WO2007035981A1

WO2007035981A1 - Contaminated water treatment process

Info

Publication number: WO2007035981A1
Application number: PCT/AU2006/001342
Authority: WO
Inventors: Jason Ian Nathaniel Beath
Original assignee: Jason Ian Nathaniel Beath
Priority date: 2005-09-28
Filing date: 2006-09-13
Publication date: 2007-04-05

Abstract

A process for treating contaminated water with a reagent, using a treatment unit (10), includes the steps of using a pump (82) to pump contaminated water such as acidic water from mine dewatering, from a contaminated water-containing pit (80), reagent being added to the contaminated water by said unit (10) by a reagent slurry being supplied to a chamber (78) on the conduit supplying the contaminated water to the inlet side of the pump (82). The mixture of reagent and contaminated water is then pumped by pump 82 to a floc pit (86), where floc is allowed to settle. Treated water is then pumped from the floc pit (86) into a holding pit (92), for re-use. Floc may be extracted from the floc settling pit (86) by a floc extraction pump (90). The pH of the water/reagent mixture is tested (84) to enable reagent output to be varied.

Description

CONTAMINATED WATER TREATMENT PROCESS

This invention relates to the treatment of waterways and watercourses to improve the quality of the water contained therein. Such remediation may include alteration of the pH of the water to the neutral value of 7.0, for example by treating acidic water with lime, or to achieve another desired pH level, the use of alum or gypsum to remove clay, the use of activated carbon to remove toxins, the removal of metals, and the removal of bacteria.

In WO 2004/067455 A1 , there is described apparatus for treating a waterway. The apparatus is in the form of a treatment unit which may be located in or close to the waterway, which unit supplies reagents to the waterway. This reagent supply is usually effected by pumping water from a source, usually the waterway being treated, passing it through the unit such that the reagent is carried, as in a slurry, by the water, and supplying it to the waterway. Reagents in powder or liquid form are able to be dispensed by such a unit.

It is an object of this invention to provide improvements in the apparatus described in WO 2004/067455 A1 or in the method of operation of the apparatus.

The invention provides a process for treating contaminated water, characterised by the steps of passing contaminated water, from a first contaminated water- containing pit or the like, through a treatment unit, said water having reagent added thereto by said unit, passing said mixture of reagent and contaminated water to a floe pit or the like, allowing floe to settle, and pumping treated water from said floe pit into a holding pit or the like, for re-use.

The invention also provides a method for treating contaminated water, characterised by the steps of:

treating said contaminated water by applying a reagent to produce first stage treated water in which a value of the contaminated water has been brought to a first desired level; allowing said first stage treated water to settle for a predetermined time.

The invention may further provide apparatus for treating a body of water, said apparatus being adapted to treat said body of water with one or more reagents, characterised in that said apparatus is controlled by a programmable control system such that the operation of said apparatus may be automated.

Embodiments of the invention will be described in detail hereinafter, with reference to the accompanying drawings, in which:-

Fig. 1 is a plan view of one embodiment of a control panel for controlling apparatus for treating waterways;

Fig. 2 is a flow diagram of a one embodiment of a process, utilising one form of the apparatus of the present invention, for treating contaminated water resulting from the workings of a mine, or from another contaminated source;

Fig. 3 is a flow diagram of one embodiment of an inline dosing process, utilising one form of the apparatus of the present invention; and

Fig. 4 is a flow chart of an embodiment of a mixing arrangement which is an alternative to that shown in WO 2004/067455 A1.

Improvements in a unit of the type disclosed in WO 2004/067455 A1 will be described hereinafter. Such a unit, which may be called a reagent mixing (and dispensing) machine, will hereinafter be termed a treatment unit, given that the unit acts to dose waterways and the like with substances such as reagents.

The improved treatment unit, denoted by reference numeral 10 in Figs. 2, 3 and 4, has been designed with a programmable logic controller (PLC). This PLC was designed and constructed to allow full control, pH correlation, liquid injection, data logging, accurate calibration, data sending, error logs and many more systems to be explained. The PLC is preferably operated by a control panel (12 in fig. 1 ) which is preferably fitted in a fully waterproof stainless steel box (not shown), is controlled by a waterproof switching membrane (also not shown), and has a liquid crystal display (LCD) 30.

The control panel includes buttons 14, which is a "Stop" button, 16, which is a button for "Pump 1", 18, which is a button for "Pump 2", 20, which is a button for "Tumbler", 22, which is a button for "Auger", 24, which is a button for "Vibrator" and 26, which is a button for "Rock". Each of those buttons, except button 14, controls the feature of the unit, with which the button is associated, On the display 30, for each button the word "OFF" or "ON" is displayed, in response to the respective button being pushed.

There are three other buttons, 28 ("Menu"), 30 ("On") and 32 ("Off"). Button 28 is associated with that part of display 30 which at initialisation displays the word "Menu" at 56, but which changes in response to the pressing of button 28. Buttons 30 ("On"), and button 32 ("Off") are associated with displays 52 ("Hour" and 54 ("Min"[ute]).

Display 30 area 34 displays the words "Total Liquid: It", with a display of the total amount of liquid. Display 30 area 36 displays the words "Injector Rate" and shows that rate in litres per hour. Display 30 area 38 displays the measured pH and shows the words "Auto Mode 8.1 " and "Limit 11.0". Display 30 area shows the word "Time" and displays the time of day.

Display 30 area 32 shows the word "Message". Display 30 area 44 displays the words "Stop Timer" and the value of that time. Display 30 area 46 displays the words "Runtime" and the value of that time. Display 30 area 48 shows the words "Total Powder: kg" and shows a value for the weight of powder. Display 30 area 50 shows the words "Powder kg/hr" and shows a value for that rate. Display 30 area 58 shows the words "Auger Inc", meaning "auger increase", which area 58 is associated with the button marked 1. Display 30 area 60 shows the words "Auger Dec", meaning "auger decrease", which area 60 is associated with the button marked 2. Other features of the control panel 12 and the display screen 30 are described hereinafter.

The treatment unit preferably has steel wire armoured cabling and IP67 waterproof glands, an improvement designed for safety and use in mines.

The treatment unit also preferably includes a liquid injector which allows accurate injection of many types of chemicals and reagents such as chlorine, hydrogen peroxide, fluoride, iron salts, aluminium sulfate, flocculants, catalysts, suspension agents, trace elements and any other liquids that could be of benefit.

The liquid is added to the system in one of three ways, either into the inlet pump, which allows mixing with the powder reagents in the tumbler (option 1 ), into the treatment unit output pump/s so as to allow mixing after powder blending (option 2), or into the boost pump system (option 3). The liquid is sucked in by the use of the pump suction but could also be added with the use of a small transfer pump or liquid dosing pump. At present, using the pump suction, rates from 3 l/hr to 21 Ol/hr may be obtained. Higher rates may be accomplished by the use of a transfer pump, or lower rates by the use of a dosing pump.

Flow is controlled by a hand-set control valve when using the pumping systems suction and the rate is visible on the aforementioned LCD screen. Flow could also be controlled by the use of a metered dosing pump and controlled by the PLC.

There are two output pumps (not shown), which may be controlled by buttons 16 and 18. A flow sensor (also not shown) is located between the two pumps. A handle (not shown) controls a ball valve (also not shown) located between the two pumps, which valve adjusts flow rate. A preferably 12.7 mm (Yz") hose connects to the output pumps on the suction, low pressure side. This draws liquid into the system through option 2.

The liquid injector can add a trace element when blending fertilizers or a flocculant when blending reagents for water treatment. The PLC shows rate per hour and total liquid output, as described previously in relation to Fig. 1. The total outputs of the last five operations are logged on the run log page as well as in a permanent data logger chip.

The pH correlator (display 12 area 38 in Fig. 1) is designed to control reagent output in relation to pH. The correlator has a setting to reverse direction of correlation for acidic or alkaline reagents. It has a setting to adjust sensitivity in relation to pH, for example 0.1 , 0.2, 0.3 pH units. It also has a correction time setting to change checking and adjustment from 10 seconds to 10 minutes. There is also a setting for change in rate per adjustment from 0.1 kg to 500 kg. The correlator mode can be set to off, auto or manual in which pH is displayed but no adjustments are made.

To operate with pH correlation, one sets the desired pH, maximum pH, pH accuracy, for example 0.2 units, change in kg per adjustment and whether using acidic or alkaline reagents.

A pH probe (84 in fig. 3) may be easily removed or fitted and placed where reagent has fully mixed with treated water. There is preferably a pH cable length setting which allows up to 400 metres of cable and allows for voltage drop over a predetermined distance.

The pH correlator is mostly used for treatment of pumping or flowing systems, for example rivers and drains, or could be used for keeping a tank or the like at constant pH.

A setting is provided for maximum pH allowable (as previously described in relation to Fig. 1 ), and a time allowable at the maximum pH. If the pH has not come below (or above) this pH setting in the preset time, the treatment unit will automatically shut down and log all data. This shutdown function assumes a major change in operation or a failure and stops over-correction of pH. This is also reversed if changed from an acidic to an alkaline reagent setting. All data, such as the date, time, total powder, total liquid, runtime and errors are logged in the data log menu screen, as has been described in relation to Fig. 1.

All data as above, including pH, is logged in the permanent data chip and downloadable via a USB connection. The data is logged at a preset interval. usually and preferably every 10 minutes. GPS positioning may also be logged if fitted. This would ensure treatment accountability in regard to the exact position of treatment and chemical output.

Data may be loaded into an external computer for accurate records, graphs and tables of treatment. This also acts as a tracker for staff and work times as well as problems on site, for example continually running out of generator fuel.

All information is shown on the LCD screen 30 of Fig. 1 , this being -liquid rate and total output -powder rate and total output -pH setting, mode and maximum limit -countdown timer

- runtime -clock -messages and errors

There is preferably a menu area 56 on the screen for 30 adjustment of settings like

-pH mode - off/auto/manual

-pH desired setting

-pH maximum limit

-pH correlator change (for example 0.2 kg to 500 kg) -pH probe cable length

-treat for - acidic or alkaline

-vibrator intermittent time on

-rock feed time on

-rock feed level -tumbler speed -auger kg/rev

-gear ratio for auger

-password

-hour meter There is also a private factory setting screen

-rock feed amps low

-rock feed amps high

-vibrator intermittent time off

-pH probe installed; yes/no -liquid injector installed; yes/no

-correlator pH window size

-error shut down time

-low rpm auger

-high rpm auger -low voltage shutoff

-data log interval min

-treatment unit size sml/lg

-small treatment unit correlator change kg

-auto start fitted

There may also be a data log page

-date

-time

-runtime

-total powder -total liquid

-errors

Menu screen and private menu screen are preferably password locked for protection. All operational functions of pumps, motors, vibrator and powder feed are button operated and sequenced so that an operator cannot start certain features of the apparatus without other features also operating. For example, the powder feed cannot be operated, without both pumps and the tumbler operating, and one pump cannot operate without the other. A count down timer can be used which stops powder feed a predetermined time, for example five minutes, before shutdown, so that the pumps and systems may be cleaned. This countdown timer may be programmed to operate on time or weight (kg) of reagent.

A range of operational error messages may also preferably appear on screen when activated, for example low water level, overflow, pH too high, or when switching on function out of sequence. All changes of parameters must be saved with a password.

A modem may be fitted to send end of operation final data to a mobile phone or website. Shutdown from errors may also be sent to a mobile phone to alert operators nearby. Starting and/or stopping of the treatment unit can be accomplished by sending an SMS from a mobile phone. These functions are in the final programming stage.

Provision for a GPS is made to provide accountability and location reports for environmentally sensitive sites. This positioning information is logged in the data file. An autostart function is in the programming stage for use on permanent sites.

It is intended that a multi hopper feed system may also be incorporated for blending of fertilizers and specialised reagent combinations, for example nitrogen, potassium and phosphorus in powder form and a liquid trace elements could be blended for fertilization of golf courses or nurseries. Each fertilizer rate would be pre-programmed to operate on a timer for sequenced watering of different parts of the golf course or nursery.

Provision for a low powder sensor has been made to the PLC with automatic shutdown and warning strobe as well as error log. Provision for a low fuel sensor as per low powder sensor. If loss of prime is sensed by the low water float switch the output pump switches off if the error is not corrected in a preset time, for example a maximum of two minutes. If the error is not corrected in this time the treatment unit will shut down and logs a low water error. This also protects the output pump from running dry. The same happens with overflow and the input pump.

For a higher or lower range in output, the auger gear ratio may be changed by changing gearboxes and adjusting ratio in the settings page.

Calibration of output in relation to different reagent bulk densities may be carried out by weighing, for example, ten revolutions of the auger, and dividing by ten. This weight may be programmed into the settings page under the auger kg/rev. Better than 1 % accuracy has been obtained when using 4000kg per hour.

To overcome some minor problems, on the large treatment unit a different output pump has been incorporated with a speed controller and linear potentiometer connected to a float in the sump.

The auger (96 in Fig. 4) and tumbler (not shown here but shown in WO 2004/067455 A1 ) are speed controlled. This allows accurate reagent output as well as tumbler speed variations to suit rock crushing or powder mixing.

The sump incorporates agitation jets to keep blended reagent from settling on the bottom of the sump.

The smallest treatment unit is 2.2 m long, 900 mm wide and 1200 mm high. Its maximum output of hydrated lime is 900 kg/hr and has all the functions of the larger machine except it has no rock belt. Rock or another hard or long wearing material is hand placed in the tumbler. Blue metal, rubber, quartz, granite, and plastics material may be used. Medium and large units may also be produced.

To transfer reagent long distances a stainless steel boost pump has been modified to have another inlet near the suction port. The treatment unit outlet is connected to this inlet and adds blended reagent into the boost pump. Because the boost pump has a greater pumping volume than the treatment unit, the original boost pump suction line allows as much water as needed to blend with the treatment unit output. There is also an input line and tap/valve to add liquid reagent to this section of the system if needed.

A boost pump and suction arrangement, not shown but preferably 76.2 mm (3") in, 76.2 mm (3") out, 12.7 mm (V₂") suction in from treatment unit into the boost pump, may be provided, and the liquid/air inject may also be 12.7 mm (A¹ ") in diameter.

An exemplary process for treating acidic water produced by mining activity, the acidic water being held in a holding pit, with a treatment unit 10 of the type described hereinbefore, as shown in Fig. 2. has the following steps.

1. Acidic water (62) is drawn from the holding pit (acid water collection pit 64) through a mixing and transfer pump; 2. A precise rate of continual and freshly blended reagent (hydrated lime) from a lime silo 66 is injected into a specially designed mixing chamber on the transfer pump in the treatment unit 10; 3. The reagent is thoroughly blended with the feed water and transferred to the floe settling pit 68;

4. A pH probe (not shown) constantly analyses the treated water pH and adjusts the reagent dose to suit a pre-programmed pH setting;

5. After the treated water is allowed to settle for several hours in the floe collection pit 68, the clean water produced by the treatment is gravity fed to the treated water holding pit 70 where it is ready for re-use, as shown by reference numeral 74;

6. Reagent is automatically fed from a silo situated beside the treatment unit and has an automatic alert in case of powder jam or when reorder of reagent is required.

7. If a thickener 72 is on site, it may be used for floe processing. This floe is extracted from the floe settling pit 68 and can be processed at any time even when the treatment unit 10 is not operational. The settling pit 68 will hold floe from the treatment of many megalitres of extremely acidic raw water if designed correctly. The floe volume will depend on acidity and metal loads of the raw water and the floe extraction rate will depend on the capacity of the thickener. The floe could also be transferred to an evaporation pond in place of using the thickener 72.

All these processes (except the floe handling) occur continuously and simultaneously. However if any part of the system fails due to loss of prime, overflow, generator out of fuel, pH overcorrection, drive jam or reagent powder block, the treatment unit 10 and all associated systems will shut down after the preset period (usually and preferably 60 to 120 seconds), log all operational data and reason for shutdown.

The by-products of the process are concentrated metals, flocced out in an insoluble form. These are in the form of iron and aluminium hydroxides and oxyhydroxides along with many other metal hydroxides, carbonates and several other complex compounds.

These compounds are said to be beneficial to crops as a supply of nutrients (macro and micro). There have been many studies done by universities around the world about the possible reuse of these products. In addition, valuable metals may be recovered from the floe. During normal operation with an average expected 700 mg/l acidity, it is expected that floe will amount to around 5% to 10% of feed flow after the first hour of settling and compaction, and may account for up to 50,000 litres of floe per hour. This floe will further compress with time and it is suggested to let it settle overnight before processing. It will still be pumpable and can be transferred in a more concentrated slurry form given adequate settling time.

The main components of the described system are:

A contaminated acidic water holding pit 64, which for example may contain any volume of contaminated water;

A treatment unit 10, including a mixing and transfer pump;

A hydrated lime silo 66 and associated control and feed systems (if a permanent system is to be installed); A floe settling pit 68, the size of which is dependent on treatment rate: for example, if a rate of VT. megalitre/hour is achieved, a capacity of 3 megalitre to 4 megalitre may be appropriate for the floe settling pit; A floe extraction system 72 (not processing); and A treated water holding pit 70 of any suitable volume if the water is to be collected, rather than being discharged to the environment.

The following results are from a trial treatment of mine pitwater which had an extreme acidity of over 4300 mg/l. These results were obtained from a sequential treatment process, in which reagent was added to bring the pH to the first of a plurality of values, after which the treated water was allowed to settle for a predetermined amount of time, before further amounts of reagent were added to bring the pH to a second predetermined level, the contents being allowed to settle for a second predetermined amount of time, and so on.

Metal untreated after treatment Aust drinking limits

Aluminium 904 0.07 0.2

Arsenic 0.29 0.05 0.007

Barium 1.3 0.03 0.7

Boron 1.32 0.14 0.03

Cadmium 0.1 <0.05 0.002

Chromium 0.06 0.01 0.05

Copper 51 0.01 2.0

Iron 274 0.02 0.3

Lead <0.01 <0.01 0.01

Magnesium 1540 1290* 50

Manganese 104 39 0.5

Molybdenum 0.11 <0.05 0.05

Nickel 0.69 0.11 0.02

Silica 35 3.3 na

Sulphate 13600 8120* na

Zinc 30 0.05 5.0 all amounts in mg/l *The reduction of sulphate will be helped by settling time in the last pit, increasing the formation of calcium sulphate (gypsum)

*Magnesium removal requires a high pH (above 9.5 to 10.0) for removal. These results were taken from a maximum pH of 9.2; as a result, there was little Mg removal.

The trial results above received a settling time of no more than 90 minutes in four separate pits. Secondary trials were conducted with a settling time of 24 hours, and in some cases better results were achieved, for instance arsenic 0.02mg/l, nickel 0.02mg/l and zinc 0.02mg/l. No additional flocculants were used in the above trials.

It is considered that a treatment unit according to the present invention may be used to treat contaminated water using a plurality of floe pits, which may be treated by multiple inlets/outlets, for treating each pit to reach a desired level of a particular value, passing the treated water from one pit to a subsequent pit, allowing material to floe out, and then treating that subsequent pitwater to be treated to a second desired level of the value. It is envisaged that, desirably, four floe pits would enable four stages of, say, desired pH levels to be sequentially obtained. It has been found that more of the metals contained in contaminated water may be removed through such a sequential process.

Fig. 3 shows a flow chart of an embodiment of an inline dosing method and apparatus, using a treatment unit 10 as described hereinbefore. The method and apparatus entails the use of such a treatment unit/reagent mixing machine to supply an accurately correlated rate of reagent to an inline transfer pump 82. With this type of system very large volumes of water can be treated quickly. Volumes over several million litres per hour can be treated.

In Fig. 3, the treatment unit is shown as 10. There is a chamber 78 on the suction line of the pump 82 to thoroughly mix the reagent with the raw contaminated water. This chamber 78 may be situated anywhere along the input side of the pump 82. The reagent could also be injected into the pump 82 itself or even into the output side of the pump 82. The pump 82 itself helps to mix and blend the reagent with the water. The reagent is preferably in the form of a slurry which is pumped along conduit 76.

On the exit side of the pump 82, where the reagent and raw water have received enough mixing time to provide an accurate measure of pH, a probe 84 measures pH, and with the use of the treatment unit 10 automatically adjusts reagent output to suit a pre-programmed setting.

The floe settling pit 86 collects the floe produced from the treatment: this could be metals from an acidic water treatment or silt, mud and clay from a turbidity treatment. Generally, when treating acidic water with dissolved metals, the floe takes around 60 minutes to settle to around 5% to 20% of the entire water volume. In this case, if one is treating one megalitre of water per hour, the floe pit 86 will need to allow several hours of settling with low turbulence. The base of the floe pit 86 is preferably V-shaped (not shown), and a simple slotted pipe (also not shown), by way of preference, may extract the floe material from the pit 86. The floe will continue to flow for several days or weeks until compaction stops this flowability. This may, in fact, take several months. The floe extraction pump 90 is used until the water being extracted becomes clean. This indicates that most of the floe has been extracted. The floe may be processed with a thickener or dewatering device or left in the floe collection pit 86 depending on volume, or pumped to an evaporation pit.

The floe separates from the clean water with a clearly defined layer and the clean water above that layer may be pumped, siphoned or gravity fed to a clean (treated) water holding pit 92.

The main advantage of the inline dosing method and apparatus is that the system is portable. The mixer/treatment unit 10 may be positioned in any suitable position, as may the transfer pump 82. The collection pit 80, the floe pit 86 and the clean water pit 92 may be built in situ with an excavator, and need not be in close proximity to each other. The floe settling pit 86 may not be needed on some sites, depending on the contamination level, and on the desired results. The floe pit 86 could alternatively take the form of a tank, rather than an excavated pit. The collection pit 80, may be a dam, lake or mine.

The treatment unit 10 of the present invention may also be used in place of a costly and complex water treatment plant. It has been shown earlier in this specification that the treatment unit of the present invention is able to clean contaminated water to Australian standards for drinking water. However, it is considered that such a unit would be most useful in treating water for use in such applications as, for example, power station cooling systems, and for use in mining.

At the moment, because of the prolonged drought in areas of Australia and/or global warming, ways are being sought to save the large amounts of fresh water used to cool power stations. It is considered that a treatment unit such as that described in this specification could be used to treat contaminated water to bring it to an acceptable level of cleanliness for use in power station cooling, and to maintain such a level in water which has already been cycled through such a cooling system. Such an arrangement may require one treatment unit of the appropriate capacity, located to treat contaminated water from a source, and to pass treated water to a holding pond or the like. The system may include treating water from a second pond, which holds water which has passed through the cooling system, and passing that water to the holding pond.

The treatment unit 10 of the present invention may also have multiple outlet pumps for dispersal of reagent-bearing water. Preferably, each pump is connected to a boost pump, from which a hose or the like may extend for ultimate dispersal of the reagent-bearing water, or each pump is flow controlled to provide an accurate and regulated output to a multi-pH pit dosing system as mentioned earlier. Such an arrangement would allow for a single unit to treat multiple adjacent or substantially adjacent bodies of water, or one large body of water or injected into the inlet flow of a separate floe pit, which the sprinkler, jet or the like at the end of each hose being separately moved around each or the body of water. In an inline dosing system, where water passes through a plurality, for example four, pits, the pH of the water is gradually altered on a pit- by-pit basis. A pH probe in the final pit provides an indication of the final pH level, and may be used to regulate aspect of the treatment unit, as described earlier in this specification.

The treatment unit 10 described in WO 2004/067455 A1 may be modified in other ways. For example, the rock conveyor 30 may be deleted, and the unit 10 operated using a powder reagent. In such an arrangement, the tumbler 14 would then contain mixing elements such as blocks of PVC or high density rubber, to mix the powder and liquid such as contaminated water.

It is also possible to replace the auger (34)/hopper (28) arrangement (and possibly also the tumbler (14)) with an alternative. For example, a mixing chamber could have mechanical and/or fluid mixing means. The mechanical mixing means could be vane/propeller-type means, or any other type of mechanical mixer, such as a bread-making type of rotating whisk. The fluid mixing means could be jets, including tangential (to the surface of what may be a conical or frusto-conical chamber) jets.

Fig. 6 illustrates another alternative mixing arrangement. The hopper 94 and auger 96 feed reagent powder into the mixing tank 98. This is preferably controlled by the PLC referred to earlier in this specification. Alternatively, it may be manually controlled.

The pump 102 is preferably of a large size, for example 76.2 mm, and may have an exemplary flow rate of 100,000 litres per hour. On the outlet side 108 of the pump 102, there is a bleed off 110 of, say, 5,000 litres per hour, which feeds into the mixing tank through, preferably, stirring jets (not shown), and which is controlled by the level control valve, so that a constant level of water is maintained inside the mixing tank 98. This would mitigate against the thickening of the mixture, with a resulting reduction in flow rate. The tank 98 may contain pieces of material, preferably blocks of material, more preferably of general dimensions 20 mm to 60 mm, square, round, oval or the like. This material moves around the tank 98 under the force of the jets, and agitates or breaks up the mixture and provides thorough mixing. The water along with the mixed reagent is removed from the mixing tank 98 through the conical base section 100 at the same rate as the feed water and is sucked with the use of the pump 102 suction. The level control may be fitted to either the mixing tank 98 outlet side or jet side. The pump transfers the blended reagent in the direction of arrow 112 to an applicating device or for other purposes.

It can be seen that this application discloses an improved process for treating contaminated water.

The entire contents of the specification of Australian provisional patent application no. 2005905332, filed on 28 September 2005, are hereby incorporated into this specification.

The claims form part of the disclosure of this specification.

Claims

1. A process for treating contaminated water, characterised by the steps of passing contaminated water, from a first contaminated water-containing pit or the like, through a treatment unit, said water having reagent added thereto by said unit, passing said mixture of reagent and contaminated water to a floe pit or the like, allowing floe to settle, and pumping treated water from said floe pit into a holding pit or the like, for re-use.

2. A process according to claim 1 , characterised in that said floe is allowed to settle for a time between one hour and several hours.

3. A method for treating contaminated water, characterised by the steps of:

treating said contaminated water by applying a reagent to produce first stage treated water in which a value of the contaminated water has been brought to a first desired level;

allowing said first stage treated water to settle for a predetermined time.

4. A method according to claim 3, characterised by the further steps of:

treating said first stage treated water by applying a reagent to produce second stage treated water in which a value of the contaminated water has been brought to a second desired level; and

allowing said second stage treated water to settle for a predetermined time.

5. A method according to claim 4, characterised in that said steps are carried out a plurality of times, until final stage treated water is obtained, with a value of the water being brought to a final desired level.

6. Apparatus for carrying out the method of any preceding claim, said apparatus being adapted to treat said body of water with one or more reagents, characterised in that said apparatus is controlled by a programmable control system such that the operation of said apparatus may be automated.

7. Apparatus according to claim 6, characterised by means to measure a value associated with the water being treated, and to adjust the supply of reagent to maintain a predetermined value.

8. Apparatus according to claim 7, characterised in that when the predetermined value is the pH of the water, the reagent is hydrated lime, calcium carbonate, soda ash, caustic soda, or the like.

9. Apparatus according to claim 7, characterised in that when the predetermined value is O₂, the reagent is peroxide.

10. Apparatus according to claim 7, characterised in that when the predetermined value is conductivity, the reagent may be a salt.