Comparison of continuous and pulse mode of operation of pilot biosand reactors treating winery effluent

Abstract

In 2020 there was approximately 260 million hectolitres of wine produced across the world. Many winemaking and cellar cleaning activities generate winery wastewater. In vine growing areas which are water stressed, this wastewater is often used for irrigation and if it is inadequately treated it can be detrimental to land and aquatic environments. It has been shown at pilot scale that horizontal flow biosand filters are suitable for treating winery effluent to comply with irrigation standards. In this two-year study, vertical flow biosand reactors with novel design features were operated in both continuous and pulse modes of operation. It was envisaged that (i) the loading rates (organic and hydraulic) could be increased by changing the flow from horizontal to vertical flow, and that (ii) higher organic biodegradation rates could be achieved consequent to the increased redox potential from draw-down of atmospheric oxygen during system drainage in pulse mode in comparison to continuous mode. It was found that system performance was higher in continuous mode, attaining a hydraulic loading rate of 113 L.m⁻³ of sand a day⁻¹, organic loading rate of 279 gCOD.m⁻³ of sand.day⁻¹ and COD removal efficiency of 70% compared to pulse mode with 90 L.m⁻³ of sand a day⁻¹, 192 gCOD.m⁻³ of sand.day⁻¹ and 70%, respectively. In comparison to other passive winery wastewater treatment systems (constructed/treatment wetlands), these biosand filters are able to treat winery wastewater at higher loading rates with smaller spatial footprints.