Brian LeBlanc | 2/5/2010 10:03:18 PM
Faculty from the W.A. Callegari Environmental Center (LeBlanc, Carney, Iqbal and Martin) have been collaborating with scientist and faculty from other AgCenter units (Sheffield, Biological and Agricultural Engineering), (Moreira, Southeast Research Station), (Achberger, Life Sciences) on studies and outreach related to non-point pollution from dairy and livestock operations in the state.
Traditionally, wastewater from southeastern Louisiana dairy operations has been collected from parlor and holding pens and stored in anaerobic/facultative lagoons for long periods of time (up to 5 years) before manure is recycled onto pasture and/or croplands. Milking parlor wastewater contains diluted amounts of manure, milk and residues of cleaning products (ammonium, phosphorus, chlorine). There are numerous reasons for hydraulic management of dairy waste and for the widespread use of anaerobic/facultative lagoons in the southern United States. High pluvial rates, lower equipment and energy input requirements, and easy handling of liquid manure are some of the most important of those characteristics. As dairies expand, they relatively reduce treatment effectiveness thus increasing the risk of nutrients and pathogen losses to the environment. Application rates are typically high because nutrient concentration in wastewater are generally low. This results in very large quantities of wastewater necessary to replace nutrients otherwise provided by commercial fertilizers for optimum plant growth. The immediate consequence of high liquid-waste application rates is an increased risk of air, soil and water pollution through volatilization, leaching and runoff/erosion.
Another major consequence of urban sprawl is that dairymen struggle with land availability and costs, further limiting the area onto which waste can be spread safely. Considering nutrient value alone, spreading manure onto land for recycling costs twice as much as commercial fertilizer for comparable application rates. There is mounting pressure on dairy producers to adopt management practices that improve wastewater treatment and reduce threats to the environment and human health. Minimizing the practice of manure application rates above agronomic recommendations will reduce nutrient and pathogen contamination of Louisiana waterways. Reducing nutrient content in treated wastewater by improving treatment will result in less land required for safely spreading waste at agronomic rates.
Anticipating potential for stricter regulation and recognizing that it may be more economical to remove nutrients from wastewater in some circumstances, we have begun a collaboration with Floating Island Environmental Solutions located in Baton Rouge, La. This project, in its early stages, is designed to test the treatment effectiveness for selected physical, chemical and microbiological characteristics in a multi-stage treatment system located at LSU AgCenter’s dairy in Franklinton, La., and is composed of an anaerobic/facultative lagoon, aerobic lagoon and constructed wetland using this floating island technology. The use of these floating islands to grow plants in a multi-stage wastewater-treatment system should improve nutrient removal from wastewater, thus reducing the risk of environmental hazards. This system will facilitate harvesting of plants of economic value to producers and hopefully boost technology adoption. Similarly, traditional wetland plants with little to no economic value make up the second part of this test. Despite the fact that the biomass grown on these islands may not be marketable, pollution abatement may be too great when compared to traditional agronomic crops to rule out the value in cultivating small amounts of these plants for their ability to mitigate pollutants in lagoon water. That phase of testing will begin immediately following the first phase.
One of the perceived additional benefits of the floating island system over traditionally planted-emergent wetlands is the ease of wetland remediation after a wetland becomes saturated and nutrient uptake slows, stops or in some case begins to actually leach out pollutants back into the waterway. Traditional wetlands systems must be periodically evaluated to determine if nutrient uptake is still continuing and at what rate. New systems are always productive because the plants are in an active and vigorous growing stage. However, at some point these systems slow or stop as the plant community and the wetland meet or exceed its carrying capacity.
Remediation, in order to restore pollution uptake, often requires drying out of the wetland and clipping the emergent tops or completely removing the plants. One perceived value of the floating island concept is that these floating island substrates can be removed from a lagoon or wetland system by using cables and tractor to bring the system onto land to work. These floating islands can be clipped back to any stage, and the substrate with the concentrated mass of roots and rhizomes can be quickly redeployed by pulling the mass back into the waterway so nutrient uptake can begin again quickly with little downtime or disruption to the lagoons. This same principal can be applied to any type of wastewater treatment system, not just agricultural systems, including storm water retention ponds and similar applications.
The main goal of the proposed research is to develop and evaluate newer, more effective wastewater treatment systems for the dairy industry in Louisiana. The specific objectives of this project are to evaluate multiple-stage wastewater treatment (anaerobic?aerobic?constructed wetlands) coupled with hydroponic plant growth (floating islands) for nutrient and pathogen content amelioration; to compare two densities of hydroponic wastewater treatment according to their abatement efficiencies for nutrient and pathogens; and to determine and compare seasonal variability of coliforms and nutrient loads in the influent and the mitigation effectiveness of the systems. For more information, contact Brian LeBlanc at (225) 578-6737 or e-mail.