STA-3/4 PSTA Cell Sample Clauses

STA-3/4 PSTA Cell. The STA-3/4 PSTA cell has provided effective treatment performance since its inception, with annual average inflow TP levels ranging from 14 – 27 µg/L and mean annual outflow levels ranging from 8 – 13 µg/L. Our ongoing work in the STA-3/4 PSTA Cell has included wet- and dry-season sampling of surface water, sediment, plants and periphyton along fixed internal transects; deployment of periphytometers at three internal locations, and monitoring water quality and periphyton before, during and after flow pulse events. This work is being complemented by additional research and monitoring efforts by District scientists. This work has offered insight on each of the five guiding research questions. For example, we observed that short (ca. 1 week) flow pulses, mimicking those provided to the full-scale STA flow paths (on a relative basis), had no detrimental effect on outflow TP concentrations (Key Question #1). Alkaline phosphatase activity (APA) is an indicator of P limitation and a measure of the ability for naturally occurring monoesterase enzymes to increase bioavailability of recalcitrant P compounds. While water column APA was depressed and/or diluted during high flow conditions, levels increased in the days following the pulses, indicating that a temporary increase in P loading during high flows does not curtail enzyme production by biota. Another concern, that flow pulses will create flow velocities high enough to disrupt the sediments and biomass, has proven unfounded within the current PSTA cell. In the largest pulse test, thought to be representative (on a relative basis) of high pulses in the full-scale STA flow paths, the biota and sediments remained intact and well-functioning. Indeed, direct measurements of enzyme activity in periphyton communities before and after the largest flow pulse demonstrated no reduction in activity as a result of the pulse. Other factors controlling enzyme activity, and the removal of DOP and PP within PSTA cells, are still under investigation. Sixteen internal water quality surveys have been performed in the PSTA cell since July 2011 and have typically shown declining or flat TP profiles, and gradually increasing phosphatase enzyme activities, within the wetland. Full-scale PSTA systems, therefore, can exhibit a reasonable ability to succeed under naturally variable flow conditions. With respect to Key Question #2, studies both within the PSTA cell and in mesocosms are yielding insight into the characteristics of sedimen...

STA-3/4 PSTA Cell. A “full-scale” PSTA demonstration area was constructed from 2004 to 2005 for the purpose of addressing uncertainties associated with large-scale implementation of periphyton-based treatment technology. The PSTA Project is located on a total of 400 acres in STA-3/4, and is comprised of a 200-acre Upper SAV Cell, a 100-acre Lower SAV Cell and a 100-acre PSTA Cell (Figure 1). The PSTA Cell is unique among existing STA treatment cells in that the peat layer was scraped and hauled away, exposing the underlying rock.