Influences of seasons, N/P ratios and chemical compounds on phosphorus removal performance in algal pond combined with constructed wetlands

Nitrogen (N) and phosphorous (P) are main contaminants and P removal was restrained by several factors: season, N/P, and chemical compounds (CCs) in water ecosystems. In this paper, two algal ponds combined with constructed wetlands were built to increase the removal performance. Different hydraulic retention time (HRT), different N/P and chemical compounds were chosen to investigate the influences of the above factors on the contaminant removal performance. The optimum phosphorus removal rate was 69.74% under the nitrogen removal of 92.85% in influent containing PO₄^3- after 3-day HRT in algal pond combined with constructed wetlands. The investigation results indicated that these factors improved the nutrient removal efficiencies. Seasonal influence on the removal performance can be avoided by choosing the optimal HRT length of 3days. The higher N/P at 60 can improve the phosphorus removal and the lower N/P at 15 showed the stronger synergistic effect between phosphorus and nitrogen removals. Compared with PO₃^- and P₂O₇^4- in influent, PO₄^3- affected phosphorus removal more significantly. The better linear fitting between organic phosphorus removal and nitrogen removal in influent contained P₂O₇^4- was found. Algae can absorb nutrients for growth, and oxygen release, microbial activity intensification and microbial carbon replenishment induced by algae will improve the performance. The study suggested that the control of HRTs, N/Ps, CCs, and algae might be an effective way to improve wastewater treatment performance.