2015/05/14

CEIT-IK4 optimises the potential for cost savings in aeration systems in wastewater treatment plants by measuring oxygen transfer via the off-gas method

aireadores galindo

Aeration is the primary system used in wastewater treatment plants (WWTP). It plays a critical role in stability, treated water quality, and operational costs; it also makes up about 75% of a plant’s total energy demand. The energy consumed by a WWTP is 1% of the national demand, and the biggest source of greenhouse gases is the generation of electric energy, which means that an optimised aeration system is indispensible for any WWTP that wants to save costs and operate a sustainable and eco-efficient system.

Given the aim of optimising the high costs of operation, it is essential to determine the efficiency of the aeration system’s oxygen transfer in field conditions. To that end, CEIT-IK4 is participating in a project by the Consortio de Aguas de Bilbao Bizkaia (CABB) by carrying out a systematic, full-scale implementation of a precise, versatile and simple methodology that will make it possible to determine the overall condition of the air diffusers, detect areas of low efficiency, and quantify the depreciation period of air leak repairs in a WWTP. The methodology will also make it possible to compare different plant operation strategies, giving operators the ability to find the one that best maximises oxygen transfer efficiency in diffusers.

This study has been carried out at the Galindo-Bilbao WWTP (population equivalent 1.5 million), where the off-gas methodology has shown potential for helping plant mangers make decisions regarding the optimisation of the aeration system’s energy consumption. The methodology has offered the following results:

- It is able to determine the overall condition of the air diffusers, identify zones of low efficiency and estimate the savings potential that comes with cleaning or replacing the diffusers for each bioreactor.
- It is able to determine the depreciation period for the repair of air leaks.
- It is able to quantify oxygen transfer efficiency as a function of the plant’s operating mode.

Additionally, the methodology is able to determine in situ the spatial and temporal distribution of efficiency throughout the aerobic areas of the Galindo-Bilbao WWTP under real performance conditions. All these data will help managers and operators appropriately prioritize and plan future renovations and modifications to the plant’s aeration system.

Based on the results yielded to date, TecnoAqua, a scientific and technology magazine for the water industry, published the study carried out at the Galindo-Bilbao WWTP under the title “Estimación del potencial de ahorro en los sistemas de aireación de las EDAR mediante la medición de la transferencia de oxígeno” * (TecnoAqua nº 9, 64-72).