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Assessment of organic matter removal during the treatment of stillage in a
constructed wetland using
Canna indica
A. López, A. López, E. León
Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco A.C.,
Avenida Normalistas 800, Col. Colinas de la Normal, C.P. 44270, Guadalajara, México.
Keywords:
Stillage, horizontal subsurface flow constructed wetland, organic matter.
Introduction
Stillage is a liquid product generated from ethanol distillation from sugarcane; it is
estimated that for each liter of alcohol, 10 to 12 liters of stillage are produced [1]. Stillage
presents particles in suspension, brown color, characteristic thin honey smell and malt
flavor, low pH (3.5 - 5), high organic matter concentration expressed like biochemical
oxygen demand (BOD), in the range of 35–50 g l
-1
, and chemical oxygen demand (COD) of
120–150 g l
-1
, presence of toxic and recalcitrant compounds, as well as nutrients and high
temperature [2]. For stillage treatment, physicochemical and biological processes have been
used, being the anaerobic process the most suitable [3]. However, the anaerobic treatment
effluent presents from 15% to 30% of the initial organic matter concentration, whose
treatment would be expensive if it is made by conventional processes.
Thus, the opportunity of application of natural systems, such as constructed wetlands, in
high load wastewater treatment of organic matter arises. The performance of these systems
depends of several factors, mainly those related to organic load, flow regime and the proper
selection of plants [4]. This study evaluates the effect of the organic load rate on adaptation
and growth of
Canna Indica
during the treatment of stillage in a subsurface flow
constructed wetland.
Methodology
Experimental System.
The laboratory experimental system consisted of horizontal
subsurface constructed wetland (CW), with dimensions of W = 0.30 m, L = 1.20 m and H =
0.20 m; planted with
Canna Indica
species. The supply of stillage to the system is constant
and distributed uniformly widthways of the wetland; the output of the wetland has a level
control device ensuring its flood up to 0.15 m. The wetland was filled with Tezontle, a
volcanic extrusive rock with an average particle diameter of ½” and porosity of 0.60. The
wetland was fed with stillage previously homogenized, pH adjusted to 7 and at room
temperature (25 °C).
Organic loading rate.
The CW was assessed during 131 days; an experimental design was
performed taking into account different organic loads from 0.13 to 1.32 kg COD m
-3
d
-1
for
three types of hydraulic retention times (HRT), 3, 4 and 5 days.
