Microbiological water quality in a large in-building, water recycling facility.

The Thames Water recycling plant at the Millennium Dome, London, reclaimed three sources of water: greywater from the washbasins, rainwater from the Dome roof and groundwater from a borehole on site. These were pre-treated separately, and the mixed stream filtered using ultrafiltration and reverse osmosis membranes. Monitoring for indicator microorganisms was undertaken throughout the plant and in the reclaimed water distribution system, as well as ad-hoc monitoring for the presence of pathogens in the raw waters. Treatment to the level of ultrafiltration was more than adequate to produce a water quality meeting existing worldwide reclaimed water guidelines for toilet flushing. Owing to the excellent quality of the water leaving the plant, no significant microbiological growth was observed in the reclaimed water distribution system during the year. The raw greywater exhibited a higher faecal bacterial load than the rainwater and groundwater, as predicted from more human contact (i.e. hand washing). Environmental strains of Legionella were observed in the three raw greywater samples analysed for pathogens, as was Cryptosporidium, Giardia and faecal enterococci. The rainwater had relatively high levels of faecal bacteria, probably of avian origin. Giardia was detected in one rainwater sample confirming the potential for this water source to contain pathogens.     

Assessment of Rainwater Availability by Building Type and Water Use Through GIS-based Scenario Analysis

Scenario analysis of rainwater harvesting and utilization (RWHU) was performed considering various non-potable water uses in different building types over a year. Six building types were identified in the study area using GIS data: residential houses, offices, commercial buildings, restaurants, public buildings, and “others”. Rainwater storage capacity was considered as 30 mm rainwater depth. Water demand for each building type was calculated as the sum of the individual water uses for toilet flushing, air conditioning, garden irrigation, and cleaning defined in this study as “miscellaneous usages”. To incorporate water quality considerations, rainwater with suspended solids level of less than 2 mg l⁻¹ was used as the quality criterion. The RWHU scenario was compared with other storage and water use scenarios. This study quantified the rainwater availability throughout a year and its seasonal variation and consumption in each building type. The analysis clarified the effectiveness of rainwater utilization for supplementing existing water resources.     

Identifying the major influences on the microbial composition of roof harvested rainwater and the implications for water quality.

Perceptions of the quality of roof harvested rainwater remain an impediment to widespread implementation of rainwater tanks on urban allotments. Previous literature reports on roof water quality have given little consideration to the relative significance of airborne environmental micro-organisms to roof catchment contamination and the issue of tank water quality. This paper outlines the findings of a recent study into the influence of weather on roof water contamination conducted at an urban housing development in Newcastle, on the east coast of Australia. Samples of direct roof run-off were collected during a number of separate rainfall events, and microbial counts were matched to climatic data corresponding to each of the monitored events. Roof run-off contamination was found to be under the strong influence of both wind speed and direction. The preliminary findings of an investigation currently under way into the microbial diversity of rainwater harvesting systems have also been presented. The results indicate that the composition of organisms present varied considerably from source to source and throughout the collection system. In all cases, evidence of faecal contamination was found to be negligible. The implications of these findings to the issues of tank water quality, health risk analysis and monitoring protocols have been discussed.     

Towards Sustainable Water Quality: Management of Rainwater Harvesting Cisterns in Southern Palestine

Environmental management of rainwater harvesting in southern Palestine is required to reduce the continuously increasing demand for fresh water from limited water aquifers and to reduce the adverse health impact on the people drinking harvested rainwater. This continuously increasing demand for fresh water requires the enhancement of environmental conditions surrounding the cistern owners’ awareness to tackle the mismanagement that contributed to rainwater contamination. In this study, 100 cisterns were sampled and tested for physiochemical and microbiological parameters. Most of the tested physiochemical parameters were within the acceptable limits of WHO and Palestinian standards except turbidity, calcium and magnesium where 24%, 47% and 32% of the samples were non-conforming, respectively. The pH values of the collected rainwater ranged from 7.32 to 8.97 with a mean value of 8.16. The nitrate analysis results range from 1.5 to 7.0 mg/L, with a mean value of 4.2 mg/L. High percentage of cisterns were found to be contaminated with total Coliforms (TC) and faecal Coliforms (FC) with percentages of 95% and 57%, respectively, rendering the cistern water unacceptable for drinking purposes. 78% of samples had a severe degree of contamination for which water needs flocculation, sedimentation then chlorination to become suitable for drinking. On the other hand, based on FC data, none of the tested samples for FC was a “high risk”, but 57% of them were categorized with “simple” to “moderate risk” and 43% were “no risk” cisterns. A cistern owner’s survey was utilized to reveal the roots behind this contamination. Different remediation measures, such as cleaning cisterns and rainwater collection surfaces and discarding water from the first season storm, were recommended to enhance and protect the cistern water quality.     

Rainwater: A Potential Alternative Source for Scarce Safe Drinking and Arsenic Contaminated Water in Bangladesh

Although Bangladesh receives plenty of rainwater during its monsoon, both rural and urban areas suffer from shortages of safe drinking water during dry season. Arsenic contamination of ground water affects many rural areas, whilst some urban areas including the capital, Dhaka City, lack sufficient potable ground water to meet the demand. To cope with the problem, this research explore: the feasibility of harvesting rainwater during monsoon as a source of quality safe drinking water in Dhaka City. A questionnaire survey was conducted about potable water shortage in four slums of Dhaka City. Rainwater was collected using a non-toxic waterproof cloth as a catchment during monsoon and stored in a ferro-cement storage tank with an initial flushing device attached at the inlet of the tank. Different important physical, chemical and bacteriological parameters were tested throughout the storage period of 4 months. The efficiency of the rainwater harvesting system increased from 51% to 80% before and after installing the system. The test results were compared with the Bangladesh water quality standards. The tests have revealed slightly higher pH value (8.1 to 8.3) and enormity of color beyond the acceptable range. Although the presence of total coliform was detected after three months, traditional filtering of that stored rainwater showed a promising solution to mitigate potable water shortages in Bangladesh.     

水景社区的雨水收集与综合利用设计

为研究城市雨水收集与综合利用,以上海郊区一生态水景社区为例,进行水量平衡计算。结果表明,该社区年均雨水可收集量约45 678 m3,占一年总降雨量的62%左右,不但满足社区每年的绿化浇灌、硬地冲洗以及水面蒸发等消耗量,而且富余雨水经过处理后可用作景观湖的补充水源及其他用水。雨水收集利用系统设计以景观湖为中心,屋面雨水通过2个总容积为675 m3的地下集蓄池来收集,集蓄水量可达1.83万m3/a;绝大部分绿地、道路广场以及极少数屋面的雨水径流通过长1 km的植草浅沟和500 m长的碎石沟渠收集,并汇入2个总面积为800 m2的暴雨塘系统内暂时储存。户外小停车场和小广场的雨水通过砂床过滤系统收集。     

低质水的价格理论与实践

低质水就是现代城市建设中促进水资源高效利用的新产物,它是指将未经处理或简单处理的原水、中水系统的回用水等低品质水作为初级非饮用水,单设管网供应,用于冲洗厕所、园林绿化、清洗车辆、喷洒道路、景观用水等。低质水系统通常是局部或区域性的,在节约水资源和降低水处理费用等方面存在优势。本文针对低质水的价格进行了理论和实践上的探讨。     

用于裂隙岩溶含水层回灌的屋面雨水径流水质特性研究

本文以北方地区裂隙岩溶水典型城市济南市为研究区，监测分析了2008年2月至8月降水过程的降雨量、降雨强度，同时对研究区13次天然降水的11项指标与位于裂隙岩溶水直接补给区7次降水形成的屋面径流的28项指标进行检测，识别出屋面径流主要污染物类型，探讨了2008年春季和夏季各次降雨形成的屋面径流中不同污染物随降雨历时、降雨强度和季节的变化规律；分析了径流污染物的来源，并对屋面径流雨水通过井回灌裂隙岩溶含水层用于饮用水的处理方法及效果进行了探讨。济南市屋面水质的研究为济南城市屋面雨水回灌裂隙岩溶含水层提供了依据。     

Assessing the Potential for Rainwater Harvesting

Rainwater harvesting is one of the promising ways of supplementing the surface and underground scarce water resources in areas where existing water supply system is inadequate to meet demand. Rainwater harvesting is one of the measure for reducing impact of climate change on water supplies. Abeokuta has a mean annual rainfall of 1,156 mm which makes rainwater harvesting ideal. Intra annual variability lies betwen 0.7 and 1.0 while the inter annual variability was 0.2. Annually 74.0 m³ of rainwater can be harvested per household. Estimated annual water demand for flushing, laundry and flushing were 21.6 and 29.4 m³ respectively. Harvested rainwater in Abeokuta can satisfy household monthly water demand for WC flushing and laundry except for November, December, January and February. The excess rainwater stored in September and October is sufficient to supplement the short fall in the dry months provided there is adequate storage.Water savings potential is highest in June and September which is the two rainfall peak period in Southwest Nigeria.     

北京某学校雨水利用设计

以北京市某中学为例,介绍一种学校雨水利用的方法。根据校区水量平衡计算结果,对利用校园内汇集的雨水作为冲厕、绿化和景观用水等进行设计;采取相应的技术措施,对雨水径流的污染进行控制,保障所利用雨水的水质达到要求,并采用生态净化的方式,使学校景观水体循环起来。虽然雨水利用工程投资较高,但其社会和环境效益显著。     

Alternative Water Resources for Rural Residential Development in Western Australia

Rainwater collected from residential roofs and greywater generated from domestic uses except toilets are viewed as possible substitutes for high grade water sources which supply nonpotable indoor uses and irrigation in Australia. This paper searches for alternatives by adopting roofwater and greywater in residential envelope as per Australian water standards. A water balance model Aquacycle was applied to determine storage capacities and to evaluate the percentage reduction in water supplying, stormwater run-off and wastewater disposal, as well as volume of rainwater use and greywater reuse. This study provides the results of greywater recycling, which contributes to the greater saving of mains water supply than rainwater use, and which reduces more than half of the wastewater to receiving waters in the rural township of Cranbrook, Western Australia. The results of this study provide greywater usage (maximum reduction 32.5%) more significantly reduces scheme water supply than rainwater harvesting (maximum reduction 25.1%). Use of greywater on individual residential lots has the dramatic effect for drainage system by reduction approximately 54.1% or 88.1 m³/lot/year. The results of rainwater use analysis show explicitly that rainwater tanks are much more effective in intercepting roof runoff, with the maximum stormwater reduction 48.1% or 68.3 m³/lot/year. This research endeavours to offer a typical paradigm for an integrated water system in the rural residential sectors.     

Performance Analysis of a Communal Residential Rainwater System for Potable Supply: A Case Study in Brisbane, Australia

Cities in developed countries have increasingly adopted rainwater tanks as an alternative water source over the last 15 years. The rapid uptake of rainwater tanks has been driven by the need to reduce demand for centralised water services that are under pressure to adapt to population growth and climate change impacts. Rainwater tanks are part of integrated urban water management approach that considers the whole water cycle to provide water services on a fit for purpose basis that minimises the impact on the local environment and receiving waters. Rainwater tanks are typically applied at the household scale for non-potable water source uses such as toilet flushing and garden irrigation. However, this paper reports on a communal approach to rainwater harvesting, where the water is treated for potable use. A communal approach to rainwater harvesting can offer benefits, such as: economies of scale for capital costs, reduced land footprint, centralised disinfection and flexibility in matching supply and demand for different households. The analysis showed that the communal approach could provide a reliable potable water source to a small urban development. However, there was an energy penalty associated with this water source compared to centralised systems that could be addressed through more appropriate pump sizing. The outputs from this monitoring and modelling study demonstrated rainwater harvesting can be expanded beyond the current mainstream practices of household systems for non-potable use in certain development contexts. The analysis contained in this paper can be used for the improved planning and design of communal approaches to rainwater harvesting.     

Assessment of ponds surrounding Imphal Valley on the basis of various biological and physicochemical parameters

The water quality is one of the major criteria for the environmental evaluation based on the parametric changes in the physicochemical and biological properties of water. The distribution patterns of physicochemical and biological characteristics of the various rivers in the Imphal Valley have been studied in this work. The objective of the work is to determine the surface water quality of Imphal Valley to assess its suitability for domestic purposes. The physicochemical parameters of water such as water temperature, pH, hardness, alkalinity, EC, TDS, chloride, calcium, magnesium, sodium, potassium and nitrate were analysed for the experimentation. The biological characteristics were estimated from the Total coliform and Escherichia coli content of water. The physicochemical parameters were within the acceptable limits on the other hand Total coliform, and E. coli values were exceeding from the acceptable and permissible limits as prescribed by Bureau of Indian Standards (BIS). The study suggests untreated domestic disposal from market and household to the water body causes heavy pollution in rivers of Imphal Valley.     

Urban Rainwater Utilization and its Role in Mitigating Urban Waterlogging Problems—A Case Study in Nanjing, China

With the acceleration of the urbanization process, urban waterlogging problems are becoming more and more serious in Nanjing, China. In order to mitigate the urban waterlogging problems, it is necessary to reduce surface runoff from the source by rainwater harvesting and utilization. An urban residential district with an area of 0.58?km² in Nanjing was selected as the study area. Based on a large-scale topographic map data and the long term rainfall data (1951?C2008), the types of underlying surfaces were classified. The potentiality of collectable rainwater and the possibility of runoff volume reduction were calculated. The results showed that exploitation of rainwater harvesting from rooftops and other underlying surfaces has high potential. The annual collectable rainwater is approximately 372,284?m³, 314,034?m³ and 275,180?m³ under different cumulative frequency of rainfall at 20?%, 50?% and 75?%, respectively. The total capacity of cisterns under assumptions of return period of rainfall and rainfall duration with 5?years and 20?min is 11,022?m³. The cistern??s capacity which is used for roof rainwater harvesting is 4,083?m³, the cistern capacity for per unit roof area (1?m²) is 0.0267?m³. The results of the feasibility analysis of setting up above-ground cisterns showed that 55?% of the total roof areas in the study area are available for setting up cisterns. In the three building types, 16?% of the commercial building??s roof areas and 77?% of that of the residential and the ??others?? buildings are available for setting up cisterns. Urban waterlogging problems can be effectively reduced through rainwater harvesting by 13.9?%, 30.2?% and 57.7?% of runoff volume reduction in three cases of the maximum daily rainfall (207.2?mm), the average annual maximum daily rainfall (95.5?mm) and the critical rainfall of rainstorm (50?mm).     

山地城市屋面雨水可利用量分析——以重庆市沙坪坝某片区为例

为定量评估山地城市屋面雨水可利用量,以重庆市沙坪坝某片区为例,分析了重庆市的降雨特征,利用改进的径流系数法定量评估了代表年屋面雨水可利用量,并分析了降雨特征对可利用量的影响;运用设计降雨量和设计暴雨强度两个指标相结合的方法确定了蓄水池规模,使其满足径流控制率和防洪减涝的要求。研究表明:在代表年降雨量为1 198.9、1 104.4和962.7 mm时,研究区域屋面雨水可利用量分别为267 951.8、247 421.3和198 917.9 m~3,雨水利用潜力较大,降雨量对可利用量的影响较大,而降雨强度对其影响很小;研究区域蓄水池总规模为9 312 m~3,屋面径流控制率达到86.4%,为山地城市雨水利用系统中蓄水池的规模设计提供了参考依据。     

Parameters Influencing the Sizing of Rainwater Tanks for Use in Houses

Rainwater harvesting has been studied in different countries as a way of easing water availability problems and reducing potable water demand in buildings. The most important factor relating to the efficiency of a rainwater system is the correct sizing of the rainwater tank. Therefore, the objective of this article is to assess the influence of rainfall, roof area, number of residents, potable water demand and rainwater demand on rainwater tank sizing. The analysis was performed by using computer simulation and by considering daily rainfall data for three cities located in the state of São Paulo, Brazil. The roof areas considered were 50, 100, 200 and 400 m²; the potable water demands were 50, 100, 150, 200, 250 and 300 l per capita per day; the rainwater demands were taken as a percentage of the potable water demand, i.e., 10% to 100% at increments of 10%; and the number of residents was two and four. Results indicated a wide variation of rainwater tank sizes for each city and also for each parameter. The main conclusion that can be made from the study is that rainwater tank sizing for houses must be performed for each specific situation, i.e., considering local rainfall, roof area, potable water demand, rainwater demand and number of residents. Therefore, sizing rainwater tanks according to local tradition is not recommended as it may incur low efficiency.     

Integration of seawater and grey water reuse to maximize alternative water resource for coastal areas: the case of the Hong Kong International Airport

Development, population growth and climate change have pressurized water stress in the world. Being an urbanized coastal city, Hong Kong has adopted a dual water supply system since the 1950s for seawater toilet flushing for 80% of its 7 million inhabitants. Despite its success in saving 750,000 m(3)/day of freshwater, the saline sewage (consisting of about 20-30% of seawater) appears to have sacrificed the urban water cycle in terms of wastewater reuse and recycling. Can seawater toilet flushing be applied without affecting the urban water cycle with respect to sustainable water resource management? To address this issue, we examined the entire urban water cycle and developed an innovative water resource management system by integrating freshwater, seawater and reclaimed grey water into a sustainable, low-freshwater demand, low-energy consumption, and low-cost triple water supply (TWS) system. The applicability of this novel system has been demonstrated at the Hong Kong International Airport which reduced 52% of its freshwater demand.     

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.     

Quality assessment of rooftop runoff and harvested rainwater from a building catchment

A major obstacle to the promotion of rainwater harvesting is chemical and microbiological concerns. To determine its suitability as an alternative water resource, water quality parameters such as pH, turbidity and metal ion concentrations and counted total coliform, Escherichia coli and heterotrophic bacteria were measured. It was observed that the stored rainwater had a neutral average pH and that its turbidity depended on the duration and intensity of the rainfall event. Metal concentrations were within the permissible limits specified in the Korea drinking water standard. In addition, counts of coliform, E. coli and heterotrophic bacteria were higher in the first flush 5 min after the start of the rainfall event. Principal component analysis and correlation analysis through 40 events in 2009 showed that the quality of stored rainwater depends on the conditions of the catchment and storage tank and the antecedent dry period.