Treatment of dairy industry wastewater by oxygen injection: performance and outlay parameters from the full scale implementation

• O2 injection was coupled to the physicochemical stage for the treatment of dairy wastewater.
• COD removal average performance increased from 35 to 75%.
• Performance increase allows for a reduction in the municipal tax from 2.5 to 0.5 €/m3.
• Reactor volume for treating 1 kg of COD by the O2 injection is 1.2% of that by an UASB.

This work presents the application of a new system for wastewater treatment in the food industry, which is based in the injection of pure oxygen in the homogenization tank of a traditional physicochemical treatment. This system operates stably under a wide variety of both input chemical oxygen demand (COD) and total suspended solids (TSS). Compared with the previous physicochemical system, it has been proved that the new one is more efficient and implies important economic savings for the dairy. Compared with a traditional anaerobic treatment, it has been shown that the oxygen injection system avoids the relatively high costs associated to the initial investment and operating costs and is environmentally friendlier. In this work it is shown that oxygen injection may be an interesting option for the dairy industry wastewater treatment.