## 4 Conclusions  
This study demonstrated that conducting sequential batch experiments with duckweed in the PBR-1 and microalgae in the PBR-2 fed by the effluent from the PBR-1 offers interesting advantages. Thus, duckweed effectively removes nutrients from the RW-based culture medium in PBR-1, resulting in an effluent that is less nutrient-/pollutant-rich and more suitable for microalgae growth in the PBR-2. This is, by separating duckweed and microalgae into sequential PBRs, it allows for the customization of growth conditions tailored to each organism's specific requirements, potentially resulting in enhanced overall productivity of both duckweed and microalgae. Sequential batching minimizes direct competition between duckweed and microalgae for nutrients and light, enabling each organism to thrive without interference from the other. Sequential batch systems offer flexibility in managing different stages of the process, allowing adjustments to optimize conditions for microalgae growth and overall system performance. The sequential approach enhances economic feasibility by maximizing the utility of each biological system, potentially improving the overall economic viability of the process. Both duckweed and microalgae offer potential for resource recovery, such as biofuel production, animal feed, and high-value compounds, allowing for the extraction of diverse resources from the effluent. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14188139/s1](https://www.mdpi.com/article/10.3390/app14188139/s1)]([https://www.mdpi.com/article/10.3390/app14188139/s1](https://www.mdpi.com/article/10.3390/app14188139/s1)). Figure S1: Morphological images of macro-phyte (_Lenna minor_ L. MO23) and microalgae (_Chlorella_ sp. MC18 and _Scenedesmus_ sp. MJ23-R) species. This duckweed strain was obtained from an optical stereoscopy (Motic SMZ-171, Hong Kong, China) equipped with a digital camera (Motic\(\otimes\), MGT101, Hong Kong, China); Figure S2: Daily average pH trends over culture time (days) in different macrophytes and microalgae cultures exposed to different concentrations of raw cheese whey (RW) y treated RW (TRW). Control cultures were carried out with the medium formulations of BG11. (A) _Lenna minor_ L. MO23, (B) _Chorella_ sp. MC18 and (C) _Scenedesmus_ sp. MJ23-R. Error bars indicating standard deviations (SD) for triplicatecultures; Figure S3: Whey cream content at the end of treatment with each _Lemma minor_ L. MO23 culture exposed to different inoculum contents and raw cheese whey (RW) concentrations. Error bars indicating standard deviations (SD) for triplicate cultures. ; Figure S4: Evaluation from a two-way multivariate ANOVA (MANOVA) of main effects MEDIUM (i.e treated raw whey, TRW%) and ALGA, and their interaction (MEDIUM-ALGA) on the following dependent variables: COD removal efficiency (COD-RE%) (A-C); Nitrate removal efficiency (NO\({}_{3}\) -RE%) (D-F); Phosphate removal efficiency (PO\({}_{4}\)\({}^{3-}\)-RE%) (G-I); Sulphate removal efficiency (SO\({}_{4}\)\({}^{2-}\)-RE%) (J-L). Every MEDIUM (A,D,G,J) and ALGA group (B,E,H,K) gathers all the results obtained for the two microalgae, _Chorella_ sp. MC18 (CH) or _Scenedesmus_ sp. MJ23-R (SC), and for the three MEDIUM levels, TRW-10%, TRW-20% or TRW-30%, respectively. Bars around points represent 95.0% confidence intervals. Overlapping bars indicate no significant difference. Conceptualization, M.A.M.C. and F.G.-C.; methodology, M.A.M.C., K.A.M.P., M.P.G.C., O.Q.H. and L.L.-R.; validation, M.A.M.C. ; formal analysis, M.A.M.C., K.A.M.P., M.P.G.C., O.Q.H., N.E.V.L. and L.L.-R.; investigation, M.A.M.C., K.A.M.P., M.P.G.C., O.Q.H. and L.L.-R.; resources, M.A.M.C. ; data curation, M.A.M.C. and F.G.-C.; writing--original draft, M.A.M.C. and F.G.-C.; writing--review and editing, M.A.M.C. and F.G.-C.; visualization, M.A.M.C. and F.G.-C.; agreed to the published version of the manuscript. This research did not receive any specific grant from funding agencies in the public or private sectors.