Long-term bioaugmentation of a carrier enhanced duckweed-based wastewater treatment system via the addition of activated sludge and denitrifying phosphate-accumulating bacterium

Abstract

Duckweed exhibits distinct advantages over other aquatic plants in phytoremediation. Bioaugmentation is a promising approach for enhancing the treatment performance of various wastewater treatment systems, including duckweed-based systems (DS). However, there is a lack of suitable inoculants for field-scale DS bioaugmentation, and the long-term viability and mechanisms of these inoculants are still poorly understood. To address this, a single strain (Pseudomonas sp. DWP1) and a mixed culture (activated sludge) were separately added into two carrier-enhanced DS to systematically evaluate their application potential for DS bioaugmentation by comparing with another control DS over a year. The results indicated that adding strain DWP1 and activated sludge increased the dissolved oxygen concentration and oxidation-reduction potential of pond water. Meanwhile, they promoted duckweed growth (by 64.95% and 41.39%, respectively), enhanced nutrient recovery (by 68.97% and 44.83% for nitrogen, and 71.43% and 42.86% for phosphorus, respectively) and pollutant removal in the DS, and reduced CH₄ emission (by 68.88% and 33.16%, respectively) from the DS. Compared with activated sludge, strain DWP1 had a more significant impact on microbial diversity, community composition, and the relative abundance of dominant assemblages probably due to its high adaptability and successful survival in the duckweed system, which results in the better bioaugmentation performance of strain DWP1 in terms of duckweed biomass production, water purification, and carbon emission reduction in the DS. Therefore, strain DWP1 has greater application potential than activated sludge for the bioaugmentation of the DS.