With homeowners living near the Chesapeake Bay expected to upgrade their septic systems starting this fall, the state is moving to clean up its act, too.

Officials traveled to Calvert County Friday to admire the first state-owned, nitrogen-removing septic system installed at Jefferson Patterson Park in St. Leonard.

Beginning Oct. 1, a new law requires that all new or replacement septic systems in the Critical Area,  within 1,000 feet of the bay and its tidal tributaries, must remove nitrogen, the chief pollutant fouling the bay's waters. The enhanced systems add thousands to the cost, but the state has been providing grants to homeowners and businesses for the upgrades.  It will continue to do so when the requirement takes effect, with funds going first to those with failing systems near the water. For more on the grants, go here.

There are about 420,000 septic systems in the state, with about 52,000 in the Critical Area, where nitrogen seeping into the ground water is more likely to reach the bay.  Planners project that another 145,000 new septic systems will be installed over the next 25 years.  Conventional septic systems do not treat nitrogen, and scientists estimate that they are responsible for 7 percent of all the nitrogen fouling the bay.  Upgrading all the new systems can cut that in half.

Meanwhile, earlier in the week, the state Board of Public Works approved spending $20.1 million to upgrade Baltimore's Patapsco sewage treatment plant so it removes more nutrients from its wastewater discharge.  When completed, the improvement should reduce nitrogen and phosphorus getting into the Patapsco River by more than 80 percent.