FIELD OF THE INVENTION
The present invention relates in general to technique for removal of anionic pollutants (free cyanide) from industrial waste water at pilot scale level. More particularly, the present invention relates to a system (reactors) for removal of free cyanide from the industrial effluent water at the flow rate of 5m3/hr in a continuous manner by facilitating complex coordination process employing a suitable solid reagent in optimum quantities.
BACKGROUND OF THE INVENTION
In steel industries during coke making process by-product such as coke oven gas is generated which contain water, oil, tar, ammonia, phenol, cresol, benzol, cyanides, thiocyanate, sulphides, pyridine, PAH, etc. The coke oven gas is processed by cooling and scrubbing to reduce ammonia and cyanide concentration. However, the effluent contains specific amount of cyanide, thio-cyanide, sulphur, etc. The wastewater from the coke plant and blast furnace (BF) blow down have been identified as the contributors of aqueous cyanide emissions in the iron and steel industries, however; the characteristics of cyanide from those sources are significantly different due to presence of lots of interferences (Table 1). Cyanide present in the coke plant discharge water is in association with other interferences such as ammonia, thiocyanate, sulfides, pyridine, oil, tar, phenol, cresol, benzol, PAH, etc. whereas, the blast furnace blow down water contains various forms of cyanide along with high concentration of chloride and ammonia including other inorganic recalcitrant e.g. Fe, Na, K, SO42-, etc. At present in the plant alkaline chlorination has been implied to reduce the cyanide concentration through charging of Sodium hypochlorite. This process reduces the cyanide but also increase the TDS of waste water. Also, it is not cost effective method and also has chance of formation of Cyanogen Chloride during the process.


With respect to the foregoing, the present applicant had filed a patent application with application number 201631044988 disclosing synthesis of a novel compound for cyanide removal from waste water at lab scale. The compound had been found to be efficient in removing cyanide ion even at low concentration and independent of pH and temperature. In spite of good removal efficiency it needs to optimize the synthesis conditions for production in large amount and utilize at large scale.
The removal process proposed in the above filed patent application (201631044988) is highly efficient and useful in removal of free cyanide but needs a novel set-up/system equipped and suited for optimizing the synthesis conditions/process parameters such as maintenance of proper residence time,

process temperature etc and to ensure continuous removal of free cyanide while reducing TDS at a pilot scale level. There is therefore a need to develop such system implementing unique reactors for removal of cyanide from waste water at large scale in a continuous manner.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to overcome the aforementioned and other drawbacks existing in the conventional set-ups implemented for removal of free cyanide in a continuous manner.
Another primary object of the present invention is to provide a system for cyanide removal at continuous pilot scale according to an embodiment of the present invention.
Yet another object of the present invention is to develop specially designed reactors for providing proper/optimum residence time during continuous removal of free cyanide from industrial effluent water according to an embodiment of the present invention.
Still another object of the present invention is to provide a system upscaled to 5m3/hr flow rate continuous pilot scale according to an embodiment of the present invention.
Further object of the present invention is to provide a system for facilitating heterogeneous phase mixing of solid reagent [L {M}].
Yet another object of the present invention is to provide a system for reducing Total dissolved Salts (TDS) in waste (effluent) water.
These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION
The present application discloses a system for continuous removal of anionic pollutants from industrial effluent water. In an aspect, the system includes a first agitated tank configured to receive the industrial effluent water and an amount of solid reagent from a feed preparation tank both together serving as a first reactant. Further, the first reactant is being constantly agitated for an optimum residence time for generating a first batch of treated water. Further, in an aspect, the system includes a second agitated tank configured to receive the first batch of treated water along with an amount of solid reagent both together serving as a second reactant. Further, second reactant is being constantly agitated for an optimum residence time for generating a second batch of treated water which is discharged through a discharge outlet because of spin created by a centrifugal pump. Furthermore, in an aspect, the amount of solid reagent dosed into the second agitated tank is less than the amount of solid reagent being dosed into the first agitated tank.
The above and additional advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above brief description, as well as further objects, features and advantages, of the present invention can be fully appreciated by reference to the following detailed description. These features of the present invention will become more apparent upon reference to the drawings, wherein:
Fig. 1: Illustrates a technique for removal of free cyanide at continuous pilot scale.
Fig. 2: Illustrates a detailed view of a pilot plant.
Fig. 3: Illustrates percentage removal of CN‾ with [L{M}] in coke waste (BOT inlet) water.

Fig. 4: Illustrates percentage removal of CN‾ with [L{M}] in BOT outlet post biological treatment.
Fig. 5: Illustrates removal of CN‾ with [L{M}] in Blast Furnace Water.
DETAILED DESCRIPTION OF THE INVENTION
Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
It will be apparent, however, to one of ordinary skill in the art that the present invention may be practiced without specific details of the well known components, designs and techniques. Further specific numeric references should not be interpreted as a literal sequential order. Thus, the specific details set forth are merely exemplary. The specific details may be varied from and still be contemplated to be within the scope of the present invention. The features discussed in an embodiment may be implemented in another embodiment.
Moreover occasional references to such conventional set-ups have been made in order to better distinguish the present inventive disclosure discussed later in greater detail from such conventional designs. Few of the details pertaining to the proposed system is known in the art and therefore, are described herein only in the detail required to fully disclose the present invention while unnecessarily obscuring the present invention.
Improving upon the conventional techniques discussed at length above (background), the present system as shown in the figures clearly makes the present application advantageous over the existing arts as would also become clearer to the knowledgeable in the art with the particulars of the proposed

system being described below in greater detail. The present invention will be described in detail below with reference to embodiments as shown in the drawings.
The present invention provides a continuous process of removing free CN¯ from the waste water containing high content of CN‾ up to its permissible limit. The ([L{M}] complex) has been synthesized continuously by reaction of amine and aldehyde containing compound followed by generation of active binding site for cyanide in the specially designed reactor. The prepared complex compound was applied to treat the BOT and Blast furnace (BF) waste water. Supramolecular metallo cage [L{M}] solid compound was prepared in lab in large amount at optimized conditions. Also, a setup has been designed for running the trial with 5m3/hr flow rate of waste water and heterogeneous phase mixing of solid compound [L{M}].
The pilot plant of cyanide removal process is installed coke plant and blast furnace near the clarification tank for easier access of the source water. Fig. 1 shows the technique of implementation at continuous scale on the said pilot plant. The reactor is specially designed so that it would handle the effluent treatment continuously. The specially designed continuous tank is used for actual chemical reaction. Proper dosing rate and the input water flow rate can be set at per the residence time maintained inside the main mixing tank. The continuous reactor is designed in such a way that it allows all the reactant to have 30 minutes residence time. In reaction chamber the feed water is introduced from top and discharge at the bottom of the tank. The effluent from tank is traveling upwards for discharging out from the top nozzle. This upward movement of the tank is so designed that it receives 0.5 hour residence time from entering as upstream to be discharged as downstream. This special arrangement is done so innovatively that the desire reaction time is being achieved by all the reactants and also it maintains a steady state continuous operation. The entire operation ensures that no short circuiting of the reactants is taking place and thus it establishes an ideal stirred tank continuous process scenario.

Fig. 2 shows the actual plant layout. The entire unit consist of two agitated tanks 1, 2/ reactor tanks, agitators 4, one feed preparation tank 5, and one centrifugal pump 6 along with a dosing pump 3. The centrifugal pump 6 is used to create spin in the treated water, thereby generating centrifugal force that channels it through a discharge outlet. Further, agitators 4 may be mechanical agitators comprising a rotating shaft and one or more impellers for mixing the waste water fast so that the CN- can be removed. Furthermore, a dosing pump 3 is used to dose the reagent into the agitated tanks (1, 2). Temperature sensors are introduced at the mixing vessel and the final settling tank to measure the temperature of the process. The technique involves removal of anionic pollutant like CN from effluent water by complex coordination reaction process by employing the above unit operation. In Fig. 1, the concept of continuous reaction is introduced. The detail description of the entire plant is illustrated in Fig. 2. Further, in an embodiment the removal of anionic pollutant like CN from effluent water by complex coordination reaction process by employing the following unit operations:
Reagent Handling
The principal raw material of the process is the developed solid reagent. These are received in car and are stored in the ground storage inside the plant premises (for feeding into the subsequent process by suitable conveying mechanism.
Effluent Water Storage and Handling
Effluent water will be pumped from the existing plant to the intermediate storage tank at tertiary treatment plant for feeding into the further treatment processes.
Pre-Mixer
Pre mixer is used for preparation of reagent before feeding into the reactor. An optimized amount of solid and water is mixed based on the duration of continuous plant trial.

Chemical Reaction
In this step, the anionic receptors are mixed with effluent water under agitation. CN and other toxic ingredients are reacted with the solid anionic receptor. This operation requires a residence time of approx. 30 minutes at ambient temperature (28 – 300C). A constant agitation is agitation is employed by Agitator 4. The Treated water was taken from the top of the first reactor produced after reaction is passed into the next processing / separation.
In an embodiment, the second reactor is installed immediately after the first one. The water inflow from first reactor is again being received by the 2nd reactor. Here again 30 minutes residence time has been given. A small amount of dosing (10%) of chemical is also introduced but significantly lower that the first one. The treated water was discharged from 2nd reactor. The trial was repeated for 6-7 days and removal efficiency was evaluated. The removal efficiency was found to be 70-75% in both types of water (Fig. 3-5).
In order to fix the optimal concentration and retention time of the supramolecular metallo cage [L{M}] for efficient and quick removal of CN‾, Many trials have been performed at the pilot plant. BOT plant here stands for biological treatment plant. This plant actually designed for removal phenolic compound and CN by microorganisms.
Furthermore, Fig. 3-5 shows the advantages and efficiency of the implemented system with respect to the cyanide (free cyanide) removal efficiency of the provided system.
Fig. 3 shows that the BOT plant inlet generally contains CN level of 10 to 20 PPM cyanide and 500 PPM phenol. BOT plant outlet contains 3 to 5 PPM CN and 10 to 20 PPM phenol. There is another effluent stream was taken into consideration which is blast furnace downstream water. This water contains as high as 5 to 7 PPM of CN.

Fig. 4 shows CN removal efficiency when the said continuous pilot unit implemented at BOT outlet. The removal efficiency is around 70 to 75%. The treated water contains CN level of 3 to 5 PPM. The figure 6 shows the treatment efficiency at BOT outlet. The efficiency is varies from 70% to as high as 80%. The treated water CN level is gone down to 0.5 PPM.
Fig. 5 shows the removal efficiency at Blast Furnace water. The developed compound and the continuous arrangement together resulted 70% of CN removal efficiency. The final discharge water CN level is again gone down to 0.5 to 1 PPM.
The experimental results prove that the optimal concentration of [L{M}] for CN‾ removal was found to be 2 mmol/lit whereas the optimal retention time was found to be 10 minutes. During the treatment process, it has also been observed that portion of the compound was found to be dissolved in waste water which turned pale green upon treatment. It means partial solubility of the compound played the pivotal role in CN‾ removal. Also, it has been estimated that the percentage loss of compound in each treatment cycle was 4.5 W% (weight percent). In addition to cyanide removal it also reduces the TDS content in waste water (Table 2).

The compound has been found to independent of variation of pH and temperature even at large scale. The waste water contained several other interfering anionic species e.g. Cl¯, SO42¯, NO3¯, NO2¯ etc. whose presence did not affect the efficiency of CN‾ removal process as the compound has specified pockets for CN‾ binding.

The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.

We claim:
1. A system for continuous removal of anionic pollutants from industrial
effluent water, the system comprising:
a first agitated tank (1) configured to receive the industrial effluent water and an amount of solid reagent from a feed preparation tank (5) both together serving as a first reactant, said first reactant being constantly agitated for an optimum residence time for generating a first batch of treated water;
a second agitated tank (2) configured to receive the first batch of treated water along with an amount of solid reagent both together serving as a second reactant, said second reactant being constantly agitated for an optimum residence time for generating a second batch of treated water which is discharged through a discharge outlet because of spin created by a centrifugal pump (6), said amount of solid reagent dosed into the second agitated tank (2) is less than the amount of solid reagent being dosed into the first agitated tank (1).
2. The system as claimed in claim 1, wherein the solid reagent is dosed into the agitated tanks (1, 2) via a dosing pump (3).
3. The system as claimed in claim 1, wherein the constant agitation is created in each of the agitated tanks (1, 2) using an agitator (4).
4. The system as claimed in claim 1, wherein the agitated tanks (1, 2) are configured to facilitate upward movement of the treated water which is discharged via top nozzles defined on a sidewall of the each agitated tanks (1, 2).
5. The system as claimed in claim 1, wherein at least one level sensor and temperature sensor are fixed to each of the agitated tanks (1, 2).

6. The system as claimed in claim 1, wherein the optimum residence time is around 30 minutes.
7. The system as claimed in claim 1, wherein flow rate of the industrial effluent water is 5m3/hr with heterogeneous phase mixing of the solid reagent.
8. The system as claimed in claim 1, wherein the solid reagent is Supramolecular metallo cage [L{M}] compound.
9. The system as claimed in claim 1, wherein the anionic pollutant
comprises free cyanide (CN-) particles.
10. The system as claimed in claim 1, wherein the industrial effluent water is pumped at an input water flow rate and an amount of solid reagent is dosed at a dosing rate, and wherein the input water flow rate and the dosing rate are fixed based on the optimum residence time.
11. The system as claimed in claim 9, wherein the (CN-) removal efficiency is 70-75% from industrial effluent water.