What is the best design approach for estimating effluent concentrations from horizontal flow treatment wetlands: the use of volumetric (k) or areal (k) removal rate coefficients?

Effluent concentrations from horizontal flow (HF) treatment wetlands can be estimated by using the Tanks-In-Series model for describing hydraulics and first-order removal rate coefficients for describing pollutant removal. In the design of conventional wastewater treatment plants, volumetric removal rate coefficients (k) are traditionally used in conjunction with the theoretical hydraulic retention time. Areal removal rate coefficients (k) coupled with the applied areal hydraulic loading rate are widely used in the literature.

What is the best procedure for determining removal rate coefficients in horizontal flow treatment wetlands: influent and effluent concentrations or longitudinal concentration profiles?

First-order removal rate coefficients (k) are used in predictive equations for estimating effluent concentrations from horizontal flow (HF) wetlands. Due to limited resources, influent and effluent concentration data from existing systems are frequently used in the estimation of k values from operating systems, but another choice is to use concentration data along the longitudinal profile of the HF wetland. Based on a dataset with 41 HF wetlands/studies obtained from a literature survey, with chemical oxygen demand (COD) measurements at different sampling points, volumetric (k) and areal (k) removal rate coefficients for the Tanks-In-Series (TIS) model have been obtained using the two estimation methods.

Nitrification cessation and recovery in an aerated saturated vertical subsurface flow treatment wetland: Field studies and microscale biofilm modeling.

In aerated treatment wetlands, oxygen availability is not a limiting factor in sustaining a high level of nitrification in wastewater treatment. In the case of an air blower failure, nitrification would cease, potentially causing adverse effects to the nitrifying bacteria. A field trial was completed investigating nitrification loss when aeration is switched off, and the system recovery rate after the aeration is switched back on.