Introduction
Irrigation with treated, poorly treated, diluted, and even raw domestic
wastewater is a widespread practice in urban and peri-urban areas in most
developing countries [1-3]. In some areas, driven by water droughts and
acute water scarcity, urban water reuse is rapidly becoming a necessity
[4-8]. Water scarcity is not the only driving force of this practice.
Nutrient recovery, water source reliability and proximity to (peri) urban
farmers, contributions to food and water security, improvements of the
livelihoods of poor farmers, and a range of environmental aspects are
also important incentives for water reuse [9-11]. Water reuse can also
help mitigate climate change impacts on crop yields and dwindling
water resources [12]. Landscape irrigation, groundwater recharge, and
industrial applications, among other activities, are also being performed
with treated wastewater [13-15].
Different types of water reuse have been identified. A common
classification defines wastewater irrigation as: i) direct, in which
wastewater is used as such in the field or ii) indirect, in which wastewater
is first discharged into a water body from which water is later taken
for irrigation [16]. Wastewater irrigation can also be planned or
unplanned, also referred to as formal or informal, depending on the
irrigation infrastructure available, the degree of social acceptance, and
the level of control from state agencies [5]. Terms such as “recycled”
or “reclaimed” wastewater usually refer to fully or partially treated
wastewater (not to raw wastewater) [17].
The terms “domestic wastewater” and “sewage” will be used as synonyms
in this paper [18]. Wastewater from households and buildings connected
to sewerage systems is the main contributor to domestic wastewater, but
raw or treated discharges from industries and urban runoff can also make
significant and usually non-defined contributions. Urban water supplies
ensure the constant availability of wastewater, since the fraction of noncollected
domestic and residential water is only 15 to 25% and the rest
returns to urban water systems [3]. There are several technological options
for sewage treatment, ranging from traditional waste stabilization ponds
(WSP) and conventional aerobic systems (like trickling filters or activated
sludge), to high-rate anaerobic reactors such as the up flow anaerobic
sludge blanket (UASB) reactor and other, more complex integrated
systems [19,20]. A detailed description of these systems is out of the scope
of this paper. Suffice to say here that the feasibility of water reuse is highly
dependent on the type of wastewater treatment system applied.
Since almost 70% of all domestic wastewater generated globally is
released untreated into the environment, of which about 90% in developing
countries [1,21], it is not surprising that most direct reuse activities are
performed with raw wastewater. This is critical to assess the feasibility of
water reuse, since wastewater flow rate and composition vary from place
to place with respect to availability. Water reuse is also dependent on
economic aspects, social behaviour, local industries, climatic conditions,
and water consumption, among other factors [20,22]. The main pollutants
in sewage are: (a) suspended solids; (b) soluble organic compounds; (c)
(in) organic nutrients and (d) pathogenic microorganisms. The types
of pathogens, for example, are markedly different in industrialized and
developing countries [23]. The same could be said of the concentration
of a variety of chemicals like heavy metals, trace elements, detergents,
solvents, pesticides, and other compounds like pharmaceuticals,
antibiotics, and hormones, which can make wastewater unsuitable for
irrigation. Wastewater treatment systems are usually selected in terms
of technical and economic criteria, such as removal efficiency of specific
pollutants, construction costs, but rarely based on their appropriateness
for potential reuse [24-28]. Yet, recycling and reuse affect the entire “water
chain”, from supply to final disposal [5]. Therefore, these practices will
necessarily influence the way we design, build, and operate water and
sanitation infrastructure. They will also impose new challenges on existing
institutions, government policies, and current modes of water governance
[29,30]. To cope with this situation, most water institutions need to adapt
and incorporate new management concepts [31]. Among these concepts,
we should also mention a variety of alternative non-treatment options that
could be part of water reuse schemes as long as risks are appropriately
assessed and addressed [10,32].
Even though activities related to wastewater reclamation, recycling, and
reuse have been traced back many centuries, the development of programs
for the planned use of wastewater only took impulse in the late 19th and
early 20th centuries [16,33-36]. With the rapid rise of sewage systems in
the second half of the 1800s, “sewage farms” became a common method
of wastewater treatment and disposal in Europe, North America, and
Australia [37]. In most cases, wastewater disposal was the main purpose
and agricultural benefits were incidental [21]. In fact, the first wastewater
treatment process applied on a large scale at that time was land treatment
[38]. Urban development in the early 1900s and some health problems
derived of this practice resulted in the loss of interest and abandoning of
almost all sewage farm projects [37]. Since the 1950s, wastewater for irrigation
use has had a significant increase, especially in water-stressed areas [27].
Over the recent decades, important advances in wastewater treatment
technologies have been made, while the amount of regulations and
guidelines for water reuse have also increased in several countries.
However, information regarding wastewater generation, treatment
and reuse is often unavailable, incomplete, limited, or outdated [39].
Moreover, official and unofficial estimates of the areas under wastewater
irrigation are largely different [40]. A recent effort to compile information
at country level was performed by Sato et al. [41]. They concluded that
only 55 out of 181 countries surveyed had data available on wastewater
production, treatment and reuse. As pointed out by Jiménez and Asano
[15], two issues affect the collection of accurate information: (a) water
reuse is measured in different ways in each country, such as total volume
reused and reuse per capita; and (b) a country totals hide locally-relevant
information. Some governments also fear disclosing information as it
may have negative effects on exports or imports [42]. In spite of these
constraints, it has been estimated that more than 20 million hectares are
irrigated worldwide with treated or untreated wastewater (around 10
percent of the total irrigated land), involving about 200 million farmers
and probably four out of five cities [15,43]. It is also believed that onetenth
of the world’s population consumes wastewater-irrigated crops [44].
Planned or unplanned water reuse has been well documented in
Europe [13,14,45], Africa [46,47] North America [48,49], Asia [50,51],
and Oceania [52,53]. Additional efforts are needed in other regions, in
order to obtain a more clear picture of the development of this practice,
especially since the new Sustainable Development Goals (SDGs) stated
by the United Nations aim to significantly increase the percentage of
recycling and safe water reuse by 2030 [54]. Water reuse is receiving
increasing attention worldwide and additional research efforts in this
area are highly needed [55].
In this paper we provide an overview of some developments in the field
of water reuse in agriculture, with a special focus on Latin America, where
this practice is rapidly growing and where an extra effort is needed to assess
and standardize it. This paper is not meant to be a totally comprehensive
review. It is rather an attempt to highlight the main features of water reuse,
contribute to the ongoing debate about its advantages and disadvantages,
and promote a wiser and safer use of all available water resources. We will
briefly discuss some of the technical, social, environmental, and political
aspects of this practice. This paper draws from published and unpublished
reports, regional travels, and personal communication with scholars and
practitioners in this field.
Benefits and Risks of Wastewater Irrigation
According to Keraita et al. [2], the main advantages of domestic water
reuse are: (a) provision of nutrients; (b) reliability in water supply; (c)
contribution to the urban food supply; (d) income generation; and (e)
livelihood sustenance. These aspects are especially important for smallscale
farmers who can obtain enhanced water and food security by
using recycled or even raw wastewater for irrigation [56,57]. From an
environmental point of view, the use of a new source of irrigation water
will impact positively on the overall water balance and will slightly reduce
the water “footprint” of agriculture [58], although the impact is merely
near urban areas. Water reuse can also contribute to the generation of
renewable energy through the irrigation of energy crops [59]. The use of
reclaimed wastewater is also said to compete well with desalinated water
in countries like Saudi Arabia [60] and with the costs of transporting
freshwater for domestic purposes from distant locations in Namibia [61].
Beyond some of the intangible benefits that can be difficult to assess, water
reuse can also generate economic profits [62-64].
On the other hand, commonly cited disadvantages of water reuse are
mainly environmental impacts and health risks [2]. These drawbacks are
mostly associated with the uncontrolled use of wastewater that promotes
the spread of excreta-related pathogens, chemicals, and other undesirable
constituents [65]. Negative effects frequently reported in soils are
salinization, sodification, and accumulation of heavy metals and various
unknown compounds that can negatively affect agricultural production
in the long run [66]. Some studies address the influence that wastewater
irrigation can have on the soil microbial community [67-69].
Sewage contains a variety of different organisms that can survive
wastewater treatment including bacteria, protozoa, helminths, and
viruses, which concentration vary depending, among other factors, on
the sanitary status of the population [10,70]. Exposure routes are mostly
contact with wastewater (farmers, field workers, and nearby communities)
and consumption of wastewater-grown produce such as crops, meat, and
milk (general consumers) [23]. Most pathogenic organisms are capable
of remaining in the environment (in the wastewater, on the crops, or in
the soil) long enough to be transmitted to humans [71]. Survival periods
vary from a few days up to one year for the extremely resistant helminth
eggs [10]. That is why helminthiases (infestation with parasitic worms)
are recognized as the greatest health risk of the use of wastewater for
irrigation [10,42]. The most common helminthiasis is ascariasis, which is
endemic in Latin America, Africa, and the Far East [42]. Other diseases
related to the use of wastewater include cholera, typhoid fever, shigellosis,
gastric ulcers, giardiasis, amebiasis, and skin problems [72]. Negative
health impacts from the use of raw or poorly treated wastewater have been
documented in many studies [23,37,72-75]. Biological health risks have a
rather immediate outcome whereas chemical risks are translated into timedelayed
illnesses, such as chronic toxic effects or different types of cancer
[10,76]. Secondary risks may also arise from the creation of habitats that
facilitate the survival and breeding of vectors and a subsequent increase
in the transmission of vector-borne diseases in irrigated areas [32,77,78].
Since the publication of the World Health Organization guidelines for
the microbiological quality of treated wastewater used in agriculture
[79], health risks have been investigated through epidemiological studies
[72] but also by applying Quantitative Microbial Risk Analysis (QMRA).
The latter approach has been broadly used to establish health risks
associated with water reuse in developed and developing countries under
different scenarios, including unrestricted and restricted crop irrigation
[80-85]. The presence of endocrine disruptors and pharmaceutical
products in wastewater is also an emerging concern, despite the fact
that risk assessment is difficult for these compounds [65,86]. Shuval [87]
highlighted the potential risk for infectious diseases in animals grazing
sewage-irrigated pastures. However, it has also been reported that, in
some cases, animals exposed to high loads of pathogens in wastewaterirrigated
forage crops show no symptoms of infection [88].
All in all, it seems clear that the benefits and risks of wastewater irrigation
need to be assessed on a site-specific basis, since the characteristics of the
wastewater are highly dependent on local circumstances, and so is the
vulnerability of both the environment and the society in which water
reuse is practiced. This is particularly sensitive in the case of health risks,
which should not be considered in isolation but addressed in the general
context of water supply and sanitation [89,90].
Social, Cultural, Institutional, and Political Aspects
Water reuse often raises public concern [91,92], especially because of the
existence of real or perceived health and environmental risks. Therefore,
the social acceptance of this practice becomes particularly important
[93-95]. Varying degrees of public reluctance to reuse water have been
reported [96]. Willingness to use (treated) wastewater in agriculture and
willingness to pay for crops grown with recycled water depend on several
underlying factors such as awareness of present or future water scarcity
[97], educational level [93,98], costs and benefits [99], magnitude of [real
or perceived] health risks [65], aesthetic attributes of the water [100], and
even religious issues [98,101].
Direct or indirect potable reuse, which can be achieved via methods
such as aquifer storage and other types of reservoir augmentation
[102], usually face strong opposition due to the increased likelihood of
human contact with wastewater, the so-called “yuck factor” [92,103,104].
However, as suggested by Ching and Yu [105], the social construction
of water reuse by the mass media, in other words the way in which the
media portrays, positively or negatively, the “yuck” factor, might be even
more significant than public opinion itself. Therefore, despite the fact
that public acceptance (or rejection) of reclaimed water has often been a
critical factor for the feasibility of several projects [13,14], public opinion
can be reshaped when governments take an active role in communicating
accurate scientific facts and making a persuasive case for water reuse
initiatives [105]. A remarkable example in this respect is the government of
Singapore, who started a positive oriented campaign on water reuse in the
public debate. Very carefully, the word “wastewater” has been abandoned
and replaced by “used water” in all communications. Moreover, all
“wastewater treatment plants” were renamed “water reclamation plants”.
This communicative strategy was part of the master plan to close the water
balance deficit in Singapore upgrading the urban wastewaters to drinking
water quality. The process of social engagement also means opening the
decision making process to actors and stakeholders who have usually been
ignored or misrepresented in water and wastewater management systems,
such as farmers, NGOs, environmental advocacy groups, water and social
scientists, minorities, indigenous peoples, and consumers [102, 106-109]. It
is increasingly accepted that participation of relevant stakeholders is vital for
water reuse schemes to succeed [5,13,110,111]. This consideration guided
studies and surveys on the importance of stakeholders’ preferences and the
degree of public acceptance of different water reuse practices [112-114].
A suitable legal framework is indispensable to manage water reuse in an
integrated way, namely a way in which irrigation, fertilization, and disposal
receive equal attention [21,115,116]. Efforts to establish a minimum set
of conditions and regulations enabling the safe use of wastewater are
not new [16]. Yet at times, overly strict guidelines may not result in a
significant change on the background level of disease and they also tend
to be ignored because they are unachievable in practice [117]. There
are some examples of guidelines for water reuse [49], but the most
common standards in many countries, particularly developing ones,
have been influenced by the World Health Organization [10,79]. Some
studies have called for a more flexible legal framework, less worried
about issues of potential liability and more focused on the integral
analysis of the water chain [110,118]. An incremental approach for the
introduction of water quality standards is recommended, particularly
for countries with high levels of excreta-related diseases and deficient
wastewater treatment systems [10,119].
Water reuse also has inescapable political facets that are usually
overlooked behind discussions of risks, legal frameworks, and
environmental or economic issues. The notion that water, and thus also
wastewater, are merely “resources” (or even “commodities”) fails to take
into account the deep social and cultural meaning of water management
in favour of a homogeneous, rationalized, and materialist perspective. As
indicated by Schmidt and Shrubsole [120], context- and place-specific
characteristics make water and wastewater management highly political
and call for modes of governance adapted to local circumstances in order
to avoid ecological and cultural violence. This discussion is central to
the search for new ways to manage water and sanitation in the future,
including water reuse, as it promotes an open and place-specific array of
possible alternatives instead of advocating for universal solutions [121].
Central to the political nature of water reuse is the fact that this activity
has traditionally been in the domain of small-scale farmers in poor and
often marginalized communities. Even though the initial motivation for
water use is usually the lack of alternative water sources, farmers rapidly
recognized additional benefits, such as availability of nutrients, low
salinity levels, a constant water provision, and reduced transport lines/
closeness to food markets. Issues of scale, income, and power relationships
are therefore relevant, when assessing and promoting the agricultural use
of (treated) wastewater, especially in the current context of increasing
“co modification”, regulation, and eventual privatization of water and
wastewater [122,123]. It has been indicated that lack of political will has
often hindered the adoption and formalization of water reuse practices
[31]. Yet allowing or formalizing the use of wastewater for agriculture
can affect the rights of poor farmers who had been informally using raw
wastewater for irrigation for a long time [124-127].
The Situation in Latin America
The need for municipal water reuse in Latin America was acknowledged
long ago [128]. Several countries in this region report large areas irrigated
with both treated and untreated wastewater [15,129]. Cities such as
Lima (Peru), Mexico D.F. (Mexico), and Santiago (Chile) have been
practicing wastewater irrigation for years [130]. In Mendoza (Argentina),
planned water reuse started in the 1990s after several decades of informal
wastewater irrigation [131,132]. A regional inventory indicated that the
area irrigated with (almost untreated) sewage amounts to more than 1.5
million hectares [133]. Figures are not completely reliable, since only 9
out of 32 countries in Latin America have updated information relating
to wastewater production, treatment, and reuse [41]. Some attempts
have been made in order to develop policies and strategies for safe water
use in the region. In Bolivia, for example, a recent survey reports 111
different reuse experiences [134]. Some of the authors of this paper are
also involved in a number of projects to reuse the domestic wastewater
produced in Tarija, one of the main Bolivian cities, for the irrigation of
vineyards and other crops. Such experiences or projects have not yet made
it to scientific journals or international databases, but are increasingly
being discussed in regional workshops and reported in local media,
raising the awareness of governments and producers with respect to
the issue of wastewater irrigation.
A summary of wastewater irrigation practices in ten countries of the
region is shown in Table 1. As we can see in this table, a wide variety of
vegetables are being produced with wastewater-irrigated agriculture in the
region, fostering better food security, but since most reuse is performed
with untreated wastewater, some concerns have been raised about the
safety of current practices. Different wastewater treatment systems are
used in the region to treat domestic wastewater, as indicated in Table 1.
Even though municipal water reuse is probably being carried out in all
Latin American countries, not all cases have been reported in readily
available documents such as journals or congress proceedings. Therefore,
the information in Table 1 should not be seen as a comprehensive account
of the extent of agricultural use of (treated) wastewater in the region.
In most Latin American countries, lack of enabling legislation, deficits
in sanitation infrastructure and weak government institutions support
unplanned and informal reuse schemes, intensifying the negative effects
of the practice [129]. As a consequence, the use of untreated or diluted
sewage for crop irrigation is a widespread practice, as indicated in Table
1. In the valley of Cochabamba (Bolivia), for example, the Rocha River is
a large recipient of untreated wastewater used downstream for irrigation
[145]. Similar situations have been documented in the surroundings
of Santiago, Chile [136], and in Brazil [146]. Treated wastewater is
increasingly being used in some coastal cities of the Argentinian
Patagonia to irrigate trees, public spaces, and golf courses [147,148]. In the
North of Argentina, vineyards and other crops have been irrigated with
poorly treated wastewater for over 40 years [149,150]. The Dominican
Republic, Ecuador, Guatemala, and Nicaragua report a small number of
direct reuse schemes [133,138,141]. In Colombia, in spite of its abundant
water resources, irrigation with treated or untreated sewage represents
almost 37% of the total irrigated area [151,152]. Water scarcity is the main
driver for water reuse in dry areas of Mexico and Peru [49]. It can be said
that wastewater from almost all Mexican cities with a sewerage system
is currently being used in agriculture despite the fact that only a small
percentage receives treatment prior to discharge [129]. The Mezquital
Valley, receiving wastewater from Mexico City, is probably the largest
and longest-standing wastewater use system worldwide. Given the health
problems and risks identified in this valley and other sites, a number of
wastewater treatment plants are now projected or under construction in
Mexico [56], particularly since the creation of Conagua (National Water
Commission) in 1989 [153]. Contrary to other Latin America countries,
Mexican farmers seem to have a rather positive perception about
wastewater irrigation [15,153]. In many Caribbean islands, including Cuba
and the Dominican Republic, wastewater is commonly reclaimed in hotels
for gardening and/or irrigating urban green spaces [139,152]. In the case
of Cuba, indirect reuse is also performed for sugar cane irrigation [154].
In Brazil, water reuse also involves a variety of industrial applications such
as cooling processes, cleaning of public spaces, and car washing [146]. In this
country, some technical, economic, and environmental studies were carried
out in order to standardize the practice of wastewater irrigation [155].
Future Challenges and Concluding remarks
Despite widespread irrigation with raw or treated wastewater, a number
of technical, economic, social, regulatory, and institutional challenges
remain. In this section we will sketch a number of issues that deserve
special attention or further research. These remarks are mostly based
on the Latin American context, but may also apply to other cultural
and geographical settings.
Before a wastewater irrigation scheme can be proposed or upgraded,
local and regional practices related to sanitation, wastewater management,
agriculture, irrigation, and wastewater use need to be carefully documented.
Ideally, such an inventory should combine literature retrieval, collection of
field data, and interviews with local policy makers, farmers, and scholars.
Wastewater treatment systems that are appropriate to local conditions
and suitable for ulterior irrigation must also be identified, adapted,
and promoted by local water companies and practitioners. Additional
efforts have to be made to combine wastewater collection, transport and
treatment with the storage facilities and distribution networks needed
for irrigation with treated wastewater. To optimize the use of resources,
wastewater treatment systems have to be flexible in the removal of
nutrients according to local agricultural demands. Irrigation and water
management techniques have to be adaptable to multiple water sources
including (treated) wastewater. These techniques and other agricultural
practices will be most sustainable if they are locally designed in order
to minimize negative effects caused by, for instance, surface runoff
and seepage. The feasibility of non-treatment options should also be
considered by means of site-specific risk assessments. Irrigation strategies
and technological innovations developed by local farmers have to be taken
into account, since they are often useful to increase or maintain yields and
minimize health risks [2].
For each particular case, the area that would be suitable for irrigation
with domestic wastewater needs to be determined by carrying out a
feasibility study. As described in [156,157]; such suitability study could
involve the next steps: i) the selection of criteria and variables that allow
or constrain wastewater irrigation, ii) the establishment of suitability
thresholds for the variables selected, iii) the quantification of wastewater
availability, iv) a preliminary estimation of crop requirements, v) a spatial
representation of the variables using Geographic Information Systems
(GIS) tools, and vi) the construction of suitability maps. The latter maps
can give a quick idea of the areas that are suitable for wastewater irrigation
and can help decision makers to allocate resources to promote this activity.
Several feasibility studies following this or similar approaches have been
reported [156,158,159]. Variables for the selection of appropriate sites
might include type of soil, slope, crops, and the distance to wastewater
sources, vulnerable sites and urban areas, among others.
A local assessment of the environmental and health impacts of
wastewater irrigation is also required. Past experiences are paramount in
this respect. For instance, the effects on human health and food chains of
micro pollutants (e.g. endocrine disrupting agents) are largely unknown
and therefore rarely included in guidelines for the use of adequately treated
wastewater. The more understanding about the risks posed by pathogens,
the greater the confidence the public will have in wastewater use [160].
Since major public health problems are related to pathogens, developing
reliable procedures to screen them is essential for an appropriate risk
assessment [161] and also to establish regulations [10]. Current methods
for the detection of pathogenic viruses, bacteria, protozoa and helminthes
tend to be inaccurate, time-consuming and difficult [24,161]. Culturebased
E. coli detection methods, for example, proved to be insufficient
in differentiating between pathogenic and nonpathogenic strains [162].
As a result, molecular techniques, including DNA or RNA sequencing,
are been used to improve the detection, monitoring and track of specific
pathogens in order to understand outbreaks occurrences, forecast
transmission dynamics, and detect antibiotic-resistant bacteria, among
other objectives [163-165]. Microarrays (hybridization assay method) and
quantitative polymerase chain reaction (qPCR) are being used to detect
specific pathogens in wastewater [165-170]. Molecular techniques are
highly sensitive, relatively cheap in the long run, and significantly reduce
detection times [165]. Molecular detection tools (qPCR) and QMRA
modeling have been used to assess the risk of Salmonella infections
resulting from the consumption of edible crops irrigated with treated
wastewater [171]. Further research is needed to refine and standardize
some of these techniques in the field of wastewater assessment and (re)
use [165].
Figure 1: Wastewater irrigation practices in Latin America. WWTS: wastewater treatment system; ND: no data available; SP: stabilization ponds; IT:
Imhoff tank; AS: activated sludge; AP: aerated ponds; TF: trickling filters; UASB: up flow anaerobic sludge blanket reactors.
a Figures were rounded up to facilitate comparisons.
b WWTS typology from [135].
Further insight into the fate of chemicals in the soil system, plants, and
groundwater is needed. The possibility of an increase in soil salinity and
the special case of soil sodicity and alkalinity (which affects the availability
of a range of trace nutrients) is also an issue that requires further research.
Environmentally-safe dosages of nutrients needs to be identified for each
particular situation, since the processes affecting the bioavailability and
mobility in the soil-plant system of a number of chemical or biological
contaminants normally present in wastewater are largely unknown
and very likely site-specific. In order to maximize year-round nutrient
uptake, the crops and cropping systems also need to be carefully selected
according to the characteristics of each site [172].
The long-term economic implications of water reclamation and reuse
need to be elucidated on a site-specific basis. Economic analyses of the
entire water chain will help to understand its complexities and detect
options for improvement on the basis of efficiency analysis and sustainable
design. Some issues related to these analyses are incentive structures
for the actors along the chain, institutional and economic barriers for
optimal water management, information requirements, and the impacts
of alternative water management systems in the long run, including
discounting and analysis of irreversible impacts. Better assessments of
the economic benefits of the use of wastewater for agricultural irrigation,
including potential payments to agricultural producers for their
wastewater treatment services, will help convince producers and policy
makers of the importance of this practice.
In many places, the appropriate institutions required to manage
wastewater irrigation need to be created from scratch. The same goes for
enabling legislation. Regional laws focus mostly on specific wastewater
discharge standards, disregarding or even banning all reuse activities
altogether [49]. When reuse standards do exist, national legislation tends
to be based on guidelines proposed by the WHO [59]. In Argentina,
for example, only two provinces have regulations on water reuse and a
national law on the subject has been under discussion for years at the
national Parliament without a positive outcome so far [173]. Such federal
laws, however, are difficult to pass since water management has been
traditionally under the jurisdiction of provincial administrations. In some
countries such as Bolivia, the absence of specific legislation has been seen
as a constraint for water reuse [145]. However, as reported for Nicaragua,
overly strict legal frameworks can also be detrimental for the promotion of
this activity [142]. Some regulations only focus on microbiological aspects,
which are not enough to accurately assess the wastewater quality [71],
since they exclude indicators such as the content of helminth eggs [15].
The establishment of realistic, enforceable discharge and reuse standards
based on appropriate decision criteria is required to minimize health risks
and allow for the beneficial use of scarce resources. It is also necessary to
establish and/or strengthen mechanisms for monitoring standards, where
public agencies interact with farmers. The role of water user organizations
and other stakeholders in those institutions and in wastewater irrigation
schemes have to be properly established, while efficient mechanisms for
the dissemination of information on water quality have to be created. For
that purpose, the driving forces of farmers and institutions ought to be
clearly understood. Training of analytical staff is also necessary. Public
perception, social acceptance, and legal aspects of the use of (treated)
wastewater in irrigated agriculture also need further site-specific research.
It is important to highlight that farmers benefiting from informal reuse
schemes might lose their traditional rights once the practice is legalized
or formalized. To minimize water conflicts and guarantee water justice,
livelihoods depending on wastewater irrigation must be protected by
adequate laws, institutions, policies, and implementation mechanisms at
the local level. To that end, the impact of sewage treatment and reuse on
the social and economic status of farmers and consumers must be assessed
for each location. Because of the prospects of increasing water shortages
in the future, a new paradigm for water and sanitation management is
needed, based on the principles of sustainability and environmental
ethics. Although some efforts have been made worldwide to regulate
water reuse [49,174], developed and developing countries still need to
establish concrete policies and practices to encourage safe water reuse in
order to take advantage of all its potential benefits for the food supply and
livelihoods, while reducing health and environmental risks.