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Water Recycling in Food Production and Manufacture
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Bega Cheese Case study <p>The aim of this project was to study the impact on the sodicity in the soil and the nutrient uptake by crops in farmlands irrigated by recycled wastewater from the Bega plant. A discussion paper outlines the regulatory framework, identifies three technology options for treating the wastewater, and tested options using the value proposition tool.</p>

Results of the modelling of nutrient uptake by crops and soil sodicity illustrate the importance of the geographic location of a pasture being irrigated with screened wastewater from dairy processing. The site-specific climate and soil conditions determine the types of crops, the intensity of cropping in a year, as well as the maximum yield and demand for various nutrients. This in turn determines the frequency and amount of wastewater that can be irrigated and over how large an area.

The results of the modelling of nutrient uptake by crops and soil sodicity illustrate the importance of the geographic location of an irrigated dairy farm.

Crop or pasture harvesting and removal strategies also impact on nutrient cycling. The irrigated pasture management system can be optimised for the sustainable use of nutrients and salts in the wastewater. However, any salt applied must be managed by leaching it out of the soil. APSIM modelling showed that as a result of the wastewater application, P accumulates in the soil profile.

Recommendations:

  • The nutrient balance in the current effluent irrigation be improved and Bega Cheese should consider different options to reduce the nutrient load in the soil when wastewater is used in irrigation. Options to consider are:
    • treating or diluting the effluent to match the loading to crop nutrient demand (200 kg N/ha, 50 kg P/ha);
    • increasing the area of irrigation (by 40–225% depending on the volume of wastewater used in irrigation); and
    • adopting suitable pasture/cropping systems.
  • As these options will have cost implications, a value proposition should be developed to choose the best one. The tool created by the CSIRO team may help Bega Cheese to develop value propositions for different wastewater treatment and irrigation options to assist in investment decision-making.
  • The Australian Water Recycling Guidelines and NSW Environmental Protection Agency (EPA) Guidelines should be referred to when developing strategies for using wastewater for irrigation at Bega Cheese.
  • The model predictions for nutrient uptake by crops, nutrient accumulation in the soil and the sodicity in the soil should be validated with actual soil data.

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