Nutrient recovery and ammonia-water production by MF-vacuum evaporation treatment of pig manure

Intensive livestock farming has negatively impacted the environment by contributing to the release of ammonia and nitrous oxide, groundwater nitrate pollution and eutrophication of rivers and estuaries. However, the nutrient rich manure has always been a major focal point of resource recovery. Microfiltration has proven to be the least complex and highly energy efficient recovery process among all the other available techniques, however, the low nutrient concentration (especially nitrogen) has always been a drawback when it comes to marketing of the final product. Here we report about the efficiency of manure microfiltration followed by the vacuum evaporation of the MF permeate to produce purified and concentrated ammonia water. MF results showed the complete removal of TSS. COD and total phosphorus removal were found above 80%. However, nearly 80% of the NH4+-N was recovered in the MF permeate. The used MF membrane could achieve 50% of the initial feed volume reduction while maintaining well the nutrient qualities in each stream. Lastly, MF permeate vacuum evaporation resulted in substantial 31 gL−1 of NH4+-N condensate concentration, which was nearly 12 times higher than the initial NH4+-N concentration of MF permeate. The vacuum evaporation of MF permeates compared to raw feed and concentrate stream have been proven to be a viable alternative to recover nutrient and produce cleaner and concentrated ammonia water. However, the evaporation system requires better mixing and temperature control tools to enable gradual thermal gradients and avoid bumping in the fluid, which led to high levels of water carry over.