Effect of flocculation pre-treatment on membrane nutrient recovery of digested chicken slurry: Mitigating suspended solids and retaining nutrients

Use of membrane filtration is attracting increasing attention for nutrient recovery from anaerobically digested slurry. However, the challenge is to reduce membrane fouling by effective solids mitigation, while maintaining valuable nutrients. In this study, the effects of several flocculation pre-treatments using polyaluminium chloride, iron chloride, and flocculant aid at various dosages were investigated. The results showed significant improvement in membrane flux from 0.8 to 27.6 mL/m(2)/s due to solid migration (up to 75% removal). Significant loss of PO43--P (99%) and humic acids (40-80%) was observed. However, the content of NH4+-N and indoleacetic acids was largely maintained in the treated slurry. Moreover, toxic metals were significantly removed through flocculation, making the final product risk-free of heavy metals for agricultural application.