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STORMWATER TREATMENT AT CRITICAL AREAS: THE MULTI-CHAMBERED TREATMENT TRAIN (MCTT)
Citation:
Pitt, R., B. Robertson, P. Barron, A. Ayyoubi, AND S. Clark. STORMWATER TREATMENT AT CRITICAL AREAS: THE MULTI-CHAMBERED TREATMENT TRAIN (MCTT). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-99/017 (NTIS PB99-156176), 1999.
Impact/Purpose:
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Description:
Past studies have identified urban runoff as a major contributor to the degradation of many urban streams and rivers. The objective of this research was to characterize typical toxicant concentrations in stormwater, and investigate the effectiveness of treatment processes to control the toxicants. A prototype treatment device (the multi-chambered treatment train, or MCTT) was tested during the final phase of this project. The MCTT is an underground device that has three main chambers: an initial grit chamber for trapping of the largest sediment and release of most volatile materials; a main settling chamber (providing initial aeration and sorbent pillows) for the trapping of fine sediment and associated toxicants and floating hydrocarbons; and a sand and peat mixed media "filter" (sorption-ion exchange) unit for the reduction of filterable toxicants. A pilot-scale MCTT was constructed in Birmingham, AL, and tested over a six month monitoring period. During monitoring of 13 storms at a parking facility, the pilot-scale MCTT was found to have the following overall median reduction rates: 96% for total toxicity, 98% for filtered toxicity, 83% for SS, 60% for COD, 40% for turbidity, 100% for lead, 91% for zinc, 100% for n-Nitro-di-n-proplamine, 100% for pyrene, and 99% for bis(2-ethyl hexyl)phthalate. The color was increased by about 50% due to straining from the peat and the pH decreased by about one-half pH unit, also from the peat media. Ammonia nitrogen was increased by several times, and nitrate nitrogen had low reductions (about 14%). Preliminary full-scale test results substantiate the excellent reductions found during the pilot-scale tests, while showing better control of COD, filterable heavy metals, and nutrients, and less detrimental effects on pH and color.