WE CLAIM:
[Claim 1]
A wastewater treatment method based on a membrane separation activated-sludge method, comprising: taking, with an optical means, an image of an activated sludge collected from a membrane separation activated-sludge tank; processing the image taken; and comparing a control parameter determined from information on the processed image with a preset control reference range to assess an operating state of the membrane separation activated-sludge tank. [Claim 2]
The wastewater treatment method based on a membrane separation activated-sludge method according to claim 1, comprising: taking, with an optical means, an image of an activated sludge collected from a membrane separation activated-sludge tank; processing the image taken to distinguish a floc region from an aqueous-phase region; acquiring image information on at least one region of the floc region and the aqueous-phase region; determining a control parameter from the image information through a calculation satisfying at least one of the following requirements; and comparing the calculated value and/or a change amount in the calculated value with the lapse of time, with a preset control reference range to assess a state of the activated sludge:
(a) the control parameter is calculated from an image information element determined separately for the floc region or the aqueous-phase region;
(b) at least two control parameters calculated from an image information element determined separately for the floc region or the aqueous-phase region are combined for each kind of regions;
(c) at least two image information elements determined separately for the floc region or the aqueous-phase region are combined to calculate the control parameter; and
(d) at least two of the values calculated in (a) to (c) are combined to calculate the control parameter.
[Claim 3]
The wastewater treatment method according to claim 1 or 2, wherein the control parameter for the floc region and/or the aqueous-phase region is any of a total value, a maximum value, a minimum value, an average value, a median value, and a deviation value each regarding at least any of area, circumference length, distance between the floc regions, the number of the region, and brightness.

[Claim 4]
The wastewater treatment method according to any one of claims 1 to 3, comprising: calculating a total area of the floc region per unit area of a field of view; and comparing the calculated value and/or a change amount in the calculated value with the lapse of time with a preset control reference range to perform the assessment. [Claim 5]
The wastewater treatment method according to any one of claims 1 to 4, comprising: calculating a total area of the floc regions each having an area not larger than a certain value and surrounded by an aqueous-phase region, per unit area of a field of view; and comparing the calculated value and/or a change amount in the calculated value with the lapse of time with a preset control reference range to perform the assessment. [Claim 6]
The wastewater treatment method according to any one of claims 1 to 5, wherein, in taking the image of the activated sludge collected from the membrane separation activated-sludge tank, the image is taken after at least any one of a liquid mixture obtained by mixing the activated sludge with a membrane filtrate water, an aqueous phase portion obtained by centrifuging the activated sludge, and the filtrate water obtained through filtration is degassed and/or stirred. [Claim 7]
The wastewater treatment method according to any one of claims 1 to 6, comprising: in a case when the control parameter has been assessed to be outside the control reference range, outputting an alarm and/or a control information regarding a wastewater treatment condition. [Claim 8]
The wastewater treatment method according to any one of claims 1 to 7, wherein the wastewater treatment condition, regarding which the alarm and/or the control information is output when the control parameter has been assessed to be outside the control reference range, is at least any one of the following:
(A) concentration of inflow water to be treated and inflow rate,
(B) filtration rate,
(C) filtration period or filtration suspension period,
(D) aeration-air feed rate or aeration period,
(E) nutrient salt addition amount,

(F) chemical addition amount,
(G) amount of activated sludge,
(H) treated-water return rate,
(I) operating conditions for pretreatment step,
(J) operating conditions for post-treatment step,
(K) temperature regulation conditions for activated-sludge tank,
(L) operating conditions for membrane elements,
(M) cleaning conditions for membrane elements, and
(N) cleaning conditions for aeration tubes.
[Claim 9]
The wastewater treatment method according to claim 7 or 8, wherein the assessment is made at a place which is remote from a place where the image of the activated sludge collected from the membrane separation activated-sludge tank is taken and which has been connected to said place by a communication appliance, thereby outputting the alarm and/or the control information. [Claim 10]
The wastewater treatment method according to any one of claims 7 to 9, comprising controlling the wastewater treatment condition on the basis of the control information output. [Claim 11]
The wastewater treatment method according to claim 10, comprising: assessing a mixed liquor suspended solid concentration (MLSS) on the basis of the control parameter obtained; and when the result is higher than the preset control reference range, performing an activated-sludge withdrawal operation and when the result is lower than the preset control reference range, performing an activated-sludge concentration operation. [Claim 12]
The wastewater treatment method according to claim 10 or 11, comprising: taking, with an optical means, the image of the activated sludge collected from the membrane separation activated-sludge tank; processing the image to assess an aqueous-phase suspended matter amount in the activated sludge; and when the result is outside the preset control reference range, performing an operation for reducing a water-to-be-treated inflow rate and/or a filtration rate and when the result is lower than the preset control reference range, performing an operation for increasing the water-to-be-treated inflow rate and/or the filtration rate.

[Claim 13]
A wastewater treatment device for treating wastewater using a membrane separation activated-sludge method, comprising: a means for collecting an activated sludge from a membrane separation activated-sludge tank; an imaging means which takes an image of the collected activated sludge with an optical means; an image processing means which distinguishes a floc region from an aqueous-phase region in the image taken, acquires image information on at least one region of the floc region and the aqueous-phase region, and determines a control parameter from the image information through a calculation satisfying at least one of the following requirements; and an assessment means which assesses an operating state of the membrane separation activated-sludge tank, on the basis of the calculated control parameter and/or a change amount in the control parameter with the lapse of time:
(a) the control parameter is calculated from an image information element determined separately for the floc region or the aqueous-phase region;
(b) at least two control parameters calculated from an image information element determined separately for the floc region or the aqueous-phase region are combined for each kind of regions;
(c) at least two image information elements determined separately for the floc region or the aqueous-phase region are combined to calculate the control parameter; and
(d) at least two of the values calculated in (a) to (c) are combined to calculate the control parameter.
[Claim 14]
The wastewater treatment device according to claim 13, wherein the assessment means has been disposed at a place which is remote from a place where the image of the activated sludge collected from the membrane separation activated-sludge tank is taken and which has been connected to said place by a communication appliance, and the assessment means comprises an output means which outputs an alarm and/or a control condition when a result of the assessment is outside a preset control reference range and a control means which performs control in accordance with any of the output control condition. [Claim 15]
A wastewater treatment system control program for controlling a wastewater treatment system for treating wastewater using a membrane separation activated-sludge method, comprising making a computer to: control a means for collecting an activated sludge

from a membrane separation activated-sludge tank, an imaging means which takes an image of the collected activated sludge with an optical means, and an image processing means which distinguishes a floc region from an aqueous-phase region in the image taken, acquires image information on at least one region of the floc region and the aqueous-phase region, and determines a control parameter from the image information through a calculation satisfying at least any one of the following requirements; and operate as an assessment means which assesses an operating state of the membrane separation activated-sludge tank, on the basis of the calculated control parameter and/or a change amount in the control parameter with the lapse of time:
(a) the control parameter is calculated from an image information element determined separately for the floc region or the aqueous-phase region;
(b) at least two control parameters calculated from an image information element determined separately for the floc region or the aqueous-phase region are combined for each kind of regions;
(c) at least two image information elements determined separately for the floc region or the aqueous-phase region are combined to calculate the control parameter; and
(d) at least two of the values calculated in (a) to (c) are combined to calculate the control parameter.