Experimental meso-scale integrated constructed wetlands for the treatment of piggery wastewater
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Date
28/11/2013Author
Harrington, Caolan M. R.
Metadata
Abstract
Since the 1950s, Constructed Wetlands (CW), have seen an ever-increasing rise
in their popularity as a viable and alternative method of wastewater treatment.
From small beginnings to a surge of guidance documentation in the latter part
of the 20th century, they have undergone many revisions and studies in their
design, implementation and operation. Several significant American guidance
documents for the design of constructed wetlands were published in the late
1980’s. These studies have led to great variations in design and performance of
constructed wetlands for the treatment of high-strength ammonia-nitrogen
(370mg /L
-1
- 230mg L-1
, 8-25 kg ha-1
day-1
) polluted waters such as swine
wastewater (also called pig slurry in Europe) dependant on their operational
mode as well as their location and regional climate. Considering that treatment
performances were often unacceptably low, more recent designs have focused
on variables such as loading rate, hydraulic retention time, pre-treatment and
recirculation of pre-treated water. Furthermore, a wide range of macrophyte
species have been studied with regard to their tolerance to nutrient levels,
uptake rates and climatic tolerance. The nitrogen cycle plays a vital role
particularly in swine wastewater management and as such the promotion of
nitrification and denitrification has been researched. However, ammonia is
toxic to commonly used wetland plants. Therefore, alternative plants such as
cash crops have also been examined, because they allow for constructed
wetlands to have potentially additional benefits such as food production,
revenue increase and employment generation.
Swine wastewater in Ireland is currently a significant issue in regards to EU
Directives directly relating to water quality. This research study was performed
to examine the potential application of a constructed wetland for the effective
treatment of swine wastewater. A highly-replicated system, based upon the
Integrated Constructed Wetland approach, pioneered in Ireland was
constructed, operated and sampled for an 18-month period in the South of
Ireland. The system received separated liquid from an anaerobic digestor unit
and this liquid was fed into the system for 18 months. Weekly sampling and
analysis showed that at low influent concentrations (up to 200mg NH4/l), the
systems were capable of removing nitrogen species to background levels and
producing a discharge that met some of Irelands provisional drinking water
standards.
The effectiveness of these meso-scale systems highlight the potential application
of the Integrated Constructed Wetland approach for the treatment of piggery
wastewaters. In an industry that is heavily reliant upon other farm/land owners
taking excess wastewater as a form of fertilizer, coupled with strict
landspreading application limits, increasing fuel costs and EU water quality
directives, they could provide a financially and environmentally beneficial
approach to a robust total nitrogen management scheme. Since the 1950s, Constructed Wetlands (CW), have seen an ever-increasing rise
in their popularity as a viable and alternative method of wastewater treatment.
From small beginnings to a surge of guidance documentation in the latter part
of the 20th century, they have undergone many revisions and studies in their
design, implementation and operation. Several significant American guidance
documents for the design of constructed wetlands were published in the late
1980’s. These studies have led to great variations in design and performance of
constructed wetlands for the treatment of high-strength ammonia-nitrogen
(370mg /L⁻¹ - 230mg L⁻¹, 8-25 kg ha⁻¹ day⁻¹) polluted waters such as swine
wastewater (also called pig slurry in Europe) dependant on their operational
mode as well as their location and regional climate. Considering that treatment
performances were often unacceptably low, more recent designs have focused
on variables such as loading rate, hydraulic retention time, pre-treatment and
recirculation of pre-treated water. Furthermore, a wide range of macrophyte
species have been studied with regard to their tolerance to nutrient levels,
uptake rates and climatic tolerance. The nitrogen cycle plays a vital role
particularly in swine wastewater management and as such the promotion of
nitrification and denitrification has been researched. However, ammonia is
toxic to commonly used wetland plants. Therefore, alternative plants such as
cash crops have also been examined, because they allow for constructed
wetlands to have potentially additional benefits such as food production,
revenue increase and employment generation.
Swine wastewater in Ireland is currently a significant issue in regards to EU
Directives directly relating to water quality. This research study was performed
to examine the potential application of a constructed wetland for the effective
treatment of swine wastewater. A highly-replicated system, based upon the
Integrated Constructed Wetland approach, pioneered in Ireland was
constructed, operated and sampled for an 18-month period in the South of
Ireland. The system received separated liquid from an anaerobic digestor unit
and this liquid was fed into the system for 18 months. Weekly sampling and
analysis showed that at low influent concentrations (up to 200mg NH₄/l), the
systems were capable of removing nitrogen species to background levels and
producing a discharge that met some of Irelands provisional drinking water
standards.
The effectiveness of these meso-scale systems highlight the potential application
of the Integrated Constructed Wetland approach for the treatment of piggery
wastewaters. In an industry that is heavily reliant upon other farm/land owners
taking excess wastewater as a form of fertilizer, coupled with strict
landspreading application limits, increasing fuel costs and EU water quality
directives, they could provide a financially and environmentally beneficial
approach to a robust total nitrogen management scheme.