Effects of flashing light–emitting diodes (LEDs) on membrane fouling in a reciprocal membrane photobioreactor (RMPBR) to assess nitrate and phosphate removal from whey wastewater

Abstract

Light is one of the most critical factors for the growth of microalgae; therefore, optimization and accessibility of light improve productivity and wastewater nutrient removal is important. The flashing light effect allows microalgae to use light effectively through intermittent exposure. Nutrient assimilation and membrane fouling were considered in a reciprocal membrane photobioreactor (RMPBR) and an LED flashing light was provided as a source of illumination. The objective of this study was to bridge the gap between light delivery and RMPBR performance. In this connection, we examined flashing lights with frequencies of 1 Hz and 1000 Hz at a constant duty cycle of 60% along with continuous light. Regarding the effect of the flashing light on RMPBR, the cells which acclimated to flashing light of 1000 Hz resulted in maximum removal of nitrate (97%) and phosphate (70%). However, the culture with the low frequency of 1 Hz was only able to remove nitrate and phosphate up to 68% and 47%, respectively. Furthermore, the reactor with 1-Hz flashing light frequency was fouled earlier within 84 h thereby reaching the highest pore-blocking. Proteins and carbohydrates were recognized as a major cause of fouling in the lowfrequency flashing light. We conclude that high-frequency flashing light (1000 Hz) could be an effective light condition for nutrient uptake in wastewater treatment.

CultureLED: A 3D printer-based LED illumination cultivation system for multi-well culture plates

“…Similar results have been achieved with Chlorella vulgaris , which was grown under 1 s/ 1 s (0.5 Hz) light/ dark LED light regimes, compared to continuous LED light regimes [ 18 ]. Nevertheless, various algal strains show different growth rates in other light regimes as shown in several publications [ [15] , [16] , [17] , [19] ]. We hope that the system users will examine other light regimes and different algal strains.…”

“…Indoor microalgae cultivation is usually done in climate-controlled growth rooms/cabinets where an orbital shaker is typically used for agitation. Small scale LED systems for microalgae cultivation mounted on orbital shakers are seldom published [ [10] , [14] ] while publications regarding microalgae cultivation under different LED source light regimes are more common [ [15] , [16] , [17] , [18] , [19] ].…”

A Comprehensive Review on Pulp and Paper Industries Wastewater Treatment Advances

“…Environmental biotechnology has received significant attention in recent years for the treatment of polluted water resources as a cost-effective and environmentally friendly approach with high efficiency to remove target compounds and being suitable for the reduction of BOD and COD from effluent. − Researchers are increasingly concentrating on using biological ways to treat pulp and paper wastewater, either as a single step or in combination with other physical and chemical procedures. When compared to physical and chemical techniques, biological approaches have a higher capacity to reduce BOD and low molecular weight chemicals such as chlorinated lignin derivatives, and as a result, these methods have been recognized as a promising alternative for pollutant elimination .…”

Grand Challenges in Application of Microalgae for Nutrient Recovery

“…As an example, the production of biomass and the removal of nutrients from wastewater can be influenced by light intensity (Azizi et al, 2021a). The optimal light intensity required for algal species or biomass concentrations can vary (Keramati and Azizi et al, 2021). In the case of culturing Nannochloropsis salina, it was observed that increasing light intensity promoted biomass production.…”