Field of the Invention

This invention relates to plants for treating water, and to a method of constructing and commissioning such a water treatment plant. The plant may typically be based on self-cleaning filters, ultra-filtration (hereinafter referred to as "LIF") and reverse -osmosis (hereinafter referred to as "RO") for treating either sea water (or brackish water) or secondary municipal wastewater. Typically, the capacity of the treatment plant will vary from 20 to 60 million litres per day. Background of the Invention

There are many existing water treatment plants around the world, which treat sea water, brackish water, municipal wastewater or other sources of impure water to produce purer treated water, including potable water. Such plants are common in arid areas, such as the Middle East, where there is limited potable fresh water,

Using conventional techniques, building a water or wastewater treatment plant is expensi ve, and subject to numerous problems.

First, a conventionally built water or wastewater treatment plant uses a linear construction method that requires each stage of the construction process to be completed before the next stage can be undertaken. Like any civil construction, any complications occurring in any one stage will directly compound a delay onto the next stage. Site, civil engineering and facilities works must be completed before any installation of water treatment equipment, pipes etc., can begin. Delays at any one point of time will impact the construction schedule, and it is common for such projects to overrun in cost and time.

Secondly, the project site may he located in an area where adverse weather may have an impact on the constraction schedule of the project. This is a particular issue for those workers engaged in civil works, site development and activities that involve outdoor weather-sensitive operations such as welding and earthwork, where a prolonged wet period can drastically delay the construction schedule,

Thirdly, most large industrial construction projects involve travelling contractors and labourers. The size of the workforce can fluctuate greatly from one project site to another. The costs of mobilising and de-mobilising a workforce are high and include accommodation, travelling expenses, medical expenses and premiums for worker's compensation benefits, liability and property losses. Further, depending on the location, finding and recruiting sufficient numbers of skilled, talented workers to perforin the necessary tasks on the site may be challenging- AH of Chose problems result in increased construction costs, as the costs need to take account of the construction schedule, contingencies for adverse weather, and the costs of mobilizing and de-mobilizing the workforce,

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior ait base or were common general knowledge in the field relevant to the present disclosure as it existed before die priority date of each claim of this application.

Throughout this specification, the word "comprise", or variations such as

"comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Summary of the Invention

In the first broad aspect, the present invention provides a process for providing, a modular water treatment plant at a desired location, comprising the steps of:

constructing a modular water treatment plant at a site remote from the desired site, typically in a fabrication yard offering protection against wet weather as a. complete modular unit having a hull which is capable of floating on water;

transporting the module by sea to desired location, and

commissioning the modular water treatment plant at the desired location, either its a floating plant or preferably installed on ground at e.g. a beac.hs.ide or inland location.

Typically, the modular treatment plant is constructed in a fabrication yard, similar to a dry dock or a shipyard, and the plant may be supported upon keel blocks during the construction process to allow access to the base of the plant, and to allow airhags to be fitted underneath the plant for launching and moving the plant once it is completed.

Where airhags are used, typically these will be cylindrical in shape, with hemispherical heads at both ends made of reinforced .rubber layer's: and have a high, load capacity. During launching, the internal pressure of the airhags may be adjusted so that the plant is able to be tilted downwards, and able to roll by gravity towards the l aunching area and into the sea,

Typically, once on the sea, the plant will be pulled by tugboats onto a serat- submersible vessel for shipping. Upon arrival at die destination port or beach, tugboats will be used to pull the plant from the semi-submersible vessel to a landing area or beach. Depending on the route to the final destination site, the plant may be hauled out by either placing lift airbags under the hull, (for hauling and jacking up) or loaded onto a custom built trailer. The plants wilt typically be located on shorelines and may serve remote mining sites in Australia and In other countries such as Chile, The plants may be used to provide water for use in industrial processes as well as potable water for drinking.

Although it is possible to transport the plant by land, because of the size and weight of the plant, accurate road surveys would have to be carried out to ascertain the feasibility of transpijrting the plant, as well identifying any foreseeable problems,, including taking into account measurements, obstacles and items to be removed, such as power lines, streetlights, road signs and other; roads to be strengthened, and temporary road supports, which might need to be positioned. In general, therefore,- the plants will he positioned as close as possible to the shore or waterway.

In a related aspect, the present invention provides a modular water treatment plant comprising a housing including a hull and a water treatment plant located inside the bull, wherein the base of the hull is general flat and the housing floats on. water unsupported.

Advantageously, and in contrast with the linear process used for the conventional construction, work at the site including site preparation, foundations and utilities can occur at the same time as construction of the modular plant at the remote site. This significantly cuts the construction timeline, Furthermore, delays in either stage would not adversely affect the construction of the other stage.

Start-up time is also minimised since the plant is fully assembled and may be tested before being shipped, thus reducing the amount of onsite start-up time. Testing of the plant prior to shipment identifies and. corrects any potential problems, which can resolved, much more easily in the fabrication site, before it is .delivered to its eventual site.

Advantageously, where the plant is to be used for an extension of existing plant, the offsite construction does not interrupt or shut down pre-existing operations at the existing plant, should there be any.

The plant may be constructed in a fabrication yard, which is optimised for the production of the plants, which may offer protection against inclement weather. The fabrication yard may be used as a site to construct a variety of modular plants and therefore it is possible to retain and attract skilled workers for the long term, and not simply for a single project. Further, the costs of mobilization and de-mobilization of the workforce and construction equipment on site are avoided. Because of the increase efficiencies and improved construction speed, the module will be constructed and finished in a significantly shorter time, compared with a _. conventionally built water/wastewater treatment plant. As a result, the expenses are reduced. Also, by fabricating the plant at a dedicated fabrication yard, better project can be applied and wastage can be imnimized by recycling materials, controlling inventory and protecting building materials from adverse weather.

Advantageously, welding, pipe-fitting and other fabrication processes are performed in the fabrication yard under ideal conditions, as opposed to on site, where conditions may be less than, ideal

Finally, it is easier to provide safe working conditions on a fabrication yard than on a remote construction site.

Typically, the plant uses one, or more typically two, membrane-based water purification, processes, in the form of UF and/or RG. Typically when used for desalination, raw sea water will be pumped and forced through the UF membrane, as a pre-treatment process, and then through the RO membrane as a main treatment process.

Brief Description of the Drawings

A specific embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which;-

Figure 1 is a diagram showing the hydraulic circuit of a desalination system; and

Figure 2 shows a cut away side elevation of a module/housing for the desalination system.;

Detailed description of a preferred Embodiment

Referring to the drawings, Figure 1 shows a part simplified hydraulic circuit of an exemplary desalination system. It will be appreciated however that the plant may also be configured to treat other types of water including brackish water and municipal. waste water.

In the case of a module for desalination 10 as shown in Figure 1 , sea water (feed water) enters the module through a feed inlet 12 into an UF storage tank 14. A pumping station (not shown) for pumping the sea water is not included in the module and is provided externally of the module. In the tank, the feed water undergoes chlorination with Sodium Hypochlorite, and optionally Sodium Bisulphite might also be dosed into the water before the feed water enters the UF section of the circuit for de-chloritiation.

LIF Feed Pump J 6 transfers the feed water front the tank into UF Self-Cleaning Strainers 18. These self -cleaning strainers are effective in removing a significant portion of the particles as fine as 100 micron in size. After straining, the feed water is pumped into one of a number of blocks 20 of an Ultra-Filtration Membrane System incorporating UF membranes. Although the Figure shows two blocks, it will be appreciated that the number of blocks may be much greater, depending on the system capacity. In the described embodiment fourteen blocks: would be provided. The water which exits the UF modules 20 will be stored in a Filtered Water Storage Tank 22, while the rejected water will be re -circulated back to the UF Feed Tank 14. Any water contaminants that accumulate on the UF membranes of the modules 20 are rejected without treatment during regular backwashes to avoid the formation of a thick fouling layer on tire UF membranes.

The UF membranes provide a physical barrier to particles thus providing consistently high quality feed water for the later RO process. This reduces the need to clean and dose the RO membranes and extends their life.

The backwash mode will now be described, in the backwash mode, a backwash water pump 24 and air compressors force water and air onto the UF membranes removing the foul ants attached to the membranes., In operation, the frequency and duration of the backwashes will depend on the quali ty of the feed water.

The cleaning system includes a storage tank 26 (elean-in-place "OP" tank) and. an associated pump 28. Various chemicals can be used to clean the membranes including, sodium hydroxide, sodium hypochlorite and hydrochloric acid.

Downstream of the Filtered Water Storage Tank 22, sodium bisulphite (SBS) and antiscalants are injected at 30 and 32. The sodium bisulphite is dosed for dechlorination of the water prior to RO treatment The antiscalants retard the growth of crystalline salt structures in the feed water and concentrate streams, thereby allowing a concentration of sparingly soluble salts in excess of the normal solubility limits.

Hie RO feed pump 34 pumps the filtered water into a group of first pass RO trains 36 (the number of trains provided will depend on the capacity of the plant). The filtered water is pressurised by high pressure pumps 38 typically to between 55 and 85 bars depending on the temperature and salinity of the water before entering the RO membranes. The. reject from the RO is released at high pressure and is directed to energy recovery device (ERD) 40 where it transfers its energy to the incoming filtered water via booster pump 42. The treated water out of the RO, referred to as permeate, is stared in the first pass water storage tank 44,

Hie RO works by increasing the pressure on the salt side across the semipermeable RO .membrane and forces the water through to the other side, leaving almost all (around 95% to 99%) of dissol ved slats behind in the reject stream.

A group of first pass RO flushing pumps 46 use RO permeate water to flush out fouling from the system. Permeate water will be pumped from the plant to tire site for use or further processing by a permeate water transfer pump 48,

The system may optionally include a tank blanketing system (not shown) in which nitrogen gas is released at the top of the first pass RO water storage tank 44 to provide a nitrogen blanket and prevent organic contamination of the permeate water. The use of positive nitrogen pressure helps prevent outside air, moisture and other contaminants from entering the storage tank 44. in addition, the positive pressure of the system provides a head pressure above the liquid to reduce vapour loss which helps prevent the tank from corrosion.

A clean in place (CIP) system is provided to restore the RO membrane efficiency. The system includes a tank 50 for holding cleaning fluid, a pump 52 and a 5 micron cartridge filter 54 for removal of particulates from the cleaning fluid. The chemicals used in the cleaning fluid are sodium hydroxide, and occasionally hydrochloric acid.

The plant also includes a neutralisation system for neutralising the dean-in- ^• piace solutions used for cleaning both the UF and RO membranes before the solutions are discharged outside the system. The neutralisation system includes a neutralisation tank 56 and an associated pump 58 (more than one tank and pump may be provided). The neutralisation chemicals will be sodium hydroxide and hydrochloric acid.

The pipes used in the plant as shown in the drawings may be made from various materials depending on performance requirements of the system including stainless steel, glass reinforced plastics, super duplex and/or thermoplastic,

The module may include various other features and systems not shown in Figure 1. la the event that a second pass RO system and remineraiisation is required for potable water production, this can be provided in a second module.

As discussed above the system includes a compressed air system (not shown) to provide clean pressurised air for various functions including the UF backwash.

The module includes other services (not .illustrated) including electrical, air conditioning, mechanical ventilation, fire suppression and detection, security and emergency response including a diesel powered, electricity generator, safety shower and emergency eyewash, plumbing and sanitary systems, including a septic tank and pumps, domestic hot water, a heavy duty elevator, a lighting and power system and building earthing and lightning protection.

As well as housing the water treatment plant and the above services the module comprises a number of floors and also provides a number of rooms. More specifically, the module includes a pump floor, a fire control room, a chemical storage area, a UF membrane, hall, an emergency generator room, a membrane storage room, separate men's and women's changing and toilet facilities, a workshop, a spare room, a switchgear room, a MV switchboard and MCC room (if required), a LV switchboard and MCC's room, control room, a RO membrane bail, a building services area, a laboratory, a storage area, a meeting room, an office, kitchen and a janitor room..

If the module is built for the purposes of recycling waste water, the main differences are in the membranes used for the RO and UF steps.

The high pressure pumps 38 are not required and the energy recovery device 40 and pump 42 are also not needed. The chemicals used may differ and aft in-line pressure ultraviolet system is provided on the permeate water line for disinfection and eradication of pathogenic organisms to prevent the spread of waterborne diseases to downstream users and the environment.

The module 10 is built a fabrication yard similar to a dry dock or shipyard, in a housing 100 (refer to figure 2), During fabrication, the housing 100 is supported by keel blocks, with sufficient space in between the biocks for stability, and sufficient height above the floor of the shipyard to allow access to the bottom plates of the .housing/module. For a first pass desalination module treating SOraillion litres of water a day (50MLD), the housing will typically be a rectangular box like structure being around 85m long by 40m wide with a height of around 30m. The dry weight of the module is typically a little less than 5.500 tons.

For a second pass system treating the permeate from a first pas system and including remineralisation to produce potable water, the module which is used in conjunction with the first module will he smaller, typically 60m long by 28m wide by 30m high and will weigh a little less than 3, OCX) tons.

As shown the module has a planar base 102, false floor 104, first floor 106, second floor 108 and a mezzanine level 1 10. The base of the module defines a flat bottomed hull 120 so that the module can float on water for transport. As shown the desalination system 10 is largely installed to one end of the system over three floors, with rooms provide at the other end. The space in between the blocks allows airbags to be fitted in between for launching find hauling out of the module. The airbags are cylindrical in shape with hemispherical heads at both ends. They are typically made of reinforced rubber layers and have a high load capacity. These airbags are placed into position according to the airhag spacing requirements at the right transverse section underneath the hull and are filled with air simultaneously. All the keel blocks can then be removed when all the airbags have been installed and filled with air. During launching, the airbag's internal pressure may be adjusted: so that the module can be tilted downwards and is able to roll under the influence of gravity towards a launching area at the fabrication yard and eventually into the sea.

The module can be used as a pontoon or a semi-submersible type floating structure, and is protected with corrosion protection measures, which may be appl ied to the reinforcing or other steel work, using for example coatings, cathodic protection, corrosion allowance, corrosion monitoring and the like.

The module includes a mooring eye to facilitate mooring and towing. Once the module has reached the sea, the module/housing 100 floats and may be pulled by tugboats; onto a semi-submersible vessel for shipping to the intended final destination of the module.

Upon arrival at the destination port or beach, tugboats are used to pull the module from the semi-submersible vessel onto a landing area or beach. Depending on the final location, the module may be hauled out by either placing lift airbags at the hull for hauling or jacking up, or may be transported inland by using a self-propelled modular trailer. Due to the difficulty in moving the module due to its size, beach or waterside locations are preferred. Typically the site will be. pie-prepared prior to the arrival of the module.

Smaller modules may also be provided for recycling municipal waste water and. will tend to cither use RO or UF, and have a capacity of 20MLD and be smaller say around 50m long by 18m wide by 16m high and weigh a little under 1500 tons. Obviously the modules can be built to provide different treatment capacities and the size and number of modules required will depend on the water source and require treatment rates.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.