Treatment and thickening of sludge from municipal wastewater treatment plants (WWTP or WWTP)

Scenario

The Ministry of Public Utilities of Trinidad and Tobago, through the Water and Sewerage Authority (WASA), awarded the 'San Fernando Complex' project to the consortium formed by Acciona and the Atlatec Group. Acciona contracted Agua SIGMA to provide the treatment of the sludge generated at the plant.

The plant has a treatment capacity of 45,000 m³/day and serves a population of 111,600 inhabitants. The facility has 16.3 kilometers of collectors, 12.5 of which are microtunnels with 11,964 service connections and 7 pumping stations with flow rates ranging from 7 L/second to 203 L/second.

For the treatment of the sludge generated in the plant, Agua SIGMA provides the design, construction and commissioning of a physicochemical treatment system with dissolved air flotation DAF FPAC.

After wastewater treatment, the plant generates a sludge load of more than 8,000 kilograms per day with an average concentration of 0.6% (6000 mg/L), which requires a thickening process for further treatment and stabilization. For this purpose, Agua SIGMA designed, built and installed two DAF FPAC dissolved air flotation units, achieving a sludge concentration of up to 6% (6,000 mg/L) at the San Fernando plant. 

The DAF units were designed to treat up to 31.25 ^m3/h with a solids concentration of 0.6 to 0.8%. The DAF dimensions are L 16.3 x W 4.2 m with a usable area of 68 m² designed to operate at a mass loading of 2.7 (2 units without polymer) to 7.3 kg DS/ m2-h (1 unit with poly of 3 kg/tn DS). The DAFs were manufactured in AISI304 steel tanks and shipped to the plant suitably protected for sea transport.

The DAF equipment is specially designed for easy operation and maintenance, with a complete control-automation system and the SMARTDAF system in pressurization and aeration, provided with micrometrically adjustable back pressure valves to control the depressurization process.

Sludge characteristics

Performance