Effect of step-feeding on the performance of lab-scale columns simulating vertical flow-horizontal flow constructed wetlands.

Environ Sci Pollut Res Int

Department of Chemistry, University of A Coruña, Rúa da Fraga 10, 15008, A Coruña, Galiza, Spain.

Published: October 2017

The effect of step-feeding (untreated wastewater by-pass) on the performance of lab-scale columns simulating a hybrid vertical flow (VF)-horizontal flow (HF) constructed wetland (CW) system was studied. Step-feeding strategies have been adopted in several kinds of CW, but this is the first report about the use of step-feeding in VF + HF hybrid systems treating domestic wastewater. Applied loading rates were 7-11 g BOD/m day and 2.1-3.4 g TN/m day (overall system). Removal efficiency reached 98% TSS and COD and 99% BOD on average, whilst a 50% by-pass improved TN removal from 31 to 50%. Maximum surface nitrification rate (5.5 g N/m day) was obtained in VF unit, whilst maximum denitrification rate (1.8 g N/m day) was observed in HF unit. Referred to the overall system, maximum surface nitrification and denitrification rates were 2.2 and 1.6 g N/m day, respectively. However, potential nitrifying and denitrifying activities (batch assays) were 15.0 and 58.9 g N/m day, respectively. Even at 50% by-pass, operational conditions in HF unit (dissolved oxygen, redox, COD/TN ratio) were not suitable enough for denitrification. However, methane emissions were not observed and nitrous oxide emissions were relatively low.

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Source
http://dx.doi.org/10.1007/s11356-017-9925-1DOI Listing

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