Treating wastewater for agricultural use is desirable, but the devil is in the details

Wastewater treatment is harmful because most experts are unfamiliar with new, existing technologies. Thanks to thermal desalination, considered a tertiary treatment but too expensive, it is possible to obtain desalinated water of very good quality. The question of costs must be taken into account. However, with Concentrating Solar Power technology, this cost is halved since there will be no phase change from the solar thermal station to the thermal desalination station.

It is important to issue new code for water reuse. The new technologies can treat the wastewater to be used safely in unrestricted irrigation. The new code should have different grades of water treatment, each grade can be appropriate for certain type of usage. Thanks for great efforts. Prof. Kamal Ghodeif - Egypt

In as much as wastewater reuse can ameliorate the high demand for irrigation, however, much still needs to be done, especially in developing countries to convince some traditional farmers on the need to reuse treated wastewater for irrigation purposes. The social acceptance of the use of treated wastewater for irrigation is very important, because without it, the acceptance of the produce obtained from such venture may not enjoy wide patronage in some localities.

Dear Nassif,
From your response, you didn't say every farmer and consumers of farm produce embrace the use of wastewater for irrigation purposes. This is a confirmation of the fact that there are exceptional cases. Studies have also indicated that irrigation with treated wastewater poses some potential risks to human health through the consumption or exposure to pathogenic microorganisms, heavy metals and harmful organic chemicals. These potential risks have led to the resistance by some persons on the use of wastewater for irrigation. A good example are some localities in southern part of Nigeria.

The post by Karim Eid-Sabbagh and Marie-Helene Nassif offers important cautions for the growing enthusiasm for treating urban wastewater and using the treated result for irrigation. There is no question but that the potential is large, but so too are concerns, and they are not only about the institutional ways that make the steps for gaining permission and establishing operations. They also stem from concerns related to the quality of the treated wastewater. Israel has long experience in treating and even desalinating treated wastewater, yet is still finding problems, as indicated by a recent article that found pharmaceuticals in edible crops irrigated with well-treated wastewater. (Ben Morechay et al. 2021, Pharmaceuticals in Edible Crops: Results of a Survey, J of Hazardous Materials, vol 416, 15 August 2021).

Well before this information, researchers had identified that soils irrigated repeatedly with treated waste wastewater became friable with lower and lower productivity per unit of water applied. The immediate approach was to desalinate the treated wastewater, which resolved the problem but at significant higher cost.(Shafran et al. 2004, Effects of Surfactants Originating from Reuse of Greywater, Proceedings of the IWA biannual meeting", Marrakech, Morocco).

Use of urban wastewater for irrigation has to be adopted if the world is to feed its increasing population, but the devil is in more than the details; it is also in the quality of the water applied in the irrigation of crops, and especially edible crops.

Hello I though I'd do a quick review to stimulate some more discussion. ...

In 2010, Drechsel Pay et al published a manual covering experience in Wastewater treatment and management. This made passing reference to a concern over antibiotic resistant genes/ (ARG) organisms. But more recently Zhao Yi et (2021) have said, in the context of waster treatment, "Although wastewater treatment is shown to be a promising technology for removing ARGs, developing countries are often lack of sufficient waste-water treatment or management for animal industries, thus the wastewater may directly be discharged to surrounding waterbodies (Gros et al., 2019). Moreover, the removal of ARGs can largely depending on the treatment technology. For example, in general farms, livestock wastewater is treated in a bioreactor through a constructed wetland without a full scale waste-water treatment. In contrast, ARGs are more efficiently removed in full scale wastewater treatment plants; and the inflow volume, the type of bio-logical treatments and the hydraulic residence time are all linked to the treatment efficiency, therefore influencing on the bacteria and ARG removal (Novo & Manaia, 2010). So a review is necessary.

In 2013, Liu Wei et al reported a High Rate of New Delhi Metallo-β-Lactamase 1–Producing Bacterial Infection in China.Then the New Delhi metallo-b-lactamase-1 gene was reported in Indonesia in 2015. Also in 2015, Mills et al. reported that "Intended water quality standards for 17α-ethinylestradiol (EE2), a synthetic oestrogen in oral contraceptives, set a much needed global precedent. Ozone and activated carbon provide effective wastewater treatments, but their energy intensities and capital/operating costs are formidable barriers to adoption. In tracing the fate of antibiotic resistance genes Zhai WC et al (2016) said "The total loads of ARGs discharged through dewatered sludge plus effluent was 1.01–14.09-fold higher than that in the raw influents, suggesting the proliferation of ARGs occurred in the waste-water treatment. The proliferation of ARGs mainly occurs in biological treatment process, such as aeration tank, an-oxic tank, sequencing batch reactor (SBR), and bio-contact oxidation, facilitates the proliferation of various ARGs, implying significant replication of certain ARG subtypes may be attributable to microbial growth. Chemical oxidation seems promising to remove ARGs,..."

In 2020, Ghernaout & Elboughdiri concluded that "Techniques have to be developed for cheap and reliable: first, bacterial clones and resistance genes origin tracking; second, detection of antibiotics in water mediums; third, disinfection of water from antibiotic-resistant populations and the resistance gene pool, and elimination of antibiotics from wastewater; and fourth, prevention policies for mixing human–animal-originated and soil–water bacteria. Lira et al (2020) reported on "Metagenomic analysis of an urban resistome before and after wastewater treatment" finding that "More recently, non-clinical environments (natural and man-made ecosystems) have been proposed to play a major role in the dissemination of AR. In particular man-made environments such as wastewater treatment plants (WWTPs) have received special attention. Within these ecosystems bacterial pathogens (several of them already carrying acquired ARGs), released within stools, coexist with different types of pollutants, including antibiotics and other selectors of AR 20 . This might make these environments highly relevant for the spread of AR. In allocations in which water is not usually treated, antibiotic resistant bacteria (ARB) can easily disseminate (for example through re-used water)"

In 2021, Kim et al "evaluated the efficacy of quantitative polymerase chain reaction (qPCR) to monitor several pertinent bacterial populations in 25 different full-scale wastewater treatment bioreactors across 9 different system designs. All the bioreactors contained a substantial quantity of total bacterial biomass and denitrifying bacteria, independent of system design. In contrast, the quantities of ammonia oxidizing bacteria (AOB) and phosphate accumulating organisms (PAOs) measured by qPCR targeting the amoA gene and the 16S rRNA genes, respectively, from the Candidatus Accumulibacter lineage significantly correlated with system design". However, previously mentioned biological contaminants were not reported on.

In reporting on "Egypt’s formal wastewater reuse sector" Tawfik et al. (2021) don't appear to recognize a need for monitoring the biological contaminants identified earlier.

I can send a zipped file with the references if you wish. best regards..

Reuse is often presented as "massive opportunity" (see for example Sadoff et al cited above) by large development agencies but given the complexities at all levels, from the administrative via the economic and social to the technical it seems unwise to oversell the potential.
Promising large gains and widespread benefits, which are unlikely to materialise in the short term or at all, as well as downplaying or not taking seriously such complex health concerns seems to carry the danger to disappoint, disencourage and discredit.
In the case of Lebanon (and probably elsewhere) a piecemeal approach appreciative of local socio-ecological setting could be a more prudent and encouraging approach to the promotion of reuse.

It is probably worth considering approaches aimed at controlling what enters wastewater streams in the first place. Plastics being on example where this discussion is at least already happening, ... such should probably be considered for the numerous other toxins and substance that enter waterstreams ... the discussion of ARG/ARMs certainly highlights the complexities involved...

Based on partial experience in France, I would like to make to make two additional points that may indeed bedevil the implementation of this ‘desirable’ solution.
* The consumer acceptability of the solution ; a survey of French inhabitants (who do not know anything about TWW) and of MSc students on Water Sciences in Montpellier suggests that 15-20% of consumers and students would stay away from products grown with treated wastewater (if they had the information); this reluctance is associated with doubts on 1) the innocuousness of TWW, 2) the trustworthiness of operators and their monitoring of water quality iii) yuk factor. This is a matter of high concern for producers of high quality products (such as wine, organic meat, etc)
* The point of view of farmers: TWW is not just an additional water source: it comes with many constraints: 1) technical limitations : generally very low waters discharges and quantity available 2) much more complexity for collective water management, with new asymmetries created between those who have access to this scarce TWW and those who don’t. 3) issues about the cost of treatment and who shoulders it at the end (full cost, cross-subsidies or not, etc), 4) very high vulnerability to failures and goodwill of the TWW distributor
The use of TWW is vigorously promoted nowadays in France & Europe as a solution to water scarcity. A hypothesis to be tested : One may wonder if the devilish ‘details’ of TWW reuse are not conveniently minimized, when not glossed over, because this technofix is seen and favored as a much less conflicting solution than the construction of reservoirs.

Thanks for this excellent blog post. I just wanted to add some findings from Thailand (from an article just published in Water Alternatives: https://www.water-alternatives.org/index.php/alldoc/articles/vol14/v14issue3/644-a14-3-7/file) which correspond to your findings in Lebanon. I found that many of the WWTPs are poorly operating. Last year a Thai NGO official told me that approximately 80% of wastewater treatment facilities were unusable or functioned poorly after they were constructed. Another Thai NGO official admitted to me: "Many municipalities borrowed money from the [central government’s] environmental fund to build wastewater treatment plants but did not operate these plants very well because they could not afford the electricity costs. This is because they did not include this cost in their budgets. When they set their budget, they always request funding for hard equipment for construction, but not for the plants’ operations." While there is no official data to back up this claim, a senior official of the Wastewater Management Authority stated that at least 35% of plants were not working well. One key reason for the poorly-functioning WWTPs I found was corruption - officials can make money from bribes during the construction process. As a result, contractors frequently overcharge for the plant’s construction materials and technology and often use those of poor quality. As a result, downstream users, such as farmers, suffered from increased wastewater and overall poorer water quality. So the sustainability of plant operations and supply of reused wastewater downstream should not be a given.

Therefore, I certainly agree with the authors that studies on the potential for wastewater reuse should not be deemed merely technical and instead need to take into account the political economy of wastewater in each country.

Thank you for the interesting read and fruitful discussion. I like the emphasis on the socio-political dynamics around the potential of wastewater as a source for irrigated agriculture. Water reuse is already widespread, though mostly as the indirect, unplanned reuse for farmer-led irrigated agriculture rather than planned reuse schemes. When approaching water quality as a ‘practical challenge’ that should be resolved with technical solutions (i.e. treatment) in order to use wastewater at its full potential, we risk overlooking deeply political questions about the distribution of burdens and benefits among water users. The benefits and risks that urban return flows carry are inseparable, so farmers benefit from what they receive while dealing with the risks (for them, but also for others along the food chain). Research I currently work on as a PhD candidate in Dar es Salaam, Tanzania, shows how farmers have very limited right to speak although they actively participate in urban water networks of use and reuse.

Water reuse is a complex subject on which we have difficulty in getting a global picture. You underline this in your article, particularly with the lack of consideration of downstream uses. From my experiences in France and Tunisia, I find other subjects that illustrate these blinkers.
- From a technical point of view, water reuse is often promoted as a solution. It is rarely presented in a panel of potential options to address local water imbalances. Moreover, the technical characteristics are not always adapted to the final use. Why are projects offering tertiary treatment to irrigate fodder?
- From a sanitary perspective, water reuse crystallizes many questions, rightly so, but rarely in comparison with the quality of the water available, which is not always of better quality.
- On the social side, institutions regularly point at the social acceptability of consumers or users, but it seems to me that skepticism is often more important on the side of elected officials, technicians and even ministry officials. Social acceptability should not be reduced to citizens alone.
- Economically, feasibility studies focus mainly on the financial costs of projects (investment and operation) while neglecting the economic consequences on a territory.

Water reuse concentrates multi-scale and multi-disciplinary management challenges. The support of a multi-stakeholders dialogue is, in my opinion, an important key to overcome these difficulties.

Waste Water Treatment and Management ensures that you comply with industry standards and regulations drafted to save the planet’s fast-dwindling freshwater reserves.
Sewage Treatment Plants and Effluent Treatment Plants play an important role in treating industrial wastewater and sewage generated from residential clusters. This gives clean, contaminant-free water for reuse, resulting in reduced wastage of water as well.
The need for wastewater treatment systems for any industrial or commercial area is increasing as these make your industry PCB pollution norms compliant.
It is significant, so the water is more cleaner and environment friendly.
Sewage Treatment plant for hospital

To finalise, two points seem to come together in this discussion. One is related to the health issues that remain important, specifically with regards to the question of antibiotic resistant microorganism and the long term consequence of their proliferation, and more generally with the health issues that remain with regards to reuse or the perception of the sanitary issues that might remain with regards to reuse.
A second point is related to the viability of treatment technologies and plants, their energy intensity, advances in energy efficiency etc. and importantly the associated cost of operation.
Both these question have important political components. Regarding water quality and health risks it is about the distribution of risk, who carries the risk and how high is the risk? Even where treated water replaces raw sewage as source for irrigation is it enough to point to a reduction of health risks? A related question could be can indirect reuse, i.e. where possible the dilution in near by rivers, reduce health risks further even where it distributes them at a larger scale?
Regarding technology politics seems to appear at numerous levels, from treatment to distribution, this includes questions regarding appropriate technology, sustainability, energy consumption, scale etc. the type of network and its management?

Drawing on the comments above, it is certain that water reuse "concentrates multi-scale and multi disciplinary management challenges" and cannot be "deemed merely technical and instead needs to take into account the political economy of wastewater in each country". I would go beyond that to point to the inequalities of the global flows of capital as well as the subjugated positions of social formations in the global south, i.e. international political economic structures, that codetermine along local context whether and what type of treatment technologies and as an extension reuse can be successful/beneficial. The implication being that treatment and reuse need to be thought of also as part of larger questions of development politics and orientations and vice versa.
It is probably worth reiterating that because of all these limitations reuse should not be presented a that silver bullet that it is often sold as and that the "details" matter.