Efficiency of Toxic Substance Removal from Aquaculture Wastewater by Duckweed (Lemna minor) and Bacteria (Bacillus sp.)

Abstract

Abstract

Bioremediation, an approach to reduce hazardous substances in wastewater effluents, was used in the treatment of wastewater collected from African catfish (Clarias gariepinus) fish farm in active production in this study. The experiment was designed to evaluate the effectiveness of duckweed, Lemna minor (Td) and the bacteria, Bacillus sp (Tb) while the negative and positive control treatments were untreated wastewater and fresh well water used in production by sampled fish farm respectively. Fifteen (15) litres of the wastewater was bioremediated ex-situ with duckweeds of an average wet weight of 49.53±0.25g and 15ml of the bacterial inoculums.After 2 weeks of bioremediation, biomass of duckweed increased by 97.51%. There was a significant reduction (P<0.05) in level of phosphate, mg/L; sulphate, mg/L; nitrate, mg/L; ammonia, mg/L; biological oxygen demand, BOD, mg/L; chemical oxygendemand,COD,mg/L; andtotalsolublesolidsTSS,mg/Lbyduckweed,withreduction efficiencies of 70.70%, 90.96%, 40.18%, 77.78%, 96.66%, 96.26%and 36.94%,respectively, compared to the positive control (initial) wastewater (P<0.05). Reduction efficiency (RE) waslowerforBacillisp and negative control compared to duckweed (P<0.05).The pHlevelin the wastewater increased in all treatments, with the highest values recorded for duckweed. However, the highest dissolved oxygen level (DO) of 4.81±0.03mg/l was recorded in the bacteria treatment, followed by duckweed (4.45±0.06mg/l) and 4.09±0.06mg/l for the untreated wastewater (negative control). The results of thisstudy indicated that Lemna minor wasmore efficient in removal oftoxic substancesin commercial aquaculture wastewaterthan Bacillussp.forsustainableaquaculturepractice.