Effects of seeding method and single versus mixed species assemblages on the performance of Filamentous Algae Nutrient Scrubbers (FANS) for the treatment of agricultural drainage

FANS have potential for on-farm treatment to remove and recover nutrients from agricultural drainage. The performance of FANS can be influenced by the seeding method and the species composition of the algal biomass. This study compared the effects of seeding approach (controlled seeded vs. natural establishment, experiment 1) and single species (Oedogonium sp.) vs. mixed species algal assemblages (experiment 2) on the biomass productivity and nutrient removal rates of FANS treating agricultural drainage in two on-farm experiments, each conducted over a three-month period. In the first experiment, biomass established five times faster on controlled seeded FANS (10 days) compared to FANS left to naturally establish (7 weeks). In the second experiment, both Oedogonium sp. and mixed species algal assemblages seeded through controlled seeding established uniformly on FANS within two weeks. Overall, the seeding method and species composition of algal seeded on FANS did not significantly affect biomass productivity and nutrient removal performance. However, biomass washed off from Oedogonium sp. FANS was four and a half times lower than the amount washed off the mixed species FANS, resulting in a higher standing crop on Oedogonium sp. FANS and a subsequently higher nutrient removal rate due to algal assimilation. Furthermore, FANS seeded with Oedogonium sp. had a lower contamination rate in terms of percentage coverage of non-target species than mixed species FANS. These results demonstrate that controlled seeding and cultivation of a single target filamentous algae species will help maintain a higher abundance of a target species over a longer period enabling the recovery of high-quality biomass.

Automated summary

This study compared the effects of seeding method and species composition on the biomass productivity and nutrient removal rates of FANS treating agricultural drainage. The results showed that the seeding method and species composition did not significantly affect biomass productivity and nutrient removal performance. However, the FANS seeded with a single species had lower biomass wash-off and higher nutrient removal rates compared to the FANS with mixed species.