WASTEWATER/District revamps solids processing, cuts odors
The 43-year-old, 105-million-gallon-per-day Morris Forman Wastewater Treatment Plant is located less than 10 miles from the downtown business district in Louisville, Ky. Operated by the Louisville and Jefferson County Metropolitan Sewer District (MSD), the plant treats its own solids and also processes solids from other MSD wastewater treatment plants.
Though the area around the plant is largely industrial, many residential neighborhoods are nearby. Importing solids from other facilities has made the plant a lightning rod for neighborhood activists concerned about odors.
To ease concerns, the city is working with Kansas City, Mo.-based Black & Veatch and St. Louis-based J.S. Alberici Construction to design and construct a new process for solids treatment at the plant.
The Alternative Solids Process (ASP) will replace a low-pressure oxidation system that had been used since the 1970s. The old system had prompted numerous odor complaints.
With ASP, primary solids are anaerobically digested then combined with thickened waste-activated sludge for dewatering and drying. Digester gas provides much of the energy needed for drying, and waste heat from drying helps heat the digesters.
The design/build team is using existing structures at the plant to house the process, totally enclosing the dryers to minimize odor and reduce construction costs. It also is working with MSD operations staff to update and restore four existing anaerobic digesters instead of building new ones, and the existing decant tanks are being converted for use in the new system.
In addition, heat-drying technology is being scaled up to minimize the number of dryers required, which contributes to procurement and construction savings. Four heat drying trains are being installed, two of which will normally be in service, with the remaining two providing capacity for peak solids production and standby. Two of the trains are scheduled to start up this month; the remaining two will go online next spring. When it is completed, the four-train installation will make the plant one of the largest heat drying facilities in the world in “installed” capacity.
The contract for the project — $64.6 million — is the largest in MSD’s history. However, the project cost nearly $32 million less than MSD had initially estimated, and it is expected to save more than $4 million a year in operation and maintenance costs. Additionally, the dried biosolids eventually will be distributed to fertilizer blenders, with landfilling relegated to “last resort” status.
