Los Lunas wastewater plant washout spills foam, biosolids into tributary

A maintenance mistake at the Los Lunas wastewater plant briefly pushed foam and biosolids into a tributary headed toward the Rio Grande, a reminder that even a behind-the-scenes utility problem can spill into the public eye. Village officials said the drinking-water system was not affected, but the plant’s treatment process was temporarily knocked off balance during upgrades.

The village said the problem began April 22 during work on the facility’s membrane bioreactor, or MBR, system. Too much wastewater was diverted into the older activated sludge process, overloading it and triggering what the village called a washout. In plain terms, that means the plant’s helpful bacteria were stripped out of the treatment process, reducing the biomass that breaks down sewage and allowing suspended solids to carry over into the discharge.

Nancy Jo Gonzales, the village’s public information officer and deputy administrator, said the problem happened because “more wastewater than the plant could really handle” was sent into a backup process that was not ready for that load. The village’s April 24 notice said the hydraulic loading exceeded treatment capacity, caused a significant loss of activated sludge solids and let some material pass through the permitted outfall.

Officials said the event did not threaten tap water because the potable-water system is separate from the wastewater plant. Even so, the incident was not just a routine maintenance hiccup. The village acknowledged that a small amount of foam and biosolids made it into the tributary that flows toward the Rio Grande, turning the episode into both a service issue and an environmental one.

The Los Lunas wastewater division operates two plants, an original activated sludge facility and a newer membrane bioreactor plant, serving more than 6,000 residential and commercial customers. Treated liquid effluent is blended before discharge to the Rio Grande, and the facility at 1960 Heaton Loop is authorized to discharge under EPA permit NM0020303. EPA’s permit fact sheet lists the plant’s design flow at 2.7 million gallons a day, a scale that shows how quickly a routing error can ripple through the system.

The village also said wastewater staff receive annual training and provide 24/7 on-call support, underscoring how much depends on the plant working properly every day. The episode comes amid ongoing regulatory scrutiny as well, with the New Mexico Environment Department posting a February 27 notice on a groundwater discharge permit renewal and modification for the effluent loadout station and earlier state and federal notices tied to the plant’s NPDES permit.

For Los Lunas, the washout points to a larger infrastructure challenge: keeping older treatment systems stable while new technology is being brought online to serve growth. Residents watching for a repeat would likely first see another village alert, and any future incident would again raise questions about reliability at one of the community’s core utilities.