Effect of Irrigation with Diluted Winery Wastewater on Phosphorus in Four Differently Textured Soils

Abstract

The wine industry needs solutions for wastewater treatment, as environmental legislation for its disposal is increasingly being enforced due to non-compliance. The feasibility of re-using diluted winery wastewater was assessed in a pot experiment under a rain shelter over four simulated irrigation seasons. Four soils varying in parent material and clay content, viz. aeolic sand from Lutzville containing 0.4% clay, alluvial sand from Rawsonville containing 3.3% clay, granite-derived soil from Stellenbosch containing 13% clay, and shale-derived soil from Stellenbosch containing 20% clay, were irrigated with wastewater diluted to 3 000 mg/L COD (chemical oxygen demand), whereas the control received municipal water. Irrigation with diluted winery wastewater increased the pH (KCl) in the shale-and granite-derived soils into the optimum range for P availability. Although pH (KCl) in the aeolic sand was initially above the optimum range, relatively high Na + levels also caused available P to increase as the pH (KCl) increased. The pH (KCl) in the alluvial sand increased beyond the optimum range, thereby causing a reduction in the available P. This indicates that irrigation with diluted winery wastewater may only enhance P absorption if the pH (KCl) shift is towards the optimum. It must be noted that the results represent a worst-case scenario, i.e. in the absence of rainfall or crops.

Alteration Index Three Facilitates Interpretation of β-Glucosidase, Acid-phosphatase and Urease Activities in Soils Irrigated with Diluted Winery Wastewater

“…Thus, soil with low clay and organic carbon contents will have the quickest turnover of organic matter after multiple WW inputs. The high clay dispersion reported by Mulidzi & Myburgh (2014) and Mulidzi (2015), together with an excessive decline of 43% in initial TOC after WW inputs caused the alteration in the St.s. Although the St.g showed signs of structural damage (Mulidzi & Myburgh, 2014;Mulidzi, 2015) it still retained around 80% of the initial TOC after 24 WW inputs.…”

“…The high clay dispersion reported by Mulidzi & Myburgh (2014) and Mulidzi (2015), together with an excessive decline of 43% in initial TOC after WW inputs caused the alteration in the St.s. Although the St.g showed signs of structural damage (Mulidzi & Myburgh, 2014;Mulidzi, 2015) it still retained around 80% of the initial TOC after 24 WW inputs. The Rv soil was well-aerated and well-drained during WW inputs and retained 80% of its initial TOC, hence its relatively unaltered state.…”

“…was most responsive to WW irrigation, followed by the St.s (2.9:1) and the St.g (1.4:1), whereas Rv remained relatively unaltered (1.1:1). The intensity of these alterations was nevertheless dependent on soil aggregate stability (Mulidzi & Myburgh, 2014;Mulidzi et al, 2015), as well as a decline FIGURE 1 Soil alteration response, % clay, silt and organic carbon contents, following irrigation with diluted winery wastewater over four simulated seasons. Bar values represented by the same letters do not differ significantly (p < 0.05).…”

Effect of Irrigation with Diluted Winery Wastewater on Enzyme Activity in Four Western Cape Soils

“…Despite this variability, each enzyme responded consistently to the water treatments across all four soils, urease and β-glucosidase activities tending to be higher (but not always significantly so) in the wastewater than the municipal water treatment (Tables 3 and 5, respectively), whilst the converse was the case for phosphatase ( (Table 2) may have contributed to the nonsignificant phosphatase activity differences between the water treatments in the Rawsonville and Lutzville soils. However, the high initial soil Bray P level in the vineyard-derived Lutzville soil (217 mg/kg, Mulidzi et al, 2016b) may also have inhibited phosphatase activity in accordance with mass action principles. It seems likely that phosphatase requires lower levels of P in the soil solution than were present in the winery wastewater treatments to function effectively.…”

“…activity (Table 4) was greater in the Stellenbosch granite than in the Stellenbosch shale. Conceivably, the coarse texture of the granite soil may have promoted phosphatase activity relative to the finer textured shale soil (Mulidzi et al, 2016b), whereas the opposite was the case for urease and β-glucosidase. The activities of both these enzymes peaked in the coarser textured Stellenbosch granite soil.…”