DWHR at ABP Foods, Cahir
Figure1: The treatment system of the ABP facility in Cahir
Background
The ABP facility in Cahir, Co. Tipperary, has its own wastewater treatment system (Figure 1) which treats between 600 and 1,200 m3 of wastewater from the ABP meat processing plant and from another meat processing facility nearby, Munster Proteins. After treatment through a number of processes, the treated water is discharged into the river Suir.
Heat Recovery Potential
Monitoring in the treatment plant in Cahir found that there was a significant potential for heat recovery from the wastewater. In 2021, we found that at the inlet and outlet of the Dissolved Air Flotation Tank, one of the treatment processes used in the plant, wastewater temperatures were higher than the ambient average air temperature (Figure 2) over several months of monitoring. Other monitoring also found that wastewater temperature is higher at the inlet of the plant as compared to the outlet due to it continuously losing heat to the air as the water is treated across the different processes of the plant.
Figure 2: Average daily Dissolved Air Flotation Tank inlet (DAFT Inlet) and outlet (DAFT Outlet) temperatures compared with air temperature across several months of monitoring from ABP Cahir. The increased wastewater temperature relative to the air temperature throughout the monitoring period shows the presence of a steady potential heating resource from wastewater heat recovery.
Test rig
To obtain some field data and confirm this heating resource, a test rig was designed incorporating both direct heating of the mains feed water using heat exchangers and ‘indirect ’ heat recovery by using a heat pump that can bring the temperature up to 45°C. The test rig is movable and is used to assess heat recovery potential in the inlet of the treatment plant, the outlet of the treatment plant and the outlet of the dissolved air flotation tank. This helps to quantify the difference in the heat resource across the treatment plant. Heat resources are highest at the treatment plant inlet but the wastewater here is also the dirtiest posing challenges for heat exchanger design.
Figure 3: Test rig performing initial tests at the treatment plant outlet
Quantify biofilm development and impact on heat exchange
Currently, after some upgrades to the test rig, we are aiming to quantify the biofilm development on the heat exchangers and the impacts on heat exchange by running the test rig for an extended period in the inlet area of the treatment plant. This will allow us to more accurately predict the actual potential for wastewater heat recovery at the treatment plant using copper heat exchangers in the long-term and identify if there is a need to use different heat exchanger materials.
Are you interested in taking a closer look at our test rig? Click below to load the 3-D tour!
https://dwruisce.github.io/ABPCahirE/