2.3.1. Microfiltration

Manure samples were initially sieved through a 1 mm sieve to eliminate the particles (≥1 mm). The samples were then prefiltered in a dead-end stirred cell membrane filtration system, manufactured by Merck KGaA Germany (Supporting Information Figure S1), by using 0.45 µm pore sized MF membranes. The internal membrane diameter was 14 cm and the effective membrane area was calculated to be 154 cm² in the filtration cell. An initial feed volume of 500 mL was introduced in the feed tank for MF experiments. The filtrations were then performed by applying 1 bar pressure (N₂ gas, air liquid) and the rotational speed was maintained at 400 rpm. Consequently, 300 mL of permeate were collected in a sterile vial. The filtration was repeated twice for each manure sample to collect a total of 600 mL of MF permeate. The temperature was 25 °C ± 1 during the prefiltration experiments. The MF permeate samples were further analyzed for retention calculation.