GB2103596A - Water treatment unit - Google Patents

Abstract

A modular water treatment plant comprises a hydraulic flocculator, a floc settler and a filter in adjacent relationship and connected in series. The plant is compact, readily transportable and conformable to ISO container measurements and is capable of providing potable water from contaminated sources in remote or disaster areas. <IMAGE>

Description

SPECIFICATION Water treatment unit This invention relates to a modular water treatment unit for the production of potable water.

The quality of fresh, (i.e. non-saline) untreated surface water varies widely according to its origin and history, from relatively pure mountain springs to fetid swamp water. Rivers are frequently a source of drinking water for nearby communities but raw river water is generally contaminated to a greater or lesser extent by natural or artificial pollutants, such as silt, decaying organic material, bacteria and detritus. These materials can render the water turbid, discoloured, a carrier of diseases and generally unfit for human consumption. Similar problems can arise with water from lakes and other inland sources.

In order to provide potable water from such sources it is common practice, particularly in developed countries, to provide water treatment plants. These are usually large scale, permanent installations requiring a considerable area of land.

The treatment takes place in several stages including aeration, flocculation, filtration and chlorination.

Such installations are suited for the function which they fulfil, the regular treatment of a constant supply of water in large quantities in a fixed location.

However, there are special requirements which they cannot meet such as an urgent, unexpected demand and/or one on a relatively small scale. For example, a disaster may disrupt the normal water supply of an area or a small community in a remote location may be in need of facilities.

A modular water treatment plant has now been invented which can meet such demands.

Thus according to the present invention there is provided a modular water treatment plant comprising a hydraulic flocculator, a floc settler and a filter in adjacent relationship and connected in series, the flocculator being connected to the settler by a discharge outlet and the water outlet from the settler forming the water inlet to the filter.

Preferably the discharge outlet from the flocculator is a weir discharge outlet.

A coarse strainer may be provided before the flocculator.

Preferably the hydraulic flocculator comprises a number of vertical parallel plates forming a series of baffles which causes a number of changes of direction in the path of material flowing through the flocculator.

In use, a flocculating agent or its precursor, such as aluminium sulphate, sodium aluminate or ferric chloride, is added to the water by associated equipment. This causes most of the impurities to coagulate into a settleable floc. The purpose of the baffles in the preferred type of flocculator is to promote mixing of the flocculating agent with the water and hence with the impurities.

In previous large scale operations, mixing in a flocculator was generally achieved by stirring or other forms of mechanical movement.

The floc settler preferably comprises a series of parallel plates, most preferably corrugated, but this time set at an angle to the vertical. Most preferably the settler also comprises a conical receptacle beneath the plates with an outlet to receive and remove the settled floc.

The weir discharge from the hydraulic flocculator is preferably sited at or near the centre of the parallel inclined plates of the settler so that the water rises up and the floc settles down. By increasing the residence time, the inclined plates increase the efficiency of the gravity separation.

The water outlet-from the settler is preferably a weir discharge which leads directly into a distributor for the filter.

As in the case of the flocculator, the settler contains no moving parts.

The filter is preferably a granular filter. The granular material is preferably sand, but other conventional materials such as anthracite may alternatively be employed.

Preferably two filters are provided so that one may be backwashed while the other continues as a forward filter.

Most preferably the filter(s) is or are of the rapid, deep-bed type.

The filter(s) give(s) a final polish to the water and remove remaining traces of particulate material down to a particle diameter of about 20 to 40 microns.

Filtration is by gravity alone and again the filter contains no moving parts.

A break tank is preferably associated with the filter(s) to ensure that the water level in the filter(s) is maintained above the level of the granular material to prevent the filter(s) from drying out.

From the break tank, the product will usually be sent to storage. If the product is pumped to an overhead storage tank then the filter(s) can be backwashed under static pressure. If, however, the product is passed to ground level storage, then a pump is necessary for backwashing.

Also associated with the module is means for dosing the water with a suitable bactericide such as sodium hypochlorite. The water is preferably dosed before filtration.

The final quality of the water will generally conform to W.H.O. standards for drinking water. It is a feature of the invention that the flocculator, the separator, and the filter form a compact assembly the dimensions of which can be made to conform to the I.S.O. dimensions for a standard shipping container. The associated equipment such as the chemicals, injectors, the break tank and all the necessary pumps, valves, pipework and controls may also be packed within the container forming a complete unit which is self-contained, readily transportable and can be brought quickly into action on arrival adjacent to a supply of water. Such a unit may provide water at a rate of up to 22 m3/hr.

The pumping and pipeworkarrangements are preferably designed to permit one filter to be backwashed whilst the other remains on stream, thus maintaining the floc in the unit.

Thus the unit overcomes the problems of packing for overseas shipment by being in itself a shipping container as well as a water treatment plant. This makes for simpler handling by docks, ships, railroads and trucks.

The unit may also incorporate a jacking device permitting it to be raised from a flat bed truck which is driven away from underneath the unit which is then lowered to ground level for installation.

A further feature of the unit is that it need not require special concrete foundations. The structure may be designed so that it can be sited on a surface with a bearing capability of 75 KN/m2. This makes its deployment in remote overseas locations and in disaster areas a practical proposition.

The invention is illustrated with reference to the accompanying Figures 1, 2, and 3, wherein Figure 1 is a schematic representation of a module, Figure 2 is a schematic section and Figure 3 is a schematic plan.

The module comprises a hydraulic flocculator 1, an inclined plate separator 2 and two sand filters 3.

Associated with the module is a break tank 4, a flocculating agent injector 5 and a bactericide injector 6.

Raw water is drawn from a river through line 7 by a a pump (not shown) situated in the separator section of the module and introduced into the hydraulic flocculator 1 before which it is dosed with a suitable coagulant and a suitable bactericide depending on the nature of the water. The water is then mixed with the flocculant by flowing up and down over a series of vertical baffle plates 8 eventually leaving the flocculator 1 and entering the separator 2 by a weir 9.

The separator contains a series of inclined baffle plates 10 and underneath them a conical collector 11. Floc settles to the bottom of the collector and is removed through the outlet 12. Water rises to the top and passes over weirs 13 into distributing channels 14 which feed the water to the sand filters 3.

Water percolates through the filters and is removed at the base by lines 15 and passed to the break tank from which it is sent to a storage tank, (not shown).

Claims (12)

1. A modular water treatment plant comprising a hydraulic flocculator, a floc settler and a filter in adjacent relationship and connected in series, the flocculator being connected to the settler by a discharge outlet and the water outlet from the settler forming the water inlet to the filter.

2. A modular water treatment plant according to claim 1 wherein the discharge outlet from the flocculator is a weir discharge.

3. A modular water treatment plant according to either of the preceding claims wherein the hydraulic flocculator comprises a number of vertical parallel plates forming a series of baffles.

4. A modular water treatment plant according to any of the preceding claims wherein the floc settler comprises a series of parallel plates set at an angle to the vertical.

5. A modular water treatment plant according to claim 4 wherein the parallel plates are corrugated.

6. A modular water treatment plant according to either of claims 4 or 5 wherein the settler comprises a conical receptacle beneath the plates with an outlet to receive and remove settled floc.

7. A modular water treatment plant according to any of claims 4 to 6 wherein the weir discharge from the hydraulic flocculator is sited at or near the centre of the parallel inclined plates of the settler.

8. A modular water treatment plant according to any of the preceding claims wherein the water outlet from the floc settler is a weir discharge which leads directly into a distributor for the filter.

9. A modular water treatment plant according to any of the preceding claims wherein the filter is a granular filter.

10. A modular water treatment plant according to claim 9 comprising two granular filters.

11. A modular water treatment plant according to either of claims 9 or 10 wherein the filter(s) is or are associated with a break tank adapted to maintain the water level in the filter(s) above the level of the granular material.

12. A modular water treatment plant as hereinbefore described with reference to Figure 1 to 3 of the accompanying drawings.