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 Non-Invasive Methods for Treating and Removing Sludge from Subsurface Flow Constructed Wetlands
L.L. Behrends, E. Bailey, L. Houke, P. Jansen, and S. Smith
Item Number: NRL2006AC-25
Shipping Weight: 0lbs. 0oz.
Price: $20.00
Vertical-flow, horizontal-flow, and reciprocating subsurface-flow constructed wetland systems can be economical and effective as decentralized wastewater treatment systems. However, with time, many gravel-based treatment systems develop chronic problems because the gravel pore spaces become filled with a sludge-like material composed of mineral matter and recalcitrant organic compounds. Sludge formation is a natural process that impacts all wastewater treatment technologies. However, in gravel-based systems, sludge accumulation can lead to failure of system hydrology and biological treatment. In severely plugged systems, remediation may entail removing, washing, and replacing the gravel substrate. This is a time consuming and costly practice, and often requires taking the wastewater system “off-line” for an extended period of time. Research scientists at the Tennessee Valley Authority (TVA), have conducted a series of experiments to evaluate various non-invasive techniques for removing sludge from gravel-based treatment systems. Techniques (individually and combined), included sludge fluidization and pump-out via air and water sparging, addition of customized microbial consortia, fertilizer nutrients, and strong chemical oxidizing agents such as hydrogen peroxide. In two replicated lab-scale studies, treated sludge samples were incubated at 20 degrees C and monitored over a 64 day period. Monitored parameters included pH, nutrient concentrations, and volatile and fixed solids. Treatment combinations which included both nitrogen fertilizer and concentrated hydrogen peroxide provided the best results in which sludge volatile solids were reduced by up to 50 percent. Results of lab and field studies will be summarized and discussed with respect to design and operations considerations.