DAF flotation for reusable organic matter recovery

Scenario

VEOLIA Water Technologies was contracted by EL POZO Alimentación for the improvement of the effluent treatment plant (ETP) at its meat processing plant in Alhama-Murcia. The improvement project incorporates DAF dissolved air flotation in the primary treatment, replacing the existing sedimentation. The PTE has a capacity of 6 ML/d and 42 t COD/d (350,000 PE). The ETP also includes an activated sludge biological treatment stage with nutrient removal and sludge treatment with anaerobic digestion of the primary sludge.

In order to improve the energy use of sludge in anaerobic digestion, EL POZO decided to replace primary sedimentation (by gravity) with a DAF flotation stage, as this is a process with higher solids removal performance in this type of meat processing effluent, which results in a greater amount of organic matter to be converted into methane in the digestion of primary sludge.

SIGMADAF designed and supplied all equipment for two FPAC200 CW units working as primary clarifiers of the meat processing factory effluent, to be installed in existing concrete tanks, including: chain type floated sludge collector (2 pcs.) in AISI316L with HDPE chain for a flotation tank of W 2.8 x L 8.5 m, recirculation pumps (2+1R) for 180 m3/h (recirc. 50%), air compressors (1+1R), air saturators (2) with 6 ML capacity vessels, aeration system (2) with 18 nozzles in AISI316L, piping (AISI316L), valves and fittings, instrumentation, control panel, spare parts for 2 years, documentation and manuals. 

Delivery of the SIGMADAF equipment was completed within 12 weeks after approval of the manufacturing documentation. 

Equipment Characteristics 

The FPAC is a particularly effective equipment to treat high flow rates of water with high content of solids, oils and fats. SIGMADAF has a wide and extensive experience with this type of DAF units in slaughterhouses and meat processing, with more than 40 references.

The use of micro air bubble flotation technology (30 to 50 micron range) increases flotation performance, as smaller bubbles easily adhere to particles of equal or larger size, increasing the overall effectiveness of the system. The SIGMADAF aerator generates the required amount of air to be injected into small-sized bubbles in quantity and well distributed in the inlet contact chamber of the tank, where the feed water mixes with the aerated recirculation flow. The mixture flows into the clarification-flotation section where the suspended solids float due to the buoyancy effect and a surface sludge layer is formed. 

The floated sludge collector with one-way drag scraper displacement against the water flow helps minimize the sludge displacement on the surface and eliminates solids entrainment with the clarified water. The floated sludge is drawn into a collection hopper with a high solids concentration of 4 - 5% conc, which benefits the anaerobic digestion process.

Water characteristics

Performance