Water Reuse
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Water Reuse
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Overview
The second section refers to the “stakeholders” point of view. Each reuse purpose demands different water quality, not only to protect health and the environment but also to fulfil the requirements of the specific reuse. Reuses considered are agricultural, urban agriculture as a special case of the former, municipal and industrial. Alongside these uses, the indirect reuse for human consumption through aquifer recharge is also discussed. The third section deals with emerging and controversial topics. Ethical and economical dilemmas in the field are presented as a subject not frequently addressed in this field. The role of governments in respect of public policy in reuse is discussed as well as the different international criteria and standards for reusing wastewater. The importance of public acceptance and the way to properly handle it is also considered.
The fourth section of the book presents contrasting case studies; typical situations in the developed world (Japan and Germany) are compared to those in developing countries (Pakistan and Brazil) for agricultural and industrial reuse. Indirect planned reuse for human consumption (Germany) is compared with an unplanned one (Mexico). The Windhoek, Namibia case study is presented to emphasize why if the direct reuse of wastewater for human consumption has been performed with success for more than 35 years it is still the only example of this type around the world. To illustrate the difficulties of having a common framework for regulating water reuse in several countries, the Mediterranean situation is described. Other case studies presented refer to the reuse situation in Israel, Spain, Cameroon, Nepal and Vietnam, these latter countries being located in water rich areas.
This book will be an invaluable information source for all those concerned with water reuse including water utility managers, wastewater policy makers and water resources planners as well as researchers and students in environmental engineering, water resources planning and sanitary engineering.
Scientific and Technical Report No. 20
Product Details
| ISBN-13: | 9781843390893 |
|---|---|
| Publisher: | IWA Publishing |
| Publication date: | 05/14/2008 |
| Series: | Scientific and Technical Report Series |
| Pages: | 650 |
| Product dimensions: | 6.12(w) x 9.25(h) x 0.75(d) |
Read an Excerpt
CHAPTER 1
Water reclamation and reuse around the world
Blanca Jiménez and Takashi Asano
INTRODUCTION
This chapter describes water reuse at a global level based on the findings contained in this book. It summarizes and compares the information considered in Chapters 2 to 9, which describe the situation in the Middle East and North Africa, the Northern Mediterranean, United States and Canada, Australia and New Zealand, Central Europe, Asia, Central and Southern Africa and Latin America and the Caribbean, with the aim of establishing general trends and main differences in the world. A preliminary survey was performed, from which the content and the structure of the book were defined. Regions were defined considering the need to assemble together countries which in principle would have similar reuse patterns produced by the social response to adapt to the local water availability. The regions with low water availability are considered first. From the beginning of the assessment, the need to have common definitions quickly became evident and these are therefore presented as the first part of this chapter. The comparison among the regions covers: (a) water availability, (b) the state of reuse around the world including an overview of the general situation per region; (c) the main drivers to reuse wastewater; (d) the list of the main countries reusing wastewater; and (e) the main objectives to reuse wastewater for agriculture, municipal and industrial uses.
1.2 DEFINITIONS
Technical terms used to describe reuse practices may have different meanings from country to country simply because they have been developed in parallel with water reclamation and reuse activities. The standardization of reuse terms is not an easy task because, in many cases, they have been incorporated into national legislations making it difficult to adopt new definitions. Thus for the purpose of this survey, the definitions used are presented in Table 1.1.
1.3 THRESHOLDS ON WATER AVAILABILITY
For a long time researchers have looked for an easy way of defining whether a region presents water scarcity problems or not. By analyzing the experience of moderately developed countries located in arid zones, different authors have identified different parameters for doing so, as presented in Table 1.2. These parameters do not represent absolute conditions but are indicative of different water stress situations where reuse can be or is an important activity.
The water availability per capita index only represents the potential usable water per person. Actually, water is used differently in each country depending on their economic activities, available water infrastructure and social patterns. Therefore, a complementary way to measure the extent of use of water within a region is the Water Intensity Use Index (WIUI), which expresses in percentage terms the relation between the amount of water used (extracted from the environment) and the total renewable water available for a region. It is considered that a value above 20% indicates water stress problems.
1.4.1 WORLD SITUATION
1.4.1 Water availability
At a global level, water availability for 2006 was 8,462 3/capita-yr but at a regional level it went from as little as 1,380 3/capita-yr in the Middle East and North Africa to almost 53,300 3/capita-yr in Oceania (see Table 1.3). These figures do not reflect the situation of individual countries (Annex 1 contains data at country level) or within a country. A list of the countries that are water scarce according to the water availability per capita index and the WIUI index are presented on Tables 1.4 and 1.5, respectively. Note that the list of countries change according to the index used. No country from Oceania, North America or South America is contained on this list although it is well known that for some of them, at a local level, water problems do exist, for example in Australia, United States and Mexico. In some cases WIUI values for some countries are even well above the threshold value of 20%, as is the case for Kuwait and the United Arab Emirates with a WIUI index above 2,000%. Even in regions with good water availability water problems may exist, as is the case, for instance, in Europe with 10,680 3/capita-yr where 11 countries out of 38 are under water stress conditions.
Water availability per capita in developed countries is 58% higher than that of developing ones, but water intensity use is similar in both groups. This means that if more water is used in the future in developing countries, for instance to produce more food to feed an increasing number of people, the Water Intensity Use index in some developing countries will be higher than in the developed countries.
At the present time it is estimated that around 700 million people (i.e. almost 11% of the total world population) in 43 countries live with less than 1000 3/capita-yr. By the year 2025, 38% of people (more than 3 billion) will live in such conditions, increasing the number to nearly half of the population and 149 countries by the year 2050 (UN, 2006). By that time, the Middle Eastern countries will be reaching the minimum water survival level of 100 3/capita-yr. According to Figure 1.1, the regions suffering the most will be North and South Africa, western Asia, the North China Plain, western and southern India, Pakistan, central and southern Mexico, the western coast of the United States, the Mediterranean region, and a large part of Australia. According to the IPCC (2007), climate change will be an additional factor that modifies water availability and could favour drought in regions already water scarce.
1.4.2. Water reuse
As result of water scarcity several countries are reusing wastewater. Figure 1.2 presents the countries reporting any type of reuse. At a regional level differences on reuse practices can be observed and are highlighted in Boxes 1.1 to 1.5 (below). Concerning reuse options, agriculture is by far the most important in terms of volume, simply because it is the activity that demands most water around the world. This reuse is expected to increase because the potential to reuse wastewater is still high (even agricultural reuse only represents <1% in volume of the total demand of water by the sector). The tendency to reuse wastewater is most common among those activities demanding the most water (Figure 1.3). The following examples illustrate this:
The tendency to reuse wastewater is most common among those activities demanding the most water (Figure 1.3). The following examples illustrate this:
(1) Pakistan and Tunisia, with a water use for agricultural purposes of 96% and 86% respectively, reuse a very large amount of their wastewater to irrigate (although in Pakistan it is non-treated wastewater while in Tunisia it is treated).
(2) Namibia and Singapore, which use 29% and 45% of total water extracted for municipal purposes respectively, are the two countries with the most important water for human consumption reclamation projects.
(3) Finally, the USA, Singapore and Germany, where 45%, 51% and 69% of water is used for industrial purposes respectively, have a large number of recycling and reuse projects across industries.
1.4.3 Main wastewater reuse drivers
Different factors (physical, economic, social and political) were detected during this survey as triggering mechanisms for water reuse, albeit with variations between developed and developing countries. The main factors are summarized in Table 1.6. The most important in terms of volume stem from the lack of water, a high level of local water demand and the need for reliable sources of water. The origin of these drivers may be physical (defined by the characteristics of the particular environment), social (arising from the public), economic, political or as a consequence of water management policies.
1.4.4 Main countries reusing wastewater
It is difficult to establish which are the main countries reusing wastewater for two reasons: (a) because reuse is measured differently in different countries (as the total volume reused, reuse per capita, as a percentage of total water use, or as a percentage of treated wastewater); and (b) total country values may hide the importance of reuse at local level. For instance, it is well known that California and Florida are important wastewater reusers, but total figures for the United States do not reflect this fact. Table 1.7 contains a classification of the countries reporting figures on wastewater (treated or not), reused based on different criteria. The numbers are uncertain especially where non-treated wastewater is involved, because censuses are rarely performed on un-planned practices, or figures are simply hidden for political and economic reasons. In total volume, China, Mexico and the United States are the countries with the largest quantity of wastewater reuse, but in the first two cases non-treated wastewater is involved, and for China the value reported is certainly underestimated considering the total number of hectares irrigated using non-treated wastewater reported in other references and shown in Figure 1.4. Also, the figure concerning the total reuse of wastewater somehow also reflects the size of the country. If the reuse per inhabitants is considered, Qatar, Israel and Kuwait are the countries highest ranked, while when reuse is considered as the percentage of the total water used, Kuwait, Israel and Singapore become the most important. Whichever way, these countrywide figures in most cases represent necessarily a mixture of the reuse situation in water rich and water poor areas within the same country.
Table 1.8 contains only data on reuse of treated wastewater. In total volume, United States, Saudi Arabia and Egypt are the most important countries, but when the amount of treated wastewater reuse per capita is considered, Qatar, Israel, and Kuwait are in the first three places; when reuse is expressed as a percentage of the total use Kuwait, Israel, and Singapore become the most important ones.
1.4.5 Agricultural reuse
Food production is a water intensive activity (76% of the total use given to water). Under prevailing land and water management practices a balanced diet represents a depleting water use of 1,300 m3/capita·yr, which is 70 times more than the 50 L/p day used for basic household water needs (SIWI-IMWI, 2006). Agriculture represents an important demand on water and, as a consequence, is the biggest reuser of wastewater in volume among all the different uses of water. Figure 1.4 contains the 20 countries reusing the greatest absolute quantities for agriculture and Figure 1.5 the 20 countries with the largest wastewater reuse per one million inhabitants; in both cases data for treated and non-treated wastewater are included. Even though the information used to construct Figures 1.4 and 1.5 is heterogeneous and incomplete it does give some appreciation of the relative importance of the reuse of nontreated wastewater. In several countries a dependency on the use of this kind of water has been created for many reasons (not only lack of water), and this needs to be understood to proper set measures to control negative effects whilst also preserving the positive. Annex 2 presents in detail the total data gathered during this survey for this type of reuse.
Irrigation is a key input for agriculture in developing countries1. Due to lack of sanitation, there are frequent examples of irrigation performed using wastewater in developing countries and not only in dry but in humid areas also. Although in most cases it occurs as an unintentional activity, with time it is becoming a recognized and increasing activity. The possibility of using wastewater is attractive to farmers for several reasons, such as its reliability, its low or zero cost and its nutrient content which increases crop production without adding artificial fertilizers (IMWI, 2003 and Jiménez and Garduño, 2001). Figures on the reuse of wastewater for irrigation are difficult to obtain, mostly due to economic penalties a country might suffer in trading its produce. However, it is estimated that at least 20,000,000 ha in 50 countries are irrigated with polluted water (United Nations, 2003), either directly or indirectly, and that 10% of the world's population consumes crops produced with wastewater (Smit and Nasr, 1992). The relative importance of this practice varies by country; in Hanoi, Vietnam, for instance, up to 80% of the vegetables consumed are produced with wastewater (Ensink et al., 2004b).
Data from some countries are presented in Figures 1.4 and 1.5 to provide an idea of the relative situation of the reuse of treated and non-treated wastewater in irrigation around the world.
Finally, Table 1.9 lists the reuse of wastewater in volume for different countries, considering here only treated wastewater.
The term "urban agriculture" has evolved to describe wastewater reuse in urban and periurban areas from developing countries in small sized parcels (0.5-2 ha) to produce fruit trees, fodder, flowers, and vegetables. Occasionally, it also involves a small amount of fish production. Urban agriculture is performed in arid and wet countries and stems from the combination of wastewater availability, demand for fresh produce by city dwellers and the presence of marginalized people (Cockram and Feldman, 1996). Generally it contributes to food security, improved nutrition and health, which in turn improves living standards (van der Hoek et al., 2001). In spite of improved nutrition and with its resistance to diseases, urban agriculture also causes diarrheic diseases. In order to control such diseases, low technology and affordable methods have been developed at local level. These methods preserve the beneficial properties of the wastewater, including its low or zero cost and the possibility of obtaining fertilizers "for free" while removing an important amount of pathogens (Jiménez, 2006). Unfortunately, these methods are poorly understood internationally, as well as having weak scientific recognition making their implementation difficult in different parts of the world (Ensink et al., 2004a; Jiménez and Garduño, 2001). Currently, there are several million farmers in developing countries practicing urban agriculture. It is estimated that 10-70 percent of people living in different cities depend on it and that up to 50 percent of the market vegetables in cities from Asia to Africa are being produced this way (Cornish and Lawrence, 2001 and IMWI, 2003). By the year 2025, it is estimated that there will be 292 cities in the world with more than 1 million people, most of them located in low-income countries (UN, 2006), and if sanitation and poor conditions are not improved, urban agriculture will increase, and with it the negative effects on public health. In short, the current risky unplanned approach to urban agriculture should and could be transformed into a planned approach to preserve its economic and social benefits while controlling the associated health issues.
1.4.6 Municipal reuse
In 20 years, 60 percent of the world's population will be living in cities (UN, 2006), thus: (a) more water will be needed for municipal use, and consequently (b) additional municipal wastewater will be produced, all in the same place and within a limited area. This situation represents both a risk and an opportunity to better use water, for example by increasing and diversifying municipal wastewater reuse. Opportunities to reuse wastewater in cities are classified into two groups: (a) those demanding relatively low quality water because they involve low health risks, and (b) those demanding high quality water because of their association with health risks. In the first group, there are several types of use, such as the filling of recreational lakes, car, truck or street washing and park irrigation. Among options demanding high water quality, reuse for drinking supply is included. There are successful experiences around the world of both types of reuse, the first group being the most common while the second, although less common, are no less important (particularly at a local level where the lack of water represents a serious barrier to the development of cities). Water reuse projects implemented for drinking supply have been thoroughly studied, are highly monitored and have wide social acceptance in countries such as Namibia and Singapore. But there are also some examples of planned projects that have never been implemented due to public rejection, as has occurred in specific areas of California (Seah, 2002) and in Australia (AASTE, 2004). It would be beneficial to spread information on successful cases in order to increase public acceptance of reused water; in fact, this should be done for any kind of reuse project.
(Continues…)
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Table of Contents
List of contributors, viii,
Introduction Blanca Jiménez and Takashi Asano, xiii,
Section 1: World Overview,
1 Water reclamation and reuse around the world Blanca Jiménez and Takashi Asano, 3,
2 Water reuse in Middle Eastern and North African countries Akiga Bahri, 27,
3 Water reuse in the Northern Mediterranean Region Marcelo Juanico and Miquel Salgot, 48,
4 Water reuse in the United States and Canada Kirsten Exall, Blanca Jiménez, Jiri Marsalek and Karl Schaefer, 68,
5 Water reuse in Australia and New Zealand John Anderson, Jim Bradley and John Radcliffe, 105,
6 Water reuse in Central Europe Peter Cornel and Alessandro Meda, 122,
7 Water reuse in Asia Naoyuki Funamizu, Xia Huang, Guan-Hao Chen, Hu Jiangyong, and Chettiyappan Visvanathan, 142,
8 Water reuse in Central and Southern Regions of Africa Frederik Schutte, 161,
9 Water reuse in Latin America and the Caribbean Blanca Jiménez, 177,
10 Section 2: Stakeholders point of views Water reuse practices for agriculture Valentina Lazarova and Akiga Bahri, 199,
11 Wastewater irrigation in urban agriculture Mark Redwood and Frans Huibers, 228,
12 Municipal water reuse John Anderson, 241,
13 Current practices of Wwater reuse in industry In S. Kim, Saravanamuthu Vigneswaran and Namjung Jang, 250,
14 Water reuse via aquifer recharge: intentional and unintentional practices Peter J. Dillon and Blanca Jiménez, 260,
15 Section 3 Emerging Topics Ethical dilemmas in water recycling Cheryl K. Davis, 281,
16 The economic dilemmas of water management and reuse Darla Hatton MacDonald and Wendy Proctor, 299,
17 Public policy and institutional capacity building: opportunities for innovation in recycling John C. Radcliffe, 316,
18 Public acceptance of water reuse John Anderson, Sue Baggett, Paul Jeffrey, Linda McPherson, June Marks, and Eric Rosenblum, 332,
19 Water reuse criteria: environmental and health risk based standards and guidelines Alan Godfree and Samuel Godfrey, 351,
20 Section 4: Study Cases Water reuse in Japan Naoyuki Funamizu, Takuya Onitsuka, and Shigeki Hatori, 373,
21 Livelihoods from wastewater: Water reuse in Faisalbad, Pakistan Jeroen H.J. Ensink, Wim van der Hoek and Robert W. Simmons, 387,