Study of a Novel Vertical Flow Constructed Wetland System with Drop Aeration for Rural Wastewater Treatment

Abstract

Constructed wetlands are recognized as a reliable technology for rural wastewater treatment. However, conventional constructed wetlands face problems with low pollutant removal efficiency and limited oxygen transfer capability. Therefore, a novel vertical flow constructed wetland (VFCW) system with drop aeration was developed in this study. Two pilot-scale vertical flow constructed wetlands of 0.75 m 2 each were constructed with the same dimensions and configuration but different media, one of which (named as CW 1 ) was filled with a 1:1 mixture (by weight) of zeolite and dolomite and the other (named as CW 2 ) with the same zeolite only. The oxygen transfer capability of a multilevel two-layer drop aeration device, organics and nitrogen removal of CW 1 and CW 2 , and pollutant distribution along the depths of CW 1 and CW 2 in different operational phases were studied. The results demonstrated that compared with the direct drop aeration process, the multilevel, two-layer drop aeration device supplied 2-6 mg/L higher dissolved oxygen per meter of drop height, and after installation of the six-level, two-layer drop aeration devices, the 5-day biochemical oxygen demand removal load was improved from 8.1 to 14.2 gm −2 day −1 for CW 1 . With regard to the different filter media, nitrogen removal was improved by the adsorption of zeolite in the first year, with 5-36% higher NH 4 + -N removal efficiency of CW 2 compared with that in CW 1 . Since it did not have a significant positive effect on phosphate removal, dolomite can be replaced by zeolite. The chemical oxygen demand removal mainly took place in the upper 15-cm filter layer in different operational phases, while nitrogen distribution along the depths of the VFCWs was different in different operational phases. In addition, as no operational problems occurred, the vertical flow constructed wetland system with drop aeration is an appropriate alternative for rural wastewater treatment, with numerous advantages of low capital and operation costs, no energy consumption, easy maintenance, high hydraulic loading rate, high pollutant removal efficiency, and no clogging.

Effects of flow speed and circulation interval on water quality and zooplankton in a pond–ditch circulation system

“…This is consistent with previous studies showing that the HRT of the wetland system affects the treatment efficiency, and the higher nutrient efficiency can be achieved with a longer HRT (Chen et al 2006;Zou et al 2012). Meanwhile, a longer HRT provides a better environment for the microorganisms and macrophytes, which, in turn, leads to higher TN reduction rates, species numbers, and diversity indexes in the PDCS.…”

Organic xenobiotics removal in constructed wetlands, with emphasis on the importance of the support matrix

“…There have been already some studies carried out in CWS where zeolites have been used at least as one of the constituents of the support matrix [117,[238][239][240][241][242]. Most of the studies focus on the removal of nitrogen, phosphorus and unspecified organics (organic matter) by such CWS, but there have been already some attempts to evaluate the removal of specific organics such as phenolic compounds [238].…”

Ex-Situ Remediation Technologies for Environmental Pollutants: A Critical Perspective

“…Lee et al ( 2013 ) Nyquist and Greger ( 2009 ) More recently, Eleocharis macrostachya used in constructed wetland prototypes showed a higher As mass retention of 87-90 % in 33 week test period (OlmosMarquez et al 2012 ). Zou et al ( 2012 ) recommended employing a new vertical fl ow constructed wetland structure with drop aeration for treating rural wastewaters. A wetland system that had operated for 11 years in 12,800 m 2 area in the mid-western USA for remediating >90 % chlorinated ethenes rapidly developed into a healthy ecosystem with diverse vegetation, supporting over 60 bird species and several other animal species (Kadlec et al 2012 ).…”