Evaluation of phosphorus runoff from sandy soils under conservation tillage with surface broadcasted recovered phosphates.

Potential new sources of phosphorus (P) fertilizer are the recovered P from livestock wastewater through chemical precipitation and the ash from combusting animal manures. Although most of the research on P losses from conservation tillage include high water-soluble P compounds from commercial fertilizer sources, information on the use of non-conventional, low water-soluble, recycled P sources is scarce. Particularly for sandy soils of the United States (US) Southeastern Coastal Plain region, research driven information on P loss into the environment is needed to determine recommendations for a direct use of new recycled P sources as crop P fertilizers. The objective of this study is to investigate the potential P runoff from sandy soils under conservation tillage, fertilized with recovered P from liquid swine manure and turkey litter ash in comparison with commercial P fertilizer triple superphosphate (TSP). The field study included two typical sandy soils of the US Southeastern Coastal Plain region, the Noboco and Norfolk. Simulated rain corresponding to the annual 30-min rainfall in the study site (Florence County, South Carolina) was applied to plots treated with recovered P from liquid swine manure, turkey litter ash, and TSP, including a control with no P added. The runoff was monitored and sampled every 5 min during the test and composite soil samples were collected from the top (0-15 cm) and subsurface (15-30 cm) soil layers in each plot. Laboratory analyses were conducted to quantify both total P (TP) and soluble reactive P (SRP) in runoff samples, and the soil test P in the soil layers. Two-way analyses of variances show significant treatment effects on both TP and SRP runoff. The quantities of SRP runoff from plots treated with the recovered P from swine manure and turkey litter ash represent respectively 1% and 7-8% of SRP runoff from plots treated with TSP. Hence, the use of the recovered P materials as crop P fertilizers through surface broadcast application present less environmental risks compared to commercial TSP.

Phosphorus recovery from pig manure solids prior to land application.

Land disposal of pig manure is an environmental concern due to an imbalance of the nitrogen to phosphorus (N:P) ratio for crop production, leading to excess phosphorus (P) in soils and potential risks of water pollution. A process called "quick wash" was investigated for its feasibility to extract and recover P from pig manure solids. This process consists of selective dissolution of P from solid manure into a liquid extract using mineral or organic acid solutions, and recovery of P from the liquid extract by adding lime and an organic polymer to form a P precipitate. Laboratory tests confirmed the quick wash process selectively removed and recovered up to 90% of the total (TP) from fresh pig manure solids while leaving significant amounts of nitrogen (N) in the washed manure residue. As a result of manure P extraction, the washed solid residue became environmentally safer for land application with a more balanced N:P ratio for crop production. The recovered P can be recycled and used as fertilizer for crop production while minimizing manure P losses into the environment.

Development of a second-generation environmentally superior technology for treatment of swine manure in the USA.

New swine waste management systems in North Carolina need to meet high performance standards of an environmentally superior technology (EST) regarding nitrogen, phosphorus, heavy metals, pathogens, ammonia and odor emissions, and remain affordable and simple to operate. The objective of this study was to develop a second-generation treatment system that can achieve high EST standards at reduced costs. The system used solids separation, nitrification/denitrification and phosphorus removal/disinfection, and was demonstrated at full-scale on a 5145-head swine farm during three production cycles (15-months). Removal efficiencies were: 98% suspended solids, 97% ammonia, 95% phosphorus, 99% copper and zinc, 99.9% odors, and 99.99% pathogens. The system met EST standards at 1/3 the cost of the previous version. Animal health and productivity were enhanced; hog sales increased 32,900 kg/cycle (5.6%). These results demonstrated that: (1) significant cost reductions were achieved by on-farm implementation and continued engineering improvements, and (2) the new waste management system substantially benefited livestock productivity.

Removal of phosphorus from livestock effluents.

For removal of phosphorus (P) from swine liquid manure before land application, we developed a treatment process that produces low P effluents and a valuable P by-product with minimal chemical addition and ammonia losses. The new wastewater process included two sequential steps: (i) biological nitrification and (ii) increasing the pH of the nitrified wastewater to precipitate P. We hypothesized that by reduction of inorganic buffers (NH(4)(+) and carbonate alkalinity) via nitrification, P could be selectively removed by subsequent hydrated lime [Ca(OH)(2)] addition. The objective of the study was to assess if this new treatment could consistently reduce inorganic buffer capacity with varied initial concentrations of N (100-723 mg NH(4)(+) L(-1)), P (26-85 mg TP L(-1)), and alkalinity (953-3063 mg CaCO(3) L(-1)), and then efficiently remove P from swine lagoon liquid. The process was tested with surface lagoon liquids from 10 typical swine farms in North Carolina. Each lagoon liquid received treatment in a nitrification bioreactor, followed by chemical treatment with Ca(OH)(2) at Ca rates of 0, 2, 4, 6, 8, 10, and 12 mmol L(-1) to precipitate P. This configuration was compared with a control that received the same Ca rates but without the nitrification pretreatment. The new process significantly reduced >90% the inorganic buffers concentrations compared with the control and prevented ammonia losses. Subsequent lime addition resulted in efficient pH increase to > or = 9.5 for optimum P precipitation in the nitrified liquid and significant reduction of effluent total P concentration versus the control. With this new process, the total P concentration in treated liquid effluent can be adjusted for on-farm use with up to >90% of P removal. The recovered solid Ca phosphate material can be easily exported from the farm and reused as P fertilizer. Therefore, the new process can be used to reduce the P content in livestock effluents to levels that would diminish problems of excess P accumulation in waste-amended soils.

Water quality improvements of wastewater from confined animal feeding operations after advanced treatment.

Current trends of animal production concentration and new regulations promote the need for environmentally safe alternatives to land application of liquid manure. These technologies must be able to substantially remove nutrients, heavy metals, and emissions of ammonia and odors and disinfect the effluent. A new treatment system was tested full-scale in a 4360-swine farm in North Carolina to demonstrate environmentally superior technology (EST) that could replace traditional anaerobic lagoon treatment. The system combined liquid-solids separation with nitrogen and phosphorus removal processes. Water quality was monitored at three sites: (i) the treatment plant as the raw manure liquid was depurated in the various processes, (ii) the converted lagoon as it was being cleaned up with the treated effluent, and (iii) an adjacent traditional anaerobic lagoon. The treatment plant removed 98% of total suspended solids (TSS), 76% of total solids (TS), 100% of 5-d biochemical oxygen demand (BOD(5)), 98% of total Kjeldahl nitrogen (TKN) and NH(4)-N, 95% of total phosphorus (TP), 99% of Zn, and 99% of Cu. The quality of the liquid in the converted lagoon improved rapidly as cleaner effluent from the plant replaced anaerobic lagoon liquid. The converted lagoon liquid became aerobic (dissolved oxygen, 6.95 mg L(-1); Eh, 342 mv) with the following mean reductions in the second year of the conversion: 73% of TSS, 40% of TS, 77% of BOD(5), 85% of TKN, 92% of NH(4)-N, 38% of TP, 37% of Zn, and 39% of Cu. These findings overall showed that EST can have significant positive impacts on the environment and on the livestock industries.

Dewatering of phosphorus extracted from liquid swine waste.

Phosphorus (P) recovery from liquid swine manure is an attractive technology when on-farm application of liquid swine manure is not an option. We developed a technology that enables separation of this P, but its high moisture content makes transportation difficult. In this work, we investigated dewatering procedures to concentrate the P product. Sludge rich in calcium phosphate (> 20% P2O5) was obtained using a field prototype, and it was further dewatered using a combination of polymer treatment and filter bags. Anionic polyacrylamide polymer treatment (> or = 20 mg/L) was effective to flocculate the P-rich sludge, which enhanced filtration and dewatering. Without polymer, filtration was incomplete due to clogging of filters. Non-woven polypropylene and monofilament filter bag fabrics with mesh size < or = 200 microm retained > 99% of suspended solids and total P. Solids content dramatically increased from about 1.5% to > 90%. These dewatered solids can be transported more economically off the farm for use as a valuable fertilizer material.