Abstract
Abstract Constructed wetlands (CWs) are effective as an advanced treatment process for the treated effluent of municipal wastewater plants. An appropriate substrate, suitable macrophytes, and proper operation are crucial for pollutant abatement. In this research, three subsurface flow CWs with various substrates were investigated. Pollutants abatement efficiency under various operational schemes were analyzed. The results showed that the satisfactory hydraulic loading rate was 0.25 m3/(m2·d). When the C/N ratio of influent was adjusted to 5.87 by adding a carbon source, the denitrification and dephosphorization efficiency would be improved, with 7–8 mg/L for total nitrogen (TN) and 0.4 mg/L for total phosphorus (TP) in the effluent, which can achieve the Class 1A Discharge Standard for discharge to natural waterways in China. A greater depth of submersion for the substrate layer resulted in a more conducive environment for the abatement of nitrogen substances. However, a 40-cm depth of submersion in CWs results in better removal efficiency of TN and TP. A plastic ring substrate (PRS) contains biological enzyme promoter formula, which was conducive to nitrifying and denitrifying bacteria. The biofilm affinity and coordination with plants made the PRS more effective than the other two substrates, especially for NO3–-N and TN abatement efficiency.
Highlights
The treated effluent from a municipal sewage plant may contain pollutants that contribute to eutrophication of waterbodies when the effluent is directly discharged
When constructed wetlands (CWs) was filled with different substrates, there were various physical and chemical reactions and biodegradation inside the CW which resulted in different pollutant abatement efficiencies
Three CWs with plastic ring substrate (PRS), FLAZS and fly ash substrate (FLAS) as substrates were investigated separately to explore the performance of the treating effluent from municipal plants
Summary
The treated effluent from a municipal sewage plant may contain pollutants that contribute to eutrophication of waterbodies when the effluent is directly discharged. Different countries have different requirements for treated effluent discharged into natural rivers, as shown in Table 1 (American Water Works Association ; Smith & Guo ). The Pollutant Discharge Standard for municipal sewage treatment plants was further restricted to Class 1A in China, which may require advanced wastewater treatment to meet. Compared with many other wastewater treatment technologies, constructed wetlands (CWs) can be constructed, which provides an advantage in denitrification and dephosphorization performance.
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