Effect of High-Strength Wastewater on Formation Process and Characteristics of Hydrophyte Periphytic Biofilms

At present, studies on hydrophyte periphytic biofilm have mainly focused on natural water bodies or low-strength wastewater due to the inability of most plants to grow in high-strength wastewater. Therefore, the formation process and characteristics of plant periphytic biofilm growing in high-strength wastewater are still unclear. Based on the microcosm experiment, the formation process and characteristics of two kinds of plants (Myriophyllum elatinoides (Me) and Pontederia cordata (Pc)) periphytic biofilms were investigated with changes in water quality. The periphytic biofilm weight (BW) of Me and Pc reached equilibrium at 21 days, while the BW of Me was higher than that of Pc under high-load conditions (total nitrogen (TN) concentration ≥ 104.0 mg/L). When the TN concentration was 201.7 mg/L, the highest BW of Me was 0.99 mg/cm2. In addition, the structural complexity of hydrophyte periphytic biofilm was higher under TN concentrations ≥ 70.9 mg/L than that under TN concentrations ≤ 56.9 mg/L. N concentration and environmental factors could affect periphytic BW and biofilm Chlorophyll a (Chla.). Through linear regression fitting, it was found that periphytic BW and biofilm Chla. were positively correlated with the concentrations of NH4+-N and TN in water, while they were negatively correlated with the concentration of NO3−-N. Random Forest results showed that NO3−-N concentration had an important effect on hydrophyte periphytic BW. The results of this study provided a new understanding of the formation process and characteristics of aquatic plant periphytic biofilm under high-strength conditions and a prospect for sustainable development in the treatment of high-strength wastewater.