Providing a Benchmark for Sustainability and Wastewater Treatment

Eight years in the making, the $92 million Little Patuxent Water Reclamation Plant Biosolids Improvement Project is the largest water/wastewater construction project in Howard County history. Serving 56% of the county’s population and producing 35 tons of biosolids each day, the state-of-the-art biosolids addition turns undigested primary sludge and waste-activated sludge into Class A biosolids. 

The Biosolids Improvement Project transitioned the facility’s biosolids production from lime stabilization to anaerobic digestion. The latter produces a more versatile product, suitable for various uses, including soil blending, fertilizer blending and direct sale to citizens. The project also conforms to Maryland’s increasingly stringent waste load allocations, treats centrate, enhances odor control facilities, and includes process and electrical equipment upgrades. 

As the first wastewater treatment facility in the United States to use the AirPrex phosphorus precipitation system and one of the country’s first installations of the ANITA Mox deammonification system to reduce nitrogen, the project provides a benchmark for sustainability and treatment. Combined, the two systems remove 85% of soluble phosphorus, 75% of total nitrogen and 85% of ammonia from the plant’s effluent. This reduces the energy required to remove nutrients and reduces the likelihood of mainstream process upsets. Expecting a 50% growth in dry sludge annually by 2024, the project team identified new destinations for the Class A biosolids. 

Little Patuxent is Howard County’s first Envision-verified project as well, awarded a Silver rating from the Institute for Sustainable Infrastructure. The team implemented several sustainability-focused items, including reef balls cast from excess concrete that restore the Atlantic Ocean’s reefs, repurposing 92% of excavated material on site, comingled dumpsters to improve recyclability and reusing digester methane to fuel the biosolids dryer. 

After project completion, the number of trucks needed to haul biosolids has now decreased from seven per day to just one per day. This reduction lowers operating costs by $2 million annually, providing a significant economic benefit to Howard County taxpayers, as well as reduced carbon emissions and strain on local roads. 

Completed on budget and on schedule, the new Little Patuxent Water Reclamation Plant Biosolids Improvement Project uses innovative technologies and care for the environment to transition the plant’s biosolids production from lime stabilization to anaerobic digestion.