Fouling mitigation in membrane distillation processes during ammonia stripping from pig manure

Over time fouling leads to membrane wetting. This is the biggest obstacle to widespread use of membrane distillation (MD) for ammonia removal from animal slurry. Feed pretreatment and cleaning strategies of membrane surMces are the most common methods to prevent or diminish fouling phenomena. This study investigates preliminary fouling of polypropylene (PP) and polytetratluoroethylene (RITE) membranes. A model manure solution was used as teed. In addition cleaning efficiencies with deionized water, NaOHIcitric acid, and Novadan agents were studied. Further microfiltration and ultrafiltration were examined as manure pretreatment to diminish fouling. To this end polyvinylidene fluoride membranes (PVDF 02 am and 150 kDa respectively) were used Organic fouling was shown to be dominant. For the model manure solution the fouling comprised lipids, carbohydrates and proteins. For pig slurry the fouling additionally contained carboxylates, free fatty acids and lignin. Among the rested cleaning strategies, Novadan agents were the most successful in removing proteins and carbohydraies from the PTFE membrane while a only removed proteins from the PP membrane. Using microffitration or ultrafiltration as a pretreament prior to MD doubled the ammonia mass transfer coefficiera for the PTFE membrane, while for the PP membrane, the ammonia mass transfer coefficient was increased 4-fold. (C) 2015 Elsevier B.V. All rights reserved.