Simultaneous Phosphorus Recovery in Energy Generation Reactor (SPRING): High Rate Thermophilic Blackwater Treatment

The present work studied the application of a thermophilic upflow anaerobic sludge blanket (UASB) reactor treating source-diverted blackwater for simultaneous energy (in the form of methane production) and nutrient (phosphorus) recovery. Our results showed that a methane production rate of 2.4 ± 0.1 NL CH4/(L d) can be achieved with an organic loading rate of 12.9 kg COD/(m3d) and a methane yield of 55.9 ± 6.2%; far exceeding previous yields reported for blackwater treatment. Most significant was the removal of phosphorus (77.7 ±8.5% PO4-P) in the form of Ca3(PO4)2 precipitates in the anaerobic granular sludge. Key factors thought to promote the observed performance included rapid protein and urea hydrolysis along with hydrogenotrophic methanogenesis (by Methanosarcina spp.), and localized pH increase enhancing granulation and phosphorous sequestration. The granule sludge rich-in phosphorus contained negligible heavy metal contamination, and could provide an alternative source for phosphorus refinery or direct agricultural use.