Abstract: A spiral wound type membrane module is formed of a plurality of membranes wound about an axis of the module to form a roll of the membranes and to form feed water channels between the membranes into which feed water flows via a front end of the roll and from which nonpermeated water flows out via a rear end of the roll, wherein the module is operated such that a differential pressure between the feed water flowing into the channels and the nonpermeated water flowing out from the channels is 0.3 kg/cm2 or less. The pressure of the feed water is kept at PFmax or an approximate value of PFmax which brings a maximum permeate flux at the moment when a predetermined period has passed after starting to supply the feed water into the membrane module continuously at a constant pressure.

Abstract: A spiral wound type membrane module is formed by winding membranes onto a shaft by way of outer spacers. An inner spacer is inserted into the membrane. Raw water is fed from one end of a membrane roll into channels between the membranes. The raw water flows in a direction substantially parallel to the axis of the roll and is taken out from the other end of the roll as nonpermeated water. Water permeated through the membranes flows in the membranes spirally in the winding direction and is taken out from the opening formed on the circumference of the roll.

Abstract: An apparatus for coagulating treatment which is capable of controlling the amount of addition of a coagulant to the optimum level thereby minimizing the water content of the dehydrated cake comprises coagulant adding devices (6), (7), and (8) for causing the coagulant to be added in a variable amount to a liquid subjected to the coagulating treatment, a heat transfer detecting meter (12) disposed so as to contact the liquid to which the coagulant is to be added, the liquid to which the coagulant has been added, or the filtrate from the liquid to which the coagulant has been added and adapted to detect a feeble change in the physical property of the liquid in the form of a change in voltage, and a control device (16) for controlling the amount of addition of the coagulant in the coagulant adding device (8) so that the value of detection of the heat transfer detecting meter (12) is minimized or kept within a desired range.