American Infrastructure Magazine


While other management plants stick to its primary function, Hornsby Bend Biosolids Management Plant is going above and beyond, and doing more than just its day job. The 1,200-acre site's primary function is to handle Austin, Texas' excrement, but it's actually several operations in one. The Austin Water Utility is committed to protecting the city's environment, and the plant plays a significant part in that effort by recycling Austin's biosolids and yard trimmings. When Austin residents flush their toilets, the contents are piped to one of the city's water treatment plants that filter out most of the water, purify it and discharge it into the Colorado River just beyond Lady Bird Lake. The remaining sewage solids are sent on to Hornsby Bend where it is treated to kill pathogens and the resulting "biosolids" are recycled. But Hornsby Bend recycles more than just biosolids. In addition to the water from the biosolids treatment process, stormwater from the composting and basin area is treated in through a pond system, in which no water is discharged from the site. Instead, the water is recycled for irrigation of onsite hay fields. Methane gas produced in the treatment process is also recycled to generate electricity	and heat. And in partnership with the city's Solid Waste Services Department, residential yard trimmings are brought to the plant rather than the landfill, where they are recycled through composting with the biosolids. This recycling results in cost savings for Austin residents and represents approximately 15 percent of all the solid waste recycled by the city. Furthering its commitment to sustainability, Hornsby Bend announced in January that it will implement a $31.8 million green upgrade to its facilities thanks to funding provided by the American Recovery and Reinvestment Act. The site broke ground in February on its green infrastructure improvements, which includes adding a methane-powered generator that could power 750 homes. The generators will convert the biogas to electricity and send up to 1.75 MW of electricity to AE's grid annually. Additionally, the site will double its capacity for turning Austin's toilet waste into nutrient-rich soil known as Dillo Dirt. "This used to be a place for waste [and] now it's a resource," said Jody Slagle, an engineer who oversees the sludge operation, in a January American-Statesman article. Dillo Dirt returns nutrients and organic matter to impoverished urban soils and is used across the city on lawns, gardens, parks and other areas.
In addition to Dillo Dirt's benefits, Hornsby Bend's recycling process saves valuable landfill space, reduces land-filling costs and reduces green-house gas emissions by diverting biosolids and yard trimmings for beneficial reuse. The project upgrade will create about 560 local jobs and further reduce the environmental impact of the plant. "This is what the American Recovery and Investment Act is all about. Once again, Austin is leading the way for other communities in Texas, as well as nationwide," said Dr. Al Armendariz, Region 6 Administrator for the U.S. Environmental Protection Agency. The improvements will also enhance onsite solids handling capacity, decrease off-site land application, reduce 30,000 gallons of diesel fuel consumption annually, improve the energy efficiency of the biosolids process and increase biogas production. And by 2012, it is estimated that the total carbon footprint reduction will be 6,500 tons of CO2 equivalent greenhouse gases, a 41 percent reduction in the use of petroleum-based compounds in the treatment process and a savings of an additional 16,000 cubic yards per year of yard waste as bulking agents in composting. Since its inception, Hornsby Bend has gained national acclaim and is known for its biodiversity and ecotourism. In addition to its day job, the site is known to be one of the best birding sites in Texas - harboring more than 370 species of birds and an abundance of other wildlife. Cielestia Calbay is an assistant editor at American Infrastructure magazine. She can be contacted at ccalbay@penpubinc.com.