Experimental meso-scale integrated constructed wetlands for the treatment of piggery wastewater

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