Effect of different light-dark cycles on the membrane fouling, EPS and SMP production in a novel reciprocal membrane photobioreactor (RMPBR) by C. vulgaris species

In this study, a novel reciprocal membrane photobioreactor (RMPBR) was designed. This system includes a PLC-programmed and a spongy blade that could clean the formed cake layer on the membrane surface. Moreover, various light-dark (L-D) cycles of 24–0, 16–8, and 12–12 for the Chlorella vulgaris cultivation were applied and the effects of these cycles on the membrane fouling time, transmembrane pressure (TMP), total extracellular polymeric substances (EPS) concentration, total soluble microbial product (SMP) concentration, the carbohydrate and protein contents through EPS (EPSc and EPSp), as well as the carbohydrate and protein contents through SMP (SMPc and SMPp) were evaluated. Obtained results revealed that this mechanical membrane revival method could reduce the total resistance at about 73–85%, without any cleaning/washing via chemical substances. Besides, the obtained results from microalgae cultures demonstrated that the contrary of the total concentration of EPS in 24–0 and 12–12, the total EPS contents for the 16–8 L/D regime did not change considerably. However, the total SMP for 16–8 L/D increased. Moreover, the SMPc and SMPp for all cycles depicted the rising trend. EPSp concentration gradually increased for 12–12 and 24–0 L/D cycles. These results could indicate that the EPSp was the main effective factor in TMP variations for 12–12 and 24–0 L/D regimes. However, the EPSp and EPSc in 16–8 L/D did not show any significant changes.