Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007
During 272 days of operation (ceasing December 12, 2005), approximately 684,000 gallons of liquid alum were consumed to treat 7,128 ac-ft of water. Approximately 1,599 kg of TP were removed at a cost of $195.67/kg TP ($88.74/lb). These values exclude the cost of constructing or operating the MFW or its acquisition cost. However, the initial fixed costs ($54,475 or 17% of the total) of the alum injection system will not be required during future use of the system. Without treatment, the annual P loading that the District has allocated to this property would have been exceeded by nearly six times.
By comparing the flow rates and water quality results some conclusions can be made as to the best way to operate this and other similar systems. The most important factor in achieving the best efficiencies appeared to be consistent flow and reduced residence times in the cells to reduce leaching of phosphorous from the soils. External factors that could not be controlled such
and the lowest
as rainfall and power outages improved throughout the period
However, procedures were also levels of discharged phosphorous
were measured during made it much easier to
the last month of operation. Switching from pumped flow to gravity flow achieve a consistent flow. A decreased alum dosing during the last month
of operation allowed for increased flow discharge concentrations as a result of the
during this period and shorter residence time.
The restoration of former agricultural lands is a complex and lengthy process. Portable alum injection systems can be used to cost-effectively reduce the influence of impacted areas on the surrounding ecosystem and shorten the restoration timeline while greatly improving management flexibility. The lessons learned have already been utilized on other District sites. For example, this particular portable system has already been mobilized to another site where it is operating off the electrical grid.
Session 4 – Page 17