Abstract
This study was aimed at evaluating gas-permeable membrane technology (N-recovery) coupled with anaerobic digestion for the treatment of swine manure. For this purpose, 66.7% of the initial total ammoniacal nitrogen contained in centrifuged swine manure (SM) was first recovered by an e-PTFE gas-membrane as an ammonium sulfate solution. The resultant manure effluent with reduced ammonia (ATM) was evaluated as anaerobic digestion (AD) substrate. It was compared with AD using the initial swine effluent (SM) without the N-recovery step (control). An organic loading rate (OLR) of 2.8 ± 0.5 g TCOD L-1 day-1 was established to ensure a stable process when working at semi-continuous mode. Regardless of the operation mode, methane yields of 105 ± 2 mL CH4 g TCOD -1 were obtained for ATM. The combined treatment resulted in an organic matter removal efficiency of 68.6%. Initial TCOD accounted for 54.69 g L-1. The results prove that it is feasible to combine gas-permeable membrane technology and anaerobic digestion for the treatment of swine manure, contributing to ammonia emissions mitigation and sustainable livestock waste treatment. Moreover, by means of this technology combination, a variety of valuable products is obtained, namely sustainable energy in the form of methane and fertilizers.
Highlights
Spain is the second European country with the highest pig population, accounting for 29,970,000 swine heads in 2017
The inoculum used for the anaerobic digestion (AD) experiments (AD inoculum) was a mesophilic anaerobic sludge that was obtained from the municipal wastewater treatment plant (WWTP) in Valladolid, Spain
66.7 % of the initial total ammoniacal nitrogen (TAN) contained in swine manure (SM) was semi-continuously recovered as an ammonium sulfate solution
Summary
Spain is the second European country with the highest pig population, accounting for 29,970,000 swine heads in 2017. SM has been traditionally applied for agricultural purposes close to the farm. This is not always possible in recent times, due to the size increase in livestock farms together with their location in concentrated areas. Since agriculture is nowadays the largest source of ammonia (NH3) emissions (EEA, 2015), which are closely related to a variety of environmental problems and to human health risks, an improved management of SM with reduced NH3 emissions is urgently required In this vein, a new European Directive was proposed in 2016 to improve the quality of the air (EC-European Commission, 2016). In the case of Spain, the reduction commitment for NH3 annual emissions accounts for Membranes and AD Manure Treatment
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