WE CLAIM:

1. A method for operating a separation membrane in which a liquid-to-be-filtrated is
subjected to filtration to obtain a filtrate, the method comprising:
5 an accumulated amount calculation step of, based on an initial value of an amount of
constituent components of a liquid-to-be-filtrated accumulated in a separation membrane, and
a change over time in the constituent components of the liquid-to-be-filtrated, a
change over time in the amount of the constituent components, and a change over time in an
operating condition of the separation membrane after setting the initial value,
10 calculating the amount of the constituent components of the liquid-to-be-filtrated
accumulated on a surface and in pores of the separation membrane after setting the initial value;
a chemical liquid cleaning effect calculation step of calculating a restoration degree
of an accumulated amount of the constituent components or membrane filtration resistance in
chemical liquid cleaning based on a result of accumulated amount calculation; and
15 a chemical liquid cleaning condition determination step of determining a chemical
liquid cleaning condition based on results obtained in the accumulated amount calculation step
and the chemical liquid cleaning effect calculation step.
2. The method for operating a separation membrane according to claim 1, wherein
20 the separation membrane is a microfiltration membrane or an ultrafiltration
membrane.
3. The method for operating a separation membrane according to claim 1 or 2, wherein
the liquid-to-be-filtrated is an activated sludge or a microorganism culture solution.
25
4. The method for operating a separation membrane according to any one of claims 1 to
3, wherein
the method for operating a separation membrane is an operation method of cleaning
the surface of the separation membrane simultaneously or intermittently with filtration.
30
5. The method for operating a separation membrane according to any one of claims 1 to
4, wherein
the membrane filtration resistance or the amount of the constituent components of the liquid-to-be-filtrated accumulated on the surface of the separation membrane, which is
calculated in the accumulated amount calculation step, is divided into a plurality of pieces of
membrane filtration resistance or amounts of the constituent components of the liquid-to-befiltrated based on a physical cleaning condition for peeling or a degree of consolidation.
5
6. The method for operating a separation membrane according to any one of claims 1 to
5, wherein
the method for operating a separation membrane is an operation method for
continuing membrane filtration while controlling a membrane filtration flow rate (flux) to a set
10 value, and in the accumulated amount calculation step, the membrane filtration resistance or
the amount of the constituent components of the liquid-to-be-filtrated accumulated on the
surface or in the pores of the separation membrane is calculated by performing a calculation
step 1a, at least any one of a calculation step 1b and a calculation step 1c, and a calculation step
2 and/or a calculation step 3 in the followings, and repeatedly performing the calculation steps
15 while updating time to calculate the amount of the constituent components of the liquid-to-befiltrated adhered to the separation membrane:
the (calculation step 1a) of calculating an amount value of the constituent components
of the liquid-to-be-filtrated adhered on the surface of the separation membrane at a time t + Δt
(here, t is any number of 0 or more, and Δt is any positive number) based on an amount value
20 of the constituent components of the liquid-to-be-filtrated and a membrane filtration flow rate
(flux) value or a transmembrane pressure difference value at a time t;
the (calculation step 1b) of calculating an amount value of the constituent components
of the liquid-to-be-filtrated present in the pores of the separation membrane at the time t + Δt
based on the transmembrane pressure difference value and/or the membrane filtration flow rate
25 (flux) value at the time t;
the (calculation step 1c) of calculating an amount value of the constituent components
of the liquid-to-be-filtrated consolidated and adhered on the surface of the separation membrane
at the time t + Δt based on the transmembrane pressure difference value at the time t;
the (calculation step 2) of calculating a membrane filtration resistance value at the
30 time t + Δt based on the amount value of the constituent components of the liquid-to-be-filtrated
adhered on the surface of the separation membrane, which is calculated in the calculation step
1a, and the amount value of the constituent components of the liquid-to-be-filtrated present in
the pores of the separation membrane, which is calculated in the calculation step 1b, and/or the amount value of the constituent components of the liquid-to-be-filtrated consolidated and
adhered on the surface of the separation membrane, which is calculated in the calculation step
1c; and
the (calculation step 3) of calculating a transmembrane pressure difference value at
5 the time t + Δt based on the amount value of the constituent components of the liquid-to-befiltrated adhered on the surface of the separation membrane, which is calculated in the
calculation step 1a, and the amount value of the constituent components of the liquid-to-befiltrated present in the pores of the separation membrane, which is calculated in the calculation
step 1b, and/or the amount value of the constituent components of the liquid-to-be-filtrated
10 consolidated and adhered on the surface of the separation membrane, which is calculated in the
calculation step 1c, or based on the membrane filtration resistance value which is calculated in
the calculation step 2.
7. The method for operating a separation membrane according to any one of claims 1 to
15 5, wherein
the method for operating a separation membrane is an operation method for
continuing membrane filtration while controlling a transmembrane pressure difference to a set
value, and in the accumulated amount calculation step, the membrane filtration resistance or
the amount of the constituent components of the liquid-to-be-filtrated accumulated on the
20 surface or in the pores of the separation membrane is calculated by performing a calculation
step 1a, at least any one of a calculation step 1b and a calculation step 1c, and a calculation step
2 and/or a calculation step 4 in the followings, and repeatedly performing the calculation steps
while updating time to calculate the amount of the constituent components of the liquid-to-befiltrated adhered to the separation membrane:
25 the (calculation step 1a) of calculating an amount value of the constituent components
of the liquid-to-be-filtrated adhered on the surface of the separation membrane at a time t + Δt
(here, t is any number of 0 or more, and Δt is any positive number) based on an amount value
of the constituent components of the liquid-to-be-filtrated and a membrane filtration flow rate
(flux) value or a transmembrane pressure difference value at a time t;
30 the (calculation step 1b) of calculating an amount value of the constituent components
of the liquid-to-be-filtrated present in the pores of the separation membrane at the time t + Δt
based on the transmembrane pressure difference value and/or the membrane filtration flow rate
(flux) value at the time t; the (calculation step 1c) of calculating an amount value of the constituent components
of the liquid-to-be-filtrated consolidated and adhered on the surface of the separation membrane
at the time t + Δt based on the transmembrane pressure difference value at the time t;
the (calculation step 2) of calculating a membrane filtration resistance value at the
5 time t + Δt based on the amount value of the constituent components of the liquid-to-be-filtrated
adhered on the surface of the separation membrane, which is calculated in the calculation step
1a, and the amount value of the constituent components of the liquid-to-be-filtrated present in
the pores of the separation membrane, which is calculated in the calculation step 1b, and/or the
amount value of the constituent components of the liquid-to-be-filtrated consolidated and
10 adhered on the surface of the separation membrane, which is calculated in the calculation step
1c; and
the (calculation step 4) of calculating a membrane filtration flow rate (flux) value at
the time t + Δt based on the amount value of the constituent components of the liquid-to-befiltrated adhered on the surface of the separation membrane, which is calculated in the
15 calculation step 1a, and the amount value of the constituent components of the liquid-to-befiltrated present in the pores of the separation membrane, which is calculated in the calculation
step 1b, and/or the amount value of the constituent components of the liquid-to-be-filtrated
consolidated and adhered on the surface of the separation membrane, which is calculated in the
calculation step 1c, or based on the membrane filtration resistance value which is calculated in
20 the calculation step 2.
8. The method for operating a separation membrane according to any one of claims 1 to
7, wherein
in the accumulated amount calculation step, an amount of inorganic constituent
25 components of the liquid-to-be-filtrated accumulated on the surface and in the pores of the
separation membrane is calculated.
9. The method for operating a separation membrane according to any one of claims 1 to
8, wherein
30 the chemical liquid cleaning condition determined in the chemical liquid cleaning
condition determination step is at least any of a chemical liquid concentration, a chemical liquid
cleaning time, a chemical liquid temperature, a chemical liquid amount, a chemical liquid
supply flow rate, a number of times of chemical liquid cleaning , a chemical liquid type, and a chemical liquid cleaning interval in the chemical liquid cleaning.
10. The method for operating a separation membrane according to any one of claims 1 to
9, wherein
5 the chemical liquid type is changed when a calculation result of the restoration degree
of the accumulated amount of the constituent components or the membrane filtration resistance
of the chemical liquid cleaning is a specified value or less.