Nutrient Removal in Pilot-Scale Constructed Wetlands Treating Eutrophic River Water: Assessment of Plants, Intermittent Artificial Aeration and Polyhedron Hollow Polypropylene Balls

Abstract

Seven experimental pilot-scale subsurface vertical-flow constructed wetlands were designed to assess the effect of plants [Typha latifolia L. (cattail)], intermittent artificial aeration and the use of polyhedron hollow polypropylene balls (PHPB) as part of the wetland substrate on nutrient removal from eutrophic Jinhe River water in Tianjin, China. During the entire running period, observations indicated that plants played a negligible role in chemical oxygen demand (COD) removal but significantly enhanced ammonia-nitrogen (NH 4 -N), nitrate-nitrogen (NO 3 -N) total nitrogen (TN), soluble reactive phosphorus (SRP) and total phosphorus (TP) removal. The introduction of intermittent artificial aeration and the presence of PHPB could both improve COD, NH 4 -N, TN, SRP and TP removal. Furthermore, aerated wetlands containing PHPB performed best; the following improvements were noted: 10.38 g COD/ m 2 day, 1.34 g NH 4 -N/m 2 day, 1.04 g TN/m 2 day, 0.07 g SRP/m 2 day and 0.07 g TP/m 2 day removal, if compared to non-aerated wetlands without PHPB being presented.

Effect of hydraulic loading rate on pollutant removal efficiency in subsurface infiltration system under intermittent operation and micro-power aeration

“…Nevertheless, intermittent operation with a HLR of 0.12 m 3 /m 2 d could result in filter clogging while higher HLR could lead to system breakdown quickly (Leuerenz et al, 2009;Li et al, 2015). As an option, intermittent artificial aeration in wetlands matrix could achieve the alternation of aerobic and anaerobic environment, and create conditions for improved nutrient removal (Boog et al, 2014;Fan et al, 2013;Foladori et al, 2013;Li et al, 2014;Tang et al, 2009). A few studies also showed that intermittent artificial aeration enhanced pollutant removal efficiency in multi-soil-layering (MSL) system, and in soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification with surface loading rate of 0.106 m 3 /m 2 d and SWIS with HLR of 0.06 m 3 /m 2 d (Kong et al, 2015;Luanmanee et al, 2002;Pan et al, 2015).…”

Seasonal Variation of Nutrient Removal in a Full-Scale Artificial Aerated Hybrid Constructed Wetland

“…CWs performances are frequently reported to be satisfactory (over 80%) for suspended solids (SS) and organic matter [6]; however, for nutrient removal, high variations in removal rates are often observed. Previous studies reported that total nitrogen (TN) and total phosphorus (TP) removal efficiencies are reported to be varied between 40%-55% and 40%-60%, respectively, in different CWs [6][7][8], suggesting the need to improve nutrient removal in order to obtain more reliable treatment performances.…”

“…Lack of dissolved oxygen (DO) in wastewater limits this microbial process [13]. Although nitrification can occur at low DO levels, the reaction rate is considerably less when DO levels fall below 2 mg/L [6]. Plants in CWs can supply oxygen in the rhizospheres and enhance nitrification processes [13,14].…”

“…Plants in CWs can supply oxygen in the rhizospheres and enhance nitrification processes [13,14]. However, a number of studies suggested that root oxygen release is far less than the amount needed to support the nitrification process [6,15]. The combination of various wetlands in a staged manner, such as subsurface vertical flow (VF) followed by horizontal flow (HF) CWs, referred to as hybrid CWs, are also used for better nitrogen removal [8].…”

Comparison of three plants in a surface flow constructed wetland treating eutrophic water in a Mediterranean climate

“…The use of subsurface flow CWs or floating systems to treat eutrophic water has also been reported by several authors (Sheng Bing et al, 2007; Tang et al, 2009; Li et al, 2008. Li et al ( 2008 ) compared the efficiencies of different types of CWs, including FWSCWs, horizontal subsurface flow CWs (HFCWs) and vertical subsurface flow CWs (VFCWs).…”