Wastewater modification processes assessment in a stabilization reservoir.

A semi-empirical mechanistic model able to simulate the dynamics of a stabilization reservoir was developed incorporating both settling of particulate components and chemical/biological processes. Several factors affecting the reservoir effluent quality were taken into account: hydraulics and hydrology, solar radiation, atmospheric reaeration, algae, zooplankton, organic matter, pathogen bacteria, and sediment-water interaction. The model quantifies the specific influence of each factor on effluent quality, evaluating the correlation between the different considered factors. State variables included in the model were: algae, dissolved oxygen, organic matter, zooplankton and indicator bacteria.The model was transferred into a computational code in order to provide a useful and versatile tool for water resource planning management issues. The model was verified by comparing simulated results with full-scale data collected from a small reservoir (Sicily, IT) filled with partially treated wastewater. The reservoir has a volume of 11,000 m(3), a maximum depth of 6.3 m and a mean depth of about 5 m. The monitoring period lasted four months during which the reservoir operated in different hydraulics conditions: as a standard batch reactor and as a continuous flow reactor. The model was able to reproduce the behaviour of the principal simulated parameters thus representing a potential tool for the management and performance optimization of these peculiar storage/treatment systems.     

小浪底水库支流倒灌与淤积形态模型试验

利用小浪底水库实体模型开展水库拦沙后期运用方式长系列年试验,对争议较大的库区支流倒灌及其淤积形态问题进行重点分析。结果表明:库区最大支流畛水河口门狭窄且库容较大,拦门沙问题最为突出,其纵坡面形态与设计有一定的差别;支流年淤积量与当年大于2600 m3/s流量时段的总水量有较好的相关性;通过优化水库运用方式可较长时期保持动态三角洲淤积形态,有利于支流库容的有效利用;水库干流河床处于动平衡状态时,支流河床仍然会逐渐淤积抬升而使得干支流淤积面高差趋于减少。     

Anoxic sulfide oxidation in wastewater of sewer networks.

Investigations on anoxic sulfide oxidation in wastewater under sewer conditions are presented. Batch tests were designed and conducted to study both chemical and biological sulfide oxidation by nitrate in the water phase. Oxidation at pH 7.0 and 8.5 was performed in parallel and wastewater with anaerobic storage period of 0, 3, 4, 6 days was used. Initial sulfide concentrations at a level of 0-4.1 g S m(-3) were applied by either addition or sulfate reduction. Results showed that wastewater in sewers was capable of biological, but not chemical, sulfide oxidation under anoxic conditions. Elemental sulfur was the end-product during the experiment. Nitrite accumulates in wastewater as an intermediate. The anoxic oxidation rates for fresh wastewater was 0.48 g S m(-3) h(-1) at pH 7.0 and 0.62 g S m(-3) h(-1) at pH 8.5, which accounted for less than 30% of the potential aerobic oxidation rates. A long-term anaerobic adaptation of the wastewater was found to inhibit the oxidation process.     

Analysing sludge balance in activated sludge systems with a novel mass transport model

In activated sludge systems the mechanically treated wastewater is biologically cleaned by biomass (activated sludge). The basic requirement of an efficient biological wastewater treatment is to have as a high biomass concentration in the biological reactor (BR) as possible. The activated sludge balance in activated sludge systems is controlled by the settling, thickening, scraper mechanism in the secondary settling tank (SST) and sludge returning. These processes aim at keeping maximum sludge mass in the BR and minimum sludge mass in the SST even in peak flow events (storm water flow). It can be, however, only reached by a high SST performance. The main physical processes and boundary conditions such as inhomogeneous turbulent flow, geometrical features of the SST, wastewater treatment plant (WWTP) load, return sludge flow, sludge volume index etc. all influence settling thickening and sludge returning. In the paper a novel mass transport model of an activated sludge system is presented which involves a 2-dimensional SST model coupled with a mixed reactor model of the biological reactor. It makes possible to investigate different sludge returning strategies and their influence on the sludge balance of the investigated activated sludge system, furthermore, the processes determining the flow and concentration patterns in the SST. The paper gives an overview on the first promising model results of a prevailing peak flow event investigation at the WWTP of Graz.     

Domestic wastewater treatment by a constructed wetland system planted with rice

The experiments were conducted in four concrete laboratory scale free water surface constructed wetland units 1 m wide, 1.5 m long and 0.8 m deep. Paddy field soil was added to a depth of 0.4 m and rice seedlings (Oryza sativa L.) were transplanted into the units at a density of 25 plants/m(2). Domestic wastewater collected from Chiang Mai University was applied into each unit via two different modes to evaluate suitable conditions for wastewater treatment and rice yield. In the first experiment, the wastewater was fed intermittently (7 h/day) with a hydraulic loading rate of 2, 4, 6 and 8 cm/day. The maximum removal efficiencies for chemical oxygen demand, biological oxygen demand, total kjedahl nitrogen and suspended solids were only 49.1, 58.7, 64.0 and 59.4%, respectively, due to the short hydraulic retention time for the biodegradation of organic substances. In the second experiment, the wastewater in each unit was inundated to a depth of 15 cm for 10, 15, 20 and 25 days in each unit and then drained and re-flooded. Removal efficiencies of chemical oxygen demand, biological oxygen demand, total kjedahl nitrogen and suspended solids were greater than in the first experiment especially at the 25 day retention time and except for suspended solids met the Thai national effluent standard. The study revealed that apart from wastewater treatment, wastewater can replace natural water to grow rice in the dry season or throughout the year. Moreover, nutrients in wastewater can be a substitute for chemical fertilizers. Rice grain production was 4,700 kg/ha and only 6% less than the production from the conventional paddy field.     

Frequency analysis of river water quality using integrated urban wastewater models

In recent years integrated models have been developed to simulate the entire urban wastewater system, including urban drainage systems, wastewater treatment plants, and receiving waterbodies. This paper uses such an integrated urban wastewater model to analyze the frequency of receiving water quality in an urban wastewater system with the aim of assessing the overall system performance during rainfall events. The receiving water quality is represented by two indicators: event mean dissolved oxygen (DO) concentration and event mean ammonium concentration. The compliance probability of the water quality indicators satisfying a specific threshold is used to represent the system performance, and is derived using the rainfall events from a series of 10 years' rainfall data. A strong correlation between the depth of each rainfall event and the associated volume of combined sewer overflow (CSO) discharges is revealed for the case study catchment, while there is a low correlation between the intensity/duration of the rainfall event and the volume of the CSO discharges. The frequency analysis results obtained suggest that the event mean DO and ammonium concentrations have very different characteristics in terms of compliance probabilities at two discharging points for CSO and wastewater treatment plant effluent, respectively. In general, the simulation results provide an understanding of the performance of the integrated urban wastewater system and can provide useful information to support water quality management.     

小浪底水库拦沙后期库容恢复试验研究

基于小浪底水库控制冲刷水位分别为210、220 m,12 d洪水过程,库区淤积量约为42亿m3及水库前期蓄水量3亿m3等条件,进行了2个组次的降水冲刷试验,对小浪底水库拦沙后期库容恢复情况进行了研究.结果表明:①洪水过程中,库区冲刷使得出库沙量大幅度增加,溯源冲刷作用大于沿程冲刷,干流冲刷量大于支流,库区下段冲刷量大于...     

小浪底水库调水调沙运用对大坝变形的影响分析

自2002年以来,小浪底水库汛前利用预泄汛限水位以上水量、腾空防洪库容的有利时机,连续5年进行集中调水调沙,获得了巨大的减淤效益.但在调水调沙期间,由于大流量下泄,水库水位下降较快,大坝变形明显增大,表现为水平位移向上游变化、垂直位移加速沉降变化的特点.监测分析结果表明,调水调沙运用不影响大坝安全稳定运行.     

A comparison of BNR activated sludge systems with membrane and settling tank solid-liquid separation.

Installing membranes for solid-liquid separation into biological nutrient removal (BNR) activated sludge (AS) systems makes a profound difference not only to the design of the membrane bio-reactor (MBR) BNR system itself, but also to the design approach for the whole wastewater treatment plant (WWTP). In multi-zone BNR systems with membranes in the aerobic reactor and fixed volumes for the anaerobic, anoxic and aerobic zones (i.e. fixed volume fractions), the mass fractions can be controlled (within a range) with the inter-reactor recycle ratios. This zone mass fraction flexibility is a significant advantage of MBR BNR systems over BNR systems with secondary settling tanks (SSTs), because it allows changing the mass fractions to optimise biological N and P removal in conformity with influent wastewater characteristics and the effluent N and P concentrations required. For PWWF/ADWF ratios (fq) in the upper range (fq approximately 2.0), aerobic mass fractions in the lower range (f(maer) < 0.60) and high (usually raw) wastewater strengths, the indicated mode of operation of MBR BNR systems is as extended aeration WWTPs (no primary settling and long sludge age). However, the volume reduction compared with equivalent BNR systems with SSTs will not be large (40-60%), but the cost of the membranes can be offset against sludge thickening and stabilisation costs. Moving from a flow unbalanced raw wastewater system to a flow balanced (fq = 1) low (usually settled) wastewater strength system can double the ADWF capacity of the biological reactor, but the design approach of the WWTP changes away from extended aeration to include primary sludge stabilisation. The cost of primary sludge treatment then has to be offset against the savings of the increased WWTP capacity.     

The Spatial and Temporal Variability of Limnological Properties of Bovilla Reservoir (Albania)

A limnological survey of a man-made reservoir in the central part of Albania was conducted from May 2006 to May 2008. This water body is being constructed 15 years ago for water supply of the Tirana, capital city of Albania. The physical and chemical quality of water in this reservoir was determined and compared against universally accepted water quality standards. Water quality parameters relevant to the study area are discussed considering the ecosystem function and interrelationship among physical and chemical parameters with the biological ones. The water quality of traditional and modern reservoir was not significantly different except for a bed odour that occurs throughout of the summer. Due to the reservoirs life the eutrophication in the nowadays is not a major problem in the reservoir, but due to an intensive sedimentation rate it is predicted that will seriously affect the water body in the near future. Management strategies to improve the water use efficiency with particular reference to eutrophication are proposed. On the other hand it is recommended that an integrated approach following the IRBM criteria will be the best way of management and administration.     

汾河二库坝前垂向表层水温变化规律研究

为探究水库垂向表层水温在年、季、日内的变化特征,给库区水体理化性质分析及养殖业发展提供重要参考,以汾河二库为研究对象,于2016年9月至2017年8月在汾河二库使用10 m长的柔性温度链进行自动化表层水温原型监测,分析了表层水温变化特性。结果表明:汾河二库垂向表层水温分布呈现出明显的季节性变化规律,符合分层型水库表温层特征;秋冬季表层水体水温均匀分布,春夏季水面下1~2 m层存在水温突然升高的现象;通过建立回归模型得知,气温与库面水温之间存在良好的线性相关关系;全年整体库面水温最大值出现时间与气温最大值出现时间一致;不同季节气温对表层水温的影响深度不同,气温升高,水温日变幅值越大,影响深度越大。     

葛洲坝及三峡工程对上游槽蓄曲线影响探讨

影响水面线及槽蓄曲线的因素可概括为河段自然地理状况及水流情势.随着水利水电工程的开发建设,人类活动影响日益凸现.以三峡工程坝址以上河段为例,根据三峡库区大量实测地形和水文资料,遵循水力学分析原理和方法,建立数学、物理模型,研究三峡坝址以上河段在天然、葛洲坝单独蓄水运行、三峡工程二期导流3个不同时期的水面线和槽蓄曲线,探讨了两项水利工程建设对上游槽蓄曲线的影响.分析表明,受工程影响,同蓄量水位抬高,同水位蓄量减小.三峡坝址至双江河段蓄量同为40亿m\+3,天然时期坝址水位为63.05 m,葛洲坝蓄水后坝址水位抬高6.38 m,三峡工程二期导流时期坝址水位抬高达8.71 m.     

Utilization of a hybrid sequencing batch reactor (HSBR) as a decentralized system of domestic wastewater treatment

This paper presents the experiments carried out in a hybrid sequencing batch reactor (HSBR), used for biological treatment of sewage. The HSBR was built in a cylindrical shape and made of stainless steel, with a volume of 1.42 m3. Besides the biomass in suspension, the reactor also carried fixed biomass (hybrid process), adhered in the support material. This consisted of a nylon net disposed in a grille for biofilm biomass adhesion. The reactor worked fully automated in operational cycles of maximum 8 hours each, presenting the following phases: filling, anoxic, aerobic, settle and draw of treated effluent, with 3 fillings per cycle. Increasing organic loads (0.14 to 0.51 kg TCOD/m3 day) and ammonium loads (0.002 to 0.006 kg NH4-N/m3.day) were tested. We monitored the reactor's performance by measuring the liquid phase (COD, pH, temperature, DO, nitrogen and phosphorus) during the cycles and by measuring the sludge through respirometric tests. The results obtained demonstrated TCOD removal efficiency between 73 and 96%, and ammonium removal efficiency between 50 and 99%. At the end of the cycles, the effluent presented ammonium concentration <20 mg/L, meeting the Brazilian environmental legislation standards (CONAMA 357/2005) regarding discharges into the water bodies. Respirometric tests showed biomass dependency on FCOD concentrations. Results have demonstrated the potential of this type of reactor for decentralized treatment of domestic wastewater.     

2017年丹江口水库精细化调度实践与探讨

针对2017年丹江口水库全年来水整体偏丰、汛期丰枯不均、枯丰急转的水情特点,以及防洪与供水矛盾突出、枢纽未经过高水位运行的问题,为提高水资源综合利用效率,确保水库防洪、供水等综合效益的发挥,对丹江口水库在不同阶段包括大坝横缝处置期间、秋汛防洪期和汛末蓄水167 m时期分别实施了水库精细化调度,并制定了精细化调度方案。方案包括加强预测预报、加密会商、电厂24 h实时待命、加密水位监测、提前预警等。通过精细化调度,让水库安全度汛,产生防洪效益7.04亿元,汛后顺利完成167 m蓄水试验工作;陶岔渠首累计向北方供水突破100亿m3,且首次达到设计供水流量350 m3/s;年累计发电量达31.23亿kW·h,枢纽防洪、供水、发电等效益显著。     

Chemical, physical and biological characteristics of Saladito Reservoir, Cienfuegos Province, Cuba

Saladito Reservoir, located in Cienfuegos Province in Cuba, lies in an intermediate position between tropical and subtropical climatic conditions. Although Cuba only had 13 reservoirs before 1959, the government has constructed 229 reservoirs since that time, with a total storage capacity of 8.81 km³, administered by the National Hydraulic Resources Institute. In 1995, it was proposed to use waste water from the Swinish Farm to fertilize small reservoirs, providing nitrogen and phosphorus to increase primary production in the reservoirs as a means of facilitating high fish production levels. Saladito Reservoir, with a hydrographic basin of 34.5 km², a mean depth of 3.4 m and a water retention time of 2 years, was constructed as the final part of the wastewater treatment system for Swinish Farm in the Palmyra Municipality. The main objective of this study is to determine the level of eutrophication in the reservoir after it had received waste water from the Farm for 17 months, based on relevant biological (phytoplankton), chemical and physical indicators sampled at five stations on 22 and 23 May 1995. Based on the measured parameters, the concentration of dissolved salts was generally high, with calcium and bicarbonate being the dominant ions. The nitrite‐nitrogen and nitrate‐nitrogen concentrations were relatively low at the surface, increasing with depth, while the ammonium‐nitrogen concentrations were extremely high, likely related to the high organic content of the reservoir. The total phosphorus concentration also exhibited high values, indicating the possible existence of soluble phosphorus in a complex with iron, which would allow algae to assimilate it like phosphate. The water transparency, measured as Secchi disk, was 0.2 m at all sampling stations. The chlorophyll‐a concentration ranged from 111 µg L⁻¹ in the surface water to 50 µg L⁻¹ at the bottom depth. The phytoplankton cell counts identified 27 algal species contained in five classes. The dominant group was Cyanophyceae, with Oscillatoria sp. being the largest contribution to the reservoir biomass. Twenty‐seven taxa were present in the reservoir in concentrations of at least 1 mg m⁻³. The results of this study indicate that Saladito Reservoir is hyper‐eutrophic, based on its measured biomass (cell counts), and chlorophyll‐α, inorganic nitrogen and total phosphorus concentrations. The possible production of algal toxins from blue‐green algal growths also could be affecting the productivity of Saladito Reservoir.     

Effects of treated wastewater irrigation on the dissolved and soil organic carbon in Israeli soils.

In many arid and semi-arid regions, the demand for drinking water and other domestic uses is constantly growing due to demographic growth and increasing standard of living. Therefore, less freshwater is available for agricultural irrigation and new water sources are needed. Treated wastewater (TWW) already serves as an important water source in Israel since more than 40 years and its usage will further be extended. Related to its high loads with nutrients, salts and organic materials its use as irrigation water can have major effects on the soil physical, chemical and biological properties, in the worst case leading to soil degradation. Additional organic matter reaches the soil with the effluent water and soil microbial activity is stimulated. Soil organic carbon (SOC) seems to accumulate in the topsoil and tends to decrease after long-term irrigation with secondary TWW in the subsoil. The amount of dissolved organic carbon increased and the aromaticity of the organic compounds in the soil percolates decreased over the irrigation period. Priming effects, occurring after stimulation of microbial activity by the addition of easily degradable substances, could be found in the soils and were stronger for subsoil (1 m depth).     

Hydrological analysis of single and dual storage systems for stormwater harvesting

As stormwater flows are intermittent, the requirement to store urban runoff is important to the design of a stormwater re-use scheme. In many urban areas, the space available to provide storage is limited and thus the need to optimise the storage volume becomes critical. This paper will highlight the advantages and disadvantages of two different approaches of providing storage: 1) a single shallow storage (0.5 m depth) in which stormwater capture and a balanced release to supply users is provided by the one unit; and 2) a dual system in which the functions of stormwater capture and supply release are provided by two separate deeper storage units (2 m depth). The comparison between the two strategies is supported by water balance modelling assessing the supply reliability and storage volume requirements for both options. Above a critical volumetric capacity, the supply yield of a dual storage system is higher than that from a single storage of equal volume mainly because of a smaller assumed footprint. The single storage exhibited greater evaporation loss and is more susceptible to algae blooms due to long water residence times. Results of the comparison provide guidance to the design of more efficient storages associated with stormwater harvesting systems.     

Multiobjective Calibration of Reservoir Water Quality Modeling Using Multiobjective Particle Swarm Optimization (MOPSO)

Water resource management encounters large variety of multi objective problems that require powerful optimization tools in order to fully characterize the existing tradeoffs between various objectives that can be minimizing difference between forecasted physical, chemical, and biological behaviors of model and measured data. Calibration of complex water quality models for river and reservoir systems may include conflicting objectives addressed by various combinations of interacting calibration parameters. Calibration of the two dimensional CE-QUAL-W2 water quality and hydrodynamic model is an excellent example where the model must be calibrated for both hydrodynamic and water quality behavior. The aim of the present study is to show how multiobjective particle swarm optimization (MOPSO) can be implemented for automatic calibration of water quality and hydrodynamic parameters of a 2-dimensional, hydrodynamic, and water quality models (CEQUAL-W2) to predict physical, chemical, and biological behaviors of a water body, and then focus on a relevant case study. So MOPSO is utilized to generate Pareto optimal solutions for two conflicting calibration objectives. A combined measure of thermal and reservoir water level is considered as the first calibration objective. The second objective is formulated to forecast the best physical, chemical, and biological behavior of the model. Realizing the strong interactions between water quality and hydrodynamic issues of water bodies and their dependencies on the same set of calibration parameters, the proposed multiobjective approach may provide a wide version of all possible calibration solutions for better decision making to select best solution from pareto front.     

Sediment distribution and its impacts on Hirakud Reservoir (India) storage capacity

Construction of dams causes reduced flow velocities, inducing gradual deposition of sediments carried by the inflowing stream, and resulting in sedimentation and ultimately diminishing reservoir storage capacity. This study focuses on sedimentation of Hirakud Reservoir in Odisha, India, using available reservoir capacity and numerical simulation data. Reduced trap efficiency, observed and projected capacity curves, rising reservoir bed level and the capacities of the different storage zones for various projected years are analysed. The area‐reduction method indicates the loss in the live, gross and dead storage will be 58%, 63% and 100%, respectively, of their original capacities by 2057, which represents 100 years of impounding of water in the reservoir. If the present sediment inflow rate continues without regular flushing of the deposited sediment, it is predicted the reservoir bed level will rise to the full reservoir level of 192.02 m by the year 2110. Brune's trap efficiency and step method indicate the gross storage zone of Hirakud Reservoir will be completely depleted by the end of 2110, with the trap efficiency reduced to zero. The empirical area‐reduction method is found to be more suitable for determining the storage capacities of Hirakud Reservoir in the absence of sedimentation survey data. An attempt was also made to solve the combined hydrodynamic and sediment transport equations numerically to predict morphological changes in Hirakud Reservoir. The finite‐element code TELEMAC‐2D and finite‐volume code for SISYPHE, respectively, were applied to solve the above set of equations in order to predict the bed profiles at different reservoir cross sections for the period of 1958–2008. Analysis of the simulated results demonstrates that, considering the model inputs, the model performs well in simulating the morphology and dynamic characteristics of a reservoir. Projection of the numerical results indicates a complete loss of reservoir operational life due to sedimentation by around 2150.     

ABR工程设计的要点分析

针对印染废水的特性和已有印染废水生化处理工艺在工程应用中存在的问题分析的基础上,提出ABR工艺方案,成功应用于印染废水的厌氧处理工段,保证了稳定的COD去除效率和脱色效果.通过分析ABR反应器的运行规律,总结出HRT、反应器内的水力流态优化是ABR设计成败的关键.