Application of Gas-Permeable Membranes For-Semi-Continuous Ammonia Recovery from Swine Manure

Abstract

Gas-permeable membrane technology is a new strategy to minimize ammonia losses from manure, reducing pollution and recovering N in the form of an ammonium salt fertilizer. In this work, a new operational configuration to recover N using the gas-permeable membrane technology from swine manure was tested in a semi-continuous mode. It treated swine manure with a total ammonia nitrogen (TAN) concentration of 3451 mg L−1. The system was operated with low aeration rate (to raise pH), and with hydraulic retention times (HRT) of seven days (Period I) and five days (Period II) that provided total ammonia nitrogen loading rate (ALR) treatments of 491 and 696 mg TAN per L of reactor per day, respectively. Results showed a uniform TAN recovery rate of 27 g per m2 of membrane surface per day regardless of the ALR applied and the manure TAN concentration in the reactor. TAN removal reached 79% for Period I and 56% for Period II, with 90% of recovery by the membrane in both periods. Water capture in the acidic solution was also uniform during the experimental period. An increase in temperature of 3 °C of the acidic solution relative to the wastewater reduced 34% the osmotic distillation and water dilution of the product. These results suggested that the gas-permeable membrane technology operating in a semi-continuous mode has a great potential for TAN recovery from manure.

Pilot-Scale Demonstration of Membrane-Based Nitrogen Recovery from Swine Manure

“…The obtained removals and recoveries were lower than those in previous laboratory studies, probably due to the lower ratio of membrane area per volume of swine manure used in the pilot plant. More specifically, the pilot plant was operated with a ratio of 0.0026 m 2 of membrane per liter of swine manure, while previous experiments at lab-scale were carried out with ratios 4–5 times higher (0.009–0.013 m 2 L −1 ) [ 6 , 7 , 10 , 12 , 13 ]. The lower ratio of membrane in the pilot plant compared to previous studies implied a lower contact surface area between manure and trapping solution.…”

“…These results fit well with previous laboratory studies recovering TAN with gas-permeable membranes, which all were carried out at room temperature (22–25 °C). More specifically, these previous investigations reported TAN recovery rates in the range of 22.7 to 30.7 g TAN m −2 day −1 [ 6 , 10 , 12 ]. Therefore, it is recommended to maintain a temperature in the manure above 25 °C to optimize TAN recovery using gas-permeable membranes.…”

“…Previous investigations using gas-permeable membranes to recover nitrogen at lab-scale in batch mode have demonstrated that the TAN recovery rate decreases with time during a batch, whereas it remains steady when operating at semi-continuous mode [ 10 , 12 ]. Since the pilot plant was operated in batch mode, the TAN recovery rate decreased with time, following a second-order curve ( Figure 6 ), with most of the TAN recovered in the first week.…”

“…The selected pressure to lift the trapping solution to the distribution sealed pipeline was 0.2 bar, being 0.5 bar the greatest outlet pressure for not damaging the membranes used. A heating blanket was placed below the ammonia concentration tank to reduce osmotic distillation of the membrane by increasing the temperature of the trapping solution [ 10 ].…”

“…This technology has been successfully applied to recover nitrogen from ammonia-rich wastewaters, such as livestock wastes or anaerobic digestates, producing valuable segregated fertilizer nutrients [ 6 , 7 , 8 ]. Diverse factors have been identified for improving the efficiency of this technology, namely the increase in the pH of the wastewater, the flow rate of the trapping solution, or the wastewater agitation [ 6 , 7 , 8 , 9 , 10 ]. For example, nitrogen recovery from raw swine manure reached 81% when pH in the wastewater was maintained in the range of 8.5–9.…”