Aquaculture wastewater contains high levels of organic matter and nutrients, which can be harmful to aquatic life if discharged improperly into surface water bodies. Coagulation-flocculation is currently the best practice for treating aquaculture effluent with biocoagulants, offering an alternative to metal-based coagulants. This study aims to investigate the potential of Tamarindus indica seeds as a biocoagulant for treating aquaculture wastewater, focusing on the optimal solvent extraction, concentration, and dose. This study also examines the toxicity of biocoagulants to aquatic organisms. Coagulation-flocculation study was conducted under jar test experiment with NaCl, NaOH, and HCl used as solvents; concentration of 0-10 g/L; and doses of 1-5 % v/v under 120 rpm (rotation per minute) rapid mixing for 1 min, 20 rpm slow mixing for 20 mins, and 60 mins sedimentation time. A characterization study showed that NaCl-treated T. indica has a positive zeta potential charge, attributed to the presence of hydroxyl, carbonyl, and amide functional groups. Under this optimum condition (NaCl-extract, 6 g/L, and 4 % v/v), the biocoagulant achieved high removal (>50 %) of turbidity, TSS (total suspended solid), and ammonia and considerably good removal of other parameters (TN [total nitrogen], BOD5 [biological oxygen demand], COD [chemical oxygen demand]). The toxicity test revealed that no mortality was observed at a concentration of 1 g/L, whereas 10 g/L resulted in a 100 % mortality rate after 24 hours of exposure. Further toxicity analysis is suggested to be conducted using treated final effluent (not directly using biocoagulant substances) to observe the direct impact of the treated wastewater if discharged into the water bodies.

The use of plants as biocoagulants in water/wastewater treatment is currently emerging. This review article explores the potential of each plant's part functioning as a biocoagulant for pollutant removal. Bibliometric analysis was employed to analyze the development of research in natural and biocoagulants, while descriptive analysis was used to clearly juxtapose the performance of each plant's part in treating water/wastewater. Bibliometric findings reveal a high increment in the publication of natural coagulants in the year 2016. The keywords of flocculation, pH, turbidity, and water purification are mentioned to be the closest node related to the coagulation. Comparison between plant parts showed that research on seeds is dominating the previous literature (26.31 %), followed by leaves (10.89 %) and peels (5.75 %). Overall performance analysis showed that plant biocoagulants are superior in removing turbidity (median 83.45 %), while the performance of removing total suspended solids, chemical oxygen demand, and biological oxygen demand are also considerably good (mean 68.38 %, 71.36 %, 67.16 %, respectively). The seeds and other parts of the plants showed the highest removal of turbidity among other parts (mean of removal 90 % and median >90 %). Other parts of the plants are composed mostly of plant extracts, including mucilage (18.47 %), gum (9.67 %), starch (8.36 %), etc. (10.37 %). Overall, the effectiveness of plant biocoagulants in removing pollutants varies compared to that of commercially available coagulants. The current development of biocoagulants indicates that research is currently in the integration and hybridization stage. Future approaches are suggested to focus on upscaling the treatment to an industrial scale, simplifying the extraction procedures, and conducting species-specific analysis to enhance and polish the current knowledge of plant bicocoagulants in water/wastewater treatment.