³ m³ - VCW Volume of canal water, 10³ m³ - VGW Volume of ground water, 10³ m³ - X _j Area under cropj, ha.     

Comparison of Real-time Control Methods for CSO Reduction with Two Evaluation Indices: Computing Load Rate and Double Baseline Normalized Distance

Water Resources Management - Real-time control (RTC) methods, which utilize real-time information to control the existing infrastructures in combined sewer systems, are effective in reducing...     

水利工程招标中项目法人风险与防范

水利工程项目结构复杂,影响其建设和经济效益的不确定性因素很多。本文对水利工程招标中的项目法人风险进行了分析,并提出了有效的风险防范对策,为项目法人选择合适的承包商以及实现项目目标提供了参考。     

On the effect of spatial variances in historical rainfall time series to CSO performance evaluation.

Historical, high-resolution rain series are the backbone of modern combined sewer overflow (CSO) structure design. These rain series are the input to the computational estimation of the performance of the measures with respect to CSO pollution abatement. However, those historical precipitation measurements are available at only a few locations. Frequently rain series have to be used from gauging stations at a significant distance. In order to judge and to compensate for this influence an estimate between rain characteristics and combined sewer outflow (CSO) performance indicators would be useful. In this paper such correlations have been sought for a collection of 37 rain series covering large areas of Europe. It was found that the mean annual rain volume can explain most of the variances for the performance indicators Number of overflows and CSO volume. For explaining the spatial differences in the efficiency of the CSO structure another rain characteristic, i.e. the maximum event with a return period of one year, is to be used.     

浅论新奥法施工的原理及其特点

简要叙述了新奥法施工的特点、理论、施工要点、支护手段与施工顺序以及新奥法的适用范围,指出了新奥法施工的优、缺点,并对新奥法施工作了简要的展望.     

"新奥法"支护在南山隧洞施工中的应用

南山隧洞局部地质条件复杂,围岩类别低,在施工过程中采用"新奥法"支护该隧洞Ⅲ～Ⅴ类围,即初期支护为锚喷,二次支护为模注混凝土和灌浆处理。"新奥法"技术在本工程中的成功应用再次证明了该技术在不良地质条件下隧洞施工的应用价值。