Effect of aeration rate on laboratory-scale IASBRs treating synthetic dairy processing wastewater

The dairy sector is a prominent industry in Ireland, accounting for over 30% of Ireland’s agricultural products. However, its potential environmental impact is quite high, generating an average of 2.28 litres of wastewater... [ view full abstract ]

The dairy sector is a prominent industry in Ireland, accounting for over 30% of Ireland’s agricultural products. However, its potential environmental impact is quite high, generating an average of 2.28 litres of wastewater per litre of milk processed. In Ireland, this sector is experiencing a period of growth due to the abolition of European milk quotas in 2015, with predicted increases of up to 50% in milk processed by 2020. This increase in production will lead to an increase in wastewater generation. The aim of this research is to investigate the efficiency of the intermittently aerated sequencing batch reactor (IASBR) technology in treatment of dairy processing wastewater. It has the potential to remove nutrients and organic matter from dairy processing wastewater with less energy usage and more cost effectiveness when compared to conventional technologies. Many dairy plants in Ireland currently remove phosphorus from wastewater using chemical precipitation techniques, which are very costly. The IASBR uses biological methods to remove phosphorus without the use of costly chemicals. Three laboratory-scale ISABR units were set up at the environmental engineering laboratory at NUI Galway to test the treatment efficiencies of the technology for synthetic dairy processing wastewater. In 200 days of testing, the nutrient removal efficiencies were investigated for five aeration phases, ranging from 2 litres per minute (LPM) to 0.4 LPM. The results show ortho-phosphate removal of up to 97% during the most efficient of these aeration phases, the 0.6 LPM phase. The average ortho-phosphate removal during this phase was 92%, 59% and 93% for Reactor 1, Reactor 2 and Reactor 3, respectively. The average ammonia nitrogen removal for each of the three reactors was 93%, 77% and 91%, respectively. The variation in results in the three reactors was due to operational differences early in the experiment, leading to different microbial ecology structures in the reactors.