The challenges facing the Chesapeake restoration effort often seem daunting, but recent data provide some good news: One group of polluters has done more than its share so far to clean up its act.

Sewage treatment plants in the watershed have upgraded their operations so much that they are meeting the pollution reduction goal set for them in 2025. That’s right — according to figures from the Environmental Protection Agency, it appears that collectively they’re 10 years ahead of schedule in reducing the amounts of nutrients they’re discharging into the Bay.

Federal, state and local officials celebrated this milestone last month with a press conference at the District of Columbia’s Blue Plains Advanced Wastewater Treatment Plant, the Bay watershed’s largest such facility.

Shawn Garvin, the EPA’s Mid-Atlantic regional administrator, said wastewater plants are “leading the way” in the multi-state effort to restore water quality in the Chesapeake and its tributaries. As a group, the plants have collectively reduced their discharges of polluting nutrients by more than 900 million pounds since 1985.

Indeed, the upgrades and improvements made at sewage plants account for the lion’s share of nutrient pollution reductions made to date in the Bay and its tributaries.

While nutrients are essential food for plants, excess nitrogen and phosphorus impair water quality by fueling the growth of large algae blooms that then cause low-oxygen “dead zones” to form in the Bay.

Since the EPA put the Bay on a pollution diet in 2010 by imposing a “total maximum daily load” for nutrients and sediment, wastewater plants have cut the overall nitrogen levels in their discharges from 52 million pounds to 38 million pounds annually. This surpasses the interim pollution reduction that EPA had ordered wastewater facilities to make by 2017; and, for now at least, it effectively meets the plants’ cumulative goal for 2025 of 38 million pounds, according to the Bay Program partnership.

Sewage plants are exceeding their pollution reduction goals in large part because of a technological windfall. Through upgrades to a treatment process known as “biological nutrient removal,” many plants are now removing more nitrogen from wastewater than had been thought possible and are achieving reductions well below what their permits require. Those upgrades and other improvements have been made possible by public funds spent on advanced wastewater treatment exceeding $7 billion throughout the Bay watershed, according to the EPA.

As a result, the wastewater plants’ share of the Bay’s nutrient pollution has shrunk over the last 30 years, from 28 percent of the nitrogen and 39 percent of the phosphorus in 1985 to just 16 percent of each last year.

The pollution reductions made via wastewater are even more impressive when considering that treatment upgrades have yet to be completed at two of the Bay’s largest facilities, Baltimore’s Back River and Patapsco River plants. But those gains are expected to diminish over time as population growth increases the flow of wastewater those plants must handle. EPA spokesman David Sternberg said upgrades still in the works at the Baltimore plants and elsewhere will be needed to continue meeting pollution reduction targets.