David Rickards, President and CEO of Birdsong Gardens offers an economically profitable and sustainable solution to the problem of Delmarva’s deteriorated water quality.
Duckweed ( Lemna minor) has been commonly treated as a rapidly growing nuisance aquatic plant to be disposed of . Generally, duckweed is controlled with copper algicide compounds, having negative impact on fish and other aquatic and estaurine life with a net deterioration of the natural biota. However, controlled harvesting and processing of lemna minor can yield useful and profitable commercial products with significant reduction in both nutrient and toxic water pollution in natural waterways and man made holding facilities.
A specific example is given for Allen Harim’s proposed deboning plant near Millsboro, DE:
1) Allen Harim has 1,200 acres planned for spray field irrigation (@43,560 square feet/acre).
2) Using 1/3 of the available area would allow for 3,484,800 linear feet of 5-foot wide channels.
3) If 3-foot deep lined channels were created, then 390,994,800 gallons of wastewater could flow through the system to successively reduce total nitrogen (N) and phosphorus (P) levels.
4) Placing a retention block to slow water flow rate every 500 linear feet and using a 5-inch floating boom to retain the duckweed would create 6,969 “stations” or segments.
5) The amount of nutrients consumed by lemna minor should allow wastewater to reach USEPA acceptable Total Maximum Daily Loading (TMDL) levels to enable discharge to a local tributary or safe offsite spray irrigation.
6) In the event of exceptionally high nutrient loading, if the discharge water does not meet EPA TMDL standards, it could be pumped back into the proposed 90,000,000-gallon holding tank and recycled through the system.
7) A controlled NSF SBIR study completed in 2012, using 1900 gallons of water from Millsboro Pond, indicated that lemna minor was capable of reducing P levels to zero within one week and N levels to zero within two weeks.
8) The amount of time available to treat Allen Harim’s wastewater in the proposed system would allow lemna minor to reduce nutrient levels to acceptable levels.
9) The duckweed biomass could be harvested weekly to be used as a poultry feed additive containing a 30 per cent protein level.
10) The system would eliminate groundwater contamination.
This is one method of an economically and ecologically sustainable solution to poultry related water quality impact. The system can be readily adapted to other forms of water pollution in and scaled up to watershed levels by removing water pollution and transforming it into useful products.
Duckweed is also adaptable to production of biobutanol as a fuel additive or alternative energy source. This would create new local industries and job opportunities and ensure long-term continuation of agriculture and existing related industries in the face of suburban sprawl by favorable alteration of agroeconomics.