First time S::Select®-plant successfully installed on a SBR waste water treatment plant

A S::Select®-plant could be successfully commissioned on a SBR-plant in Chile some weeks ago. The existent WWTP had massive problems with the sludge properties. This became evident as a massive layer of floating sludge on the aeration tank. Furthermore, the sludge settling velocity was appallingly low. Additionally, the plant was considerably overloaded. The plant had been designed for 60,000 PE, but further increase had already been predicted due to increasing collection by septic tanks.

Accordingly, it had been planned to increase the plant from 4 to 6 SBR tanks (increase by 50 % to treat 90,000 PE, calculated as load) to manage the problems in load and with floating sludge. Subsequently also the pumping stations, the sludge thickening and the sludge dewatering units should be extended and some roads on the plant should be relocated. Before starting this comprehensive measures, it had been decided to install the S::Select®-technology. This technology achieves significantly better sludge settling velocity by granulation of the sludge. The guaranteed settling velocity is 3 m/h in minimum! Furthermore, the selectors or hydro cyclones, which are characteristic for this technology, not only keep the granular sludge safely in the aeration tank system, what will stabilize and increase the performance of the aeration tank system. The selector will also separate the fast-growing bacteria, which are forming the floating sludge, as surplus sludge. Thus, it prevents the formation of floating sludge layers.

During commissioning the predicted results could be over fulfilled. In a specially designed test cylinder, which imitates the sludge settling behaviour in the SBR tank verifiable realistic, the improvement of the sludge settling velocity during adaption phase could be illustrated impressively. Starting with values of 0.2 to 0.4 m/h under old conditions, continuously stable values of 7 to 8 m/h had been realized with S::Select®.

By means of these continuously high values of the sludge settling velocity the cycle times of the SBR system could be significantly shortened. Thus, the capacity of the SBR system in total could be increased accordingly. Furthermore, the metabolic rate of the sludge is significantly higher in the granular form. This fact increases the capacity additionally.

Finally the installation of the der S::Select®-technology supersedes the formerly intended extension of the WWTP by 50 %! Now it is possible to treat the load of 90,000 PE in the existing tanks, which had been designed for only 60,000 PE. Additionally, it overcomes the problems with floating sludge clearly.
Afterwards, during not to be delayed replacement of the aerators in the tanks, the genuine capability the S::Select®-technology became obvious:
To execute the replacement, the tanks had to be emptied one by one, so that only 75 % of the former capacity was available for a distinct time (this means a volume designed to treat 45.000 PE). Even under this challenging condition the SBR-system had worked stable and proper. All effluent values for 90,000 PE have been kept in the allowed range!
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