Cesar Narvaez

Cesar Narvaez did not come to wastewater from a sanitation background, and the reason he cares about it at all goes back to his childhood. He grew up in Peru in a place where the tap ran for only two hours a day, so the whole household revolved around buffer tanks and the logistics of hoarding enough water to last the other twenty-two. That scarcity stuck with him, and his actual training was in fishing engineering, which pulled him toward aquaculture, the business of growing fish and shellfish, where you have to treat water both biologically and physically to keep the animals alive. Narvaez slowly realised the part he loved was not the fish, it was the water.

Cesar Narvaez got the idea for NXO Engineering in a lab, while he was producing microalgae to feed those shellfish. To grow that algae as biomass he had to constantly feed the reactors nitrogen and phosphorus, and at the same time he was looking at sewage, where nitrogen and phosphorus are exactly the nutrients that cause eutrophication, the runaway algae blooms that choke rivers and lakes. He connected the two on the spot: if algae are desperate to eat nitrogen and phosphorus, why not let them eat the surplus straight out of the wastewater. That single connection became the company he founded in 2016.

Cesar Narvaez builds a new kind of municipal wastewater plant where microalgae and bacteria do the cleaning in partnership, a piece of water technology that runs the biology in reverse of the usual playbook: the algae photosynthesise and release the oxygen the bacteria need to digest the organic load, so the plant captures carbon dioxide rather than emitting it, and it skips most of the energy-hungry aeration that a conventional activated sludge plant runs on. Narvaez designed his process to let water move by gravity wherever it can, which is how he gets a full treatment plant down to about five motors and three to four kilowatts. The company reports running at roughly 0.12 kilowatt-hours per cubic metre, against a French average closer to 0.8, and it pairs the algae reactors with dissolved air flotation, a standard technique that floats the algae back out of the cleaned water.

Cesar Narvaez built the first plant the hard way, and he is honest about it. He was told from the start that a treatment plant sized for a hundred people could never be profitable, and the team, who he openly calls autodidacts, taught themselves how to size and build the whole thing rather than subcontract it, leaning on renowned French research institutes like the CNRS and INRAE for the science. The pilot was vandalised and degraded repeatedly, eight times by his own count, and the first time set them back about four months and a lot of money when there were only three people in the company. He likes telling people they built a wastewater treatment plant with three, because the reaction is always that it is impossible.

Cesar Narvaez is chasing one specific finish line, and it is the thing that still bugs him about his own technology. His plant is biological and low-energy, but it still leans on a few chemical coagulants to pull the algae out, and that single compromise nags at him, because a critic can always point at it. So NXO has been engineering the chemicals out, testing natural coagulants from moringa and chitosan before landing on something he finds far more promising, a coagulant made from cactus slime:

“We're going to get to that place where we're going to be able to say, yeah, this is chemical-free, this is CO2 negative, this is energy positive, and there's no one argument against it.”

Cesar Narvaez is, in the end, an outsider who refused the standard answer: a fisheries engineer with no sanitation pedigree, betting that the cheapest way to clean water is to let the living thing that grows in it do the work. Whether VOLTA, his next plant built around vertical photobioreactors to shrink the land footprint, proves that at city scale is the open question, but the conviction is not in doubt.