Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/15/2015
Publication Date: 1/14/2016
Citation: Vanotti, M.B., Dube, P.J., Szogi, A.A., Hunt, P.G. 2016. USDA-ARS research update: Improved solid-liquid separation using polymers in flushing systems and new technology to recover the ammonia from covered lagoons. Proceedings of 1st Confined Animal Manure Managers Conference: CAMM 2016. p.8-10.
Technical Abstract: Part 1: Improved method for recovery of organic solids from diluted swine manure: Solid-liquid separation of the raw manure increases the capacity of decision making and opportunities for treatment. The high-rate separation up-front using flocculants allows recovery of most of the organic compounds, which can be used for manufacture of high-quality compost materials. However, the use of flocculants and dewatering equipment is costly on high-volume, diluted wastewater. Before this research was done, the use of flocculants and dewatering equipment was not effective in swine operations that use flushing systems and produce much diluted wastewater (< 0.5% solids). Scientists at USDA-ARS, Florence, South Carolina, in cooperation with industry, conducted on-farm research to determine at full-scale if rapid settling in a decanting tank can be used to concentrate solids in flushing systems and reduce the manure volume to be treated with flocculants and dewatering presses. Subsequently, the ammonia nitrogen in the liquid was treated with nitrifying bacteria adapted to high-strength wastewater and cold temperatures, and the treated water reused for flush tank recharge. The harvested manure solids were composted in a centralized facility and converted into value added commercial products. This innovation was successful: it increased polymer use efficiency 5.4 times (from 52 to 279 lb/lb) and reduced chemical expenses by 81%. It also reduced the manure volume processed by the separator press by 26,000 gallons per day (95% reduction) that significantly reduced size of the dewatering equipment. This lower volume is one of the major advances of the third generation project: It increased solid separator press capacity and lowered operating expenses when adapted to flushing systems. Part 2: Enhanced recovery of ammonia from swine manure through gas membranes. Ammonia emissions from animal husbandry operations in the USA were estimated at 2.4 million tons/year in 2010, and the costs of fertilizers have rapidly increased in recent years, especially nitrogen fertilizer such as anhydrous ammonia which is made from natural gas. ARS researchers at Florence, South Carolina, have developed a new technology to recover concentrated ammonia from liquid manures. A US patent was awarded in 2015 (US 9,005,333 B1). The new technology uses gas-permeable membranes at low pressure that are submerged in the manure liquid. Low-rate aeration replaces alkali chemicals to raise the pH and enhance nitrogen recovery. The low-rate aeration reacted with the natural carbonates in wastewater and increased pH, which accelerated ammonia uptake in the gas-permeable membrane system without the use of alkali chemicals. The new strategy worked quite well with swine manures. Digested effluents from covered anaerobic swine lagoons containing 1375 to 2089 parts per million (ppm) ammonium nitrogen were treated using the submerged membranes, low-rate aeration and a small amount of nitrification inhibitor (22 ppm). Ammonia recovery of anaerobically digested swine wastewater using gas-permeable membranes was enhanced using the low-rate aeration. The low-rate aeration reacted with the natural carbonates in wastewater and increased pH, which accelerated ammonia uptake by the gas-permeable membrane system without the use of alkali chemicals. The pH of the manure with aeration rose from 8.6 to 9.2 while the manure without aeration decreased from 8.6 to 8.1. Utilizing aeration, more than 96% of ammonium was able to be recovered in about 4 days of operation. In contrast, without aeration it took 25 days to treat the ammonium. Completing ammonium removal more than 5 times faster using gas-permeable membranes represented a 70% reduction in costs. This new system is expected to offer livestock producers a better way to manage ammonia in manure.