Root Zone Leachate from High Chemical Oxygen Demand Cannery Water Irrigation

Abstract

Food processing frequently results in substantial land application of wastewater of impaired quality, which requires consideration of soil and groundwater degradation. Of particular concern is the potential for impact by high organic loadings from this practice. This study evaluated the consequences of irrigating soil columns with fruit cannery wastewater (CW) at high chemical oxygen demand (COD) loadings. A CW having a COD of 9216 mg L−1 and Na adsorption ratio of 11.4 (mmolc L−1)−1/2 was applied weekly to grassed soil. Loading rates equated to 467, 701, and 934 kg COD ha−1 d−1, the lowest rate equivalent to the historic loading rate for the soil. Percolate chemistry was evaluated during dosing and after a rest period followed by rainfall. Nearly all organic constituents were mineralized (88–99%); the balance of COD‐sourced C was retained in the soil. There was no evidence of COD waste in the percolate, suggesting that the CW was primarily labile. However, CW dosing resulted in modestly alkaline post‐study soil conditions and Na+ leaching below the rooting zone. Neither NO3−–N nor total salt concentration in the leachate was high enough to warrant environmental concern under the circumstances of this study. Outcomes substantiate CW COD loadings in land application at rates exceeding current practices in some locations, although high‐COD CW loading rates are not necessarily recommended best management practices. Sodium management and loading rates matching the site evapotranspiration potential can minimize the potential for soil and groundwater degradation from CW land application.