Written by Lance Bartlett, Utility Engineering Manager for City Corporation and Tom Welch, Southeast Regional Sales Manager for Schwing Bioset, Inc.
April 25, 2016
In early 2015, City Corporation, the commission established by the City of Russellville to operate the municipal water system, completed a construction project to abandon existing fixed film treatment facilities and convert the wastewater treatment plant to a denitrifying activated sludge facility. Activated sludge technologies produce more sludge than fixed film and initial calculations predicted an increase of 6 to 7 times the current production rate when operated at the design capacity of the facility.
City Corporation had processed sludge through aging aerobic digesters and produced a Class B biosolid under 40 CFR 503 that was then dewatered and land applied to three nearby fields. Two of the three permitted fields were no longer available, leaving only 49 acres for use. The increase of sludge production was predicted to require around 160 acres.
The expected increase in sludge production and lack of land available for land application prompted staff to explore options. The alternatives explored included composting, additional aerobic digesters, dryers, and the Bioset process from Schwing Bioset, Inc. (SBI). The Bioset process was selected for piloting in February and March of 2015 due to its low cost, simple operation, and the high quality Class A product that it produces. The lone concern was with respect to the increase in volume due to the addition of chemicals, and staff wanted to get the new process up and running to obtain empirical data on sludge volume. The engineering firm performing the preliminary study had built in a large contingency due to not being familiar with the Bioset technology and the uncertainty in sludge volume, thus raising concerns that the Bioset technology would be the proper process for the future of the Russellville WWTP. Ultimately the volumetric increase was less than 10%, and with the Class A designation the number of outlets and demand for the material exceeds production rates.
Following that successful pilot test, in April of 2015, Schwing Bioset agreed to continue to lease the pilot machine under a monthly contract basis for the sludge handling process. By the fall, City Corporation had a good feel for their solids production and had a great experience with the Bioset full scale pilot equipment. Given the years of struggling with the Class B sludge process, management and staff were very pleased with the Class A process and end product and the thought of returning to a Class B process was taken off the table. With all the uncertainty taken out of the equation, staff was ready to make a decision and chose to move forward with a permanent Bioset installation. City Corporation and Schwing Bioset continue to operate under a contract that allows City Corporation to operate the pilot unit until the permanent unit is installed and operational. This arrangement allows City Corporation to manage their sludge and operate the plant in accordance with the design parameters, keeping the facility in compliance with the ADEQ, which otherwise would not be possible. The new facility is anticipated to be operational in mid-October 2016. The current digester will only be used as a sludge holding tank, thus reducing the power consumption needed for complete aerobic digestion to meet Class B standards, and allowing just WAS sludge to be converted to Class A EQ fertilizer through the Bioset process.
To learn more about our Bioset process or this project specifically, contact this blog’s author, Tom Welch, and/or visit the SBI Bioset Process page. For other inquiries, call 715.247.3433, visit our website, or find us on social media.