Rio de Janeiro goes for H2O2 for better tap water
Tapping into the efficiency of hydrogen peroxide for water treatment
There are many advantages to using hydrogen peroxide instead of chlorine for the treatment of drinking water. Following a lengthy collaboration with Solvay, the municipality of Rio de Janeiro decided to introduce hydrogen peroxide for the pre-oxidation of its tap water in 2018 — an example soon to be followed by other Brazilian cities.
The largest potable water treatment facility in the world is located in Rio de Janeiro. Run by the local authority CEDAE (Companhia Estadual de Águas e Esgotos), it serves 10 million people but draws its water from a very polluted river in Brazil, Rio Guandu, strongly affected by organic pollutants from sewage and industrial effluents upstream.
Because of this, the treatment of tap water must comprise a pre-oxidation step that neutralizes the pollutants. Chlorine is the traditional go-to product for this, but hydrogen peroxide is actually more efficient. It also produces better-tasting water without any chemical smell, and it’s cheaper overall, as well as being more environmentally friendly since it decomposes into water and oxygen. Furthermore, using H2O2 avoids the formation of trihalomethanes, carcinogenic chemicals that are a by-product of chlorine when it reacts with organic matter in the water.
Water treatment that answers environmental concerns
“The problem is that there is strong resistance to change; people are used to using chlorine, which remains an efficient solution,” explains Cedric Schmitt, Commercial Manager at Solvay’s Peroxidos do Brasil. “But as people and municipalities become more aware of sustainability and public health concerns, the will to switch to a more sustainable solution is increasing.”
Additionally, there is a global trend towards the enforcement of lower limits of micropollutants, which weighs in favor of a solution offering more efficiency. In short, chlorine-based pre-oxidation of drinking water is on the way out – though chlorine still remains necessary for the final disinfection stage, to meet regulatory requirements.
Nevertheless, it still took Solvay ten years of work with the authorities in Rio to make the change happen. “The biggest challenge was to prove the validity of hydrogen peroxide as an alternative method for pre-oxidation,” continues Cedric. “Over time, we established a real long-term partnership.” Technical staff and experts from both Solvay and the CEDAE held meetings, lab tests and demonstrations, leading to what can be considered a work of co-creation.
Our success in Rio proved the efficiency of hydrogen peroxide and helped us replicate the operation in other municipalities.
Disinfectant boosted by the 2016 Olympics
Rio’s 2016 Olympic Games helped accelerate the project. “During the Olympics, we conducted a large-scale test of the solution,” explains Cedric. “The huge international visibility provided a favorable context to accelerate the approval process.” Especially since the tests proved highly positive, with hydrogen peroxide yielding higher water quality than with chlorine. Its efficiency also allowed a 10% reduction in costs related to other chemicals needed to treat the water.
After all these efforts, in 2018, Solvay won the bid launched by the local government for 2.1 kilotons of Interox® hydrogen peroxide to supply Rio’s largest water treatment plant – the one with the 10 million users. The bid was renewed for 2019 and expanded to four more treatment plants. In addition, Solvay provides technical support through monthly visits, and is in charge of on-site maintenance. Resorting to H2O2 for the treatment of drinking water was a first in Brazil, though the product is already used for other applications, such as algae control in reservoirs.
“We used our success in Rio as a case study to prove the efficiency of hydrogen peroxide,” says Cedric. “It offered us great visibility that helped us replicate the operation and accelerate the introduction of hydrogen peroxide in other municipalities. We have already started working with local authorities in Sao Paulo, the largest city in Brazil, as well as in the province of Pernambuco”.