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Hydrilla verticillata-Sulfur-Based Heterotrophic and Autotrophic Denitrification Process for Nitrate-Rich Agricultural Runoff Treatment.

Abstract：

:Hydrilla verticillata-sulfur-based heterotrophic and autotrophic denitrification (HSHAD) process was developed in free water surface constructed wetland mesocosms for the treatment of nitrate-rich agricultural runoff with low chemical oxygen demand/total nitrogen (C/N) ratio, whose feasibility and mechanism were extensively studied and compared with those of H. verticillata heterotrophic denitrification (HHD) mesocosms through a 273-day operation. The results showed that the heterotrophic and autotrophic denitrification can be combined successfully in HSHAD mesocosms, and achieve satisfactory nitrate removal performance. The average NO3--N removal efficiency and denitrification rate of HSHAD were 94.4% and 1.3 g NO3--N m-3·d-1 in steady phase II (7-118 d). Most nitrate was reduced by heterotrophic denitrification with sufficient organic carbon in phase I (0-6 d) and II, i.e., the C/N ratio exceeded 4.0, and no significant difference of nitrate removal capacity was observed between HSHAD and HHD mesocosms. During phase III (119-273 d), sulfur autotrophic denitrification gradually dominated the HSHAD process with the C/N ratio less than 4.0, and HSHAD mesocosms obtained higher NO3--N removal efficiency and denitrification rate (79.1% and 1.1 g NO3--N m-3·d-1) than HHD mesocosms (65.3% and 1.0 g NO3--N m-3·d-1). As a whole, HSHAD mesocosms removed 58.8 mg NO3--N more than HHD mesocosms. pH fluctuated between 6.9-9.0 without any pH buffer. In general, HSHAD mesocosms were more stable and efficient than HHD mesocosms for NO3--N removal from agricultural runoff during long-term operation. The denitrificans containing narG (1.67 × 108 ± 1.28 × 107 copies g-1 mixture-soil-1), nirS (8.25 × 107 ± 8.95 × 106 copies g-1 mixture-soil-1), and nosZ (1.56 × 106 ± 1.60 × 105 copies g-1 mixture-soil-1) of litter bags and bottoms in HSHAD were higher than those in HHD, which indicated that the combined heterotrophic and autotrophic denitrification can increase the abundance of denitrificans containing narG, nirS, and nosZ, thus leading to better denitrification performance.

journal_name

Int J Environ Res Public Health

journal_title

International journal of environmental research and public health

authors

Hang Q,Wang H,He Z,Dong W,Chu Z,Ling Y,Yan G,Chang Y,Li C

doi

10.3390/ijerph17051574

subject

Has Abstract

pub_date

2020-02-29 00:00:00

issue

eissn

1661-7827

issn

1660-4601

pii

ijerph17051574

journal_volume

pub_type

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Hydrilla verticillata-Sulfur-Based Heterotrophic and Autotrophic Denitrification Process for Nitrate-Rich Agricultural Runoff Treatment.