Abstract Title

Session S-10B: Cleaning Our Waters: Moving Forward on Green Infrastructure

Keywords

Stormwater

Start Date

2-5-2014 1:30 PM

End Date

2-5-2014 3:00 PM

Description

Wapato Lake in Tacoma, WA is a 23-acre urban lake that has had problems of eutrophication and toxic algae blooms for over a hundred years. Inputs of phosphorus from both environmental and anthropogenic sources contribute to this problem. Much of the 900-acre watershed consists of residential or commercial development, increasing the amount of stormwater containing increased levels of phosphorus. Past management efforts designed to control eutrophication at Wapato included constructing a diversion structure to route phosphorus rich stormwater around the lake. This plan increased the retention time of Wapato to ≈ 8.5 years. We have been tasked by the City of Tacoma to research the prospects of introducing filtered stormwater runoff into the lake to reduce retention time. Our plan includes creating a media filter using a waste product from the drinking water industry “Water Treatment Residuals” (WTR) as an amendment to a sand filter to adsorb and trap phosphorus. To determine WTR’s viability as a media filter we have compared WTR from three drinking water facilities with commercial stormwater filtration media. The WTR and media mixes were compared using a series of experiments including kinetic and batch adsorption isotherm tests to determine the contact time and maximum adsorption of phosphorus as well as tests looking into and dissolved metals in the leachate. In phase 2 of this experiment we will compare the best working WTR mixture to proprietary mixes in terms of its physical filtration capabilities, total and ortho-phosphorus removal using water from Wapato Lake.

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May 2nd, 1:30 PM May 2nd, 3:00 PM

Assessing Water Treatment Residuals as a Filtration Media for Phosphorus Removal at Wapato Lake - Tacoma, WA

Room 608-609

Wapato Lake in Tacoma, WA is a 23-acre urban lake that has had problems of eutrophication and toxic algae blooms for over a hundred years. Inputs of phosphorus from both environmental and anthropogenic sources contribute to this problem. Much of the 900-acre watershed consists of residential or commercial development, increasing the amount of stormwater containing increased levels of phosphorus. Past management efforts designed to control eutrophication at Wapato included constructing a diversion structure to route phosphorus rich stormwater around the lake. This plan increased the retention time of Wapato to ≈ 8.5 years. We have been tasked by the City of Tacoma to research the prospects of introducing filtered stormwater runoff into the lake to reduce retention time. Our plan includes creating a media filter using a waste product from the drinking water industry “Water Treatment Residuals” (WTR) as an amendment to a sand filter to adsorb and trap phosphorus. To determine WTR’s viability as a media filter we have compared WTR from three drinking water facilities with commercial stormwater filtration media. The WTR and media mixes were compared using a series of experiments including kinetic and batch adsorption isotherm tests to determine the contact time and maximum adsorption of phosphorus as well as tests looking into and dissolved metals in the leachate. In phase 2 of this experiment we will compare the best working WTR mixture to proprietary mixes in terms of its physical filtration capabilities, total and ortho-phosphorus removal using water from Wapato Lake.