Evaluation of UV disinfection technologies for water reuse and rainwater harvesting in the Irish dairy industry

The Irish dairy sector processes approximately five billion litres of milk annually and is Ireland’s largest growing indigenous industry with exports reaching a record €3 billion in 2013. In 2015, quotas on milk production... [ view full abstract ]

The Irish dairy sector processes approximately five billion litres of milk annually and is Ireland’s largest growing indigenous industry with exports reaching a record €3 billion in 2013. In 2015, quotas on milk production were abolished with predictions of the industry’s expansion by 50% in the following five years. Dairy produce encompasses a wide range of products including butter, cheese, whey and milk powders for which a considerable amount of water is required. Water consumption ratios in the Irish dairy sector are approximately 2.5m3/m3 of milk processed and 14.9 m3/tonne product. However, water is also used for other activities within the plant such as steam generation, cooling duties and cleaning in place (CIP). Of these, studies have shown CIP duties to account for the majority of water consumption in dairy plants with the average annual volume of water use per plant in Ireland estimated at 875,000 m3. Indeed, water consumption rates have decreased in recent years in terms of quantities used for product make-up however fieldwork surveys on Irish dairy plants have revealed that the majority of water utilised outside of food production is not reused within the plant nor is the treated wastewater effluent. Tertiary treatment technologies applicable for dairy wastewater reuse include membrane filtration, ultraviolet irradiation (UV) and ozone treatment. While membrane filtration can restore used water to potable standards, it can be expensive and labour intensive. UV and ozone treatment may be used to produce water to CIP standards which could decrease costs while providing enhanced pathogen free wastewater. In addition, rainwater harvesting also has the potential to decrease water consumption by utilizing on-site stormwater and tertiary treatment technologies. The aims of this project are; (i) to investigate the use of UV and potentially ozone as tertiary disinfection systems for dairy wastewater effluent (ii) to evaluate the potential for water and wastewater reuse within dairy plants and (iii) to analyse the potential for on-site rainwater harvesting at dairy plants.