WATER TREATMENT APPARATUS COMPRISING MEMBRANES

Abstract: Water treatment apparatus comprises: first and second treatment lines (12, 16) between a common inlet (10) and a common outlet (11); a first membrane (13), operable under relatively low pressure, at the inlet or in the first line; and a second membrane (19), operable under relatively high pressure, and a pump (18) therefor, in the second line.

Description: WATER TREATMENT APPARATUS COMPRISING MEMBRANES Field of the Invention This invention relates to water treatment apparatus. In particular, it relates to apparatus in which a combination of treatments is used to obtain a product of a quality appropriate to a variety of end uses. Background of the Invention Many systems are known for purifying, or generally increasing the quality of water. For example, it is known to treat part of a water flow, and combine the treated water with untreated water to give a blend. The quality of the blend, however, may be unsatisfactory for a variety of uses. Various different membrane treatment systems are known. They include membranes that are operated under relatively high pressure, e.g. by nanofiltration, hyperfiltration up to reverse osmosis, and those operated under relatively low pressure, e.g. by microfiltration or ultrafiltration. While each system may be very satisfactory in itself, it may not be best adapted for the intended purpose. Thus, for example, a low pressure system may be relatively economic but give insufficient water quality. Conversely, the use of a high pressure system may give water quality that is actually unnecessarily high for the intended purpose, at unnecessary expense. Summary of the Invention A novel water treatment system, according to the present invention, involves a hybrid membrane system. More particularly, novel apparatus comprises: first and second treatment lines between a common inlet and a common outlet; a first membrane, operable under relatively low pressure, at the inlet or in the first line; and a second membrane, operable under relatively high pressure, and a pump therefor, in the second line. By virtue of the present invention, water can be treated to any of a variety of suitable standards. By choosing the standard appropriate to the desired use, an optimally economic system is provided. Description of the Invention It will be readily appreciated that the present invention involves treatment of water in at least one of two separate lines, the respective products then being blended. By way of example, water may be partly softened and completely disinfected. A system of the invention is of particular value to the food industry, and in the production of beverages such as beer. The hybrid system can produce a range of high quality waters, all of which may be totally free from parasites such as Cryptospirid±a and G±ardia , bacteria and viruses. This cannot be achieved economically by the use of a single membrane system, and probably cannot be achieved at all by using a blend of treated and untreated water. As is often the case when using membranes, a preliminary filter, e.g. a cartridge filter, may be provided, at the inlet or in each line. This will serve to remove, say, sand. The pressure of the water feed may be sufficiently high to operate such a filter and also the low pressure membrane; in this case, the apparatus of the invention requires only a pump to "step up" the pressure of water supplied to the high pressure membrane. Alternatively, or as desired, a low pressure pump may be included in the system. In one embodiment of the invention, the respective membranes are in each of the two lines. Appropriate associated pumps may be provided independently, in the separate treatment branches. Preferably, however, the low pressure pump is provided "at the inlet", by which is meant anywhere in the system prior to the point at which the separate lines take off from the common inlet. This arrangement takes advantage of the fact that the operating pressure for, say, microfiltration or ultrafiltration is the same as the pressure supplied as feed to a high pressure pump (in the second line) used for, say, nanofiltration or reverse osmosis. In an alternative embodiment of the invention, the low pressure membrane and any associated pump are provided at the inlet. In this case, the first line is in effect a bypass with respect to the high pressure membrane, so that all the water passes through the low pressure membrane and then part only passes also through the high pressure membrane. This arrangement may be particularly suitable for treating nitrates. Typically, a high pressure membrane operates at a feed pressure of 5 to 20 bar. A low pressure membrane may operate at a feed pressure of 0.5 to 2 bar. The relative amounts of water passing through the first and second lines, which dictate the composition of the blend, can be predetermined. Alternatively, means may be provided whereby the relative amounts are controlled, as desired. Control may be achieved by, for example, operation of the high pressure pump, or by automated valves. The desired quality can be monitored, for example, by the conductivity of the blended water; a feedback loop may be provided, in order to adjust the water quality as desired, depending on the analysis of the blend. In certain circumstances, e.g. where it is desired to remove pesticides from the water, a recycle system may be simply included. In this system, reject water from the high pressure membrane is passed to the inlet of the low pressure membrane. This reject stream may be dosed or otherwise treated, to remove pesticides or any other undesired contaminant, while allowing natural salts, e.g. calcium, to be put back into the water. Apparatus of the invention may comprise an inlet for dosing in a disinfectant such as ozone or chlorine. This will typically be provided in advance of one or both membranes, e.g. the low pressure membrane. The invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic view of apparatus embodying the invention; Figure 2 is a schematic view of alternative apparatus embodying the invention; and Figure 3 is a schematic view of yet further apparatus embodying the invention. Fig. 1 shows a common feed 10, e.g. from a mains supply, and a blended water outlet 11, a first line 12 including a cartridge filter 13, a low pressure membrane microfiltration or ultrafiltration unit 14 providing a waste stream 15, and a second line 16 including a cartridge filter 17, a high pressure pump 18 and a high pressure membrane nanofiltration or reverse osmosis unit 19 providing a waste stream 20. A low pressure pump 21 is provided at the common inlet, and operates the cartridge filters, the low pressure membrane and the feed to the high pressure membrane system. A control valve 22 allows control of the quality of the blended water output. Fig. 2 shows, in addition to components shown in Fig. 1 (other components which may also be present are not shown), means whereby the waste stream is recycled, as described above. Thus, in the apparatus of Fig. 2, the reject stream line from the high pressure unit 19 includes a valve 23 on a waste outlet 24 and a chemical dosing inlet 25, and leads into the line 13. Fig. 3 shows an embodiment of the invention, utilising many of the same components as the embodiments of Figs. 1 and 2, in which all the input water is passed through the low pressure membrane, and then part is passed through the high pressure membrane. As in the other embodiments, means such as the valve 22 is provided to control the relative amounts of water passing through the respective lines, and thus the quality of the final blend. Apparatus of the invention is useful in any context where quality needs improvement. Further, the desired quality can be obtained by simple control of the blend. Waste streams can be recirculated and treated, as necessary or desired.

Claims: £ 1. Water treatment apparatus comprising: first and second treatment lines (12,16) between a common inlet (10) and a common outlet (11) ; a first membrane (13) , operable under relatively low pressure, at the inlet or in the first line; and a second membrane (19) , operable under relatively high pressure, and a pump (18) therefor, in the second line. 2. Apparatus according to claim 1, additionally comprising a pump (21) for the first membrane, in the first line or at the common inlet. 3. Apparatus according to claim 2, wherein the additional pump is at the inlet. 4. Apparatus according to any preceding claim, wherein the first membrane operates by microfiltration or ultrafiltration. 5. Apparatus according to any preceding claim, wherein the second membrane operates by nanofiltration or reverse osmosis. 6. Apparatus according to any preceding claim, wherein either or each line also includes a cartridge or other preliminary filter (13,17). 7. Apparatus according to any preceding claim, which additionally comprises means (22) for controlling the relative amounts of water that pass to the outlet from the first and second lines. 8. Apparatus according to any preceding claim, wherein the first membrane is in the first line. 9. Apparatus according to claim 8, which includes an additional line for the passage of reject water from the second membrane to the first membrane. 10. Apparatus according to claim 9, wherein the additional line includes means (25) for dosing the reject water.

Inventors: MURRER EDWIN WILLIAM JOHN, MURRER, EDWIN, WILLIAM, JOHN
Applicants: AW CREATIVE TECHNOLOGIES LTD, MURRER EDWIN WILLIAM JOHN, AW CREATIVE TECHNOLOGIES LIMITED, MURRER, EDWIN, WILLIAM, JOHN
Application year: 1997
Main classification: B01D61
IPC codes: B01D61, C02F1