Solving Solids Handling – Fruitland, MD – Mem-TAD™ Technology
INTRODUCTION AND BACKGROUND
George, Miles & Buhr, LLC (GMB) was contracted by the City of Fruitland, Maryland to improve the solids handling facility for their wastewater treatment project. The previous solids handling facility at the Fruitland WWTP had conventional aerobic digesters which had issues such as excessive solids production resulting in an increased solids disposal cost, a lack of solids-holding time due to the poor thickening performance from decanting, and high nitrogen and phosphorus concentrations from the digester decant, which created concerns with meeting their stringent nitrogen and phosphorus effluent limits.
In order to achieve Class B biosolids stabilization while increasing the solids-holding capacity within the existing digesters, with a reduction in solids disposal costs, and minimal construction costs associated with building new process tanks, GMB considered three thickened aerobic digestion alternatives: Gravity Thickened Aerobic Digestion, Mechanical Thickened Aerobic Digestion, and Membrane Thickened Aerobic Digestion Systems.
EVALUATION OF THE ALTERNATIVES
The capital cost difference between all the alternatives was pretty similar. The gravity thickened option had the poorest thickening performance out of all the alternatives and required the construction of an additional aerobic digester to meet Class B stabilization requirements, resulting in the highest energy and construction costs of all three choices.
The mechanically thickened option required a separate building to house a thickener, a substantial capital cost that excludes the additional costs of added polymers and staff to operate and maintain the thickener, resulting in the highest overall operating costs of the three options.
Although the membrane thickened alternative had the highest overall capital costs out of the three alternatives that GMB considered, this option had the lowest operating and construction costs. The membrane thickening aerobic digestion system only required the construction of an anoxic and membrane thickening basin to meet Class B stabilization. In addition, this system is capable of thickening the solids up to 3% concentration and does not require polymers or extensive operator attention for thickening. This system also produced a reuse quality permeate with very low levels of nitrogen and phosphorus that allowed the facility the option of combining the permeate with the plant effluent. The benefits offered by the Mem-TAD™ system qualified the proposed facility as a “Green Project” and helped the city secure funding from the Maryland Department of Environment (MDE). All these benefits were very advantageous to the city and the Mem-TAD process was ultimately selected by the GMB.
FRUITLAND, MARYLAND WWTP – MEM-TAD™ SYSTEM
The Mem-TAD™ system at the Fruitland WWTP is the first in the state of Maryland. The system was commissioned in March of 2016.