ALLEN’S BLOG
The Chinese are using Managed Aquatic Plant Systems (MAPS) on a Large Scale to Resolve Cyanobacteria Blooms-Why Don't We?
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E. Allen Stewart III P.E.
October 8, 2018​
Offered in the slides below, as generated by Dr. Zhiyung Zhang, is a summary of a Chinese project located on Lake Caohai in which confined areas of water hyacinth within the lake are managed to reduce nutrients and attenuate influence of Cyanobacteria blooms. The lake is about 2,590 acres of which about 1,310 acres are used for confined hyacinth cultivation. The project has been successful in nutrient reduction and management of Cyanobacteria (commonly called blue-green algae). The technical papers related to this effort are included in the technical document section within this website. Use the reference buttons below to upload these papers.
The findings by Qin et. al. show
"Results from the present study confirmed the great potential to use water hyacinth for Cyanobacterial bloom control and nutrient removal in algal lakes such as Lake Dianchi"
This Chinese experience is quite encouraging, and stands as supportive testimony to the research that has been done in this country over several decades. The mechanisms involved in the repression of Cyanobacteria by aquatic plants include shading, nutrient competition, and allelopathy--i.e. the production of antagonistic proteins which impede productivity of Cyanobacteria. I personally have experienced this phenomenon, as I reported in my previous blog.
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If your recall in my blog of August 23, 2018 entitled "A Long-Term Environmental and Economic Enhancement Strategy for Removal, Recovery, and Exportation as Value Added Product(s) of Phosphorus Imported and Stored as Rogue (Legacy) Phosphorus in the KOEEA Using Managed Aquatic Plant Systems (MAPS)"I presented a strategy which could work most effectively in the KOEEA, as shown in the schematic below.
For application in the KOEEA I would suggest some deviation from the Chinese model for the following reasons.
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Managing large plant corrals in a lake the size of Okeechobee would be difficult, vulnerable to weather, and harvesting would require extensive transport energy. The preference is to move water to a fixed, land based facility. It is easier and cheaper to pump water than it is to run equipment loaded with biomass across the lake.
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Land based facilities offer many logistical advantages, and facilitate reduced energy and labor demands.
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Labor is less expensive in China so they have more operational flexibility related to harvesting and processing.
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A diversity of aquatic plants should be included in the unit process train because the nutrient levels in Lake Okeechobee, while high, are much lower than what is typically found in the Chinese Lake Caohai. The effectiveness of hyacinths diminishes as total phosphorus levels drop to about 30-50 microg/L (ppb) and total nitrogen to less than 1 mg/L. The Algal Turf Scrubber and STA-MAPS type facilities will better facilitate reduction of total phosphorus to 10 ppb or less.
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Harvesting and processing facilities will be more efficient when they are integrated, so transition from plant removal to plant processing is not hindered by prolonged transport or storage times.
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Release of final effluent back into the lake will be of high quality with reduced nutrient levels and very high dissolved oxygen levels, which will result in immediate improved fisheries in the vicinity of these discharges. See the picture below at the discharge from an Algal Turf Scrubber (10 MGD) in Indian River County--note the large bass within the circle.
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A Large Bass in the vicinity of the discharge from the Indian River County 10 MGD Algal Turf Scrubber --Egret Marsh Stormwater Park
So let me offer some suggestions. First of all, lets get the involved agencies, such as SFWMD, FDEP and FDACS to send a contingent of qualified objective scientists, engineers, and agriculturists to China to visit this Lake Caohai site and speak with the Chinese researchers. Then have them write a findings report to share with all involved parties, including the public at large. From this, establish feasibility and develop an implementation strategy with budgetary needs for presentation to the Florida Legislature and U.S. Congress.
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By the way, before I close, I have received comments from those concerned about using an invasive such as hyacinths as a target for cultivation. The irony here is that the more nutrients removed by the hyacinths in a controlled facility the less productive will be those hyacinths remaining in the lake. This is the same strategy we use for treating domestic wastewater--the very bacteria and micro-organisms we use to treat the organics in wastewater are the same organisms that would deplete oxygen levels in the receiving stream if there were no treatment. It is the same as fighting fire with fire.
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Comments are welcomed. In my next Blog I want to get into a review of the herbicide spraying program and its impact upon water quality and ecological and human health within our waters.