ADVANCES WITH WATER MANAGEMENT IN THE DAIRY INDUSTRY.

1. Overview: Practices of water use.

Apart from rainwater, dairy pasture-based systems use irrigation to promote productivity of pastures; the general use being high compared to other agricultural systems and with the further implication of nutrient leaching and pollution of watercourses and wetlands. However, recent developments and initiatives around water in the South African Dairy Sector are steadily contributing towards creating a culture of circularity and sustainability. A water stewardship program has been introduced by the MPO in collaboration with the WWF-SA, which encompasses increased improvement in water usage, a reduction in all water related impacts and a commitment to collective action which includes other businesses, NGO’s, communities, and government departments. The program is being rolled out to as many participants as possible, following a survey to establish needs and application.

A second initiative was to develop guidelines [‘’Best Practice Guidelines for improved wetland and river management on dairy farms in South Africa’’] for determining and development of aquatic and wetland buffer zones for dairy farms. The supporting research commissioned by Milk SA has refined the approach through focusing on sector specific aspects that would allow for improved wetland and watercourse management This is supported by a cost-benefit analysis to inform sustainable wetland and watercourse management.

With the envisaged impact of climate change contributing to progressively increasing temperatures and therefore more evaporation, together with decreasing precipitation, it has become important to pay attention to irrigation water use efficiencies which have been calculated to vary between 150 and 190 litres/litre milk produced. The numbers can improve and is being addressed. In the same vein, minimum water requirements of forage species are being established. Some limited data suggest that depending on accompanying precipitation, 25mm irrigation water on average is required per week, varying between 10 mm when evaporation is low, such as in winter, and increasing to 30+ mm in summer. There may, however, be substantial differences between species/cultivars, whether established in monoculture or mixed pastures, and grazing intensity and frequency. Water requirements in combination with irrigation scheduling and their suitability to topography, climate, soil, irrigation system and water availability should therefore be studied further.

2. Potential sources of water for reuse and end-use applications.

From a dairy processing perspective, organizations across South Africa have adopted a wide range of approaches to improve their water resilience and operational efficiencies. As such, by employing technological advancements in the re-use of water as well as wastewater recovery and treatment, processors are driving down consumption while reducing the demand on municipal water supply systems. With respect to water intake (requirements) in factories, efficiency benchmarking results show that the industry is on par with international water use efficiencies, yielding benchmarks (litre water used/litre product produced) of 2.25 for milk, 1.5 for UHT milk, 2.25 for yoghurt, 3.00 for butter and 2.75 for cheese, or on average: 2.4L/L in 2022.

In addition, many Dairies have placed their focus on areas of water consumption that can readily be managed and where immediate reductions in water usage are possible: Optimization of ‘clean in place’ (CIP) systems has presented dairies with steady water savings through efficient sequence planning of product batches as well as modifications which enable the re-routing of rinse water to ensure collection and re-use. Water use efficiency (typically the volume of water used per volume of product manufactured) reporting is the key metric to initiate and measure continuous improvement programs or projects related to water consumption.

3. Treatment technologies and storage options to enable water that is fit for purpose.

Typical effluent management on dairy farms in South Africa relies on the waste stream to be collected and stored in ponds before being spread onto lands or pastures using a variety of methods. It is essential that this should be carefully managed to prevent seepage and pollution of sub-surface water, while alternatively not resulting in the gradual accumulation of nutrients in the soils to unsustainable levels.

There are examples of farms where all slurry manure is collected in specifically designed concrete-lined channels and diverted to a contained sump. From there, the solid and liquid manure fractions can be separated, either by gravity or mechanical means. Liquid-solid separation of manure slurry provides several benefits including the production of value-added products (e.g. bedding).

Care is taken to divert, collect and contain liquid effluent run-off from stalls and cow housing. Ground water and soil contamination with faecal coliforms, nitrates and salts can occur through the leaching of run-off if not controlled properly. Numerous farms across South Africa have well-designed, appropriate effluent management measures in place and there are examples of innovative practices in this regard. Farmers, furthermore, use the slurry water after separation in the ponds for irrigation, which is commendable in terms of circular economy principles, although chemical analyses of the water often indicate that high levels of major constituents which substantially exceed the regulatory guidelines for irrigation and discharge, still remains. This is addressed through research commissioned by Milk SA, doing physico-chemical analyses of dairy wastewater from farms, and secondly carrying out socio-spatial assessments of the suitability of such farms for low-cost biological wastewater treatment solutions, for example by testing the efficacy of algae species to reduce NH_4, PO₄^-2 and COD levels in dairy wastewater from the parlour.

4. Case studies in water use, reduction and re-use.

It has proved possible to augment water through other than usual means, yet still doing so in an environmentally beneficial manner. This was demonstrated by the establishment of an integrated water and waste recovery system implemented by a prominent processor in South Africa: A wastewater treatment plant was required due to under-capacity and inefficiency of the municipal wastewater treatment system to effectively deal with the factory effluent. The integrated system can recycle wastewater using reverse osmosis technology to convert it back to a potable standard. This allows for reuse of the water inside the factory. In addition to reclaiming water, an anaerobic bioreactor enables methane to be produced from the organic content. This methane in turn serves as a fuel source to drive a boiler which supplements a portion of the processing plant’s steam requirements.