Investigating helminth eggs and Salmonella sp. in stabilization ponds treating septage.

Sludge management arises as a relevant problem after being accumulated in primary ponds of septage treatment plants. One of the most attractive options for sludge disposal is its use in agriculture and then specific guidelines regarding hygienic quality must be fulfilled. This study aimed at evaluating the storage time needed to inactivate Ascaris eggs and Salmonella in sludge accumulated in a primary pond treating septage. Raw septage exhibited very low concentrations of viable Ascaris eggs, thus experiments with Ascaris suum eggs spiking were conducted. The concentration of Ascaris eggs in the solids accumulated at the bottom of the pond was 20 eggs/g of total solids (g TS) at the time of pond closure. Although it decreased, some eggs remained viable (0.59 mean viable eggs/g TS) up to 20 months of in-pond storage of the biosolids. Salmonella survival was studied after developing an analytical method that inhibited the native flora. Sludge was seeded with Salmonella enteritidis. An equation adequately describing Salmonella die-off in biosolids subjected to 115 days of in-pond storage/dewatering, was found to be represented by the regression: y = log MPN Salmonella/g TS = 6.67 x t(-0.086), with t = storage time elapsed in days. The initial concentration was 7.0 x 10(6) MPN/g TS and the removal efficiency was 99%.     

Integrated faecal sludge treatment and recycling through constructed wetlands and sunflower plant irrigation.

Faecal sludge (FS) from the on-site sanitation systems is a nutrient-rich source but can contain high concentrations of toxic metals and chemicals and infectious micro-organisms. The study employed 3 vertical-flow CW units, each with a dimension of 5 x 5 x 0.65 m (width x length x media depth) and planted with cattails (Typha augustifolia). At the solid loading rate of 250 kg total solids (TS)/m(2).yr and a 6-day percolate impoundment, the CW system could achieve chemical oxygen demand (COD), TS and total Kjeldahl nitrogen (TKN) removal efficiencies in the range of 80-96%. A solid layer of about 80 cm was found accumulated on the CW bed surface after operating the CW units for 7 years, but no clogging problem has been observed. The CW percolate was applied to 16 irrigation sunflower plant (Helianthus annuus) plots, each with a dimension of 4.5 x 4.5 m (width x length). In the study, tap water was mixed with 20%, 80% and 100% of the CW percolate at the application rate of 7.5 mm/day. Based on a 1-year data in which 3 crops of plantation were experimented, the contents of Zn, Mn and Cu in soil of the experimental plots were found to increase with increase in CW percolate ratios. In a plot with 100% of CW percolate irrigation, the maximum Zn, Mn and Cu concentrations of 5.0, 12.3 and 2.5 mg/kg, respectively, were detected in the percolate-fed soil, whereas no accumulation of heavy metals in the plant tissues (i.e. leaves, stems and flowers) of the sunflower were detected. The highest plant biomass yield and oil content of 1000 kg/ha and 35%, respectively, were obtained from the plots fed with 20% or 50% of the CW percolate.     

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.     

高水头下不良地质体防渗补强技术研究与应用

针对200 m以上水头下复杂不良地质体的防渗补强技术难题,研发了高强度、高浸润渗透性、高粘结性、可操作时间长、胶凝时间精确可调和环保性能优良的CW系高性能环氧树脂灌浆材料,开发了针对不同受灌体和灌浆工况的水泥-化学复合灌浆精细控制工艺和配套灌浆设备,并形成了高水头下不良地质体处理成套技术。该技术已成功应用于溪洛渡、向家坝、清远抽水蓄能等重点水利水电工程,也可推广应用到交通、矿山等行业,具有广阔的应用前景。     

Constructed wetland as a low cost and sustainable solution for wastewater treatment adapted to rural settlements: the Chorfech wastewater treatment pilot plant

The paper presents the detailed design and some preliminary results obtained from a study regarding a wastewater treatment pilot plant (WWTPP), serving as a multistage constructed wetland (CW) located at the rural settlement of 'Chorfech 24' (Tunisia). The WWTPP implemented at Chorfech 24 is mainly designed as a demonstration of sustainable water management solutions (low-cost wastewater treatment), in order to prove the efficiency of these solutions working under real Tunisian conditions and ultimately allow the further spreading of the demonstrated techniques. The pilot activity also aims to help gain experience with the implemented techniques and to improve them when necessary to be recommended for wide application in rural settlements in Tunisia and similar situations worldwide. The selected WWTPP at Chorfech 24 (rural settlement of 50 houses counting 350 inhabitants) consists of one Imhoff tank for pre-treatment, and three stages in series: as first stage a horizontal subsurface flow CW system, as second stage a subsurface vertical flow CW system, and a third horizontal flow CW. The sludge of the Imhoff tank is treated in a sludge composting bed. The performances of the different components as well as the whole treatment system were presented based on 3 months monitoring. The results shown in this paper are related to carbon, nitrogen and phosphorus removal as well as to reduction of micro-organisms. The mean overall removal rates of the Chorfech WWTPP during the monitored period have been, respectively, equal to 97% for total suspended solids and biochemical oxygen demand (BOD5), 95% for chemical oxygen demand, 71% for total nitrogen and 82% for P-PO4. The removal of E. coli by the whole system is 2.5 log units.     

黄浦江河口建闸挡潮效果初步分析

在探讨计算水情和水闸调度运行方案的基础上,采用3种尺度的河网模型对黄浦江河口建闸的挡潮效果进行定量分析,并研究了不同调度参数(起关潮位和关闸历时)对挡潮效果的影响。研究结果表明,在遭遇千年一遇风暴潮时通过合理调度黄浦江河口闸门可将进潮量减少约80%,闸内干流段高潮位降低1.7~2.4m,能有效提高上海市区的防汛能力。     

Nitrogen mass balance and microbial analysis of constructed wetlands treating municipal landfill leachate.

Experiments were conducted to investigate the feasibility of applying constructed wetlands (CW) to treat a sanitary landfill leachate containing high nitrogen (TN) and bacterial contents. Under the tropical conditions (temperature of about 30 degres C), the CW units operating at a hydraulic retention time (HRT) of 8 days yielded the best treatment efficiencies with BOD5 removal of 91%, TN removal of 96%, total and fecal coliforms (TC and FC) removal of more than 99%. Cadmium removal in the in the SFCW bed was found to be 99.7%. Mass balance analysis, based on TN contents of the plant biomass and dissolved oxygen (DO) and oxidation - reduction potential (ORP) values, suggested that 88% of the input TN were uptaken by the plant biomass. Fluorescence in situ hybridization (FISH) results revealed the predominance of bacteria including the heterotrophic and autotrophic bacteria responsible for BOD5 removal. Nitrifying bacteria was not found to be present in the SSFCW beds.     

三峡左岸电站ALSTOM机组大负荷特殊振动归纳分析

三峡水电站2008年圆满的完成了所有机型蓄水至172 m稳定性及相对效率试验,也全面掌握了左岸电站ALSTOM机组在各个不同水头下的运行特性,并明确了不稳定涡带工况区和特殊振动区。主要介绍三峡左岸电站ALSTOM在各水头下机组大负荷特殊振动情况,并对其进行了归纳分析。     

Vertical flow constructed wetlands for municipal wastewater and septage treatment in French rural area.

This paper presents the purification performance of 20 wastewater treatment plants with vertical reed bed filters (Macrophyltres), built between 1998 and 2003 by SAS Voisin, for communities of between 150 and 1400 PE. The first stage vertical reed bed (directly fed with raw wastewater by intermittent feeding) achieved high removal of SS, BOD and COD (mean respectively 96%, 98%, 92%). The second stage permitted compliance easily with effluent standards (SS < 15 mg/l, BOD < 15 mg/l, COD < 90 mg/l and mean TKN < 10 mg/l). Performance was not significantly influenced by variations of organic and hydraulic load, nor by seasonal variations. Rigorous operation and maintenance were required to obtain optimal performances. Another application of vertical reed beds is the treatment of septage (sludge from individual septic tanks). The results obtained on two sites operating for 2 and 3 years are presented. The first site achieved complete treatment of septage (solid and liquid fraction), the second permitted a pre-treatment for co-treatment of percolate with wastewater.     

A measure for provisional-and-urgent sanitary improvement in developing countries: septic-tank performance improvement

Although many cities have planed to develop sewerages in developing countries, sewerage establishment still requires huge investment and engineering efforts. Improvement of existing sanitation facilities may contribute the betterment of urban sanitation before sewerage establishment. The purpose of this study is to propose a measure to improve urban sanitation in areas where a sewerage development plan is proposed but has not been yet established, based on a case study in Hanoi, Vietnam. We found that 90.5% of human excreta flowed into septic tanks. However, 89.6% of septic tanks have never been desludged in the past and their performance was observed to be at a low level. The study also showed that if they introduce regular desludging with a frequency of once a year, they can eliminate 72.8% of COD loads from septic tanks. It was indicated that the performance can be dramatically recovered by regular desludging, which could contribute urban sanitation improvement in Hanoi. In conclusion, the performance recovery of septic tanks by regular desludging was proposed as a provisional-and-urgent measure for urban sanitation improvement, together with the septage treatment in sewage sludge treatment facilities, which should be established earlier than other facilities of sewage treatment systems.     

水布垭电厂机组全水头下稳定性分析

以大量的PSTA2003状态监测及趋势分析系统的特征数据为基础,分析各机组在不同水头下的运行工况的特征表现,为电厂合理安排机组运行方式、确保机组在最优工况下运行提供了参考,还可通过对机组运行特征数据变化趋势的分析,及时掌握设备运行状态,及早发现设备隐患。     

Tolerance to hydraulic and organic load fluctuations in constructed wetlands.

This paper describes a two-year performance evaluation of four different constructed wetland (CW) treatment systems designed by IRIDRA Srl, located in central Italy. All four CW systems were established to treat wastewater effluent from different tourist activities: (1) one single-stage CW for secondary treatment of domestic wastewater (30 p.e.) at a holiday farm site; (2) a hybrid compact system consisting of two stages, a horizontal flow (HF) system followed by a vertical flow (VF) system for the secondary treatment of effluent from a 140 p.e. tourist resort; (3) a single-stage vertical flow (VF) CW for a 100 p.e. mountain shelter; and (4) a pair of single-stage, HF CWs for the secondary treatment of segregated grey and black water produced by an 80 p.e. camping site. These tourism facilities are located in remote areas and share some common characteristics concerning their water management: they have high variability of water consumption and wastewater flow, depending on the season, weather and weekly regularities; they have no connection to a public sewer and most sites are located in a sensitive environment. Total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammonium (N-NH4+), nitrate (N-NOx), total nitrogen (Ntot), total phosphorus (Ptot), total coliform (TC), faecal coliform (FC), E. coli removal efficiencies for all four CW systems are presented. The results from this study demonstrate the potential of CWs as a suitable technology for treating wastewater from tourism facilities in remote areas. A very efficient COD reduction (83-95%) and pathogen elimination (3-5 logs) have been achieved. Furthermore, the CWs are easily maintained, robust (not sensitive to peak flows), constructed with local materials, and operate with relatively low cost.     

Application of a water quality model for determining instream aeration station location and operational rules: A case study

Instream aeration has been used as a supplement to secondary treatment or a substitute for tertiary treatment for meeting dissolved oxygen (DO) standards in rivers. Many studies have used water quality models to determine the number, location, and capacity of instream aeration stations (IASs) needed to meet DO standards in combination with other pollution control measures. DO concentrations have been improved in the North Shore Channel and North Branch Chicago River by the Devon Avenue IAS for more than 35 years. A study was initiated to determine whether it was better to rehabilitate or relocate this station and to determine appropriate operational guidance for the IAS at the selected location. A water quality model capable of simulating DO concentrations during unsteady flow was used to evaluate the proper location for an IAS and operational guidance for this IAS. Three test years, a dry year, a wet year, and an extreme year, were considered in the evaluation. The study found that the Devon Avenue IAS should be rehabilitated as this location performed as well as or better than any of 10 alternative locations. According to the new operational guidance for this IAS, the amount of time with blowers operating could be substantially reduced compared to traditional operations while at the same time the attainment of the DO standards could be increased. This study shows that a carefully designed modeling study is key to effective selection, location, and operation of IASs such that attainment of DO standards can be maximized while operation hours of blowers can be minimized.     

Water Management of Irrigation Dams Considering Climate Variation: Case Study of Zayandeh-rud Reservoir, Iran

Dependency of reservoir operation on the climate variation occurs especially in regions, where agricultural demand has a significant share of the total water demands. The variability between demands that are based on annual climate conditions may be larger than the uncertainty associated with other explanatory variables in long-term operation of an irrigation dam. This paper proposed a rule curves to the water managers of the Zayandeh-rud reservoir in Iran in long-lead reservoir operation. A regional optimal allocation of water among different crops and irrigation units is developed. The optimal allocation model is coupled with a reservoir operating model, which is developed based on the certain hedging that deals with the available water and the water demands mutually. This coupled model is able to activate restrictions on allocating water to agricultural demands considering variation of inflow to the reservoir, variation of demands and the economic value of allocating water among different crops and irrigation units. The resulted rule curve is presented with a number of tables for more details and accuracy and a simple curve, which is more useful for operational purpose.     

保温保压浇筑蜗壳二期混凝土的施工对策

蜗壳二期混凝土被称为电站厂房混凝土的“心脏”，是最关键和最难浇筑的部位。三峡左岸电站厂房采用对蜗壳充水保温保压模拟运转状态浇筑二期混凝土是一项新技术，目前在国内外属首例，施工质量对机组的安全运行及振动稳定具有至关重要的作用。     

Numerical modelling: a tool for better constructed wetland design?

There is a need for a simplified computer-based design tool for subsurface flow constructed wetlands (CWs) which is based on process-based numerical models. Parameters of existing design guidelines and rules have been derived from experiments under specific conditions. Therefore designing CWs using these parameters is limited to these conditions (i.e., temperature, wastewater composition, filter material, etc.). Process-based numerical models describe the main processes in CWs in detail. If the design of CWs is based on these models it will be possible to design CWs for a variety of different boundary conditions and therefore the main limitation of existing design guidelines and rules could be overcome. The use of process-based models is currently limited mainly due to their complexity in structure and use. To make numerical modelling a useful and applicable tool for design, a simplified computer-based design tool that does not require special knowledge of numerical modelling is needed. Additionally, simple models for pre- and post-treatments are also required. Besides allowing designs for various boundary conditions, design tools based on process-based models can also predict the dynamic behaviour of the designed system thus showing e.g., the higher robustness of CWs against fluctuating inflows and peak loads compared to other treatment solutions. Such a tool could increase the quality of CW design and the acceptance and use of CW simulation in practice.     

Modernization of heat exchangers in steam turbine units taking features of their operation at specific thermal power plants into account

The authors’ experience in the modernization of commercial heat exchangers in steam turbine units is discussed with the individual features of the operation of these exchangers at specific thermal power plants taken into account. The variety of conditions under which heat exchanges operate in specific engineering subsystems requires an individualized approach to the model solutions that have been developed for modernizing these systems. New piping systems for commercial heat exchanges have undergone industrial testing and are in successful operation at a wide range of thermal power plants.     

Hydraulic behaviour and removal efficiencies of two H-SSF constructed wetlands for wastewater reuse with different operational life

This work focuses on the performance evaluation of two full-scale horizontal suburface flow constructed wetlands (H-SSF CWs) working in parallel, which have an almost equal surface area (about 2,000 m2) but with different operational lives: 8 and 3 years. Both H-SSF CWs, located in Southern Italy (Sicily), are used for tertiary treatment of the effluent of a conventional wastewater treatment plant. This study evaluates and compares H-SSF CW efficiency both in terms of water quality improvement (removal percentage) and achievement of Italian wastewater discharge and irrigation reuse limits. The mean removal percentage, for the overall operational life, of TSS, COD and BOD (80%, 63%, 58% obtained for H-SSF1 and 67%, 38%, 41% for H-SSF2), confirm the high reliability of CWs for wastewater treatment. However, despite the satisfactory removal of microbial indicators (the mean E. coli removal was up to 2.5 log unit for both beds), CWs didn't achieve the Italian limits for wastewater reuse. Information on hydraulic properties of the CWs were extracted from breakthrough curves of a non-reactive tracer (NaCl). By comparing the nominal (tau(n)) and actual residence time (tau), hydraulic behaviour was revealed.     

等壳水电站冲刷漏斗模型试验研究

通过等壳电站坝前冲刷漏斗物理模型试验,对冲刷漏斗形态进行了研究,总结了不同运行工况下的漏斗纵、横坡度变化规律.通过类似原型和其他模型试验对比分析,认为等壳水库冲刷漏斗试验结果合理.可以保证电站安全运行.根据试验成果,提出了减缓水库有效库客损失的排砂孔运行方式.     

基于开关控制策略的厂内经济运行模型及应用

通过划分机组的约束限制条件为安全运行区和非安全运行区，提出了一 种基于开关控制策略的厂内经济运行模型。该模型有效地反映了机组的运行状态，并且保证 了设备的可利用率，较好地解决了影响水轮机效率、使用寿命、甚至可能危及电站运行安全 的机组不可运行区等约束限制问题。算例表明，该方法是有效的。