Pollutant removal performance of an integrated upflow-constructed wetland filled with haydites made of Al-based drinking water treatment residuals

ABSTRACT

This study examined the pollutants removal performance of an integrated upflow-constructed wetland (IUCW) system in a 1.5 years’ continuous operation. The average concentrations of chemical oxygen demand (COD), NH₄–N, total nitrogen (TN), and total phosphorus (TP) in the effluent were 21.9, 1.47, 2.63, and 0.18 mg/L, respectively, which corresponded to 90.1%, 23.3%, 86.1%, and 97.2% removals from the raw water, respectively. The residual concentration of COD was 219 mg/L at start-up and decreased notably to 52.8 mg/L after 50 days of operation. NH₄–N was difficult to remove because the average concentration of dissolved oxygen in the IUCW system was lower than 0.6 mg/L. In contrast, the residual concentrations of both TN and TP in the effluent were stable, with average removal rates as high as 89% and 99%, respectively, at start-up of the system. Changing the organic loading rates from 45.0 g/(m²·day) to 20.0 or 60.0 g/(m²·day) both inhibited the removal of TN. Further study showed that the removal of organic matter mainly occurred within 10–20 cm of the wetland cell. Considering its strong organic, nitrogen, and phosphate removal capacity, the IUCW system was determined to be effective in decentralized wastewater treatment.

KEYWORDS:

• Domestic wastewater
• drinking water treatment residuals
• haydite
• integrated upflow-constructed wetland
• organic loading rate

Acknowledgements

The authors are grateful to J. Mitchell Spear for his helpful suggestions and advice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China under Grant 21007050; the Science and Technology Nova Program of Shaanxi under Grant 2014KJXX-66; and the Science and technology overall plan of Shaanxi Province under Grant 2016KTCG01-17.