Horizontal subsurface wetland for dairy farm wastewater treatment: a sustainable model based on circular economy

PANIGATTI, MARÍA CECILIA; GRIFFA, CARINA; GUTIERREZ, GONZALO; BOGLIONE, ROSANA; SCHIERANO, MARÍA CELESTE; MAINE, MARÍA ALEJANDRA; TAVERNA, MIGUEL

Viena

Simposio; 9th International Symposium on Wetland Pollutant Dynamics and Control, WETPOL 2021; 2021

BOKU UNiversity

volumes of effluent. Its treatment is essential for the environment protection. Circular economy isan approach that describes how several natural resources, most classified as wastes, can be usedas inputs to produce value-added products and services. In this way, Constructed Wetlands (CW´s)have potential for sustainable wastewater management based on circular economy concept, dueto the fact that they can treat water towards particular reuse purposes.This paper focuses on a robotic dairy farm that treats effluents through stabilization ponds.However, effluent quality could be improved to be reused in the same facilities for cleaningpurposes. CW?s could be a suitable alternative for this goal. Both laboratory and pilot scaleexperiments were performed in order to evaluate CW´s efficiency. Laboratory experiments wereconducted using batch microcosms and real effluents (March 2017-December 2017). Reactorswere filled with light expanded clay aggregate (LECA) and planted with Typha domingensis. Meanremoval efficiencies obtained (after a residence time of 7 days) were 78.3% por chemical oxygendemand (COD), 95.6% for total suspended solids (TSS), 95.9% for ammonium, 17.1% for nitratesand 77.7% for total phosphorus (TP). Total coliform and fecal bacteria decreased seven and eightorders of magnitude, respectively. In January 2018, a pilot scale horizontal subsurface CW (2 mwidth, 6 m length and 0.7 m depth) was built next to stabilization ponds. CW was planted with T.domingensis and river gravel was used as substrate due to at that moment, LECA was not availableat a convenient cost. 20 samples were collected and analyzed weekly from March -December 2018.Satisfactory removal efficiencies were obtained: 48.0% for COD, 71.5% for TSS, 41.2% forammonium, 35.8% for nitrates and 27.6% for TP. Both, total and fecal bacteria decreased oneorder of magnitude. High evapotranspiration rates were obtained, which represented a problem interms of available volume of effluents for reuse. In summer season, river gravel warms due to highambient temperatures and contributes to evapotranspiration rates increase.In September 2020, a full-scale horizontal subsurface CW was built. For this purpose, pilot scalewetland dimensions were extended to 4 m width (same length and depth), followed by a channel(1 m width, 16 m length and 0.7 m depth). This channel flows to a dumpsite where treatedwastewater is pumped back to dairy facilities. Both CW and channel were filled with river gravel(0.5 m) and Arqlite® (0.1 m). This is an innovative material obtained entirely from plastic waste. Itcan replace traditional substrates, providing a reduction in weight, cost and evapotranspirationrates. It also contributes to circular economy, transforming plastic waste into a valuable product.Macrophytes were currently collected from natural environments and will be planted graduallywithin the next weeks. The monitoring period of CW is expected to begin in July 2021. The reuseand recycling of wastewater is a promising environmental solution based on circular economy,specially in dairy production, one of the most important primary activities in Argentina.