FIELD OF INVENTION

The present invention relates to a method and apparatus for treatment and purification of water using membrane filtration.

BACKGROUND OF INVENTION

Water is an essential yet scarce resource. The difficulty to access fresh drinking water is a growing problem globally. In 2019, the World Economic Forum considered water scarcity as one of the largest global risks, with only 0.014% of all water on Earth deemed fresh and easily accessible. This scarcity of water is unfortunately compounded by alarming rates of pollution usually by chemical, microbial, and biological contaminants and plastics as a result of human activity. According to UNESCO, an estimated 300-400 mega-tonnes of waste is discharged by industry into water bodies annually. Consequently, 1 in 9 people worldwide use water from unimproved or unsafe sources resulting in waterborne diseases. Also, the pollution of freshwater ecosystems has led to the reduction in biodiversity by 83% since 1970 (World Wildlife Fund, 2018).

Membrane filtration is currently regarded as one of the most commonly employed water and wastewater treatment technologies. Membranes are thin layers of semi- permeable materials that separate substances upon application of a driven force across the membrane. Their performance is mostly dependent on their physico chemical properties including surface chemistry, thickness, surface charge, porosity, hydrophobicity, chemical, biological and thermal stability, durability, chlorine tolerance, surface roughness and cost. Membranes are generally classified according to their water affinity (hydrophobicity and hydrophilicity), pore size, molecular weight (MW) and water applied pressure.

The use of membranes in water and wastewater treatment has grown in popularity due to their efficiency in reducing contaminant concentration levels in water and wastewater. This advantage of membrane technology stems from a membrane’s low space requirement, ease of operation, use of standard CIP practices (depending on configuration), selective separation and reduced operation units. However, the major limitation to the efficient use of membranes is the inability to maintain filtration flux for a long period of time as a result of membrane fouling.

Membrane fouling is a major problem encountered in membrane filtration processes, and it is a major factor in determining their practical application in water and wastewater treatment and desalination in terms of technology and economics. There are different types of membrane fouling, including: organic fouling, inorganic fouling/scaling, particulate/colloidal fouling and biofouling (or microbial/biological fouling). Biofouling causes the loss of membrane performance due to biofilm formation on and inside the membrane as a result of interaction between membrane material, feed water and micro-organisms. It is regarded as the most common type of fouling, contributing to almost 45% of all membrane fouling. Unfortunately, biofouling can cause several adverse effects on membrane systems, including: 1) membrane flux decline due to the formation of a low permeability biofilm on the membrane surface; 2) membrane biodegradation caused by acidic by-products which are concentrated at the membrane surface, for example, a cellulose acetate membrane has been found to be susceptible to being biodegraded; 3) Increased differential pressure and feed pressure being needed to maintain the same production rate due to biofilm resistance; 4) increased energy consumption due to higher pressure being required to overcome the biofilm resistance and the flux decline; and 5) increased salt passage through membrane and reduced quality of the product water due to the accumulation of dissolved ions in the biofilm at the membrane surface thus increasing the degree of concentration polarization.

Biofouling of a surface, i.e. formation of a biofilm, can be described by a cycle of three phases: transport of the micro-organisms to the membrane surface, attachment to the substratum, and growth at the surface to form the biofilm. Unfortunately, once the biofilm has formed, it is difficult to remove it as biofilm micro-organisms can continuously multiply over time. Even if 99% of them are removed, there are still enough remaining micro-organisms which can continue to grow at the expense of the biodegradable substances/materials in the feed water. Fleming et al. showed that biofouling of a surface takes about 3 days to completely cover a reverse osmosis membrane with a biofilm. While minimal bacterial attachment occurred in a very low ionic strength solution, significantly higher numbers of attached microbes occurred when using salt concentrations corresponding to wastewater. Additionally, Flemming and Schaule demonstrated that after a few minutes of contact between a membrane and raw water, the first irreversible attachment of micro organisms occurs. Their results suggest that manufacturers of membrane filtration systems should consider methods that prevent the initiation, or at least disruption, of the biofouling cycle.

Several strategies and methods have been developed throughout the years to remedy biofouling. For instance, membrane material modifications (such as surface grafting, coating technologies, inorganics additives, anti-microbial additives, etc) are used to manage biofouling. However, each of these methods has its own limitations which eventually contributes to the prevalence of biofouling. Additionally, these methods are not preventative methods designed to pre-empt the kick-start of the biofouling cycle initiation. By default, the design of most membrane filter vessels/housings, particularly vertically installed membranes, offer internal zones for water stagnation (or water traps), which favour the accumulation of micro-organisms and biological materials resulting in the attachment of micro-organisms on the membrane surface, rendering them as biofouling prone areas.

STATEMENTS OF THE INVENTION In this invention, a membrane anti-biofouling method is achieved by providing apparatus for water treatment comprising a housing having an inlet and an outlet and defining a flow path for water therethrough, a membrane filter being located within the housing and the flow path extending through said membrane filter and at least part of the flow path, downstream of said membrane filter, extending downwardly, in a downstream direction, at an angle of from 1 ° to 10° to the horizontal.

Preferably, said angle is from 2° to 5°, more preferably about 2°.

Preferably, the housing is substantially cylindrical and the flow path extends along the longitudinal axis of the housing.

The membrane filter may be provided within a cartridge. Preferably, the apparatus comprises a plurality of said housings, more preferably four housings, and the flow path extends in series through each of them.

The or each housing may be attached to a metal plate, preferably a stainless steel plate.

Preferably, the stainless steel plate forms the front wall of the apparatus and comprises one or more machined circular holes providing access to the or each housing and further comprises at least one water pressure gauge.

Preferably, the or each circular hole is covered by a clamped circular cap cover that is provided with a handle and a tube-like projection on its inner side for locking engagement with a membrane carrying unit within the housing.

Preferably, the housings are locked into the plate in a configuration in which two housings are placed side-by-side and below two other side-by-side placed housings.

Preferably, the housings are interconnected by tubes, gaskets and flange faces so as to cause the water to flow in a sequence starting from the bottom left housing, then to the bottom right housing, or vice versa, then to the top right housing, then to top left housing, or vice versa, and then exiting via the outlet tube.

Preferably, the inlet feed water is caused to flow into the apparatus by an external pump causing a 2 Bar differential pressure.

Preferably, the apparatus has a footprint of approximately 588cm (width) x 504cm (length) x 600cm (height), a weight of about 70kg and is made from food grade materials.

Preferably, the pump is configured to cause water to flow through the apparatus at a flow rate of from 20-40 litres/min. Various types of filters and membrane filters of different materials types and sizes can be housed inside the said vessels in a variety of configuration to provide multi-stage water purification.

A system may be provided in which a plurality of such apparatuses are arranged in a configuration and connected to external pipework via a manifold to treat inlet feed water at flow rates higher than 40 litres/min.

The present invention also provides a method of treating water comprising passing the water through a housing having an inlet and an outlet and defining a flow path for water therethrough, a membrane filter being located within the housing and the flow path extending through said membrane filter and at least part of the flow path, downstream of said membrane filter, extending downwardly, in a downstream direction, at an angle of from 1 ° to 10° to the horizontal.

By setting-up an apparatus comprising membrane housings or vessels that are downwardly orientated, there is enabled passive downward movement of trapped water away from membrane surfaces and towards a drainage point. Such apparatus prevents the formation of water stagnation traps leading to diminished likelihood of trapped water accumulation and subsequent microbial attachment and biofouling. Also, it prevents upstream and downstream cross-contamination of membranes during filter changes.

In addition to the above, it is noted that most end-users of membrane filtration systems, including farmers, property residents, office managers, industrial workers, etc are not knowledgeable about water treatment and purification systems and therefore not competent enough to install and maintain their systems which may lead to biofouling, loss of operation, system damage and subsequent consumption of impure water resulting in ill-health and spread of disease. The present invention provides apparatus for a system that efficiently performs the required water purification and treatment and yet is easy to install and maintain. The apparatus is easy to install as it is directly plugged into the in-house water system and pipes (i.e. plug and play), has a small footprint, and requires no additional support (floor-standing) while comprising vessels that house membrane filters that facilitate efficient water sterilization and deliver water that is suitable for human consumption (potable) and for agricultural/industrial applications.

The present invention is concerned with a water membrane filtration apparatus in which large volumes of water can be treated and purified (in an apparatus that houses membrane filters) and is easy to install, has a small footprint, and equipped with anti- biofouling measures. The water produced by this apparatus is suitable for human consumption and agricultural/industrial applications.

The apparatus in the present invention is easy to install as it has one entry point pipe for inlet water and one exit point pipe for outlet water. Both pipes (inlet and outlet pipes) can be easily connected into or attached to external pipework for the delivery of inlet water into the apparatus and the delivery of the outlet water into the external pipework. The pipes can be configured to any industrial connectors.

The apparatus may comprise four tubular shaped vessels which are clamped into tri clamp tube fitting connections (four for each vessel, four in total in each apparatus). The connections are then welded into a stainless-steel plate. The stainless steel plate is part of the external framework and forms the front wall of the apparatus. Access to the vessels can be covered by portable circular cap covers in which handles are welded into, from the outside, for ease of manual operation. On the other hand, a tube like projection may be welded into each circular cap cover from the inside. Additionally, round shaped holes may be machined into the circular shaped cover and connected to hygienic sampling/drainage points to enable drainage of water from inside the said vessels.

The vessels provide an enclosure into which cartridges and/or filters, including but not limited to 20 inch membrane filters and others, can be installed. A variety of membrane filters can be housed including, but not limited to, synthetic membrane filters such as, but not limited, polycarbonate membrane filters, polypropylene membrane filters and cellulose acetate membrane filters. The aforementioned membrane filters may have various pore sizes including, but not limited to, 0.5pm filters and 0.02pm absolute filters.

A variety of confirations of water membrane filters and other filters can be housed inside the vessels. By way of example, a system having four vessels may comprises a configuration of a sediments filter inside the bottom left vessel, a carbon filter inside the bottom right vessel, a 0.5 pm membrane filter in the top right vessel and a 0.02 pm absolute filter inside the top left vessel. In another example, a system a stainless-steel mesh filter inside the bottom left vessel, a particular filter inside the bottom right vessel, a 0.5 pm membrane filter inside he top right vessel and a 0.02 pm absolute filter inside top left vessel. To prevent ingress of contaminants and biofouling, the vessels may be clamped into tri-clamp tube fitting connections at a downward inclination angle of 2 degrees to the horizontal plane. This is to facilitate passive downward movement of the inlet water away from the membrane filter and drain it via the said round shaped holes machined in the said circular shaped cover. Also, this prevents upstream to downstream cross- contamination of membranes during filter changes.

The vessels can house cartridges that can convert the inlet feed water into stable alkaline water (pH 7-10.5) by using the non-magnetic suspended agitation process (n- MSAP) as described in patent applications Nos. PCT/GB2016/000033, PCT/GB2019/000084 and GB1906865. The said bottom left and top right vessels may be equipped with water pressure gauges to measure the water inlet and outlet water pressure and monitor the differential pressure within the apparatus. The reading of the gauges can be viewed through gauge display screen via purposely machined holes on the said front stainless-steel wall. The apparatus may be designed to treat inlet feed water at flow rates ranging from 20 litres/min (minimum) to 40 litres/min (maximum) depending on the configuration and number of filters/membranes used. The apparatus can be modified to treat higher flow rates by changing the dimensions and configuration of the said vessels. To measure the flow rate of the water inside the apparatus, the said exit point tube is equipped with a flow meter.

The apparatus can be equipped with optional water quality meters, detectors and sensors which can also be connected to a wireless dongle for remote online monitoring. These aforementioned water quality meters, detectors and sensors could measure water pH, temperature, conductivity, presence and other parameters. The apparatus can also treat larger volumes of water by installing two or more of each modular apparatus in this present invention in parallel or series configuration. The inlet feed water is caused to flow into each of the said apparatuses in configuration by external pumps and via manifold that split the inlet water into separate tubes and each is connected to an individual apparatus in configuration. The outlet water from the apparatus in such configuration is caused to flow outside the said apparatus in this configuration and collected by a manifold which then delivers the outlet water to its end-use.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are:

Figure 1 is a diagrammatic, perspective view of apparatus in accordance with the present invention;

Figure 2 is a front elevation of the apparatus of Figure 1 ;

Figure 3 is a side view of the apparatus of Figure 1

Figure 4A and Figure 4B are perspective views of the vessels, pipework, and connectors in the apparatus of Figure 1 ; and

Figure 5A is a longitudinal section of the apparatus of Figure 1 and Figure 5B shows detail of this section.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described, by way of example only, with reference to the accompanying drawings.

Referring to Figure 1 of the accompanying drawings, the apparatus has an overall substantially cubic shape with an external metal framework 1 . The front wall comprises a stainless-steel plate 2 in which six circular shaped holes are machined to provide connections to vessels within the framework 1 and also water pressure gauges and their display screens 4. Access to the vessels is covered by circular shaped clamped cap covers 3.

Referring to Figure 2 of the accompanying drawings, the apparatus has a width of approximately 588cm and a height of approximately 599cm. The apparatus is connected to external pipework via one entry point tube 5 for inlet water and one exit point tube 6 for outlet water. These tubes are plugged into or attached to external pipework via tubes, clamps and flange faces. The tubes can be configured to any industrial connectors. The inlet feed water is caused to flow into the apparatus via tube 5 by an external pump at 2 Bar of differential pressure. The stainless-steel plate 2 enables access to the vessels via the cover caps 3 in which circular shaped holes 8 are machined to facilitate drainage of water outside the vessels via hygienic sampling/drainage points. The holes 8 are equipped with gaskets. The operator has to remove the circular shaped cap covers 3 to enable installation of cartridges or filters (including membrane filters and other types of filters) into the said vessels. Once installed, the circular shaped clamped cap covers can be placed back into the stainless-steel plate 2.

The apparatus comprises four substantially cylindrical vessels 9 that provide housings for filters (which may be provided in the form of cartridges and may include one or more membrane filters). The vessels 9 are inclined downward at an angle of approximately 2 degrees to the horizontal plane which is represented by dotted line 10. This downward inclination facilitates passive downward movement of the water inside the vessels 9 away from the installed filters to avoid ingress of contaminants and potential subsequent biofouling. Also, the downward inclination prevents upstream to downstream cross-contamination of membranes during filter changes. The vessels 9, as well as the rest of the apparatus, are manufactured from food grade materials.

With particular reference to Figure 4 of the accompanying drawings, the four vessels are arranged as follows: top left - vessel 11 ; top right - vessel 12; bottom right - vessel 13; and bottom left - vessel 14. The inlet feed water is caused to flow into vessel 14 of the apparatus via the inlet tube where the first stage of water purification/treatment takes place. The vessel 14 is connected to the side of vessel 13 by tube 18 (as well as a gasket and a flange face) and the water flows into vessel 13 where the second stage of water purification/treatment takes place. The vessel 13 is connected to the bottom of vessel 12 via tube 19 (and a gasket and flange face) and the water flows to vessel 12 where the third stage of water purification/treatment takes place. Vessel 12 is connected to the side of vessel 11 via tube 20, (and a gasket and flange face) and the water flows into vessel 11 where the fourth stage of water purification/treatment takes place. Vessel 11 is connected to the external pipework via the outlet tube 21 and the water flows into the external pipework via outlet 6. The tube 21 is equipped with a flow meter 17 providing water flow rate measurement.

The two water pressure gauges 15 are installed at vessels 11 and 14. The apparatus can be, optionally, equipped with additional water quality measurement monitoring systems, including but not limited to meters, detectors and sensors for water pH, temperature, presence and conductivity. These devices can be installed at any suitable location on or within the apparatus.

With particular reference to Figure 5 of the accompanying drawings, the vessels (numbered 24 in Figure 5) are connected to the front stainless-steel plate 2 by clamps, gaskets and flange faces. The access to each vessel 24 is covered by a circular shaped cover cap 3. Each cap 3 has a handle 23 welded to it on the outside for ease of manual handling. On its inside, each cap 3 has a tube-like projection 22 welded to it, this projection 22 lock-engaging into an installed cartridge or other filter device. The apparatus can be installed into a closed water loop system which enables recycling of used water. The used water downstream of the closed loop system is caused to enter into the apparatus via the said inlet water entry point 5 for purification and treatment further usage/consumption. The treated/purified water is then caused to flow back into the closed loop system via the outlet water exit point 6. The apparatus can treat or purify various types of water including, but not limited to, waste water, borehole water, ozonated water and spring