Post treatment of swine anaerobic effluent by weak electric field following intermittent vacuum assisted adjustment of N:P ratio for oil-rich filamentous microalgae production

Abstract A weak electric field (EF) was applied to decolorize the swine anaerobic effluent, which was followed by N:P ratio adjustment via intermittent-vacuum stripping (IVS) system for oil-rich filamentous microalgae Tribonema sp. cultivation. A higher electric field strength, higher temperature, and lower pH conditions showed higher efficiency in decolorization and nutrients removal during EF application. In the group of 30:1 (N:P) ratio, Tribonema sp. had the largest biomass accumulation (2.04 g·L−1) after 14 days cultivation. However, the 20:1 group had highest oil accumulation (oil content 55.4 ± 3.4%), while 30:1 (N: P) group was 42.3 ± 1.8%. Under the conditions of sufficient nitrogen (50:1 group), the highest contents of α-linolenic acid (15.5%) and ω-3 fatty acids (21.8%) were reached. The integrated treatment of EF, IVS and microalgae cultivation demonstrated to be effective for nutrients recycling and sustainable biomass production.