STERAPORE 5600 Series (FF) Instruction Manual
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Chapter 4
Pretreatment
4-1
Pretreatment
The aims of pretreatment are as follows.
To prevent inflow of raw water that may inhibit the MBR system's functions and damage MBR facilities.
To use devices safely and stably.
To effectively carry out biological processes.
This section describes these pretreatment procedures.
4-1-1
Pretreatment of Raw water
●
Screenings (impurities such as fibers, hairs, and plastic debris in raw water)
Remove screenings using a screen.
C AU T I O N
Use screens (drum screens or wedge wire screens from which fibers and hairs can be removed)
with openings of 0.5 to 1 mm.
●
pH (acidity or alkalinity)
If raw water is acidic or alkaline, add neutralizer to raw water to adjust its pH to neutral (around 6 to 8). If
raw water is so strongly acidic or alkaline as to make it difficult to neutralize it using one-step treatment,
two-step treatment may be required. Sulfuric acid or caustic soda is generally used as a neutralizer.
Operate a pH meter and a chemical feeding pump together to control the amount of neutralizer added.
●
Grease and oil
Grease and oil widely cover the membrane surface and clog its micropores, preventing stable operation
of the system. Grease and oil can be quantitatively analyzed as hexane extracts. They can further be
separated into animal and vegetable fats and oils and mineral oils, and the amount of each of these can
then be determined. Treatment methods for grease and oil include natural flotation and dissolved air
flotation (DAF). If the grease and oil content exceeds 150 mg/L, please reduce it to 150 mg/L or less
using these methods or similar.
Animal and vegetable fats and oils can be decomposed in a biological process tank if their
concentration is 20 % or less of BOD, by keeping the BOD-SS load at or below 0.1 kg-BOD/(SS
•
day).
As mineral oils do not biodegrade easily, they have a worse impact on the membrane than animal and
vegetable fats and oils. As a rule, avoid mixing mineral oils into raw water.
Figure 4-1
Example Procedures for Wastewater That Contains Oils