Low-Cost Stormwater Filtration System to Improve Urban Water Quality: The Case of Addis Ababa, Ethiopia

Urbanization in developing countries often negatively impacts water re-sources by polluting surface waters. Addis Ababa, Ethiopia, is currently experiencing rapid urbanization accompanied by significant water shortages, unmanaged stormwater, and increasing river water pollution. To supplement the need for non-potable water and address stormwater runoff pollution, we constructed a low cost stormwater filtration system. The filtration system is comprised of a sedimentation area followed by three gravel grain sizes arranged horizontally from coarse to medium to fine filter media. We compared the quality of pretreatment water with post-treatment water by measuring physicochemical parameters, heavy metals and nutrients. We found that the filtration system reduced turbidity by 87%, TSS by 80%, Cu by 87% and Zn by 90%. Further, it positively increased the concentration of DO by 42%. However, the filtration system did not remove nitrates and nitrites. Implementing this system at outfalls in the rapidly expanding condominium housing areas can increase residents’ supply of non-potable water and reduce the amount of polluted stormwater entering nearby streams and rivers.

Study on Planning an Ecological Stormwater Regulation System Based on Low Impact Development Mode： A Case Study in China

This paper sets Chaihu Town, Zhongxiang City of Hubei Province as an example, analyzing the ecological and hydrological conditions of Chaihu Town, applying LID （low impact development） mode and putting forward the ecological stormwater regulation system planning strategy which adapts to the development of small towns. The main conclusions are as follows： （1） The ＂three-low＂ development mode is put forward, which means low impact, low cost and low carbon, using this construction mode to minimize the ecological impact, relying on natural green space and water to achieve the function of rainstorm regulation; （2） Through the analysis and calculation of the local amount of precipitation, this paper scientifically calculates the required area of storage water and green space, taking the roads as trunks, green spaces as stems, water as veins, and building the green infrastructure system; （3） The author has been repairing and integrating the original drainage ditches of the planning area, replacing traditional rain drainage pipes, establishing ＂two-loop＂ water network system which aims at the detention and purification of rainwater, maximizing ecological benefit, economic benefit and landscape benefit.

Stormwater management of urban greenway in China

In order to improve the stormwater regulation functions of urban greenways on the basis of literature research and case study the relationships between urban greenway and low impact development LID and green stormwater infrastructure GSI are analyzed. Then the classification system of urban greenways is proposed based on their stormwater regulation function and the suitable technical measures for stormwater management which can be used in different kinds of greenways are selected. According to China’s urban planning system the greenway planning method combined with the urban drainage system is developed and the design methods of the greenway stormwater system and individual stormwater facilities are put forward. The relationships between the greenway stormwater system and other systems are also analyzed in terms of stormwater inlet vertical design and overflow.Finally the waterfront greenway and street greenway demonstration projects in Jiaxing City which adopts the above concept and method are introduced. The results show that the reduction rates of annual total stormwater runoff and average total runoff contaminants TSS of the stormwater system are not less than 30% and 40% respectively.

Development, assessment and implementation of integrated stormwater management plan: a case study in Shanghai

An innovative stormwater master plan based on low impact development LID is proposed.Unlike the traditional urban drainage plan this plan employs a sustainable stormwater management approach in communities utilizing LID practices to reduce runoff and pollution load. An integrated hydraulic model which combines the traditional drainage sewer system with LID practices is adopted to assess the master plan.Through a long-term continuous simulation for 20 years the results reveal that the runoff volume will be reduced by over 80% following full implementation of this plan. Combining with the local conditions technical guidelines are established to provide assistance in implementing the stormwater master plan. Bioretention facilities for three main roads are constructed and other areas of development are being implemented sequentially under the guidance of the plan. This project provides an alternative method of stormwater management through the implementation of LID and it acts as a good example for other developing districts in China.

Adsorption characteristics of Pb from urban stormwater runoff by construction wastes

Construction wastes were selected as the adsorbents and static and dynamic adsorption batch experiments were carried out to investigate the adsorption of Pb to construction wastes with different particle size gradations in the simulated stormwater runoff system.The experimental results show that the pseudo-second-order kinetics model can better characterize the adsorption process of Pb than the pseudo-first-order kinetics model.The adsorption equilibrium data can be well fitted by the Freundlich isotherm model. The construction wastes with different tested size gradations can greatly remove Pb from stormwater runoff and their average removal rate can reach up to 99%.The construction wastes with narrow size distribution can better remove Pb but with worse permeability than those with wide size distribution. The particle size gradation of construction wastes greatly influences the equilibrium time rate and the capacity of Pb adsorption.The equilibrium adsorption rate and capacity are 18.1 μg/min and 5.5 μg/g respectively for the construction wastes with the size of 2.36 to 4.75 mm which are the greatest among the different size gradations.The present study provides a scientific basis for effectively controlling Pb pollution from stormwater runoff and the construction wastes resource utilization.

Feasibility assessment of LID concept for stormwater management in China through SWOT analysis

The strengths weaknesses opportunities and threats SWOT analysis method is applied to assess the feasibility of traditional stormwater management and low impact development LID in China.The results show that traditional stormwater management has many disadvantages e.g.only stormwater collection and discharge or flooding peak-flow regulation is taken into consideration but lack of many important functions such as on-site infiltration non-point pollution control ecological treatment etc.Meanwhile as a new stormwater management concept the LID system has many advantages e.g.LID can not only control rainwater quantity but also effectively prevent non-point pollution. Moreover LID is easy for implementation and cost effective and operation and management can also be done easily.LID has attracted more and more attention from governmental authorities at different levels and the majority of practitioners. Therefore LID has bright prospects for wide applications in China.

Application of constructed wetlands treatment technique for stormwater runoff pollution control

In order to improve the pollution control effect of nitrogen phosphorus and heavy metals in stormwater runoff by using the constructed wetlands factors such as medium plants pretreatments etc.that may influence the removal efficiency are discussed based on the current studies. The pollution control effect can be enhanced by the improvement of the design methods the components and management of constructed wetlands.The design methods aimed at controlling the stormwater runoff should be based on the hydrological data accumulated for years.The development of novel medium and the selection of plants i.e. flood-tolerant and economical should be considered in advance. The management of constructed wetlands should be enhanced and the database of the stormwater in wetlands should be built.The discussion above should be effective in improving the pollution control effect in stormwater runoff by applying constructed wetlands.

Influence of Physical and Chemical Parameters on the Treatment of Heavy Metals in Polluted Stormwater Using Zeolite—A Review

Zeolite-based technology can provide a cost effective solution for stormwater treatment for the removal of toxic heavy metals under increasing demand of safe water from alternative sources. This paper reviews the currently available knowledge relating to the effect of properties of zeolites such as pore size, surface area and Si:Al ratio and the physico-chemical conditions of the system such as pH, temperature, initial metal concentration and zeolite concentration on heavy metal removal performance. The primary aims are, to consolidate available knowledge and identify knowledge gaps. It was established that an in-depth understanding of operational issues such as, diffusion of metal ions into the zeolite pore structure, pore clogging, zeolite surface coverage by particulates in stormwater as well as the effect of pH on stormwater quality in the presence of zeolites is essential for developing a zeolite-based technology for the treatment of polluted stormwater. The optimum zeolite concentration to treat typical volumes of stormwater and initial heavy metal concentrations in stormwater should also be considered as operational issues in this regard. Additionally, leaching of aluminium and sodium ions from the zeolite structure to solution were identified as key issues requiring further research in the effort to develop cost effective solutions for the removal of heavy metals from stormwater.

Adsorption characteristics of a novel ceramsite for heavy metal removal from stormwater runoff

Urban sediments have rapidly increased in recent years around the world,and their effective management has become an important problem.To remove heavy metals from stormwater runoff and use sediments as a resource,a novel ceramsite was developed using sewer pipe sediments(SPS),river bed sediments(RBS),urban water supply treatment sludge(WSTS),and wastewater treatment plant excess sludge(WWTS).The optimal composition was determined based on the Brunauer–Emmett–Teller specific surface area and an orthogonal test design.The adsorption characteristics of the novel ceramsite for dissolved heavy metals(Cu^(2+)and Cd^(2+)) were investigated through adsorption isotherms and kinetic experiments at(25±1)℃.Both Cu^(2+) and Cd^(2+) were effectively removed by the novel ceramsite,and their equilibrium adsorption was 4.96 mg·g^(-1) and 3.84 mg·g^(-1),respectively.Langmuir isotherms and a pseudo-first-order kinetic equation described the adsorption process better than other techniques.Characterization analysis of the ceramsite composition before and after heavy metal adsorption showed that the Cu^(2+) and Cd^(2+) contents in the ceramsite increased after adsorption.The results revealed that adsorption is both a physical and chemical process,and that ceramsite can be used as a bioretention medium to remove heavy metals from stormwater runoff while simultaneously converting problematic urban sediments into a resource.

Strategies for Enhancing the Efficiency of Bioretention Swales and Basins for Urban Stormwater Management in Temperate Region

Among various schemes to reuse and recycle the limited urban fresh water resources, sustainable urban stormwater management, such as water sensitive urban design and rainwater harvesting, has been recognized as one of the most efficient and economically viable approaches. Storm runoff shall be treated as close as possible to its source before it is reused or discharged into public drainage network or receiving waters to enhance the water environment quality. Bioretention swale/basin, which has been commonly applied to treat runoff from roads, car parks, cyclist and pedestrian paths, rooftops, etc., is recognized to be the most efficient and aesthetic pleasing way to harvest rainwater in urban settings, and other longish shape runoff catchment area. This paper studied over 10 bioretention swales/basins applications in temperate region worldwide covering China, Germany, Norway, Austria, USA, and Australia. Key steps in bioretention swale/basin design and implementation in temperate region were investigated, such as strategic bioretention scheme selection, flow conveyance and hydraulic capacity design, filtering media profile, vegetation scheme selection and maintenance scheme, and suggestion and key design parameters. The critical path and parameters of bioretention swale/basin design which enhanced the effectiveness and efficiency of its application for rainwater harvesting in temperate regions were derived.

On-site stormwater detention for Australian development projects: Does it meet frequent flow management objectives?

On-site stormwater detention (OSD) is a conventional component of urban drainage systems, designed with the intention of mitigating the increase to peak discharge of stormwater runoff that inevitably results from urbanization. In Australia, singular temporal patterns for design storms have governed the inputs of hydrograph generation and in turn the design process of OSD for the last three decades. This paper raises the concern that many existing OSD systems designed using the singular temporal pattern for design storms may not be achieving their stated objectives when they are assessed against a variety of alternative temporal patterns. The performance of twenty real OSD systems was investigated using two methods:(1) ensembles of design temporal patterns prescribed in the latest version of Australian Rainfall and Runoff, and (2) real recorded rainfall data taken from pluviograph stations modeled with continuous simulation. It is shown conclusively that the use of singular temporal patterns is ineffective in providing assurance that an OSD will mitigate the increase to peak discharge for all possible storm events. Ensemble analysis is shown to provide improved results. However, it also falls short of providing any guarantee in the face of naturally occurring rainfall.

Purification of Stormwater Using Sand Filter

Rain water is an important source to feed the groundwater aquifer, whether directly or by harvesting and recharging. The importance of purification is for reducing the risk of pollutants from recharging runoff rainwater. The use of sand filter as a technique considered not expensive and commonly used for removing contaminants from water and wastewater treatment industries. The methodology used laboratory testing, by designing and constructing pilot plant to experiment the sand filter for purification, and made simulation for the infiltration of storm water through sand filter of 2 meters depth, in order to find the relationship between the depth on one hand, and the removal of suspended solids and fecal coliforms bacteria on the other hand, to know the effective depth that gets the purification. The research results during three days of infiltration show that the sand filter can remove fecal coliforms bacteria at a depth of 150 cm, and provide purified water with a concentration of suspended solids less than 20 mg/liter at a depth of 75 cm.

Adsorption characteristics of construction waste for heavy metals from urban stormwater runoff

Stormwater runoff has become an important source of surface water pollution. Bioretention, a low impact development measure in urban stormwater management, has been proven to be effective in the removal of pollutants from stormwater runoff, with appropriate bioretention media. In this study, construction wastes were selected as bioretention media to remove heavy metals from stormwater runoff. Static and dynamic adsorption batch experiments were carried out to investigate the adsorption of heavy metals in simulated stormwater runoff system with construction wastes in different particle sizes. The experimental results show that the pseudo-secondorder kinetic model characterizes the adsorption process and the adsorption equilibrium data are well described by Freundlich isotherm model. The construction wastes used can remove heavy metals from stormwater runoff effectively, with their average removal rates all more than 90%. The particle size of construction wastes greatly influences the equilibrium time, rate and adsorption capacity for heavy metals.

Research on Stormwater Management of Cultural Heritage Ilmpark in Weimar Germany Based on Urban Resilience

With the development of cities, problems like natural and social disasters appeared more and more frequently. For example, rapid urbanization and climate change have caused both increasing flood probability and the severity of flooding. Consequently, there is a need for all cities to develop new strategies to maintain their vitality in numerous challenges and crises. This paper in the first place reviews the concept and research fields of urban resilience;besides, according to the characteristics of the Ilmpark situated in Weimar, This paper analyzes the necessity and potential on stormwater management of this area and then it concludes the alternative strategies of improvement based on the theory of urban resilience.

Removal Efficiency Simulation and Characterization Analysis of Particles Behavior in a Stormwater Wetland During Dry Days:A Case Study in Janghwa-do,Korea

Particles behaviour was monitored and analyzed in a stormwater wetland over a period of 4 months (June-September,2009).The results indicated that the particles behaviour can be affected by many processes,such as sedimentation,resuspension,adsorption and release in stormwater wetlands during dry days.Due to the effects of these factors,the particles removal efficiency calculated based on the settling theory was significantly higher than the value obtained using the measured particles number concentration.And the measured efficiency showed a turning point in the range of 2-4 μm,which was within the colloidal particles range.Analysis of particle size distribution showed that particles were finer in the outflow than inflow due to sedimentation of the coarse particles and resuspension of the fine particles in the wetland.Particles in different size ranges play different roles in their contribution to turbidity and total suspended solids concentration.The finer particles (less than 10μm) showed a closer relationship with the turbidity while coarser particles (>4μm) were more related to total suspended solid concentration.

Phenoxyacid Herbicides in Stormwater Retention Ponds: Urban Inputs

Surface water runoff from urban centers is a major source of environmental pollution which impacts water quality in downstream aquatic habitats. Phenoxyacid herbicides are some of the most widely globally used herbicides in agriculture and urban environments for weed control. Their transformation products which in- clude chlorophenols can be more toxic than the active ingredients. We used LC/MS/MS to analyzed simul- taneously these acid herbicides and their transformation products in stormwater retention ponds taken from an urban environment to examine the occurrence and potential release of these herbicides from urban inputs into downstream waters. 2,4-dichlorophenoxyacetic acid and mecoprop were detected in all samples col- lected from the ponds and at the highest concentrations, while 2-methyl-4-chlorophenoxyacetic acid was de- tected only in spring and summer. Two transformation products, 4-chloro-2-methylphenol and 2,4-di- chlorophenol were detected in samples primarily at inlet locations on the ponds indicating that degradation had occurred in surface soils prior to surface water runoff.

Application of Urban Green Stormwater Infrastructure in Wetland Park Construction

The positive role of urban green stormwater infrastructure(GIS)and wetland park construction in the process of“sponge city”construction is analyzed by expounding the connotation and problems of“sponge city”construction.Through the analysis of relevant cases,the realization approaches of combing different types of GIS with wetland park landscape design are interpreted,and it is pointed out that different types of GIS can guide the further practice of“sponge city”construction.

Planning and Design of Beautiful Countryside Based on the Concept of Stormwater Resilience: A Case Study of Shanbei Village, Yunfu City, Guangdong Province

Shanbei Village is a village in Yunfu of Guangdong,which has been seriously affected by flood disasters.In the context of the construction of beautiful countryside,utilizing the concept of resilience stormwater,construction ideas of beautiful countryside of combining the prevention and control of village flood disasters with economic and social development and cultural heritage are proposed.The planning methods of adjusting the planting way of crops,demolition of dwellings in submerged areas and development and utilization of ancient dwellings,sorting out drainage systems and planning“large,medium and small sponges”,and improving the drainage capacity of culverts are summarized.

Stormwater Management Practices and Green-Blue Infrastructure in Urban Areas: an Overview

Water quality,flooding risk,and water consumption in urban areas are emerging issues.Urban impervious surfaces increase stormwater runoff,affecting ecosystems and leading to hydrogeological instability and flooding risk.Sustainable urban design strategies can contribute to counteract the negative impact of anthropic activities both at city-scale and global scale.Green and Blue Infrastructure(GBI)approaches,in particular,are an alternative to stormwater traditional management.In Europe,Sustainable Drainage System implementation copes with impervious surfaces to achieve water quality,amenity,and biodiversity increase.Best Management Practices,developed mainly in the USA,focus on specific measures for sustainable stormwater treatment.Water Sensitive Urban Design,spread in Australia and England,also aims to minimise the impact of developed areas preventing flood risk,limiting water consumption and enhancing environmental quality.In the USA and Canada,Low Impact Development offers design strategies to manage runoff and deliver structural practices to mimic predevelopment processes of infiltration,filtration and detention.