Removal and Reuse of Phosphorus as a Fertilizer from CAFO Runoff

Eutrophication is the process in which nutrient saturated waters promote algal blooms on the surface of the water. This limits the amount of dissolved oxygen content in the water, effectively limiting the range of species that can survive in a body of water. Concentrated animal feeding operations (CAFO) can contribute to this issue. The animals in a CAFO produce large amounts of nutrient-rich waste streams that can enter natural waterways if not properly managed and increase the problem of eutrophication. The ability to treat these waste streams and recover the excess nutrients would allow for not only the reduction of nutrient leaching and runoff but would help create sustainable phosphorus practice. Phosphorus is vital in terms of food production, and there is no replacement for phosphorus for plants or humans. As the population continues to increase, food demand will as well. This means that at any point that phosphorus can be recovered, it should be. To recover phosphorus effectively from waste water sources, reverse osmosis, anion exchange, or adsorption are all viable options. Woo Pig Pooie researched these options for recovering phosphorus, and adsorption was found to be the most promising from standpoints of low maintenance and cost effectiveness. Multiple adsorption materials were ranked based on appropriate performance of cost, particle size, adsorption qualities, and the effects of application of the material. Water treatment residuals, WTR (i.e. spent alum from a drinking water treatment plant), was determined to be the most effective adsorbent. WTR, a waste product, is 80% water as it exits the water treatment plant. It must be pelletized and dried before use as an adsorbent. Pelletized and dried WTR was utilized in a full-scale facility treating 62 GPM of feed using two 11,000 gallons packed columns with associated equipment. If the cost of pelletizing and drying the WTR is included, an alternative strategy for implementation on individual farms is for several farmers to form a cooperative, which would allow the minimization of the $1,460,000 fixed capital cost and the $504,000 cost of manufacturing of the drying pelletizing facility. This would allow for the maximum amount of WTR to be treated increasing the revenue of the operation to $731,500. The cooperative would have an operation of 10 years with a net present value of $5,000. Experimental results using WTR packed columns have shown non-detectable levels of phosphorus in the effluent. The produced phosphorus saturated WTR could be land applied to reduce the level of nutrients in runoff from fields, making a safer agriculture operation