The municipal wastewater treatment plant in Punta del Hidalgo (Tenerife, Canary Islands) has successfully closed the water cycle in its area: it regenerates 100% of the wastewater it processes in the village and reuses it for agricultural irrigation in the area and other municipal uses.
“Many people do not understand what treated water discharge means; they think it is dumping sewage into the sea,” clearly summarises Eduardo Alemán, head of urban drainage and treatment at Teidagua, the company that manages the plant.
He explains that for decades, the plant operated as a conventional treatment facility to comply with regulations and discharge clean water into the sea. “But four or five years ago, farmers began asking us for water,” he adds.
The lack of rainfall and the salinisation of wells raised alarms for the 200 hectares of crops that depend on the waters of the Tomadero ravine, named precisely after the source from which local farmers draw water for their irrigation systems.
This is about to change, as the crops of Punta del Hidalgo will increasingly be irrigated with regenerated water sourced from the village residents’ usage and the rainwater collection network.
Technology for quality water
The plant has been completely transformed with a membrane ultrafiltration system, which allows for the production of Category A regenerated water, the highest quality according to European regulations. “It is essentially passing the water through membranes with pores small enough to retain all solids, including bacteria and parasites. With this system, you can irrigate everything, even crops that come into direct contact with the water,” he details.
The quality achieved is such that the turbidity of the water measures 0.45, lower even than that of many bottled waters for human consumption. “The filtration removes all suspended solids. It also retains microplastics, which even rainwater cannot prevent,” he notes.
Furthermore, the plant has installed a small auxiliary desalination unit that reduces the salinity or conductivity of the water, which occurs because the collected water increases its concentration of salts when mixed with detergents and other household products, from 1,200 to 800 µS/cm, an optimal value for banana cultivation. “It is essentially to make it more comfortable for the farmer. With 1,200, you can irrigate, but 800 is much better,” he explains.
The system is currently in testing phase and will be fully operational in August.
Direct savings for farmers
One of the most valued aspects by users is the cost: the price of regenerated water only includes expenses for energy for pumping, maintenance, and quality analysis, with no additional surcharges applied. “It is a fairly economical rate,” says Alemán.
But the greatest savings lie in the system’s efficiency: “When a farmer buys water from a gallery, they often only receive 50% due to losses. If we are asked for 100 cubic metres, we provide the full 100. Each farm has its own flowmeter, and the control is total.”
Moreover, the regenerated water contains natural nutrients that reduce fertiliser usage. “We are providing nitrates, phosphates, and potassium. We have calculated that for every 100 m³, we provide 40 kilos of nitrate. They are noticing that,” he adds.
Supply guarantee, even in summer
Today, the system supplies 14 farms that irrigate 45 active hectares, but the installed infrastructure can extend to 90 hectares without expansions. “Many farmers still do not believe that there will be water every day. We tell them: ‘As long as there are people living in Punta del Hidalgo, we will have water.’ And in August, with the increase in summer visitors, we will have more,” he assures.
This continuous supply may prevent the abandonment of farms that has affected this area, as farmers with unworked land are reconsidering putting it into production thanks to the ease of reusing water from Punta del Hidalgo.
Furthermore, pressure on aquifers has decreased, which also allows the water to have lower salinity due to seawater encroachment caused by emptied galleries.
A self-sufficient municipal plant
Alemán emphasizes that the project has not only transformed the hydraulic system of the region, but has done so from a municipal model: “That is the real milestone. There are regional treatment plants with similar systems, but this is completely managed by the town hall, which is not common.”
In terms of energy, significant strides have also been made: the plant has increased its treatment capacity from 7,000 equivalent inhabitants to 15,000, and it has 30 kW of solar energy, with plans to reach 70 kW and 80% energy self-sufficiency.
Water for irrigation, cleaning, and returning to the land
In addition to agricultural use, the regenerated water is employed for watering gardens, cleaning streets, and other municipal services in Punta del Hidalgo, Bajamar, and even Tejina. “We use it for festivals, for clean-ups, and there is no difference. I could give you three glasses of tap water, bottled water, and this, and you wouldn’t be able to tell which is which,” he states.
The long-term objective is clear: to close the water cycle at its source. “The very water that was used by the tenant, which was flushed down the toilet, is reaching the farmer below to irrigate. That is very important. It is efficiency, sustainability, and territorial justice,” concludes Alemán.
European funding
The project has been financed through a grant obtained from European Next Generation funds, channelled by the Anaga Biosphere Reserve in collaboration with the Ministry of Ecological Transition of the Government of the Canary Islands. According to Alemán, it was this entity that proposed presenting the initiative to apply for a specific call aimed at protected areas.
