STERAPORE 5600 Series (FF) Instruction Manual
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4-2
Activated sludge
4-2-1
MLSS Concentration (Membrane Tank)
Recommended range: 5,000 to 10,000 mg/L (min: 3,000 mg/L, max: 15,000 mg/L)
As the MBR system separates liquid and solids using a membrane, there is no need to allow sludge to
settle. Therefore wastewater can be treated while maintaining a high MLSS concentration. Operate the
system with an MLSS concentration within the range of 5,000 to 10,000 mg/L.
C AU T I O N
As the MLSS concentration in the sludge rises it also becomes more viscous, which reduces the
effectiveness of membrane scouring aeration. In particular, as viscosity rises sharply if the MLSS
concentration exceeds 10,000 mg/L, keep the MLSS concentration within the recommended
range. However, as viscosity may be high even when the MLSS concentration is low, maintain
and control the viscosity as described in 4-2-2 Sludge Viscosity.
If the condition of the activated sludge is poor
＊
or if the MLSS concentration is below the lower
limit (for instance, during sludge acclimation), the membrane surface will become smeared with
untreated organic matter as water is filtered, which accelerates a rise in trans membrane
pressure, thus preventing stable operation of the product. In such cases, set the membrane flux
lower than normal when operating the product.
Before operating the system at the normal membrane flux level again (after operating with the
membrane flux set lower than normal due to the above conditions), confirm that biological
processing using activated sludge has been restored to satisfactory levels.
*
This refers to the condition where the supernatant of activated sludge is muddy when sludge volume is
measured in accordance with the Gesuishikenhoho (Japan Sewage Works Association) or JIS B9944. (Although
SV30 is normally measured when measuring sludge volume, but for MBR systems which have high MLSS
concentration, the mixed liquor in the aeration tank is diluted fourfold with treated water when measuring SV30.)
4-2-2
Sludge Viscosity
Recommended range: 30 mPa•s or less
＊
C AU T I O N
When treating industrial wastewater, both MLSS concentration and sludge viscosity need to be
controlled. If sludge viscosity exceeds the upper limit of the rec
ommended range of 30 mPa•s
＊
,
membrane cleaning performance declines, which can cause sludge to widely cover the
membrane surface and clog its micropores, preventing stable operation. Therefore, lower the
viscosity by reducing the sludge concentration or by any other appropriate means.
*
Based on measurements made using a B-type viscometer. If any other device is used, please consult its
manufacturer and use the above recommended range as a reference.
4-3
Supplements
4-3-1
Antifoaming Agent
If an antifoaming agent is to be put into aeration tank due to sludge foaming, use a high grade alcohol,
ether, or ester antifoaming agent.
Our recommended antifoaming agent is DIAFLOC AF102 (made by Mitsubishi Rayon Co.,Ltd.) If you
are considering purchasing this product, please contact our sales representative.
If foaming occurs in sludge, use physical antifoaming methods, such as spraying water on the foam
surface, to minimize the amount of antifoaming agent required.
C AU T I O N
The use of silicon antifoaming agents is prohibited.
If silicon antifoaming agents are used, the antifoaming agent is absorbed into the membrane
surface causing trans membrane pressure to increase. As it is difficult to clean off absorbed
silicon antifoaming agents using chemicals the membrane must be replaced.