Treatment and valorization of a primary municipal wastewater by a short rotation willow coppice vegetation filter

Abstract

The objective of this study was to evaluate the treatment efficiency of a short rotation willow coppice (SRWC) vegetation filter for the treatment of wastewater from a municipal primary effluent in a humid continental climate context. The experimental work was carried out at pilot scale on a willow plantation located in Québec, Canada. The experimental design included nine plots that were irrigated with groundwater (L0 = 14 mm/d) or two primary effluents (L1 = 10 and L2 = 16 mm/d) for 111 days. This research showed that SRWCs operated on coarse-textured soils allow efficient removal of organic matter (91 % of COD for L1 and L2) and nitrogen (98 % of TKN for L1 and L2) from wastewater. It was also shown, in this case, that the total nitrogen loading should be used as the limiting design parameter to minimize the risk of contaminating underground drinking water sources with nitrates. Almost complete removal of total phosphorus was observed during this experiment (98 % for L1 and L2). However, a significant increase in soil available phosphorus was observed following the L2 treatment, which suggests an eventual phosphorus soil profile saturation in the event of continued wastewater irrigation. Avoiding such a saturation would require chemical phosphorus removal upstream of SRWC vegetation filters. Finally, an imbalance between irrigation and willows needs was observed as a result of irrigating plots at a constant hydraulic loading rate. Thus, irrigation of an SRWC with wastewater should be modulated according to willow seasonal transpiration trends to allow a better allocation of water and nutrients according to plant needs, and in doing so, increase treatment efficiency and resources valorization. Highlights • Efficient removal of OM and nitrogen (TKN) by coarse textured SRWC vegetation filter • TN should be used as the limiting design parameter of SRWC vegetation filter • Eventual P soil profile saturation in the event of continued wastewater irrigation • Irrigation should be modulated according to willow seasonal transpiration trends

Nature-Based Units as Building Blocks for Resource Recovery Systems in Cities

“…The biomass production of Phragmites australis, the most common plant used in TWs, is 19 ± 13 t ha −1 y −1 when used for the secondary treatment of domestic wastewater [34]. A special type of TW, so-called evapotranspirative systems, wherein short-rotation willows are planted in the treatment beds, can produce more biomass as reeds, e.g., 22-26 t wood chips ha −1 y −1 [35,36].…”

Ectomycorrhizal Fungi Dominated the Root and Rhizosphere Microbial Communities of Two Willow Cultivars Grown for Six-Years in a Mixed-Contaminated Environment

“…Fast-growing willow shrubs (Salix spp.) present attractive economic values as woody crops for biomass production [22,23], and they shown interesting versatility to be used in various environmental projects, to minimize the leaching of pesticides from agricultural fields [24,25], to treat contaminated leachate [26,27], or to remediate contaminated soil [28][29][30]. Consequently, the microbial community of Salix spp.…”

Short-Rotation Willows as a Wastewater Treatment Plant: Biomass Production and the Fate of Macronutrients and Metals

“…The exception is P, which was reported to be 30% higher in influent wastewater than in biomass; however, the P balance also depends on the use of P-containing detergents in the household(s) producing the wastewater [12]. Consequently, a significant increase in available P in the soil was reported [22], suggesting that soil may become saturated with P after a period of time. This may lead to a problem in SRWC vegetation filter treatment performance and reduces P recovery via woody biomass.…”

“…This may lead to a problem in SRWC vegetation filter treatment performance and reduces P recovery via woody biomass. Therefore, Lachapelle-T et al [22] suggest that fertigation should be adjusted according to seasonal transpiration rates and plant nutrient requirements; however, in the case of EWS, wastewater is constantly applied according to the production in the household(s) and stored in the EWS as an elevated water level over the winter. Therefore, in the case of EWS, P accumulation in the system can be expected, resulting in a P-rich substrate that can be reused as fertilizer.…”