Potential impacts of on-site greywater reuse in landscape irrigation

This study investigated the effects of irrigation with different types of waters on soil, plants, and public health. The test plant was ryegrass grown in 12 planters filled with sandy loam soil and irrigated with three types of waters (4 planters for each type): freshwater, raw domestic light greywater (GW), and treated domestic light GW. The sodium adsorption ratio (SAR), EC, pH and alkalinity of the three types of irrigation waters did not differ significantly, suggesting that raw or treated light GW should not exhibit negative effects. Concentrations of anionic and cationic surfactants in the freshwater and the treated GW were about the same, while their concentrations in the raw GW were higher. Surfactant levels in the three drainage water types were low. Some accumulation of surfactants occurred in planters irrigated with raw and treated GW. The COD of the drainage water of planters irrigated with raw GW was higher than the COD of other two drainage water types. Although raw and treated GW contained faecal coliforms, they were hardly detected in the drainage waters. All plants did not show any signs of stress. This may be due to the fact that the GW originated mainly from showers and washbasins.     

Water reclamation, reuse and public health.

The number of people who have limited access to high-quality water has increased, and while this is a growing global crisis, water issues, problems and solutions are often seen as localised. Water reuse and reclamation will play a significant role in achieving sustainability and public health protection in the future. The wastewater and reuse community should be responsible for monitoring sewage impacts and improvements as demonstrated through pathogen reduction with appropriate treatment. Viruses, Cryptosporidium and Giardia can all be reduced during treatment anywhere from 99% to 99.9999%, achieving drinking water quality, if so desired. Recommendations to achieve better access to scientific information for decision making include: 1) developing a global data base for biological contaminant loading from wastewater and 2) defining the public health protection via reuse and reclamation.     

Role of irrigation and wastewater reuse: comparison of subsurface irrigation and furrow irrigation.

Two different irrigation systems, subsurface drip irrigation and furrow irrigation, are tested to investigate the level of viral contamination and survival when tertiary effluent is used in arid and semi-arid regions. The effluent was injected with bacteriophages of PRD1 and MS2. A greater number of PRD1 and MS2 were recovered from the lettuce in the subsurface drip-irrigated plots as compared to those in the furrow-irrigated plots. Shallow drip tape installation and preferential water paths through cracks on the soil surface appeared to be the main causes of high viral contamination in subsurface drip irrigation plots, which led to the direct contact of the lettuce stems with the irrigation water which penetrated the soil surface. The water use efficiency of the subsurface drip irrigation system was higher than that of the furrow irrigation system. Thus, subsurface drip irrigation is an efficient irrigation method for vegetable crops in arid and semi-arid regions if viral contamination can be reduced. Deeper installation of drip tapes, frequent irrigations, and timely harvests based on cumulative heat units may further reduce health risks by ensuring viral die-off under various field conditions.     

Water reuse for irrigation from waste water treatment plants with seasonal varied operation modes.

Irrigation periods are usually limited to vegetation periods. The quality requirements for treated wastewater for disposal and for reuse are different. The reuse of water for irrigation allows partly the reuse of the wastewater's nutrients (N and P). Outside the irrigation period the water must be treated for disposal, thus nutrient removal is often required in order to avoid detrimental effects on the receiving surface water body. Only wastewater treatment plants with different operation modes for different seasons can realise these requirements. The nitrification is the most sensitive biological process in the aerobic wastewater treatment process. At low water temperatures the nitrifying bacteria need several weeks to re-start full nitrification after periods without NH4-removal. Therefore it is necessary to develop options for waste water treatment plants which allow a fast re-start of the nitrification process. Based on theoretical considerations and computer simulations of the activated sludge treatment process, one possibility for implementing a wastewater treatment plant with different seasonal operation modes is evaluated.     

Semi-intensive treatment plants for wastewater reuse in irrigation.

Semi-intensive technologies are a middle term between intensive ones (e.g., activated sludge with a retention time of hours) and extensive ones (e.g., stabilization ponds with a retention time of several weeks). The most common semi-intensive configuration used in Israel is made of anaerobic ponds followed by aerated lagoons. These small low-energy units remove about 75-80% of the BOD and are followed by wastewater reservoirs for storage and complementary treatment. The reduction in loading allows a flexible operation of the reservoirs for the removal of other pollutants, while providing storage capacity to cope with the changes in water demand for irrigation during the year. In schemes for wastewater reuse in irrigation, this lay-out has proved to be low-cost, low-energy, flexible, reliable and efficient. Variations of this basic configuration are the use of UASB reactors instead of anaerobic ponds, aerated lagoons in series or low-rate trickling filters instead of aerated lagoons, constructed wetlands or rock-filters for algae removal, etc. Semi-intensive technologies use less energy than intensive ones, and less land than extensive ones. They can remove as much BOD as intensive ones, and as much pathogens and refractory pollutants as extensive ones. They release no or very small amounts of sludge.     

Hybrid membrane systems for secondary effluent polishing for unrestricted reuse for agricultural irrigation.

Field experiments are in progress for secondary wastewater upgrading for unrestricted utilization for agricultural irrigation. The integrative approach of secondary effluent polishing is based on using a hybrid UltraFiltration (UF) and Reverse Osmosis (RO) membrane pilot system with a capacity of around 1 m3/hr. The UF effluent is used to feed the RO membranes. The RO permeate is subsequently applied for vegetable irrigation. Field results indicate the importance of the UF component in the removal of the organic matter and the pathogens that are still contained in the secondary effluent. Under specific conditions, when the dissolved solids content is relatively low, regarding sanitary and health aspects, the UF effluent can be applied for unrestricted irrigation. During the RO stage most nutrients are removed, allowing application of the effluent without jeopardizing the soil fertility and the aquifers. Preliminary economic assessment indicates that the extra cost for effluent polishing via the UF stage only is in the range of 5 to 15 US cents/m3. The extra cost for the RO stage is also assessed at 10 to 25 US cents/m3. The additional cost depends to a large extent on the quality of the incoming raw secondary effluent and local requirements of the command region.     

E. coli transport in soil columns: implications for reuse of treated wastewater in irrigation.

Reuse of treated wastewater in irrigation is gaining recognition as a vital element in the water resources management plan of developing countries, especially those situated in arid and semi-arid regions. An understanding of the transport of residual pollutants from treated wastewater, such as bacteria, in soil as a result of irrigation is critical to assessing health risks and the possible contamination of limited groundwater resources. In this work, retention of E. coli is evaluated for a soil that is irrigated by treated wastewater for growth of non-food crops near Egypt's Red Sea coast. In particular, the effects of soil organic fraction (SOF) and hydraulic loading rate (HLR) were investigated in laboratory soil columns. The matrix of experiments included three HLRs and three SOFs. The retention of bacteria by adsorption was observed at HLRs of 5 and 13 cm/h, with the magnitude of the adsorption increasing proportionally to the SOF. The impact of SOF was greater for the lower HLR. At the lowest HLR investigated (5 cm/h), filtration was also observed for the two higher SOFs (0.674 and 2.04 per cent). At a high HLR (66 cm/h) simulating flood irrigation, retention of bacteria was minimal regardless of the SOF. Since the bacterial solution is applied to a dry soil column to simulate field conditions, E. coli breakthrough after two pore volumes of throughput (vs. one) provided a meaningful comparison of bacterial retention as a function of HLR and SOF.     

城市绿地的喷灌设计简介

从园林角度出发 ,介绍城市绿地喷灌系统的组成 ,喷头种类和应用范围。根据绿地灌水量 ,灌水周期 ,喷头布置形式以及喷灌制度等 ,确定了喷灌管道的水力计算设计步骤 ,达到节水灌溉的目的 ,并能形成良好的景观效果     

Analysis of treated wastewater reuse potential for irrigation in Sicily

In Mediterranean countries, water shortage is becoming a problem of high concern affecting the local economy, mostly based on agriculture. The problem is not only the scarcity of water in terms of average per capita, but the high cost to make water available at the right place, at the right time with the required quality. In these cases, an integrated approach for water resources management including wastewater is required. The management should also include treated wastewater (TWW) reclamation and reuse, especially for agricultural irrigation. In Italy, TWW reuse is regulated by a quite restrictive approach (Ministry Decree, M.D. 185/03), especially for some chemical compounds and microbiological parameters. The aim of the paper is the evaluation of TWW reuse potential in Sicily. A Geographic Information System (GIS) was built at regional level to quantify and locate the available TWW volumes. In particular, the characteristics of wastewater treatment plants (WWTPs) were integrated, through the GIS, with data on irrigation district areas. Moreover, in order to evaluate the Italian approach for reuse practice in agriculture, the water quality of different TWW effluents was analysed on the basis of both the Italian standards and the WHO guidelines.     

Technical and sanitary aspects of wastewater disinfection by UV irradiation for landscape irrigation.

Water reuse for landscape irrigation requires the production of high quality virus-free effluents to minimize risk for human health. In order to establish the relevance of MS2 phages as an appropriate biodosimeter for UV design, a pilot plant study has been carried out with different types of wastewater effluents. The two pilot systems tested (low-pressure high output and medium-pressure UV units) were able to achieve 4 and 5 log MS2 reduction in tertiary filtered effluent at high calculated UV doses of 170 _ 10 and 300 mJ/cm2, respectively. UV disinfection was extremely efficient for MS2 inactivation in high quality effluents after reverse osmosis: detention times as low as one second and UV dose of 40 mJ/cm2 were sufficient to reach 5 log inactivation of MS2. UV irradiation also produced rapid inactivation of human pathogens such as poliovirus type 1 and indigenous enteroviruses at UV doses up to 3 times lower that those for MS2 disinfection. It was concluded that accurate UV unit design for a given type of wastewater could be ensured by pilot tests using laboratory-propagated MS2 as biodosimeter and collimated-beam tests as the calibration-check.     

城镇污水处理厂出水作为河道景观用水的探讨

一些观点认为按照现行的《城镇污水处理厂污染物排放标准》(GB 18918—2002),污水处理厂出水达到了一级A标准后就可以作为河道景观用水, 笔者以为,应根据当地情况具体分析,例如在江南平原河网地区,未必可行。     

再生水用于绿化灌溉的健康风险评价研究

以北京市某再生水利用工程为例,用健康风险评价的方法,对再生水用于公园绿化灌溉时接触人群的暴露水平和健康风险进行了系统研究,建立了再生水用于公园绿化灌溉的健康风险评价模型,提出了再生水对职业人员和公众的暴露参数,对再生水中氯仿等19种主要污染物的健康风险进行了定量评价.结果表明:职业人群致癌的总危险度为3.91×10-6;非职业人群致癌的总危险度中青年和老年分别为2.12×10-6、1. 27×10-6,均小于可接受健康危险水平10.     

谈城市杂用水的应用与《城市污水再生利用城市杂用水水质》国家标准的修订

国家标准《城市污水再生利用城市杂用水水质》(GB/T 18920-2020)于2021年2月1日正式实施,这一标准是对GB/T 18921-2002的修订,贯彻和响应了国家政策,可促进循环经济和水资源的保护和有效利用.介绍了标准修订的原则和标准的核心内容,重点讨论了在国内外污水再生利用特别是城市杂用水的应用情况和相关标...     

Grey water characterisation and its impact on the selection and operation of technologies for urban reuse.

Characterisation of grey water reveals a source water that is similar in organic strength to a low-medium strength municipal sewage influent but with physical and biodegradability characteristics similar to a tertiary treated effluent. The characteristics of the water suggest biological processes are the most suitable unit processes for treating grey water. The highly variable nature of the source requires that selected technologies must be inherently robust in their operation. One potential area of concern is the high COD/BOD ratio and nutrient deficiency in terms of both macro and micro nutrients which grey water exhibits potentially retard the efficacy of biological processes.     

Centralised urban wastewater reuse: what is the public attitude?

Public support is crucial for successful implementation of wastewater reuse projects. This paper analyses the findings of a questionnaire-type survey (256 participants) conducted to determine the attitude of Israeli urban public towards possible urban reuse options. The paper summarises the support/objection to 13 reuse options and the correlation between support and environmental awareness and perceptions. Results show that a high proportion of the participants supported options perceived as low-contact, such as irrigation of public parks (96%), sidewalk landscaping (95%) and use in the construction industry (94%), while higher-contact reuse options found less support (e.g. commercial launderettes, 60%). No correlation was found between biographical characteristics and support (education, gender, income, age). Based on the results, public campaigns in Israel should focus on disseminating information regarding wastewater treatment technologies, discuss health related issues, highlight the positive economic impact of water reuse and generate a positive public opinion, as these factors tend to influence individuals to support reuse projects.     

Screening health risk assessment of micropullutants for indirect potable reuse schemes: a three-tiered approach.

Indirect potable reuse schemes are an important consideration in the sustainable management of scarce water resources. However, communities still hold real concerns about the potential health risks of micropullutants in recycled water entering their potable water supply. Microfiltration or ultrafiltration followed by reverse osmosis is currently the standard treatment technology for potable use of recycled water. Nevertheless, membranes are not 100% efficient in the removal of trace organic contaminants and the potential health risks of these micropullutants need to be assessed. The aim of this paper is to present a three-tiered approach for the preliminary assessment of micropullutants in recycled water. A risk quotient is calculated by comparing measured concentrations against benchmark values. Tier 1 corresponds to regulated chemicals; the maximum contaminant level in drinking water is used as benchmark value. Tier 2 corresponds to unregulated chemicals with toxicity information; slope factors or risk specific doses are used to calculate benchmark values. Tier 3 corresponds to unregulated chemicals without toxicity information. The "Threshold of Toxicological Concern" concept is used to calculate benchmark values. The characterization of chemicals of concern following reverse osmosis in a water reclamation plant and the application of the three-tiered approach for the evaluation of the potential health risks is presented.     

城市污水回用的系统动力学模型构建及应用——以常州市为例

利用SD理论构建了常州市污水回用系统模型,并选择常州市人口、GDP、城市工业总产值等主要变量进行了模拟分析。结果表明,利用SD模型进行系统仿真,模型模拟结果与实际数值拟合较好,模型具有很好的适用性,对常州市污水回用发展规划具有一定参考价值。     

再生水回用于景观水体存在的问题及防治对策

简要介绍国内外再生水的工程实例,并对再生水回用于景观水体进行了潜在风险的分析,包括水质、富营养化、安全性分析等。并结合工程实例提出了水质保障措施,如净化水质的生物、生态修复工程等,为再生水回用于景观水体的工程实施提出应完善水质标准,根据实际情况适当降低水体功能,因地制宜利用水质净化措施等建议。     

《水回用导则再生水厂水质管理》国家标准解读

面对再生水厂运营管理和水质保障需求,为适应再生水标准化工作需要,国家市场监督管理总局和国家标准化管理委员会于2021年首次发布了《水回用导则再生水厂水质管理》国家标准.该标准是《水回用导则》系列国家标准之一.针对目前再生水厂的水质管理缺乏统一标准,全流程水质风险识别与过程管控不健全等问题,该标准规定了再生水厂水质管理的...     

深圳特区城市中水道系统规划研究

在实现污水再生利用的诸多方式之中,城市中水道是实现污水回用的适宜工程系统,是城市供排水走向水健康循环利用的桥梁。介绍了深圳特区城市中水道系统规划,规划特区中水道供水能力2005年达22万m3/d,2010年为49万m3/d。届时将大幅度缓解水资源不足的压力,显著改善特区水环境。