Effect of African catfish (Clarias gariepinus) culture wastewater on the growth of Chlorella sp.

The direct discharge of wastewater from African catfish culture into natural water bodies represents a major source of environmental pollution. One potential solution is to reuse aquaculture wastewater as a growth medium and nutrient source for the microalga Chlorella sp., which requires nitrogen for growth. We aimed to evaluate the effect of African catfish culture wastewater, applied at different concentrations, on the growth of Chlorella sp. A completely randomized design was used with five treatments: P0 (100% freshwater, control), P1 (75% freshwater + 25% catfish culture wastewater), P2 (50% freshwater + 50% catfish culture wastewater), P3 (25% freshwater + 75% catfish culture wastewater), and P4 (100% catfish culture wastewater), each replicated four times. The main parameters observed were the cell density and growth rate of Chlorella sp. The results showed that the wastewater concentration significantly affected the growth of Chlorella sp. The average cell density and growth rate were highest at 25% concentration (P1) and lowest at 100% concentration (P4). These findings indicate that an appropriate concentration of African catfish culture wastewater will support the production of Chlorella sp. and may enable its use as a natural feed source. Future studies should explore strategies to reduce nitrate concentrations in African catfish wastewater exceeding 50% to levels that are optimal for microalgal growth. Moreover, this study was conducted at a laboratory scale, and further study is needed on a mass/field scale, as laboratory-scale study can provide different results than field scale.