Autothermal Thermophilic Aerobic Digestion: more than just big words | Fort Collins - Loveland Water District

SFCSD now able to process biosolids onsite

Odds are that you have never even heard the words Autothermal Thermophilic Aerobic Digestion (ATAD) strung together. And no, it’s not some new fancy workout or celebrity diet. What it means is the South Fort Collins Sanitation District (SFCSD) has a new innovative way to process waste onsite.

Simply put, ATAD is liquid composting on a mass scale. Once the organic materials, that are produced during the treatment of wastewater undergo ATAD, they become a Class A biosolid that can take on a new life. Biosolids are an organic solid material that is recovered from the sewage treatment process and used as fertilizer or soil amendment.

ATAD is an aerobic digestion process that creates its own heat to reduce bacteria and pathogens to a level that is considered Class A by the Environmental Protection Agency (EPA) and is safe for unrestricted use. This means there is no hazardous bacteria or potential for harm to the general public or environment when the product is used for other applications.

During the process, a material is produced from the leftover bacteria used in the treatment process. With the treatment plant expansion and new regulations in place, the biosolids produced will be safer than cow manure and most commercial fertilizers.

Thanks to our recent plant expansion, the SFCSD is now able to use this ATAD process on-site as part of our treatment process as opposed to having to transport the treatment byproduct to an offsite facility, which is how it has worked in the past.

The SFCSD is down with ATAD

Before the latest construction project, SFCSD did not have a digestion process for the byproduct from wastewater treatment. We simply had a waste holding tank with a limited capacity and had to use the landfill or third-party composting for disposal or reuse of biosolids. The benefit of ATAD is it reduces the volume of solids produced through its digestion process. SFCSD expects up to a 50% reduction in the hauling costs we had with our previous treatment process.

With the ATAD process, SFCSD is equipped with greatly expanded solids handling capacity as part of the wastewater treatment process. Thanks to mechanical thickening for expanded holding capacity as well as advanced digestion and volume reduction, the ATAD process will allow for unrestricted use of Class A products, meaning the byproduct is safe for anyone to use for anything, such as fertilizer. For now, the biosolids will be sent to a local composting company where they’ll be repurposed by commercial landscapers. There is also the future opportunity for us to sell the Class A biosolids or even give them away.

Why Class A biosolids get an A+

You might be thinking it’s gross to keep and use a wastewater treatment byproduct. But rest assured, biosolids are highly regulated with strict quality standards and are completely safe for use by the public. Biosolids are commonly used as fertilizer once they’ve undergone the treatment process. Such biosolids are made up of organic materials and are completely natural and safe. Through treatment and testing, they can contain fewer bacteria than eggnog! (Not that SFCSD recommends drinking the biosolids by any means.)

The EPA Biosolids regulations outline the different uses of biosolid classes that SFCSD adheres to. Our goal is to not only meet our discharge permit requirements put forth by the State and the EPA but to continually exceed our permitted limits in the treatment of the wastewater. We do this by producing the highest quality reclaimed water, efficiently and dependably, using the latest technologies to continually protect human health and the environment.

The EPA’s existing requirements and guidance help ensure that biosolids are processed, handled and land-applied in a manner that minimizes potential risk to human health. Biosolids are divided into Class A and Class B designations based on treatment methods, according to the EPA.

Our ATAD process produces Class A biosolids which means we eliminate pathogens, including viruses, ensuring they are safe for harvesting crops and turf, for grazing of animals and public contact. While a very small percentage of Class A biosolids have the potential for transmitting illness and requires restrictions to ensure the public’s safety, we are dedicated to following all requirements to ensuring our Class A material is safe for many uses.

These biosolids are rich in nutrients such as phosphorus and nitrogen and other constituents like organic content that benefit plants and soils. Many places use this type of product to maintain parks, golf courses, croplands and many times it’s available to the public for gardens and even home use. In fact, numerous biosolids recycling programs have actually shown improvements for the environment and nearby waterways because they enrich soils and help vegetation grow more vigorously.

What’s next for SFCSD with the new ATAD process

The SFCSD has provided wastewater services to businesses and citizens since 1961. We are dedicated to providing our more than 45,000 customers with this essential public service and are always looking for new, more efficient ways to treat the water you send us down your drains and pipes.

By installing the ATAD capabilities, we’re not only creating a process that saves money, but we’re also preparing for future growth in our community, while at the same time creating a beneficial nutrient for the environment. It’s a win, win, win!

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