Described are wrapped fluid treatment elements, comprising: a composite material; an interleaf; and an inner core; wherein the composite material and the interleaf form layers wrapped around the inner core. The composite material and interleaf may be wrapped in a spiral configuration around the inner core. The invention also relates to a method of separating a substance from a fluid, comprising the step of placing the fluid in contact with an inventive device or element, thereby adsorbing or absorbing the substance to the composite material contained therein.

A multistage reverse osmosis system for processing a fluid, the system comprising a first fluid processing membrane; a second fluid processing membrane, the second fluid processing membrane having an inlet for unprocessed fluid from the discharge of the first membrane; a third fluid processing membrane, the third fluid processing membrane having an inlet for receiving processed fluid from the first and second processing membranes, a high-pressure pump operatively connected to the inlet for the third fluid processing membrane, the high-pressure pump controlling the quantity of processed fluid from the first and second fluid processing membranes supplied to the inlet of the third processing membrane.

A reciprocating concentration system includes: a gas output device, first and second liquid accommodating tanks, a selection device, first and second liquid sensors and a computing control device. The gas output device is controlled to output pushing gas through a first gas channel or a second gas channel. The first liquid accommodating tank is in communication with the first gas channel. The second liquid accommodating tank is in communication with the second gas channel. The selection device is in communication with the first liquid accommodating tank and the second liquid accommodating tank through a first liquid channel and a second liquid channel, respectively, and has a filtered liquid outlet. The first liquid sensor and the second liquid sensor are disposed at the first liquid channel and the second liquid channel, respectively. The computing control device is connected to the gas output device and the first and the second liquid sensors.