Enhancement of swine manure anaerobic digestion using membrane-based NH3 extraction

The influence of suspended solids and pH in anaerobically digested piggery wastewater on membrane-based NH3 extraction was evaluated in batch tests. The increase in pH in the anaerobic broth from 8 to 9 resulted in an increase in NH3 removal efficiencies from 15.8 % ± 0.1 % to 20.9 % ± 0.4 % regardless of the suspended solids. The influence of membrane based NH3 extraction on piggery wastewater treatment was also assessed in a CSTR interconnected with PTFE membrane modules. The decrease in TKN concentrations mediated by membrane operation induced an increase in CH4 yield from 380.4 ± 84.9 up to 566.1 ± 7.8 NmLCH4 g VS fed−1. Likewise, COD and VS removal efficiencies significantly increased from 33.0 % ± 2.0 % and 25.7 % ± 2.3 % up to 61.8 % ± 1.3 % and 37.9 % ± 1.8 %, respectively. Interestingly, the decrease in NH3 concentration entailed a complete assimilation of VFA.