Section 8. LAND DISPOSAL
EFFECT OF COD LOADING AS GLUCOSE ON CRITICAL DESIGN
PARAMETERS IN LAND TREATMENT SYSTEMS
Peter N. Coody, Graduate Student
Lee E. Sommers, Professor
Agronomy Department
Purdue University
West Lafayette, Indiana 47907
Darrell W. Nelson, Professor
Agronomy Department
University of Nebraska
Lincoln, Nebraska 68583
INTRODUCTION
The soil environment is an appropriate site for the treatment of many industrial and municipal
wastewaters [1,2]. In particular, land treatment of many wastewaters containing oxygen-demanding
organics has been demonstrated to be a viable means of pollution abatement at reduced cost compared to traditional unit processes [3,4].
The ability of a land treatment system to degrade organic C in wastewater depends on the transfer
of oxygen into the soil zone of active microbial growth. Therefore, maintenance of aerobic conditions
necessitates that the oxygen demand in a treatment system not exceed the maximum rate of O, exchange by the soil. Overcash and Pal [5] evaluated an O, diffusion model of McMichael and McKee
[6] to calculate maximum 02 exchange estimates of 7.3 to 11.0 Mmol O./ha/yr depending on soil
texture. However, these estimates do not account for a reduction in air-filled soil pores caused by a
heavy hydraulic input and the accumulation of microbial by-products as is often encountered in land
treatment systems. As a result, O, transfer into soils used for land treatment is likely to be somewhat
lower than predicted by the diffusion model, and it will likely be a function of both application
frequency and amount of waste added.
In many cases, researchers have attributed an observed reduction in plant growth to the depletion
of oxygen in the root zone after adding oxygen demanding organics to soils [7,8]. However, studies
to quantify the effects of heavy COD loading on covercrop yields or soil physical properties are not
readily available in the literature.
The objective of this laboratory study was to quantify the effects of labile organic carbon (i.e.,
glucose) on physical properties and crop productivity of a simulated land treatment system. A glucose-rich synthetic wastewater was used to simulate wastewater produced in the corn processing industry and was applied to both cropped and non-cropped soil columns.
MATERIALS AND METHODS
This study involved applying a synthetic wastewater containing glucose to soil columns maintained
under controlled conditions. Experiments were conducted using twenty four columns filled with soil
and randomly arranged in a growth chamber. Each column consisted of pvc pipe (10 cm dia. x 42
cm length) fitted with an acrylic base-plate containing a 1.25 cm hose barb to allow the column to
drain freely. Nylon mesh was placed over the hose barb to retain the soil and leachate collection
bottles were connected via plastic tubing. Gas sampling ports were located 5, 15, 25, and 35 cm from
the bottom of each column. These ports consisted of a 14 cm section of 2 mm (ID) polypropylene
tubing which transected the column at its diameter. One end was sealed and glued to the pvc pipe
while a 7 mm (OD) rubber septum was used to seal the other end. Each sampling tube had four 2
mm holes located along the lower wall to allow air to pass into the tube. The dead space in the
sampling port was approximately 0.6 cm3.
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