More Efficient and More Effective: New Equipment Makes a Big Difference at Fountain Sanitation District
Back in 2017, Pool administrator Joe DePaepe had the opportunity to visit Fountain Sanitation District (FSD) and was introduced to the district’s new equipment for sludge dewatering, the BDP Screw Press. Joe immediately recognized the potential benefits of the equipment to other sanitation districts and believed it would make a great member spotlight feature for an issue. Recently, we had the privilege of speaking with Assistant Operations Superintendent Josh Watkins about the merits of the BDP Screw Press and how it has positively impacted district operations.
Who They Are and What They Do
Fountain Sanitation District has two facilities and not including the administrative personnel, employs 4 system operators, 4 plant operators, and a GIS analyst. They serve a population of around 22,000, and maintain just over a 100-miles of collection system and 4 lift stations. The state of Colorado mandates that these pipes are checked and maintained once every three years; FSD performs the maintenance once every two.
Like other sanitation districts involved with wastewater treatment, there comes a point in the process that you cannot keep everything within the treatment process. That’s when “wasting” comes into play. The treatment process is a continuous process of keeping the microorganisms balanced. Fountain Sanitation District utilizes aerobic digesters for solids handling. They have 4 aerobic digesters that are used to hold the liquid waste for further treatment into biosolids. Wasting to the aerobic digesters is required daily, over time they need to make room in the aerobic digesters to continue wasting and keep the process in balance. To make room, the digested liquid is disposed by one of two ways: they either send it to the new screw press or they use the originally constructed drying beds, weather permitting.
Past Operations
Fountain Sanitation District updated from a 6-cell aerated lagoon system back in 1997. The upgrade consisted of moving to an extended aeration facility. The designed method to deal with waste activated sludge (WAS) was aerobic digestion. Shortly after the plant came online it was apparent that the aerobic digesters were not able to keep up with the treatment needs for removing bio-solids. Making additional room for wasting becomes a priority. FSD initially constructed 5 drying beds. This process entailed using a trailer-mounted blending unit, and dosing polymer and blending sludge together, allowing solids to be poured out across the bed. Having a porous bottom, the bed allowed the solids that flowed across the top to stay together and form a cake, while the water dissipated through the bed surface. Over time, the only thing left would be the cake from the solids. This, in turn, would allow the cake to naturally dry out before removing it and preparing the drying bed for the next time. The solids removed from the drying bed are then stored until hauled away for ultimate disposal.
As the City of Fountain grew and the flow to the facility increased, using drying beds to remove bio-solids wasn’t enough and turned to a third-party contractor to help keep up with removal needs. The third-party contractor brought in a trailer mounted belt press and were able to process more solids in less time, making room for the new WAS. The bio-solids from FSD’s facility are considered Class B, which allows them to be land applied. With Fountain continuing to grow, the district did as well. Within the last 3 years, FSD has been operating two facilities. The new treatment facility treats more than half of the flow, leaving the old facility to continue treating wastewater and dealing with bio-solids removal.
Under the guidelines of the US Environmental Protection Agency’s Part 503 Biosolids rule, FSD produces Class B Biosolids that can be used and distributed for land application such as agricultural land. However, unlike Class A Biosolids, Class B Biosolids require additional farm management practices and have more site restrictions for land application (for example, Class B Biosolids cannot be land-applied to lawns and home gardens). Additionally, agricultural land that has Class B Biosolids applied have to follow their own additional guidelines when it comes to harvesting crops, farm animal grazing and public contact.
Screw Press Benefits
When the new facility first came online, they had the WAS liquid from the older facility trucked down to the new facility because the new facility was equipped with a large Phoenix Belt Press when constructed. While utilizing the drying beds like they did in the past. The district would focus on using both methods in the warmer months but mainly trucked the bio-solids during the colder months.
With the high cost of hauling liquid sludge, FSD didn’t see this as a long-term solution for solids handling. Their first introduction to the BDP Screw Press during a demo at Security Water and Sanitation District. This inspired a way of improving the solids-handling process at the FSD facility. In January of 2017, the installation of the screw press was complete and ever since then, the district has been dealing with the bio-solids in a more efficient manner. A big deciding factor to pursue the screw press was cost-efficiency as the press ultimately has a payoff of just over four years.
Within that first year, Josh tells us that FSD has been able to process year-round, and the cost of solids handling operations is lower. Not having the hauling costs was a big factor. Overall, this has been a positive improvement. The screw press does require an operator’s attention, but that hasn’t been a deal breaker. Operator Matt Brady says, “It can be a little finicky, due to quality of sludge somedays” he says. “But when it’s running great, it runs great the majority of the day.” The district now processes an average of 76 gallons per minute and an average daily processing amount of 47,000 gallons per day. FSD has used roughly 375 gallons of polymer since start up or a little less than two totes of polymer. They currently average 13.5% solids from the screw press which is comparable to what the third-party contractor was doing with their mobile belt press. In comparison the screw press (12-22, when fine tuned) is able to keep up with more traditional methods such as using rotary drum thickeners for their sludge conditioning and treatment, where the cake averages around 3-5%, or centrifuges which yield roughly 20-25%, or even belt presses at 15 – 19%.
Josh believes the screw press would benefit many sanitation districts from smaller communities for several reasons: the machinery’s mechanical dewatering isn’t contingent on the weather, and could be run 24-hours a day, 365-days a year. The relatively short return on investment is also plus. Josh tells us that a few districts are looking to implement the screw press in their own operations, but the technology is still fairly new and is not the prevalent method within the industry.
We want to thank Josh Watkins, the operators and Fountain Sanitation District for volunteering their time and bringing the screw press to the Pool’s attention. We believe this innovative technology can benefit our other district members and we invite you to share your stories if you’ve implemented new technology in your own operations.
