Purification of small-scale stagnant water in urban regions: Human-powered water lift and bank-based constructed wetland

To purify small-scale stagnant water, an on-site ecological system with human-powered water lift and bank-based constructed wetland was built, and bank-based constructed wetland was consisted of two absorption substrates of clinker and volcanic ash, and yellow iris (Iris pseudacorus L.). During the experiment period for 90 days, the system can effectively circulate stagnant water, increase dissolved oxygen (DO) by more than 45%, and decrease chemical oxygen demand (COD) by 20–45%, but it showed lower nitrogen and phosphorus removal rate in water (<10%). In two substrates of clinker and volcanic ash, the nitrogen accumulation in the total plant reached 244.3 mg and 170.7 mg, significantly higher than the phosphorus accumulation, which only reached 12.0 mg and 5.8 mg, respectively. Nutrients absorption of plant is important way of removing nitrogen and phosphorus pollutants from water, while proper plant harvest should be conducted to avoid decay in autumn, and bank-based wetlands may provide a convenient method of doing so. The experiment demonstrated that this type of ecological system is option way for purifying stagnant water.