Claims:1. A process for reducing chemical oxygen demand (COD) in a pesticide effluent comprising the steps of:
subjecting the untreated pesticide effluent to an advanced oxidation process, wherein the advanced oxidation process comprises the steps of:
a) purging ozone at a predetermined rate into the untreated pesticide effluent;
b) adding hydrogen peroxide to the effluent to form a reaction mass; and mixing the reaction mass to obtain treated effluent.

2. The process as claimed in claim 1, wherein the process is carried out at a temperature in the range of 25? to 35?.

3. The process as claimed in claim 1, wherein the untreated pesticide effluent has a pH in the range of 1 to 2.

4. The process as claimed in claim 1, wherein the concentration of hydrogen peroxide ranges from 3% v/v to 15% v/v of the total volume of the effluent.

5. The process as claimed in claim 1, wherein the rate of ozone is in the range of 1kg/hr to 4 kg/hr and the concentration of ozone is in the range from 0.1 to 1% v/v of the total volume of the effluent.

6. The process as claimed in claim 1, wherein the ratio of ozone to hydrogen peroxide is from 0.5:10 to 1.5:25.

7. The process as claimed in claim 1, wherein the COD of treated effluent is reduced at least by 70%.

8. The process as claimed in claim 1, wherein the ozone is purged through a nanobubble pump.

9. The process as claimed in claim 1, wherein the pesticide is selected from organothiophosphate pesticide, organodithiophosphates, thiocarbamates and dithiocarbamates.

10. The process as claimed in claim 1 wherein said pesticide effluent is generated from manufacturing of terbufos or from manufacturing of mercaptan.

11. A system for reducing COD in pesticide effluent comprising:
a) A reservoir (203) for supplying hydrogen peroxide;
b) An oxygen generator (204) for ozone generation; and
c) An effluent treatment apparatus (205);
wherein the said effluent treatment apparatus (205) is filled with the pesticide effluent from manufacturing unit (201); the effluent solution is then subjected to a treatment with hydrogen peroxide (H2O2) and ozone (O3) supplied by hydrogen peroxide reservoir (203) and oxygen generator (204) respectively; the hydrogen peroxide and the ozone combine to form peroxone which oxidizes the effluent in the treatment apparatus (205) to form treated pesticide effluent with reduced COD.

12. The system as claimed in claim 10, wherein the COD of treated effluent is reduced at least by 70%.
, Description:
FIELD OF INVENTION
The present invention relates to a process and system for treating effluents from the pesticide manufacturing industry. Particularly, the present invention relates to a process for reducing the chemical oxygen demand (COD) of high organic load pesticide effluents.

BACKGROUND OF INVENTION
Effluents from the agrochemical industries contain many hazardous chemicals and their release causes severe environmental impacts. These effluents are rich in organic compounds that are barely degradable by nature; so, they remain as a serious threat to the environment. They may accumulate in human and animal tissue upon long distance transportation. Particularly, effluents released from the pesticide industry results in pollution problems due to its high COD, Biochemical Oxygen Demand (BOD) and high Total Dissolved Solids (TDS). Moreover, the effluent shows wide variation in the effluent characteristics depending on the type of pesticides manufactured and on the use of raw materials utilized.

Effluent Treatment process is a systematic process for treating the industrial waste water for its reuse or safe disposal to the environment. The system of effluent treatment plant is highly dependent on industry and site. Untreated effluent standards and treated effluent standards are important parameters taken into consideration in process of wastewater treatment plant design. Also coming to selection treatment process, it involves consideration of treatment efficiency, cost and reliability. Abatement of water pollution is a major concern to be dealt with. Treatment of pesticide industrial wastewater prior to disposal plays an important role. Regulators enforce limits on COD content allowed in effluent before it enters the environment.

There is a long felt need to develop an efficient process and system for treating the pesticide effluents which is safe, simple, cost effective, environmentally friendly technique and significantly reduces COD content in the effluent without any further treatment.

OBJECTS OF THE INVENTION
It is an object of the present invention to provide an efficient process for treating pesticide effluents.

It is another object of the present invention to provide a process for reducing COD of pesticide effluents having a high organic COD load.

It is another object of the present invention to provide a process for reducing COD of sulfur containing pesticide effluents.

It is another object of the present invention to provide a process for reducing COD of pesticide effluents which is safe, simple, economical and environmentally friendly technique.

It is another object of the present invention to provide a system for treating pesticide effluents having a high organic COD load.

SUMMARY OF THE INVENTION
In an aspect, the present invention provides an efficient process for treating pesticide effluents.

In another aspect, the present invention provides a process of reducing chemical oxygen demand (COD) from pesticide effluent. The process comprises the steps of treating the effluent with advanced oxidation process. The advanced oxidation process comprises the steps of purging ozone at a predetermined rate into the untreated pesticide effluent. Adding hydrogen peroxide to the effluent to form a reaction mass. Further, the reaction mass is mixed for a predetermined time to obtain a treated effluent having COD content reduced at least by 70%.

Another aspect of the present invention provides a system (200) for reducing COD in pesticide effluent comprising a reservoir (203) for supplying hydrogen peroxide, an oxygen generator (204) for ozone generation, and an effluent treatment apparatus (205). The said effluent treatment apparatus (205) is filled with the pesticide effluent from manufacturing unit (201) wherein the effluent solution is then subjected to a treatment with hydrogen peroxide (H2O2) and ozone (O3) supplied by hydrogen peroxide reservoir (203) and oxygen generator (204) respectively. The hydrogen peroxide and the ozone combine to form peroxone which oxidizes the effluent in the treatment apparatus (205) to form treated pesticide effluent with reduced COD.

BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings wherein:

Figure -1 illustrates a flow diagram of the conventional process for treatment of pesticide effluent.

Figure-2 illustrates a flow diagram of the present process for treatment of pesticide effluent according to an embodiment of the present invention.

Figure-3 illustrates a flow diagram of the present process for treatment of pesticide effluent with advanced oxidation process in combination with nanobubble technology.

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings but are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the scope of the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, steps or components but does not preclude the presence or addition of one or more other features, steps, components, or groups thereof.

The term "pesticide" as used herein means compounds that are used to kill or control pests. In agriculture, this includes herbicides, insecticides, fungicides, nematocides, and rodenticides.

The term “effluent” as used herein means wastewater/ discharge flowing out of industries. In the context of present invention, effluent relates to the discharges released from pesticide manufacturing industries and comprising a complex nature of pollutants and includes organic and inorganic compounds.

The term “Chemical Oxygen Demand (COD)” as used herein means the amount of oxygen needed for complete decomposition of organic matter. COD is used to gauge the short-term impact wastewater effluents will have on the oxygen levels of receiving waters. Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.

The term “Total dissolved solids (TDS)” as used herein means a measurement of inorganic salts, organic matter and other dissolved materials in water. High TDS can cause toxicity to aquatic life through increases in salinity, changes in the ionic composition of the water, and the toxicity of individual ions.

In an aspect, the present invention relates to a process for the treatment of effluents from the pesticide manufacturing industry. Particularly, it relates to a process for reducing the COD of high organic load pesticide effluents.

Effluents originating from pesticide production are a mixture of inorganic and organic components and are characterized by various physico-chemical properties. Biological treatment generally is not sufficient and capable to remove the recalcitrant organic contaminants in the pesticide effluent which are not biodegradable and/or are inhibitory to microbiological activity. A chemical pre-treatment is required to be done for treating the high COD effluent stream before its treatment in Effluent Treatment Plant (ETP) which increases an additional process step as well as the overall cost of effluent treatment.

Thioalcohols, also called mercaptans, correspond to the general formula R–S–H, wherein R can be lower alkyl. The most common ones are ethyl mercaptan C2H5SH, propyl mercaptan C3H7SH, butyl mercaptan C4H9SH, amyl mercaptan C5H11SH. Mercaptans are used as an intermediate in the production of pesticides, particularly fungicides, and animal feed additives. Mercaptans are organic compounds with a distinct pungent odor. Effluents of sulfur-containing pesticides contain a large amount of mercaptans as unreacted material and because of the degradation/decomposition of pesticide compounds during the manufacturing process which results in the generation of mercaptans. The presence of mercaptans in the pesticide effluents is undesirable from an environmental point of view as well as for handling and field application purposes. The odor can negatively impact not only the production facilities but also the surrounding communities.

A conventional treatment for removing high organic COD load from mercaptan-containing pesticide aqueous effluents involves batch distillation wherein 25% of cut is removed which goes as incinerable waste and bottom mass is mixed with another aqueous effluent. This composite stream is then treated with H2O2 which further goes for biological treatment. However, recalcitrant organic contaminants which are not biodegradable and/or are inhibitory to microbiological activity requires chemical oxidation for removal. The extent of contamination is measured in terms of COD. These hard COD contaminants mainly go for incineration in the convention process to avoid its contact with biological activity.

However, the conventional treatment of aqueous pesticide effluents suffers from various drawbacks. Typically, during the batch distillation, the condenser gets chocked in every 10 to 15 days and dechoking/cleaning of condenser is highly toxic for human health. Furthermore, incineration of the distilled material leads to generation of foul odour and also increases the incineration load which further contributes towards environment damage.

Advanced Oxidation Processes (AOPs) are the treatment technologies aimed at oxidizing and degrading recalcitrant organic matter from wastewater through reaction with hydroxyl radical (•OH). These hydroxyl radicals degrade the organic compounds in the wastewater by oxidizing them. The present inventors have found that an advanced oxidation process employing peroxone i.e., ozone in combination with hydrogen peroxide effectively treats the high COD pesticide effluent stream and thereby overcomes the drawbacks associated with conventional process of reducing COD for pesticide effluent.

Peroxone Treatment: Hydrogen peroxide (H2O2) is added into ozone (O3) for initiating the ozone decomposition cycle, resulting in the formation of OH• radicals:
H2O2 ? HO2– + H+
HO2– + O3 ? HO2• + O3•–

The reaction continues along the indirect pathway described above and OH• radicals are produced. The combination of different reaction steps shows that two ozone molecules produce two OH• radicals:
2O3 + H2O2 ? 2OH• + 3O2

The generated hydroxyl radicals oxidize the recalcitrant organic contaminants from the pesticide effluent, thus reducing the COD load.

In an embodiment the present invention provides a process of treating pesticide effluent to reduce the COD. The pesticide effluents are treated using advanced oxidation process. The effluent is transferred to a reaction vessel, and it is purged with ozone at a rate in the range of 1 kg/hr to 4 kg/hr, simultaneously hydrogen peroxide 50% is added to form a reaction mass; ozone purging is continued for a period of 10-20 hours. The process is performed at a temperature in the range of 25? to 35?. Total concentration of hydrogen peroxide is not more than 20% v/v. Typically, the concentration of hydrogen peroxide can vary based on the treatment at large scale. The ozone purging is discontinued, and different parameters of treated effluent are evaluated for example the colour, odour and COD content.

An exemplary embodiment of the present invention provides a process of reducing COD in pesticide effluent comprising the steps of:
subjecting the untreated pesticide effluent to an advanced oxidation process, wherein the advanced oxidation process comprises the steps of:
a. purging ozone at a predetermined rate into the untreated pesticide effluent;
b. adding hydrogen peroxide (50%) to the effluent to form a reaction mass; and
c. mixing the reaction mass for a predetermined time to obtain treated effluent
wherein the COD content of the treated effluent is reduced at least by 50% when compared with untreated effluent.

In an embodiment, purging of ozone and addition of hydrogen peroxide is performed at a temperature in the range of 25? to 35?.

In an embodiment, the reaction mass is mixed for a predetermined time ranging from 10 to 20 hours.

In an embodiment, the untreated pesticide effluent has a pH in the range of 1-2.

In an embodiment, hydrogen peroxide (50%) addition and ozone purging is performed simultaneously.

In an embodiment, the concentration of hydrogen peroxide ranges from 3% v/v to 20% v/v of the total volume of the effluent.

In an embodiment, the concentration of ozone is in the range from 0.1 to 1% v/v of the total volume of the effluent.

In an embodiment, the rate of ozone is in the range of 1kg/hr to 4 kg/hr.

In an embodiment, the ratio of ozone to hydrogen peroxide (O3/H2O2) ranges from 0.5:5 to 2:20.

Alternatively, purging of ozone in the process is carried out with nanobubble technology.

In an embodiment the pesticide effluent to be treated is an effluent generated from the manufacturing of terbufos.

In an embodiment, the COD of effluent treated according to the present invention is reduced at least by 50%, preferably at least by 75% and more preferably at least by 85% as compared to the COD of untreated effluent.

In an embodiment the present invention provides a process of reducing COD content from mercaptan containing pesticide effluent comprising the steps of:
subjecting the untreated mercaptan containing pesticide effluent to an advanced oxidation process, wherein the advanced oxidation process comprises the steps of:
a. purging ozone at a predetermined rate into the mercaptan containing untreated pesticide effluent;
b. adding hydrogen peroxide (50%) to the ozone treated effluent to form a reaction mass; and
c. mixing the reaction mass to obtain treated effluent.
wherein COD content of the treated effluent is reduced at least by 50% when compared with untreated effluent.

In an embodiment, purging of ozone and addition of hydrogen peroxide is done at 25?-35?. In an embodiment, the process is carried out for about 10 to 15 hours.

In an embodiment the COD of untreated effluent is in the range of 65000 to 70000 ppm.

In an embodiment the COD of treated effluent is in the range of 10000 to 15000 ppm.
In an embodiment, the rate of ozone is in the range of 2 kg/hr.

In an embodiment, the dosage ratio of ozone to hydrogen peroxide (O3/H2O2) is 1:10.
In an embodiment, the concentration of hydrogen peroxide (H2O2) is 5% of the total volume of the effluent.

In another embodiment the pesticide effluent to be treated according to the present invention is an effluent generated from the manufacturing of terbufos.

In an embodiment the present invention provides a process of reducing COD in the untreated effluent generated from the manufacturing of propineb comprising the steps of:
subjecting the untreated effluent to an advanced oxidation process, wherein the advanced oxidation process comprises:
a. adding ozone at a predetermined rate into the untreated pesticide effluent, wherein ozone is added with a nanobubble pump; and
b. adding hydrogen peroxide (50%) to the ozone treated effluent to obtain a treated effluent.
wherein the COD content of the treated effluent is reduced at least by 50% when compared with untreated effluent.

In an embodiment, purging of ozone and addition of hydrogen peroxide is done at a 25?-35?.

In an embodiment, the untreated pesticide effluent originating from propineb synthesis has a pH in the range of 10-12.

In an embodiment the COD of untreated effluent is in the range of 2000 to 3000 ppm.

In an embodiment the COD of treated effluent is in the range of 200 to 550 ppm.

In an embodiment, total duration of the treatment is in the range of 12-18 hours.

In an embodiment, the rate of ozone is 1 kg/hr to 4 kg/hr. Preferably the rate is 4 kg/hr.

In an embodiment, the dosage ratio of ozone to hydrogen peroxide (O3/H2O2) is in the range of 0.5:10 to 1.5:23.

In an embodiment, the effluent to be treated by present process is generated from manufacturing of propineb wherein the COD is reduced at least by 50%, preferably at least by 80%. Preferably, the COD of untreated effluent is reduced from about 2500 to 3000 ppm to about 200 ppm to 550 ppm.

The present process can be performed as a batch process or continuous process.

In an embodiment, the present process can be applied to treatment of effluents generated from manufacturing of various pesticides which include, but not limited to, organothiophosphate pesticide, organodithiophosphates, thiocarbamates and dithiocarbamates.

In an embodiment, the organothiophosphate pesticide is selected from terbufos, phorate, ethoprop, dialifos, carbophenothion, ethion, dioxathion, fonofos, phosmet, parathion, methyl parathion, ethyl parathion, disulfoton, chlorpyrifos and malathion, dimethoate, fenitrothion, metha idophos, acephate, diazinone and prophenophos. Preferably, the organothiophosphate pesticide is terbufos.

In an embodiment, the thiocarbamate pesticide is selected from molinate, pebulate, triallate, butylate, cycloate, and thiobencarb.

In an embodiment, the dithiocarbamate pesticide is selected from mancozeb, maneb, metiram, Na-dimethyldithiocarbamate, thiram, ziram, ferbam, propineb and metam sodium. Preferably, the dithiocarbamate pesticide is propineb.

In an embodiment, the pesticide effluents comprise mercaptan as the recalcitrant chemical contaminant.

In another embodiment the present invention provides a system for reducing COD content in the pesticide effluent.

In an embodiment the system for reducing the COD content from pesticide effluent is described in detail herein below with reference to the figures.

Reference is now made to figures which illustrate the system for effluent treatment according to the present invention. The examples are presented to exemplify the invention and are not to be considered as limiting the scope of the invention.

Figure -1 illustrates a flow diagram of the conventional process and system (100) for treatment of terbufos pesticide effluent involving batch distillation wherein 25% of cut is removed which goes as incinerable waste and bottom mass is mixed with another aqueous effluent. This composite stream is then treated with H2O2 which further goes to the ETP for Biological treatment. The distillation condenser gets choked after every 10-15 days which must be manually cleaned by operator thus exposing him to toxic compounds. Also, the incineration load is additionally increased due to the incineration of the 25% cut. This process is not feasible and tedious and time consuming.

Figure-2 illustrates a flow diagram of the present process for treatment of pesticide effluent according to an embodiment of the present invention. In an embodiment, the pesticide is Terbufos.

According to the present invention there is provided a system (200) for reducing COD in pesticide effluent comprising a reservoir (203) for supplying hydrogen peroxide, an oxygen generator (204) for ozone generation, and an effluent treatment apparatus (205). The said effluent treatment apparatus (205) is filled with the pesticide effluent generated from manufacturing unit (201) wherein the effluent solution is then subjected to a treatment with hydrogen peroxide (H2O2) and ozone (O3) supplied by hydrogen peroxide reservoir (203) and oxygen generator (204) respectively. The hydrogen peroxide and the ozone combine to form peroxone which oxidizes the effluent in the treatment apparatus (205) to obtain treated pesticide effluent with reduced COD.

This treated effluent may be further subjected to effluent treatment plant (ETP) (206) for further biological degradation of the treated effluent. Any gaseous emissions are vented to incinerator (209) for thermal destruction.

Referring to figure 3, it represents a batch process for the treatment of pesticide effluent. In an embodiment the pesticide is propineb. As illustrated in figure 3 the present process includes a pot for effluent in batch mode which is under circulation by combination of centrifugal pump, mix pump (gas/liquid mixing pump) and orifice of 2 mm at the discharge to generate nanobubbles. Ozone is introduced in the discharge of centrifugal pump with the help of venturi that is directed to gas/liquid mix pump to generate nanobubbles of ozone in combination with orifice at the discharge. H2O2 (50%) is added in the pot directly and it is mixed by intercirculation of pump. The mixture is mixed to obtain treated effluent with reduced COD content.

Advantages of the present invention are:
• The present process is easy to operate as distillation is avoided and maintenance load is also reduced.
• No direct contact of the toxic contaminants such as mercaptan with humans.
• Incineration load reduction.
• Elimination of Unit operation/distillation, utility saving
• No condenser dechoking required; thereby eliminating the risk of exposure to toxic chemicals.
• Elimination of toxicity
• Cost effective process.
• Complete smell elimination of Mercaptan in effluent, Odour/smell reduction in surrounding area.
• Effluent colour elimination.
• Clean and green technology as part of sustainable development goal (SDG).
• Improvement in Bio-treatability.
• Reduction in carbon footprint.

EXAMPLES:
The following examples are meant to illustrate the present invention. The examples are presented to exemplify the invention and are not to be considered as limiting the scope of the invention.

EXAMPLE -1:
Process of COD reduction in Terbufos pesticide effluent:
6.5 KL of the untreated pesticide effluent was added in an Ozone treatment reactor and was kept under circulation with the help of a canned pump. Initial COD of the effluent was measured. Ozone was pumped through the effluent into the reactor with the help of a non-return valve and venturi in circulation line at a rate of 2 kg/hr. Ozone required per KL of effluent treatment was 7-8 Kg. Simultaneously 300 to 320 kg of hydrogen peroxide (H2O2) was added by gravity in the ozone treatment reactor. Ozone addition and mixing was stopped after 16 hrs. After completion of H2O2 addition in 8 to 10 hrs, the sample was taken for COD analysis.

Table-1: Characterization of Terbufos Pesticide Effluent before and after treatment with AOP.

Parameter Untreated Effluent (i.e., before treatment) Treated effluent by present process (O3/H2O2)
COD 65000-70000 ppm 10000-15000 ppm
pH 1.5-2 1.5-2
Odour Pungent Odourless
Colour Light brown Colourless

The process was carried out with different concentration of ozone and H2O2 at lab scale. The difference in COD reductions was observed and recorded as follows:
Sr. No. Feed Qty. (kg) Ozone consumed (gm) H2O2 Added in gm Initial COD (ppm) Final COD (ppm) % COD reduction
1 0.600 4 48 65141 13991 79
2 0.600 6 60 65141 16656 74
3 0.600 7 60 65141 15931 76

From the above table it is clear that with the current process, COD of about 65000 of the untreated effluent is reduced to about 13000 which is more than 70% reduction in COD.

EXAMPLE -2:
Process of COD reduction in effluent originating from propineb synthesis:
20 Kg effluent mass was added in a 30 KL Stainless Steel cylindrical pot. Ozone was injected to the system at a rate of 5 to 5.5 gm/hr with the help of venturi cum Non return valve. The gas/liquid mixing and bubble formation happens through arrangement of mix pump with orifice. Ozone Nanobubbles formed in pot causes COD reduction with ~95% utilization of Ozone. H2O2 is added from top of the pot with the help of dosing pump with consumption of ~15 Kg/Kl. COD reduction occurs in 16 to 18 hrs from 2500 ppm to < 250 ppm with Ozone consumption of 113 gm (~5.65 Kg/KL). Addition of ozone through nanobubble technology reduces quantity of ozone required per liter of effluent.
Sr. No. Description Total Run time (Hrs) Untreated Effluent qty. (Lit) Initial COD (ppm) Final COD (ppm) Ozone consm. (gm) % COD reduction
1 Nanobubble Ozonation with H2O2 14 15 2211 278 113.8 87.4

Thus, present invention encompasses feature that involves technical advance as compared to the existing knowledge and it also has economic significance and that makes the invention not obvious to a person skilled in the art.

It is to be understood that the present invention is susceptible to modifications, changes, and adaptations by those skilled in the art. Such modifications, changes, adaptations are intended to be within the scope of the present invention.